Developing seismic data processing software packpage

Seismic reflection method is one of the most important geophysical methods used in petroleum and natural gas exploration. Multichannel seismic reflection can be discussed under three titles: data acquisition, data processing and data interpretation. Data acquisition is the process of sampling seismic signals that measure physical conditions and converting the resulting samples into digital numeric values. Some consecutive mathematical operations are used to convert this digital numeric values into a subsurface image and be ready for interpretation. These mathematical operations are called data processing. Seismic exploration has had a significant impact on the discovery and production rates of oil and gas reserves around the world. Developments in the software industry over the past 50 years and intensive use of workstations allows the seismic data processing stages to be implemented entirely on the digital platform. During this period, many companies in the oil and gas industry have developed their own seismic data processing packages. Most of this packages need powerful workstations and the Linux operating system and this situation restricts access to professional software. In this thesis, it is aimed to develop a packet program that performs basic seismic data processing steps. C# programming language which is developed by Microsoft is used to write the software, and this programming language was compiled using the Microsoft Visual Studio 2015. Open GL library, which is a cross-language, cross-platform application programming interface for rendering 2D vector graphics, is used to form seismic graphics and sections. The software is prepared on Windows platform and tested on different versions of Microsoft Windows which are Windows 7, Windows 8 and Windows 10. Menus and manuals of this software are in Turkish. On the startup screen, there are options to add and remove users. When a new user is added to the system, a folder with the same name is created in the database. All flowcharts, seismic files and tables, which are created by the user are stored under this folder. On the other hand, when one of the existing users is deleted from the system, the file belonging to that user is deleted from the database. The main screen is displayed after user selection. There are 6 windows on the main screen: Data Processing Center, Projects, Database, Tables, Terminals and Screenshots. On the Data Processing Center window, the flowcharts are created and the output files are generated by running these flowcharts. The saved flowchart can be accessed on the Projects window. On the Database Window, user can access their own seismic output traces. Tables in which certain parameters are stored are displayed on the Tables window. On the Terminal window, user can reach the details for each channel of the chosen seismic data. Users can take a screenshot from the program and access the file paths through the Screenshots window. On the Database window , users can open the display screen by right click of the desired seismic data. The right and top panels can be used to zoom in and out of the seismic section. From the display settings screen, the amplitude values of each sample and display type of the data can be changed. Shot gathers can be displayed one by one, as well as side by side depending on the user's request. On the other hand, with the Channel / Shot option, the traces which are recorded on the same reciever from different shots can be displayed side by side. The quick-view buttons allow the user to monitor the seismic traces automatically to forward and backward. The SEG-Y (sometimes SEGY) and SEG2 file formats are two of several standards developed by the Society of Exploration Geophysicists (SEG) for storing geophysical data. Data Loading module converts the raw seismic data from SEG2 or SEGY formats into the internal format and stores it in the database. Geometry Defination module updates header information for each channel using coordinates of source and receivers. Other preliminary data processing steps (data editing, trace editing, amplitude adjustment, mute and filtering) intend to increase the signal to noise ratio. In mathematics, deconvolution is an algorithm-based process used to reverse the effects of convolution on recorded data. It compresses the basic wavelet in the recorded seismogram, decreases noises and short-period multiples, thus increases temporal resolution and yields a representation of subsurface reflectivity. Two different deconvolution methods can be applied on shot gathers via software. Spiking deconvolution shortens the embedded wavelet and attempts to make it as close as possible to a spike. Predictive deconvolution uses information from the earlier part of a seismic trace to predict the latter part of the same trace, and it is an goal to attenuate multiples. Each trace is defined to the midpoint between the shot and receiver locations based on the field geometry information, and those traces with the same midpoint location are grouped together. This procedure is called Common Depth Point (CDP) and CDP Sorting module sorts the data as a CDP gather using header information of each seismic trace. Acoustic impedance is the product of density and seismic velocity, which varies among different rock layers. The difference in acoustic impedance between rock layers affects the reflection coefficient. The acoustic impedance variation is generally depends on the seismic velocity, because the range of the seismic velocity is larger than the range of density of rock layers. Velocity analysis is one of the main seismic data processing step performed during the processing of seismic data. The velocity information is estimated from the seismic traces by using velocity spectrum via software. Estimated seismic velocities and two way travel time values are recorded in a table, and this table can be updated on 2-D velocity section window. Normal moveout (NMO) defines the effect that the distance between a seismic source and a receiver has on the arrival time of a reflection. A reflection arrives first at the receiver nearest the source. The distance between the source and other receivers is called offset and it causes a delay in the arrival time of a reflection from a surface at depth. A graph of arrival times versus offset has a hyperbolic curve. NMO module flatterns these hyperbolic curves on the CMP gathers by using the velocity table. Stack is the sum of the traces from different shot records with common reflection point. This procedure improves signal noise ratio and reduces noise, as a result it effects seismic data quality. Full Stack module is applied after NMO correction to sum each CDP gathers, and creates 2-D seismic section. Synthetic data and real data were used during the development of this software. The real data is collected with MTA Sismik-I vessel offshore Bababurnu and it involves 303 shots and 96 channles for each shot. The created algorithms are tested at every step and the accuracy of the results was investigated.