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Akış performans eğrilerinin oluşturulmasında kullanılacak bilgisayar programının geliştirilmesi ve petrol saha verileri ile test edilmesi
Petrol üretiminde rezervuar basınç dağılımının, kuyu dibi basıncının ve üretim hızı ile kuyu dip basıncı arasındaki ilişkinin belirlenmesi çok önemlidir. Kuyu dibinden rezervuar sınır yarıçapına kadar olan mesafedeki herhangi bir noktada basınç değerinin hesaplanmasında kullanılacak denklemlerin seçimine, log yaklaşımının belirlenmesinde kullanılan X değeri hesaplanarak karar verilir. X<0,01 durumunda log yaklaşımı geçerli olurken, diğer X değerlerinde log yaklaşımı gerçekleşmemektedir. Bu hesaplamaların bilgisayar destekli yapılabilmesi için eksponansiyel integral verilerinin modellenmesi ve model denklemlerinin türetilmesi gerekmektedir. Bu çalışmada petrol mühendisliği ile ilgili çeşitli bilimsel kaynaklarda verilen eksponansiyel integral verileri Curve Expert Basic 2.2.3 programının deneme sürümü kullanılarak modellenmiş ve farklı veri aralıkları için yüksek korelasyon katsayılarına sahip model denklemleri geliştirilmiştir. -Ei(X) için geliştirilen bu model denklemleri kullanılarak rezervuardaki basınç dağılımı, tek fazlı akış performansı ve kısmi iki fazlı akış performans ilişkisini hesaplamak için C++ programlama dilinde 3 program kodlanmış ve Türkiye saha verileri kullanılarak test edilmiştir. Rezervuar basınç profilini elde etmek için kullanılan denklemler gözeneklilik, geçirgenlik, sınır basıncı, rezervuar alanı ve yüksekliği, oluşum hacim faktörü, viskozite ve zar faktörü gibi birçok parametreyi içerir. Her parametrenin sonucu azaltma veya artırmadaki etkisi, parametreler cinsinden yazılan denklemlerde görülse de, diğer parametrelerin sabit değerlerinde, herhangi bir hesaplama yapmadan bir parametrenin değişen değerlerinin basınç profil eğrisi trendi üzerindeki etkisine doğrudan karar vermek mümkün değildir. Rezervuar basıncı değişiminin belirlendiği bölümde denklemde geçen her bir parametrenin etkisi, belirli bir adım büyüklüğü kullanılarak Türkiye saha parametrelerinin alt sınır ve üst sınır değeri aralığında araştırılmıştır.Petrol üretim hızı ile dip delik akış basıncı arasındaki ilişkiyi hesaplamak için C++ programlama dilinde bir bilgisayar programı daha geliştirilmiştir. Hazırlanan program yardımıyla iç akış performans ilişkisi (IPR) denklemlerindeki her bir parametrenin etkisi araştırılmıştır. Çalışmada yapılan hesaplamalar hem mevcut üretim kuyuları hem de benzer parametre değerlerinde daha sonra üretime alınacak kuyular için üretim planlaması konusunda fikir verecek şekilde düzenlenerek sunulmuştur. Bu çalışmada yapılan örnek hesaplamalar, özellikle yeni keşfedilen petrol sahalarında kapsamlı jeolojik model geliştirilinceye kadar üretimle birlikte kuyu ve çevresindeki basınç değişmelerinin tahmininde faydalı olabilir. Geliştirilen bilgisayar programı aynı zamanda programlardaki kuyu parametrelerini değiştirerek yeni rezervuar ve kuyular için kolaylıkla hesaplama yapma olanağı da sağlamaktadır. Anahtar Kelimeler: Kuyu Dibi Akış Basıncı, Giriş Performans İlişkisi (IPR), Rezervuar Özellikleri, Türkiye Petrol Sahaları, Rezervuar Basınç Dağılımı.
Kil içerikli formasyonların sondaj problemlerinin deneysel olarak araştırılması
Türkiye'nin Güneydoğu Anadolu Bölgesi, ülkenin en büyük petrol rezervlerine sahiptir. Ayrıca en çok petrol üretiminin yapıldığı alandır. Ülkenin bu alanlarından özellikle Batman ve Diyarbakır Bölgeleri formasyon özellikleri bakımından yoğun kil mineralleri içermektedir. Bundan kaynaklı bu bölgelerin petrol sondajlarında meydana gelen stabilite sorunları kuyu problemlerinin yaşanmasına sebebiyet verir. Yaşanacak olan her bir problem maddi ve manevi kayıplara neden olur. Petrol kuyularındaki faaliyetlerin artması ile oluşan veri kaynağındaki artış bu formasyonların farklı sondaj akışkanları ile ıslah edilip daha verimli sondaj operasyonlarının gerçekleşmesine yardımcı olmuştur. Bu çalışmada, Batman ve Diyarbakır Bölgelerinde yer alan A ve B petrol sahalarında bulunan A-1 ile B-1 kuyuları inceleme alanı olarak seçilmiştir. İncelenen bu alanlarda yoğun kil formasyonlarının sondajı ile yaşanmış olan sondaj problemleri ele alınmış ve adım adım ıslah yöntemleri dinamik koşullardaki deneysel çalışmalar ile incelenmiştir. Çalışma alanı olarak seçilen A ve B petrol sahalarında stabilite sorununa karşı uygulanan KCl polimer çamur ile stabilite sorunu minimuma indirilmeye çalışılmıştır. Sondaj boyunca kullanılan KCl polimer çamurun içermiş olduğu özellikle potasyum ile iyonik inhibisyon ve polimerler ile sıvı kaybı kontrolü ve reolojik özellikleri kontrol altında tutulmuştur. Sondaj boyunca devam eden ıslah yöntemleri sondajın sorunsuz devam etmesini sağlamıştır. Bu tez çalışmasında yer alan A-1 ve B-1 kuyularında stabilite sorununa sebebiyet veren kil içerikli Germav-Kastel formasyonlarının sondajı boyunca kullanılan KCl polimer çamurun günlük laboratuvar deneyleri API standartlarına göre yapılmış ve rapor edilmiştir. Deneylerin analizlerine göre ıslah yönetmeleri belirlenmiştir. KCl polimer çamurun dinamik koşullarda killi formasyonlar üzerindeki etkinliği bu çalışmada gösterilmiştir. Belirtilen bu formasyonların bulunduğu A-1 kuyusunda, çamur özellikleri pilot deney sonuçları referans alınarak yapıldığında ve doğru ıslah yöntemleri sağlandığında KCl polimer çamurun etkin ve güvenli sondaj sağladığı sonuçları elde edilmiştir. Fakat B-1 kuyusunda yaşanan lojistik kaynaklı aksaklılar ile B-1 kuyusunun arama kuyusu olmasından kaynaklı KCl polimer çamur etkinliği sağlanamamış ve yıkılma, kaçak gibi sondaj problemlerine sebebiyet vermiştir. Bu çalışmanın ele aldığı her iki kuyu ve pilot deney sonuçları KCl polimer çamurun doğru kullanım şekilleri ile maddi ve manevi kayıpları önlediği göstermiştir.
