Değirmenköy yeraltı gaz depolama sahasının modellenmesi

The major source of energy essential to life comes from fossil fuels, and the dominant fossil fuels used today by most industrialized and developing countries are oil, coal, and natural gas. Among these fossil fuels, the natural gas is a versatile, clean-burning, and efficient fuel that is used in a wide variety of applications. According to the International Energy Agency (IEA), since the beginning of the 70s, the share of gas in the world energy balance has increased from 16 to 21% in 2008. According to the British Petroleum (BP) Statistical Review of World Energy, this share in 2010-2014 in global energy consumption was even higher - about 24%. BP forecasts that natural gas will be the fastest growing type of fuel in the next 25 years. The experts of IEA believe that the share of gas in the world energy by 2035 will increase to 25%, the gas will be the second energy source after oil, shifting coal into third place. Stable development of the gas industry and its individual factors are related to the capital investment of both new construction and in the maintenance of the achieved level. Improving the reliability of gas supply to consumers is particularly important. Consequently, one way to increase the security of gas supply is the underground gas storage facilities. Underground gas storage is an independent sub-sector of the gas industry. It plays an important role in ensuring the stability of gas supply by creating the reserve volume of gas in case of emergency situations in the gas pipeline system, which require prompt increase in supply. Involvement capacities of underground gas storage allows to balance the work of the gas supply system by increasing the productivity of the gas transportation system, or accumulating excessive amounts of commercial gas in the period of low demand. Gas is stored most commonly in underground storage facilities under pressure. These underground facilities are depleted oil and/or natural gas reservoirs, aquifers, and salt cavern formations. Natural gas is also stored in liquid or gaseous form in aboveground tanks. Gas is the major energy source consumed in Turkey. Today, Turkey needs to import substantial amount of energy since indigenous energy resources are not sufficient to meet increasing in demand. By virtue of this, the main goal of Turkish energy policies has been set as the supplying of required energy in a timely, dependable, cost-effective, environmentally sound and in a high-quality basis to support the development impulse and social progress. Turkey's energy security is closely related with the amount of gas stored. In Turkey there exist surface storage in form of tanks and underground gas storage. However, underground gas storage provides significantly large volume and meets various strategic requirements and delivery rates. At present Turkey does not have significant underground gas storage volumes comparable to other countries, despite the presence of suitable geology of both salt cavern and depleted field storage. One of the depleted underground gas storage of Turkey is the Degirmenkoy field. The Degirmenkoy is one of the two reservoirs of Silivri underground natural gas storage facility. The field is located in the Thrace region of Turkey. It is an onshore gas field located 16 km northern-west of the Northern Marmara field. The feasibility of creating gas storage in the Degirmenkoy field was examined based on process design, geologic factors, and preliminary economical analysis. The purpose of the design for an underground storage reservoir is to obtain the maximum working gas capacity for a given configuration of reservoir and surface properties under the influence of economics. The method of selecting the appropriate number of wells, wellhead pressure and base gas requirements is to fix one of the parameters and determine how the other parameters change depending on each other. In this study, the Degirmenkoy natural gas field is designed for storage purposes using RUBIS simulator. Approaches to designing the Degirmenkoy gas field as underground gas storage are as follows: - To design the current state of field maintaining the working gas capacity of 14.37 bscf for a given number of wells, reservoir and well properties. - To observe the reservoir performance of field with additional wells. The storage cycle for one year in Degirmenkoy UGS field is planned as follows: 180 days of injection period followed by 35 days of shut-in period, then 150 days production period is followed. It is assumed that all wells have the same wellbore and flow characteristics, accordingly simulated data are obtained from well #5. To achieve a desired result, firstly the model is simulated with already existing six wells. By using RUBIS simulator, two approaches for operation of the underground gas storage facility, namely the constant flow rates for both injection and production periods and the constant bottomhole and wellhead pressures are investigated. After that, new six wells are added to maximize the working gas capacity. The capacities of six wells and twelve wells are compared. In addition, the mechanical skin effect is considered. Increasing the skin factor causes to decrease the working gas capacity, which is not desirable. Hence, the efforts to minimize wellbore damage is the cause for concern. The wellhead pressure is the key parameter for defining the quantity of horsepower requirements for compressing the gas to the market. Therefore, the wellhead pressure effect on performance of the underground gas storage reservoir is studied. The result show that decreasing the wellhead pressure leads to an increase in working gas capacity for a fixed number of wells.