Çeşitli tarımsal atıkların kayıp önleyici malzeme olarak kullanımının araştırılması
Sirkülasyon kaybı, sondaj operasyonları sırasındaki en büyük sorunlardan biridir ve bir sondaj operasyonu sırasında sondaj çamurun, kuyu cidarından formasyona geçmesi durumunu ifade eder. Sirkülasyon kaybı, sondaj deliğinin çökmesi, ekipman hasarı ve sondaj süresinin uzaması, bileşiminin bozulması ve sirkülasyon çamuru ile birlikte taşınan kesintilerin çökerek birikmesi gibi bir dizi zorluğa neden olabilir. Oluşan tüm bu sorunlar sondaj operasyon maliyetlerini de olumsuz etkilemektedir. Bu nedenlerden dolayı, sondaj operasyonunun, öncesinde dikkatlice planlanması ve sirkülasyon kaybı için gerekli önlemlerin alınması gerekmektedir. Sirkülasyon kaybını önlemek veya azaltmak için çeşitli yöntemler kullanılmaktadır. Kuyu deliği güçlendirme teknikleri, çamur keki özelliklerini iyileştirmek veya sondaj sıvısına kayıp önleyici malzemeler ekleyerek çamur ağırlığını arttırmak iyi bilinen ve çokça karşılaşılan uygulamalardır. Atıkların petrol sektöründe kayıp önleyici malzeme olarak kullanılması ise son yıllarda üzerinde çokça durulmaya başlanan bir konu olmuştur. Bu çalışmada hem maliyet hem de kuyu stabilitesi açısından sorun yaratmayan KCl çamuru kullanıldı. Çeşitli gıda atıkları ve kuru yemiş kabuklarının hazırlanan KCl çamurunda kayıp önleyici malzeme olarak kullanılabilirliği araştırıldı. Gıda atıkları olarak ay çekirdeği, ceviz, Siirt fıstığı, yer fıstığı, fındık gibi çeşitli kuruyemişlerin kabukları, buğday samanı, limon kabuğu ve kereviz sapı tozu kullanıldı. Çamurun fiziksel özelliklerinin belirlenmesi amacıyla deneyler yapılmış, eklenen malzemelerin reolojik özelliklere ve filtrasyon özelliklerine etkileri incelenmiştir. Farklı maddelerin, tanecik çapının, madde miktarının ve çamur tipinin etkileri çalışıldı. Ayrıca çamura farklı miktarlarda XCD, nişasta ve pektin eklemenin çamur özelliklerinde ne tür bir değişim yaptığı da incelendi. Genel olarak eklenen tüm malzemeler çamurun reolojik ve filtrasyon özelliklerinde iyileşmeye sebep olmuştur. İncelenen maddelerin çamura eklenen miktarının artması hem viskoziteleri, kopma noktasını ve jel mukavemetini artırmış hem de sıvı kaybını ve filtre keki kalınlığını artmıştır. İncelenen tüm deney koşullarında jel mukavemet değerlerinde bir miktar değişiklik gözlenmesine rağmen çamurun genel özelliklerinde herhangi bir değişiklik olmamıştır. Siyah ayçiçeği kabuğu, limon kabuğu tozu ve kereviz sapı tozu, çamurun reolojik özelliklerini bu çalışmada kullanılan diğer katkı maddelerine göre daha fazla geliştirmiştir. Başta limon kabuğu tozu olmak üzere buğday samanı ve ceviz kabuğu hem düşük sıvı kaybı hem de ince filtre keki oluşturarak çamurun filtrasyon özelliklerini geliştirici etki yapmıştır. Çamura eklenen XCD, nişasta ve pektin miktarlarının atması hem reolojik özelliklerin hem de filtrasyon özelliklerinin artmasına neden olmuştur. Bu maddeler içinde çamura XCD ilavesinin etkisi çok büyüktür.
Kalsiyum kirlenmesinin lignosülfonat, kireç ve potasyum klorür çamurları üzerine etkisi
Türkiye'de üretilen petrolün büyük bir kısmı Güneydoğu Anadolu Bölgesi'nden çıkarılmaktadır. Bu bölgede petrol üretiminde önemli bir yere sahip olan Batman ve Diyarbakır çevresinde yapılan sondajlarda, formasyon kaynaklı problemler yaşanmakta, bu da sondaj maliyetlerinin artmasına ve zaman kaybına sebep olmaktadır. Yaşanan bu problemlerin başında kuyu stabilitesi, kil ve kalsiyumun sondaj çamuruna bulaşması gelmektedir. Bu tez çalışmasında Batman ve Diyarbakır bölgelerinde yer alan A bölgesinde A-1, A-2 ve A-3 kuyularında, B bölgesinde ise B-1 kuyusunda deneysel olarak incelemeler yapılmıştır. Yapılan incelemelerde formasyon kaynaklı kuyu stabilite sorunları, kalsiyum ve kil bulaşması gözlemlenmiş ve gerçek kuyu verilerine dayanan sondaj çamuru deney testleri yapılarak formasyon kaynaklı sondaj çamurundaki değişimler ele alınmıştır. A-1 ve B-1 kuyularında jips ve anhidrit içeren formasyonların sondajı lignosülfonat çamuru ile yapılmış, bu sırada sistem çamurunda yoğun kalsiyum bulaşması meydana gelmiş ve bu bulaşma nedeniyle sondaj operasyonlarında problemler oluşmuştur. A-2 kuyusunda Kayaköy formasyonuna ait jips ve anhidrit, Kastel ve Karadut formasyonlarında ise şeyl ve marn formasyonlarının sondajı KCl/Polimer çamuru ile yapılmış, sondaj çamuru üzerinde gerçekleştirilen deneyler gözlemlenerek çamurdaki değişimler ve sondaj operasyonlarında ortaya çıkan sorunlar incelenmiştir. A-3 kuyusunda ise aynı formasyonlara ait kayaçların sondajı yapılmış, bu kuyunun sondajında kuyudan gaz gelme ihtimali, kalsiyum bulaşması ve karbonat-bikarbonat kirliliğine karşı kireç çamuru kullanılmıştır. Yapılan deneyler sonucunda kalsiyum kaynaklı ortaya çıkan sorunlar, sondaj çamurunun özellikleri iyileştirilerek giderilmeye çalışılmış ve değerlendirmeler yapılmıştır.
Yüksek basınç ve yüksek sıcaklıklı raudhatain sahasında asitle çatlatmanın tasarlanması ve etkisinin araştırılması
Dünya ekonomileri, modern planlama ilkelerine uygun şekilde gelişirken büyük ölçüde fosil yakıt bazlı enerji kaynaklarına bağımlı hale gelmiştir. Ayrıca yenilenemeyen kaynaklara dayalı enerji tüketimi sürekli artmaktadır. Petrol ve doğalgaz sektörü bu enerji arzını karşılayan ilk kaynağıdır ve şimdiye kadar enerjinin dayanım noktası olarak sayılmaktadır. Ancak, petrol ve gazın genel küresel enerji tüketiminin bugünden 2030 yılına kadar % 34 olarak artması beklenmektedir. HPHT kuyuları, ek rezervler için araştırma amacıyla odak noktası haline gelmiştir. Kuveyt'teki Jura rezervlerinde Yeni yapılan projelerle birlikte 40 kuyu sondajını yaparak ve 13 workover operasyonların tamamlanması ile 2024 yılına kadar üretilen ilişkili olmayan gaz miktarı 1 Bcf'e yükseltmesine planlamaktadır. Kuezy Kuveyt'in jura formasyonun bazı kısımları ise sıkı doğası, düşük geçirgenliği, formasyonun heterojenliği ve düşük üretim oranları nedeniyle kazılan kuyulardan optimum üretime ulaşmak için yeni stimülasyon teknolojiler ve asit çalışmalar uygulanmaktadır. Bu çalışmada, Raudhatain sahasında bulunan ve Orta Marrat rezervuarını hedefleyen RA-X kuyusunun asit çatlatma tasarımı irdelenmiştir, bu çalışmanın amacı ise optimum üretimi elde etmek için ve çatlaklar istenilen yönde açılınca formasyonun sıkı doğasına rağmen rezervuarın bir itme mekanizması oluşturmaktadır ve Orta Marrat'ta 180 ft'den daha uzun yarı uzunlukta ve ana rezervuar drenaj alanı içinde etkili bir iletken oluşturmaktır. Bu çalışmada, doğal çatlaklı kuyularda üretimi artırmak için çatlak iletkenliği ve asit penetrasyon mesafesi incelenmiştir. RA-X kuyusunda yapılan asit çatlatma operasyonunda, SRT ve mini-frac testleriyle çatlak ve kapanma basınçları belirlenmiştir. SRT testi ile çatlak genişleme basıncı 8920 psi olarak belirlenmiştir. Bunun yanı sıra, mini-frac testi kapanma basıncının 7262 psi olduğunu ortaya koymuştur Marrat formasyonunun sıkı yapısı nedeniyle yüksek enjeksiyon yüzey basıncı (11.500 psi) ve yüksek sızıntı gözlenmiştir. Asit çatlatma sonrası kuyu verimliliğindeki artış, rezerv hedeflerine ulaşmada önemli katkılar sağlamıştır. Kuyunun simülasyonu için StimPlan ve MEM programları kullanılmıştır ve asit iletkenliği hesaplamalarında Nierode-Kruk korelasyonu uygulanmıştır. Simülasyon sonuçları, 266 ft çatlak uzunluğu, 234.1 ft yükseklik ve 0.24 ft çatlak genişliği göstermiştir. Karbonat rezervuarları asitle temas ettiğinde yüksek reaktivite nedeniyle solucan delikleri oluşmuş ve asit sızma katsayısı artmıştır.
Türkiye'de jeotermal bir sahanın karbondioksit üretiminin matematiksel modellenmesi
Turkey's non-condensable gases production from geothermal fields is very high when compared to other countries' average production values. A big predominance of these gases is generally carbon dioxide (CO2) and the origin of this CO2 is generally meteoric for the studied area as reservoir rocks are carbonate-dominated metamorphic rocks such as dolomitic marbles and marbles.The dissolution of calcite mineral within the reservoir rocks, where it equilibrates with water, results in CO2 release from the system. And this release occurs because of meteoric waters. When a field is put on production, a CO2 decline is observed during the production life time and this decline can be addressed in three different scenarios. First, re-injected brine does not include any CO2 as it is released to the atmosphere after production. When this brine reaches to the production wells due to the strong hydraulic connectivity, a sharp CO2 decline occurs in the reservoir. Second, there might be a weak hydraulic connectivity between the production and re-injection wells and a gradual CO2 decline may be observed with time due to the natural recharging. Last, a CO2 decline may occur as a result of a sharp pressure decline in an excessively producing well because of the water invasion that comes from the upper part/shallow part of the geothermal system and this sub-surface water has less amount of dissolved CO2 in it. This study aims to clarify modelling of CO2 declines for an Alaşehir geothermal field. It has been observed that CO2 declines show the best matches with the hyperbolic decline method introduced by Arp's in 1945. In this study, the reasons of the observed declines in Alaşehir geothermal field showed that a strong hydraulic connectivity between the re-injection and production wells resulted in a sharp CO2decline. On the contrary, a gradual CO2 decline has been observed when there is a weak hydraulic connectivity between the wells.
İzotermal olmayan koşullarda matriks – çatlak transferi
A numerical and experimental study was carried out to investigate matrix-fracture transfer in fractured porous media. Film type heat flux sensors were installed in four different synthetically fractured core plugs to measure the temperature and heat flux in fracture during cold water injection. Experimental values of heat flux were used to calculate convective heat transfer coefficient. Fracture temperatures were used to calibrate numerical model developed using CMG-STARS simulator to evaluate contributing matrix thermal properties. The results show that the temperature decrease in fracture is lower when rock matrix has higher thermal properties. The variations in heat flux and temperature difference along matrix-fracture interface with respect to time necessitates the use of variable convective heat transfer coefficients for accurate analysis of matrix-fracture heat transfer. Moreover, results of tracer experiments where Rhodamine B solution was injected at a flow rate of 1 cc/min and outer temperature of 70 °C was used to determine dispersion coefficients using aforementioned numerical model. Sensitivity analysis of the numerical model indicated that thermal properties of matrix are effective in matrix-fracture mass transfer similar to injection rate. To illustrate, the solute penetration is higher in core plugs with larger matrix thermal properties that provide larger temperature gradient over matrix-fracture interface. This can be explained by the Soret effect that is kind of coupled heat and mass transfer at non-isothermal conditions.
Deneysel koşulların doğal gaz hidrat oluşumuna etkisi
Global request will increase considerably in the following decades as population of the earth proliferates. US DOE 2016 International Energy Outlook, claims that the universal energy consumption will augment from 549 quadrillion BTU in 2012 to 815 quadrillion BTU in 2040, indicating 48% augmentation. As methane hydrates are able to comprise between 150 and 180 v/v at standard temperature and pressure conditions, they provide both gas storage characteristics and transportation characteristics. Stirring procedure is the best way to ameliorate heat and mass transfer in methane hydration procedure: induction time was shortened, formation rates accelerated and storage capacity was augmented when stirring was applied. 24 experiments were conducted by methane with two different impellers such as pitched blade turbine upward (PBTU) and rushton turbine (RT) with mixed and radial flow respectively. The design of the experiments was different by the use of baffles (full baffle, half baffle, surface baffle) or no. The 24 experiments were divided in 8 single experiments and 16 dual experiments with all possible combinations such as PBTU/PBTU, RT/RT. PBTU/RT and RT/PBTU. Calculations such as rate growth, induction time, process of hydrate formation, hydrate productivity and conversion of water to hydrates are included to our research. Furthermore other 24 experiments were conducted by mixture methane (95%)-propane (5%) with PBTU and RT impellers. The design of experiments was the same like methane with thedifference in pressure , temperature and in the number of single and dual experiments. There were 16 single experiments. 8 experiments with same driving force of methane hydrate formation and 8 experiments with driving force almost double. The 8 dual experiments were conducted with the double driving force compared to methane hydrate formation. Calculations such as rate growth, induction time, process of hydrate formation, hydrate productivity, split fraction and separation fraction are comprised in our research. Finally 6 experiments were conducted with 5 different amino acids and with no amino acid (just water), hence to investigate which of these acids behave as prompters or as inhibitors in mixture (methane 95% - propane 5%) hydrate formation. Calculations such as rate growth, induction time, process of hydrate formation were included together with images during hydrate formation. RT experiments have highest rates of hydrate formation compares to PBTU ones in single and dual impellers in both methane and methane-propane hydrate formation. Their main difference is that in single impellers, the rate of hydrate formation is higher for RT experiments also in first 30 minutes while in dual experiments happens the opposite. The RT experiments although they form more quickly and for less time hydrates (smaller induction time compared to PBTU ones), they have higher power consumption values, hence they consume more energy. RT experiments convert more water and methane to hydrates although these values are very small due to high water quantity. In methane-propane hydrate formation, the split fraction of methane has higher values in single experiments with T=8.5C compared to single experiments with T=2C. Final, all amino acids that are used to form methane-propane hydrates in our system behaved like promoters and none of them as inhibitor.
Jeotermal kuyularda yaşanan buru ve kaçak problemlerinin sondaj sıvısı yönünden incelenmesi
Drilling in a lost circulation zone has long been a challenge in geothermal wells due to its strong potential for high torque and wellbore instability. Excessive torque and friction values cause overpull, pipe stuck and severe problems ending up with losing the well in some cases. High temperature-high pressure (HTHP) drilling fluids design; which minimize loss rates and friction values, is critical for the success of these challenging drilling practices. Known fact is that, oil/synthetic based drilling fluids have the best lubricity performance. However, application of these drilling fluid systems is limited because of high cost and environmental constraints. At this point, water-based drilling fluid compositions with high lubricity performance, HTHP resistance and high loss zone plugging performance, are investigated. In this study, HTHP drilling fluid system; frequently used in Turkey and worldwide, is selected for the experiments. Several chemical commercial lubricants are added in this fluid system to find the compositions for the highest lubricity performance closest to oil/synthetic based drilling fluid systems. Also, considering the formation characteristics and drilling limitations; best fluid compositions are formulated to plug the potential seepage and partial loss zones and reduce the differential-sticking tendency by using proper lost circulation materials. Results reveal that lubricity and pore plugging characteristics of the selected compositions are highly innovative and noteworthy to be used in field applications for geothermal drilling industry.
Rota hesaplama yöntemlerinin Türkiye'nin Ege Bölgesi'ndeki jeotermal kuyular üzerinde uygulanması
Productive sections of geothermal wells generally exceed hundreds of meters which is substantially longer than that of the oil and gas reservoirs. This brings a flexibility and cost-effective solutions in the application of directional drilling activities during geothermal drilling. Well trajectory, especially the bottom hole position, is critical for geothermal operators and three parameters (measured depth, inclination, and azimuth) obtained from MWD surveys are used to carry out survey calculations. The minimum curvature method (MCM) is considered the most accurate and the industry standard, although there exist several other calculations. The novelty of this thesis is to find out the geothermal well directional needs, on Aegean part of Turkey, in terms of survey calculation methods; later on, recommend which method(s) should be utilized at what conditions. In order to address this gap, 5 methods were chosen taking into account popularities and complexities; tangential, balanced tangential, average angle, radius of curvature, and minimum curvature methods. Afterwards, these 5 procedures were applied on 9 drilled pre-selected geothermal wells by using Python programming language. As a result, most divergence from MCM was observed with tangential method, having the easiest calculation formulas, on J type wells with increasing dogleg, inclination, and depth; which is around 5-6 m. Under the usual conditions the geothermal wells drilled in Turkey, it will be maximum of 10 m; even though it is quite satisfactory for most of the operators, average angle method, which is the easiest one after tangential, would also be utilized to have better results. This means that the operators, willing to establish their own directional drilling departments to decrease the costs of directional operations, may utilize a basic software or a spreadsheet, for their each well, depending on average angle, or even tangential method, to eliminate complicated formulas, while calculating the positions of each survey or interpolation depths. An only advanced software may be preferred for operator office.
Petrol sızıntısının yüzeydeki akıbetinin rastgele yürüyüş methodu aracılığıyla parçacıkların taşınmasıyla beraber voronoi diyagramı içinde modeli
Oil spilling is a hazardous case to the marine environment by increasing the risk of the destruction continually by flowing on the sea, expanding into sea and mixing into the air. Its potential threats can be prevented after the determination of its pathway. So, knowing the extent of oil contaminated sea as accurately as possible helps to decide the clean-up techniques like using skimmer, boom or dispersants and efficiently perform one of them. A well-defined models with the true reflection of the mechanisms behind the oil fate and transport can supply the oil extent to a great degree. Our main motivation in the study is to approach the oil surface processes with care and to numerically obtain the result from their equations in a good precision for instantaneously and constinuously spilled oils. So, a numerical solution for oil spreading is provided by an algorithm already written and updated in this study. It is compared for many scenarios with an analytical solution, an experiment and another numerical solution applying finite element method. The numerical approach in the algorithm uses Nihoul's equation with the Gaussian random walk technique stepping the particles with a diffusive length for the spreading treated like diffusion. The oil surface contamination is demonstrated by Voronoi diagram. Also, the particles are drifted with a velocity of 3% wind speed for the advection in the algorithm. The flexibility of the algorithm are checked through the slick parameters in this study. Besides, detailed analyzes on the slick shape, oil distribution on the surface and the contribution of the spreading regimes are carried out through the algorithm tried on the prescribed cases. Finally, the algorithm is evaluated with a software embodying the solution to the main oil spreading processes and proposing the clean-up techniques. This study will be evolved by the addition of dispersion, evaporation and other processes expanding the algorithm to three dimensional model in the future.
Ev sahibi devlet petrol sözleşmeleri ve Türkiye derin deniz lisansları için bu sözleşmelerin uygulanabilirliklerinin karşılaştırması
In the boundaries of sovereign nations, which has a legal dominion over of its geographical area, including natural resources, the vast majority of the World's energy sources are developed. If a country opens the resources for exploration and development which is referred to host country and the agreements signed between host country and National Oil Company (NOC), private companies or any combination of them to explore and/or develop petroleum licences are called as host government petroleum contract. The fiscal system of host government contract is expected to encourage exploration and development activities, allow special incentives for some challenge fields and enable to provide fair sharing of economical incomes for Host Countries (HC) and International Oil Companies (IOCs). Especially, expenditures and risk factors are very high for deepwater operations during exploration and development phases until reaching first commercial production for Operator that might be HC only, JV or an IOC. Therefore petroleum law, regulations, host government contracts and tender strategy should be arranged by considering items: geology (prospectivity of field, reserves, productivity and HC quality and type "gas or oil"), political stability of HC and abroad, legal system, fiscal system, transparency, market conditions and operational challenges. Deepwater Offshore Operations are the most challenge ones in exploration and also production stages. In order to start and continue such deepwater projects, HCs prefer to announce tender for opening offshore licences to investors. Before issuing such tenders, HC has to be sure about the status of above items to create an attractive atmosphere for potential bidders. Also tender strategy, financial terms/fiscal regime, contract methodology should be re-evaluated in every stages which are without discovery, after discovery, in exploration and production phases. The petroleum law of Turkey published in 2013 and the regulations has been in effect since 2014. However there have been major changes in Turkey deepwater offshore activities after this year and some serious developments have taken place such as inclusion of 3 drillships in Turkish Petroleum (TPAO) Inventory, drilling one after another deepwater wells in Mediterranean and Black Seas, a gas discovery in the Black Sea, following potentials in the deepwaters and a deepwater service company established with own capital of TPAO. As a result, petroleum contract type, tender strategy and fiscal regime of Turkey for deepwater operations should be re-examined and all related terms to be re-evaluated by considering current market conditions and any changes in the neighbouring countries. The modern fiscal terms which are currently used by most of countries could be considered while making these evaluations. One of this modern term is royalty systems based on sliding scales as per daily production or cumulative production. A sample deepwater project economics will be run to understand and compare the economic impacts of this system.
Yapay olarak kırılmış ve jel işlemı görmüş karotlarda akışkan akışının modellenmesı ve sımülasyonu
The dynamics of fluid flow in the matrix and in the fractures are significantly different from each other. Fractures are highly permeable flow pathways and are generally considered as the main flow unit. On the other hand, the matrix occupies most of the porous medium's volume and is considered as the main storage unit. The main objective of this thesis is numerical modeling of water flooding experiments in artificially fractured and gel-treated core plugs. MATLAB Reservoir Simulation Toolbox (MRST) is used to create the numerical models. Three main cases, namely non-fractured core plug, fractured core plug, and polymer gel treated core plugs, were created by using MRST. 2 PV water injection into these core samples simulated by using MRST. Additional 2 PV water was injected after polymer gel treatment operation for artificially fractured core plugs. Hydrocarbon recovery vs. time plots, as well as 3-dimensional fluid saturation profiles, are obtained. Standard Buckley-Leveret solution is used to validate the model, and Embedded Discrete Fracture Network (EDFM) was used to model the fractures. Results of the numerical models were compared with the results of core flooding experiments. During the experiments, results are obtained and recorded after 2 PV water injections, and for the polymer gel treated core plugs, 2 PV additional water was injected after the operation, and results were recorded again. Models and simulations are done to represent the core flooding experiments described. The non-fractured core plug oil recovery after 2 PV water injections was found to be 42.5% and 42.8% experimentally and with an MRST solution. For the artificially fractured core plugs, oil recovery was increased from 28.87% to 42.85% in experiments and from 28.87% to 40.83% in MRST solution after polymer gel operation. Similarly, in experiments, 8.16% and in MRST model 7.07% increase in the mean water saturation observed after polymer gel treatment. Additional oil recovery was observed in both experiments and in the MRST model after the polymer gel operation. In addition, how fracture permeability and aperture affect recovery was also investigated. When the fracture permeability is constant, fracture aperture directly affects the hydrocarbon recovery for the low aperture values. Similarly, when the fracture aperture is constant, fracture permeability directly affects recovery for the high values.
Çift kuyu modeli kullanılarak jeotermal kuyuda NCG enjeksiyonunun jeokimyasal modellemesi
Geothermal energy is regarded as an environmentally friendly source of energy. However, the amount of non-condensable gases (NCG), which are co-produced with brine, are significantly high in the geothermal fields of Turkey. To overcome the NCG emission produced by power plants, which is mainly CO2, one of the efficient methods is re-injecting the captured NCG into the reservoir. The ultimate aim of the reinjection is to mineralize CO2 in the reservoir as carbonate minerals. In this thesis, a reactive transport modeling study is conducted with TOUGHREACT to scrutinize a potential operation of brine-CO2 injection in a deep fractured metamorphic reservoir formation. A comprehensive geologic model is constructed and utilized in TOUGHREACT with Petrasim interface to simulate reactive transport phenomenon during NCG injection. The developed doublet well model in which a re-injection and a production well are included is calibrated with field measurements. PHREEQC is used to evalaute the reaction-paths between minerals and aqueous species. These evaluations help to determine possible secondary minerals to select in reactive transport model developed with TOUGHREACT. Three rock types with various mineral compositions are introduced to inspect the interaction between different mineral contents and CO2 charged brine injection in high temperature geothermal reservoirs. Three different injection scenarios are examined as the brine-CO2 mixture, supercritical CO2 injection and brine-CO2 mixture injection at lower temperature to observe amorphous silica precipitation. The results are compared to those obtained with injection of brine-only. Composition results demonstrate that the reactions of aqueous species and reservoir minerals are highly dependent on the pH and temperature. Results show that Calcite formation is only observed in a scenario where brine and CO2 is injected as a mixture, whereas in the first two scenario of the study which represent injection of brine-only and injection of CO2-only, Calcite dissolution is observed. Limited mineralization due to CO2 occurs and CO2 is mostly trapped in solution. Moreover, the impact of CO2 injection is examined on Silica reactions. The results demonstrate that lower injection temperature at 85 °C should be selected for CO2 injection. For lower injection temperatures at 85 °C, amorpheous silica precipitation around the injection well may be trigerred. This study may guide innovative injection strategies, which will be conducted in Turkish geothermal fields in the near future.
Çatlaklı şeyl rezervuarlarında kararsız akış modellemesi
Oil and gas production from shale reservoirs has been popular in North America for more than two decades. Commercial production from these extremely low permeability reservoirs is only achieved by multi-stage fractured horizontal wells. However, production performance of these wells is quite different than wells drilled in conventional reservoirs. Main distinct behavior seen in these wells is very long period of transient flow due to tightness of such reservoirs. This thesis questions validity of existing dual-porosity reservoir simulation technique for fractured shale reservoirs. In this respect, analytical solutions of pressure diffusion are presented for constant fracture pressure, constant rate and constant fracture pressure followed by linearly declining fracture pressure boundary conditions. According to these solutions, time-dependent shape factors are derived for 3D rectangular anisotropic matrix. Obtained shape factors and proposed simplifications are verified against fine scale single-porosity numerical models. Key finding from this study is that matrix – fracture transfer function (shape factor) is not constant, but rather decreases with time until reaching to a constant value. Therefore, dual-porosity simulation of fractured shale reservoirs using constant shape factor does not capture actual physics of matrix to fracture flow and yields inaccurate performance prediction. Also, proposed simplifications either as an empirical function or reduced form are robust in modeling this phenomenon. In addition to those, common features of decline curve analysis are tested for fractured shale reservoirs. Time dependency of b-parameter used in hyperbolic decline curve analysis is assessed for different reservoir properties by sensitivity analysis. Proposed empirical functions are used to obtain b-parameter for these cases and results are compared with actual ones.
Karbon dioksitin depolanması ve gelişmiş petrol kurtarımının birlikte uygulanması
The worldwide growth of industry leads to continuous rise of anthropogenic emission amount into the atmosphere, which causes greenhouse effect all over the world, that is heating up the atmosphere and changing the global climate. On the other hand, carbon dioxide injection into oil reservoirs for the purpose of enhancement of oil recovery (CO2-EOR) has been commercially used for nearly 50 years. The operations in petroleum sector are being carried out in a way to maximize the recovered oil while keeping the amount of CO2 injected at its minimum due to the purchase cost of carbon dioxide. To overcome the economic restrictions for CO2 sequestration during EOR, it is necessary to simultaneously maximize economic oil recovery and the volumes of CO2 injected in oil reservoirs using an engineering approach. This process is named as co-optimization. For this purpose, several simulations for different scenarios are being carried out to find the maximum amount of CO2 that can be stored, maximum amount of oil that can be produced, and an optimal point for simultaneous maximization of both numbers. Results show, that using inverted 5 spot pattern and implementing water-alternating-gas (WAG) injection can significantly contribute to the co-optimization, while other parameters, such as pattern area and injection rate need to be evaluated on case by case basis, considering economical factors as well.
Hidrat oluşumunun olası üretim mekanizmalarının deneysel incelenmesi
In this study, temperature, pressure and mole values of methane hydrate formation and dissociation are analyzed using different production methods under laboratory conditions. During the experiments, a cylindrical high-pressure hydrate cell in a constant temperature room was used. In order to provide the real field conditions of the hydrate reservoirs, methane gas was injected at high pressure into the cell filled with sand and water at low temperatures, and the hydrate reservoir was formed in a 21.2 *liter hydrate formation cell by providing necessary thermodynamic conditions. A ¼ inch production line was used for production of methane and water in 3 different experiments. Production phase of the first two experiments were not discussed due to discrepancies arising from the production data. Two different production stages were applied in the third experiment. The first stage was carried out by combination of pressure reduction and thermal recovery method by providing constant temperature water circulation through the spiral pipe inside the cell. The thermal recovery method's effect decreased and disappeared in the second stage. It left its place only to the depressurization method. As a result of the endothermic dissociation process of the production stage, the heat taken from the environment caused pores to be clogged due to reformation of the hydrate. This slowed down the production and made it stop from time to time. Using the depressurization method with the thermal recovery method, hydrate production became more effective and the hydrate dissociation rate increased. Depressurization method alone became less effective and the rate of dissociation decreased.
Şeyl gazı ve petrolü için arama, üretim, rezerv kestirimive araştırma çalışmalarının incelenmesi ve değerlendirilmesi
Shale is a fine-grained sedimentary rock that consists of significant amount of clays, in addition to sand and silt size minerals. During the sedimentation period, depending on the aqueous sedimentation environment, some organic material in the form of the remnants of dead organisms might accumulate along with some inorganic material, such as the organic or inorganic compounds nickel, zinc, vanadium, molybdenum, selenium, etc, among the grains of shale constituents. Shale is formed as the result of compaction of its constituents under the overburden stress (pressure) of overlaying strata that are accumulated later and under the rising temperature with increasing burial depth, throughout the vast geological time periods. During the millions of years of diagenesis, the period in which the sediments go through various physical and chemical alterations and deformations, the in-situ water in between the granules provides the means for the consolidation and cementation of compacting constituents to form a somewhat firm rock of shale, while some part of the in-situ water being expelled out due to compaction. In addition to pressure the increasing temperature and the radiation from the radioactive elements among the constituents cause shale to experience thermal maturity. Contained organic material, if there is any, in shale would eventually be decomposed into hydrocarbons, partially in the form of kerogen and partially in the form of petroleum, until thermal maturity has reached a certain level. Kerogen is the organic material with long and complex molecular chains that was not converted into petroleum. During diagenesis, oil and gas type hydrocarbons may escape out of shale into other adjacent, preferably sedimentary, formations via the pathways, such as pore networks, cracks, fractures, joints, or faults, and form conventional oil and gas reservoirs if they get hydrodynamically trapped. Therefore, shale is a easy-splitting laminated soft rock and such feature makes it different than the rock called mudstone. Economic oil and gas accumulations in shale formations are classified as unconventional reserves, since pore size and permeability levels in such rocks are much below microscopic scale and, hence, the application of conventional production and reserve estimation techniques is invalid. In this study the interest is in the shale formations that contain unconventional reservoirs of oil and gas. A shale formation is considered to have a prospective reservoir if its organic kerogen content is between 2 to 14 percent. The hydrocarbon that can form in shale is determined by the kerogen type and thermal maturity level in shale. Kerogen, as a solid matter, might have pores with size in the range from few nanometers to few hundred nanometers. Production of oil and gas from shale formations was started during the World War II by the U.S.A. to fuel war tanks. After the war, however, it was uneconomical to produce from the shale formations due to unfeasible technology and low price of oil and gas. The adverse effect of significant increase in oil and gas prices, due to Yom Kippur war between Egypt and Israel in 1973, has forced the U.S. to explore new technology for feasable exploitation of oil and gas in shale formations. In the past two decades, many researchers have introduced new and various methods and techniques for classifying shale formations, estimating oil and gas reserves, and drilling, completing, and stimulating wells for producing unconventional shale plays. Substantial investment in research has led to the development and use of horizontal well drilling and hydraulic fracturing technology that has draw a massive interest in the industry and has enormously increased the shale gas and oil production in the U.S., e.g. the U.S. hydrocarbon gas reserves have increased about 35 percent in 2008. Such success has led many countries worldwide to attempt to explore unconventional oil and gas in shale formations in their sedimentary basins. While research is still continuing worldwide for futher improvement in aforementioned methods and techniques to maximize ultimate recovery from shale formations, only Russia and China other than the U.S. had some limited success in shale gas and oil play so far. Among the shale classification methods, real-time classification is based on well logs to estimate the petrophysical, compositional, and elastic properties of shale rocks. Another technique attempts to identify hydrocarbon-bearing shale groups, based on similar compositional properties exhibited on a combination of well logs, and also to minimize the shoulder-bed effects using the inversion of log derived layer properties. Other method integrates core analysis and well log information to classifying shale in terms of porosity, capillary pressure, mineralogy, and TOC. Though, all the methods are found to yield good results, all of them have to be applied on the same formation to ascertain which method is better than the others, since each shale play is unique. Although conventional reserve estimate methods seem not to work in unconventional shale gas and oil reservoirs, a group of researchers tried to use the usual hyperbolic decline curve analysis technique on a production rate versus time plot to estimate the recoverable reserves. They came up with a nine–equation bivariate regression model based on initial test and recovery data to estimate the reserves in the Devonian shale. A new volumetric total-gas-in-place estimation equation that incorporates Langmuir adsorption isotherm was formulated to take the pore space occupied by the sorbed phase into account. Hydrocarbon phase behavior is realized to be quite different in pores and capillaries with characteristic length less than 100 nanometers, since gas density varies under the influence of organic pore walls of kerogen. Interest in drilling and completion of horizontal wells has increased during the last two decades to enhance productivity and ultimate recovery from shale reservoirs. The most commonly used completion method is casing and perforating the horizontal section of wells. In horizontal wells an optimized multi-stage hydraulic fracturing through perforations is the inevitable stimulation technique to create interconnected fracture network for maximizing the flow into wellbore. Various explosive or impact methods of dynamic fracture and fragmentation data on shale rocks has showed that the interaction of transient wave with the local free surfaces in rock generates tension in some regions of rock where fracture and fragmentation is initiated. Studies has also showed that the static strength of a rock can be less than the dynamic fracture strength as much as one order of magnitude. A researcher with the objective of intersecting as many natural fractures as possible with the hydraulic fractures has developed a rationale for stimulation design for the Devonian shale. The MHF (massive hydraulic fracturing) technique has long been used for the same purpose. It has been found that shale thickness and fracture density are important factors in determining the stimulation technology and strategy. A new hydraulic fracturing technique is CHF (channel hydraulic fracturing) that was first applied in Marcellus shale. In CHF technique; which integrates the geomechanical modeling and perforation strategy, fiber-laden fluid is pumped in a unique manner to create high-conductivity stable channels in the proppant pack placed in the created fracture. Hydrocarbon fluids flow through these high conductivity channels rather than being dependent on the permeability within the proppant pack. Appreciable increase in fracture conductivity by these flow channels has been proven in practice. Reliable forecast of production from shale reservoirs has been another requirement in the industry. The methods of analytical simulation, numerical simulation and various decline curve analyses (DCA) have been utilized. Each method has its own particular advantages and disadvantages. Rapidity and extent of accuracy in production forecast are among the factors considered in these methods. Another model, called the Shale Gas Predictive Model (SGPM), was developed with an alternative approach and was proposed to mitigate the challenges associated with shale gas production. Simple and easy to use model focuses essentially on the flow around individual wells while conserving overall mass. The model has the advantage of generating rapid and repetitive results, in situations where quick turnaround is required to estimate the production and reserves from a large number of wells in a single or multiple shale gas plays. Such situations arise frequently if the operating companies plan to drill hundreds of wells year by year on the millions of acres of land. The model can be run in conjunction with a fracture mechanics software for better fracture design. Production forecasting capability of the model was validated against the actual production from various shale gas plays in different regions. Thus, the model can be reliably used for both matching the past production history and the future production forecast. Oil-rich play and multi-phase flow features of the model provides insight to the condensate production. However, the inaccuracies in recovery prediction are highlighted if the presence of condensate is not considered. When the development of Eagle Ford shale in South Texas was started in 2008, there was not any data analysis available on the production from this shale at that time. Linear dual-porosity type-curve analysis technique was employed for modelling the production behavior and for estimating the essential reservoir parameters. The type curves used were constructed based on the transient production rate at constant well pressure and closed-boundary double-porosity stimulated reservoir volume (SRV.) Two different approaches of Bello-and-Nobakht method were employed to account for apparent skin in analyzing the early-time and the late-time production data. The production from Eagle Ford shale exhibited linear flow, bilinear flow, and boundary dominated flow regimes. Based on bilinear flow analysis and the assumption of slab-type fracture model, the fracture permeability was estimated to be about 820 nano Darcy. On the other hand, the matrix permeability was estimated to be in the range of 181 to 255 nano Darcy, based on linear matrix flow analysis. The results were validated by means of numerical simulation, due to the fact that the permeability values obtained from the numerical simulation study were in the range of agreement with those obtained from the type curve analysis. In order to carry out production forecasting for Eagle Ford shale different adsorption isotherms were used. It was deduced from the results of production forecasting that the gas desorption depends on both the reservoir pressure and adsorption isotherm. The gas desorption in early times, when the reservoir pressure is high, was found to be usually not that important. However, based on the laboratory measured adsorption isotherms, long-term production forecasting is needed for desorption to be effective. A genesis of decline curves with the use of a simple hydrodynamic analogy was also provided. Some physical factors that are critical to well productivity were also examined, based on several studies on production decline curves. It was observed that an exponential or hyperbolic decline curve would adequately fit the production decline data for the wells producing from Devonian Shale. An attempt has also been made to characterize the production decline based on open flow, rock pressure, and specific shale production mechanisms. An analytical tri-linear-flow solution was presented to simulate the transient pressure behavior and production behavior in fractured horizontal wells in unconventional shale reservoirs. Though the model is simple, it is versatile enough to incorporate the fundamental petrophysical characteristics including the intrinsic properties of both matrix and natural fractures of a shale reservoir. Various reservoir components in addition to the special characteristics of fluid exchange may also be considered. A practical analytical model is presented and discussed in this study for the analysis of pressure transient responses in multiple fractured horizontal wells in unconventional shale reservoirs. Oil and gas production from unconventional shale reserves in the U.S. has become feasible both technically and economically, after the remarkable rise of oil and gas prices. Among the mature shale plays in the U.S., and in the World, Barnett shale near Forth Worth, Texas, is the one for which there is satisfactory production history. Therefore, the examination of the economics of exploitation of Barnett shale, as the field had been developed with more than 6000 producing wells, can be considered as the role model for establishing an idea of how shale plays can become commercial. For the costs and prices during this thesis work is conducted, an ultimate recovery of about 550 to 900 million standard cubic feet of gas has to be produced to pay out for one well. In oil production from shales, for a mature field with 100 000 barrels per day oil production the minimum oil price should be at least 43 USD per barrel.
Türkiye derin yeraltı sıcaklığı ve sıcaklık gradyanı dağılımının belirlenmesine yeni bir yaklaşım
A deep subsurface-temperature gradient distribution map of Turkey is generated by a never before applied approach, in which the Curie-Point-Depth (CPD) temperature data and the available deep well temperature measurements across the country are utilized. All the maps in the present work are generated using the Generic Mapping Tools (GMT) software. The CPD values are obtained by digitizing the contours of the Curie-Point Depth Map of Turkey, published by the MTA (General Directorate of Mineral Research and Exploration), Turkey. The contour digitization is performed with the 500-meter intervals between the depths from 6000 to 27500 meters, below the reference of MSL (mean sea level). In this study, the Curie isotherm of 560 ºC at CPDs, where crustal rocks lose permanent magnetization, is assumed beneath Turkey. The CPD data and its subsequent contours from the ground level (GL) are obtained by combining the digitized CPD data and the surface topography data of Turkey, the latter of which is above the reference of MSL. The exact coordinates for CPDs that correspond to those for the deep wells, for which the temperature data are available, are determined using the GMT software. Then, the depth interval and temperature difference for each pair of CPD and deep-well are used to calculate the subsurface temperature gradient at the coordinate of each pair. Subsequently, the temperature gradient data are mapped and the deep subsurface-temperature gradient distribution map of Turkey is generated. Since, the Curie isotherm of 580 ºC is also considered for the continents by some researchers in the literature, another deep subsurface gradient distribution map of Turkey is also generated based on the Curie isotherm of 580 ºC. In between the both maps a detectable or significant difference is not observed. If the deep subsurface temperatures are assumed to vary linearly with depth, the estimates of deep-subsurface-temperature gradients are found to be in between 2.28 to 11.10 C/100m, based on the Curie isotherm of 560 C, and are found to be in between 2.37 to 11.56 C/100m, based on the Curie isotherm of 580 C. The highest values of the deep-subsurface-temperature gradient are concentrated in the area between Mardin and Şırnak, in the Southeastern region of Turkey. On the other hand, the lowest values of the deep-subsurface-temperature gradient are located in the area of Şebinkarahisar, Reşadiye, Alurca and Gümüşhane, in the eastern Pontides Mountain regions. The highest value of the deep-subsurface-temperature gradient in the Western Anatolia is about 8.33 ºC/100 m in the area around Alaşehir, Baklacı, Akkeçili and Erenköy. When the variation of the deep subsurface-temperatures from the measurement point in wells to the corresponding CPDs is fit with exponential function, the resultant exponential temperature gradients yielded the estimate of subsurface temperatures that vary of from 20 to 265 ºC at 2-km depth and that vary of from 40 to 455 ºC at 5-km depth beneath Turkey. Based on the subsurface temperature gradients with exponential behavior, the extensional region of Western Anatolia has the highest subsurface temperature estimates. In Mardin-Şırnak region, however, the subsurface temperatures may be as low as has 58 ºC in average at 2-km depth and may go up to 193 ºC in average at 5-km depth. At an average depth of 7654 meters in this region, the subsurface temperature is expected to reach 560 ºC. Thus it may be said that the Mardin-Şırnak area has low temperatures to depths of about 4 km but experiences a high gradient change at depths beyond about 5 km. A very important feature of the deep subsurface temperature gradient and the subsurface temperature distribution maps is the indication of potential hot dry rock resources in the active extensional province of Western Anatolian, portions of Central Turkey, Southeastern region of Turkey, and the Central Pontic belts of the NAFZ (North Anatolian Fault Zone). These resources may also lie within reach (at about 5 km depth in Western Anatolia and Central Turkey) of the current drilling technology and could be exploited to augment the energy budget of the country if the enhanaced geothermal systems (EGS) technology is given serious attention.
Destek vektör regresyonu yöntemi ile ilerleme hızı optimizasyonu
Drilling operations constitute the major part of the exploration costs. During operations, drill bits are the primary part needs to be changed frequently due to its quick wearing nature. In order to reduce the drilling cost, the optimum bit pulling time must be determined. To determine the optimum bit pulling time, either rate of penetration or the tooth wearing parameter must be estimated. The most common method that developed for estimating the optimum time for bit change is "Bourgoyne and Young" method. In this method, eight parameter coefficients are needed. To obtain these coefficients, thirty different data which can be taken from either different shale zones inside thirty different wells in a field or thirty different shale points from one well is needed. However, when there is not enough data taken from thirty different shale sections, the accuracy of "Bourgoyne and Young" method decreases. To construct the functional relationship with the data and parameter coefficients, a regression analysis must be performed. In this study, two kind of regression technique is used and the results are compared to each other. First technique is the multiple regression analysis, which is also used in "Bourgoyne and Young" method. This analysis applies least-squares-principled-regression to the data and calculates the parameter coefficients in order to estimate the target function. The second technique is one of different types of machine learning algorithms, called Support Vector Regression. In this technique, first, the data is divided into train and test datasets. Then, the regression model is constructed by using train datasets. At last, the model is applied to test datasets in order to predict the target values for the function. For the calculations, the selection of training and testing data sets are divided into cases with different scenarios. The results of different predictor methods for each scenario are compared with each other in the corresponding case. The results show the significant effect of data selection on the accuracy of penetration rate prediction. One of the most powerful methods in machine learning, Support Vector Regression, is used for rate of penetration optimization for the first time in the literature with this thesis study. In this way, the chance for further investigations and studies on the practicability of Support Vector Regression on penetration rate optimization is created.
Ağır petrol sahalarında sagd uygulamalarında kuyu testleri
Thermal Recovery is one of the common EOR recovery methods. Thermal recovery methods are used worldwide to recover heavy oil and bitumen. Thin layer of water between the quartz and the bitumen makes the oil sands water-wet, this plays an important role in the separation of bitumen from the quartz by use of a hot-water extraction technique. High oil prices are pushing the application of horizontal wells in thermal recovery methods. The possibility of horizontal drilling has created a pathway for SAGD (Steam Assisted Gravity Drainage), which is the most preferred heavy oil and bitumen recovery method. Oil recovery by steam injection requires knowledge of the steam-swept pore volume. The determination of the swept volume in a thermal oil recovery process makes it possibile to do early economic evaluation; it means rapid measurement of the fuel concentration for an in-situ combustion operation, and the heat loss from a steam zone. In field operations, the swept volume has been determined by coring and/or temperature observations made at wells during passage of the displacement front. Well testing evaluates the steam-swept volume by inexpensive and a relatively quick way. The aim of the thesis will be to estimate swept volume and steam chamber mobility by using pressure falloff tests of vertical well. Satman, Eggenschwiler and Ramey (1980) presented a method to estimate the steam zone mobility and swept volume using pressure falloff test; assuming two regions of highly contrasting fluid mobility and an impermeable boundary interface in a composite reservoir. Consequently, for a short duration, the swept zone acts as a closed reservoir, during which the pressure response shows the pseudo steady state behavior. Falloff tests are simulated by shutting-in the injector and recording the wellbore pressure with time. The MDH (Miller-Dyes-Hutchinson) method for the analysis of falloff data is used because the shut-in time is much less than the injection time in practical steam injection falloff tests. The pseudosteady state (PSS) method is used to estimate the swept volume, from pressure fall off testing of vertical wells. A homogeneous square box reservoir, in CMG (STARS) simulator, is used to model steam chamber profile. Injection rate, injection time, steam injection quality and gas (steam) mobility relations with time are investigated by using simulator and comparison with PSS method. The simulation and application of case model is described and finally, comprehensive discussion of the analyses, results and conclusions are given. The results obtained in this study yields reliable results when the swept volume is sufficiently large, so that a proper Cartesian straight line behavior exist.
Hershel-Bulkley modeli kullanılarak surge basınçlarının tahmini ve sonuçların analitik ve yazılım karşılaştırılması
In drilling hydraulics, the estimation of surge and swab pressures is important due to the fact that, the excessive surge pressures generated by pipe movement in tripping operations may result in serious consequences such as blowout and formation damage. Tripping operation can be performed due to several reasons such as adding pipe stand to drillstring, changing worn bit, removing fallen parts from borehole (fishing) or running logging tools. The time spent in tripping operation is a significant portion of the total time spent during overall drilling operations. During the drilling of offshore wells in deep waters, extended reach drilling (ERD) wells and highly deviated wells, small margins are encountered between pore pressure and formation fracture pressure. In such cases, the proper prediction of surge and swab pressure may exhibit paramount importance in order to ensure trouble free and cost effective drilling operations. In this work, the method for estimating surge pressures by analytical calculations using Herschel-Bulkley rheological model is presented and the results are compared with those obtained from Paradigm Sysdrill software, version 10. In calculating the frictional pressure losses for Herschel-Bulkley model the equations introduced by Merlo, et al. (1995) are employed. The barite-weighted and unweighted fresh water sepiolite muds are used in this study. The results estimated with Sysdrill software shows discrepancy, and the surge pressures are lower as compare to the results taken from analytical model. The surge pressures are also estimated using Bingham Plastic and Power Law model, and results are compared with Herschel-Bulkley rheological model. Additionally, a sensitivity analysis is performed to investigate the major parameters that affect surge pressures. The effect of tripping speed and fluid density exhibits the direct relationship, while the effect of borehole clearance exhibits the inverse relationship to the surge pressures. The study shows that, upto the certain degree of temperature, the surge pressures decrease with the increase in formation temperature, and then afterwards the surge pressures display an increment. For better understanding of formation temperature effect on mud rheology and surge pressures, the rheological constants for the mentioned mud samples are taken, using both Fann35A rotational viscometer and Fann50SL high temperature and high pressure (HTHP) rheometer. It is also determined that at the formation temperature up to 350°F, the use of both weighted and unweighted sepiolite muds allow to fasten the tripping speed of the drillstring.
Bir jeotermal rezervuarın birimleştirilmiş ve rekabetçi yararlanma koşulları altındaki performansı
Population growth and rising living standards remain as two of the key drivers for the increase of energy demand. Towards meeting such demand, as the technological advancements are crucial for diversifying energy sources, the adoptation of proper management strategies might be necessary for the efficient capacity development in existing sources. Geothermal energy, classified as a renewable energy resource is playing a vital role in this pursuit because the production system is able to sustain production levels over long periods. The longevity of production can be secured and sustainable production can be achieved, by using moderate withdrawal rates, while considering the local resource characteristics. A geothermal reservoir is indivisible by nature and so unregulated development of straddled leases overlying a reservoir, results in physical waste and under-utilization of resource, economic waste, environmental hazards, and inefficient resource management. The solution put forward to tackle this problem is unitization, which is defined as the voluntary or involuntary agreement by working interest owners of separate leases overlying the same reservoir to exploit and operate the resource as a cooperative and coordinated joint body under a designated operator. This concept delivers sustainable and efficient resource management, economic opportunities, and environmental benefits. The objective of this thesis concerns reservoir behaviour under production with time, where two leases of different reservoir temperatures are operated under competitive and cooperative development strategies, and coming out with the optimum development design to generate 20 MWe power. The study incorporates two stages. The first stage dwells on the comparison of reservoir behaviour under production with respect to time for competitive and cooperative utilization schemes. Reservoir pressure and reservoir temperature are the benchmarks for the analysis. The second stage is about the design of the appropriate development approach for a reservoir shared by two leases, assuming a constant electricity generation capacity throughout the project life. The lumped parameter modelling is an analytical technique used for projecting the pressure response of a geothermal system to extraction. Non-isothermal tank model is selected as the tool to account for significant temperature changes associated with marked differences between recharge temperature and reservoir temperature, variations resulting from injection operations, and decrease in reservoir temperature due to production of fluids. Three hypothetical cases of one-tank and two-tank models are proposed and analysed to study reservoir pressure and reservoir temperature behaviour relative to fluid production and time, with reinjection, under competitive and cooperative management of the two leases for constant electricity generation. The cases are set as, (a) Case 1: competitive approach with two leases, (b) Case 2: cooperative approach with unitized two leases, (c) Case 3: cooperative approach with unitized two leases (production in one lease and reinjection in other lease). The assumptions made in this study are, (i) arbitrarily chosen reservoir rock and fluid properties in both leases, (ii) constant electricity generation from binary power plants, (iii) a binary power plant with 10 MWe electricity generation capacity is installed on each competitive geothermal lease of different reservoir temperatures; or a binary power plant with 20 MWe electricity generation capacity is installed on the unitized leases, (iv) temperature of the recharge (aquifer) and its connected Lease 1 are equal at 180°C in all cases, (v) reservoir temperature in Lease 2 is 160°C, and (vi) project design life is limited to 10,000 days for all cases. The significance of this thesis is emphasized on selection of the most suitable development approach for a reservoir utilized by two straddled leases of different working interest owners. All the cases are evaluated in terms of the variation in average reservoir pressure, average reservoir temperature, net heat produced, and thermal efficiency of the power plant. Out of the three cases investigated the unitized approach, in which production is from Lease 1 and reinjection in Lease 2, is found to be the desired mode of operation to feed the 20 MWe capacity binary plant for the purpose of electricity generation. This case works best, because of well coordinated and informed technical decisions on appropriate well planning, based on extensive integrated data. Hot fluid zones are identified for production and are well separated from cooler regions, in which reinjection wells are to be located. The purpose of proper location of wells is to achieve the most efficient and sustainable energy production. As the reservoir section under Lease 1 is directly connected to the recharge source, from which the reinjection well is located far away in Lease 2, replenishment of produced fluids is at an adequate rate ensuring high average reservoir pressure. Locating the reinjection wells at a safe distance from the production wells in Lease 2, the temperature of the hot water zone is kept under control. Thus, the net heat produced would be very favourable, since the reinjected fluid is channelled through the reservoir section under Lease 2 to ensure minimal drop in temperature of the reservoir section under Lease 1, which enjoys hot liquid influx from the infinite size recharge source (aquifer). Case 3 also experiences the least drop in thermal efficiency of the binary power plant by the end of the design life. It can be concluded that the owners of straddled leases should be encouraged or imposed on to act in a cooperative strategy for an unitized management of land, geothermal energy, any heat or energy source surrounding the geothermal waters, and ecosystem to derive maximum benefits for all stakeholders and safeguard public interests.
Batı Raman petrolünün yerinde yanma kinetiğine basıncın etkisinin alışılagelmiş ve eşdönüşüm yöntemleri ile incelenmesi
Crude oils are often grouped into three categories based on specific gravity range as either; heavy oil (10o – 20o API), intermediate oil (20o – 30o API), or light oils (> 30o API). A fourth classification is the so-called extra heavy oils (<10o). Heavy oils have higher viscosities (> 100 cp) and contain larger molecular weight components. Conventional oils (light oils) consist of only 30 % of the world oil resources and therefore technology and resources must be focused on how to extract the abundant heavy and bitumen resources in the various parts of the world. Current methods for extracting heavy and bitumen resources are usually grouped as thermal and non-thermal methods. For very viscous oils, thermal methods, which employ the use of heat to reduce oil viscosity, are usually preferred. Thermal methods include, steam injection, in situ combustion, and hot water injection. On the other non-thermal methods of oil recovery such as waterflooding, CO2 flooding etc. are employed for less viscous oils. Surface mining is usually employed in bitumen extraction, since there is practically no mobility in bitumen reservoirs and waterflooding is a preferred choice in North Sea area where heavy oils are less viscous. Steam injection, which is by far the most popular of the thermal methods, involves the use of an injection well to introduce steam into the reservoir and the use of a production well to produce the mobilized oil from the effect of the steam. The main problem with steam injection method is heat losses. Heat losses for steam injection occurs in the surface lines used for the transportation of steam, in the wellbore to the surrounding formations and in the reservior to overburden and underburden. In addition, problem of gravity override is experienced in relatively thicker formations. In situ combustion, which has been around for a while, is not as limited as steam injection. It is mainly applied as dry forward combustion, in which dry air is injected to a reservoir to create a hot air sweep within the reservoir, as wet forward combustion in which a water alternating gas process is employed to utilize the heat generated efficiently through the water vapor and the hot air sweep and finally as reverse combustion, where injected air and burning zones move counter currently. The main advantage of the in situ combustion process is the generation of heat in situ within the reservoir and the containment of combustion products within the reservoir. The air required for injection is free and can be found in any environment – onshore or offshore. The in situ combustion process is however complex and difficult to engineer and requires several laboratory studies to acquire kinetic parameters and to formulate appropriate reaction models to understand the burning characteristics of the oil involved during the combustion process. The main objectives of this study is to formulate reaction models for the Bati Raman crude oil, a 12o API heavy oil from the Southeastern part of Turkey, to study pressure effect on the isoconversional kinetic analysis, and finally to predict the suitability of the crude oil to undergo combustion using isoconversional methods. Combustion kinetic studies within the literature usually fall under conventional and isoconversional methods. Conventional in situ combustion kinetic studies done by Tadema (1959), Bousaid and Ramey (1968) and Fassihi (1981) all apply a sort of straight-line approach in their interpretation of kinetic data. In these studies, reactions are grouped and lumped together but in reality, crude oil combustion involves several complex reactions. The isoconversional approach, however, provides model free methods which can by-pass the complex reaction model for activation energy estimation. The isoconversional method also provides screening criteria for determination of good and bad candidates for combustion. Conventional and isoconversional studies, which have been done previously point to three main reactions during in-situ combustion process. These reactions are namely: Low Temperature Oxidation (LTO), Middle Temperature Reactions (MTR) and High Temperature Oxidation (HTO). LTO reactions occur below 300oC (573.15 K) as a result of injected oxygen reaction with oil. It produces water, partially oxygenated compounds and carbon oxides MTR occurs between 300o – 400oC (573.15– 673.15 K) and show the characteristic negative temperature region where oxygen consumption decreases as temperature increases. More coke (carboneous material) deposits on the rock matrix during this reaction period. HTO reactions occur above 400oC (673.15 K) as a result of reaction between injected air and deposited coke. Fuel combustion occurs during this period and it produces carbon dioxide, carbon monoxide and water as its main products. In this study, kinetic experiments were conducted at 100, 150, 200 and 250 psig to study the in situ combustion kinetics of Bati Raman oil. In addition effect of pressure on the isoconversional analysis was investigated. The ramped temperature oxidation method was employed, and the produced gases were analyzed for the oxygen and carbon oxides in the effluent gas composition. A plot of gas composition versus time at all heating rates for all operating pressures give a curve that shows the three regions of the three major reactions that take place during crude oil oxidation namely; LTO, MTR and HTO. Using the gas composition plots at various heating rates, it is observed that peak oxygen consumption increases with increasing heating rate. Conventional methods of kinetic studies employ straight-line approach for kinetic data analysis. Activation energy values are estimated for high temperature oxidation region by Fassihi's method. For this method activation energy values generally decrease with increasing heating rate and increase with increasing pressure. The isoconversional technique which is model-free and deconvolve multi-step reactions naturally is also used in the calculation of activation energy in the high temperature region and compared with those obtained with the Fassihi method. The Fassihi method activation energy values are generally higher than those estimated with the isoconversional method. Pressure effect on activation energy is studied using the isoconversional fingerprints generated at different pressures for consumed oxygen with the isoconversional method. The isoconversional fingerprint comparisons show that increase in pressure has a corresponding activation energy increase in estimated values for Bati Raman crude in HTO region. In addition, reaction models were formulated for all operating pressures. Finally, using the various fingerprints obtained at different pressures, Bati Raman crude oil is viewed as a good candidate for combustion.