USING AVO ANALYSIS TO DETERMINE THE GAS RESERVOIRS IN THE SOUTH THRACE BASIN, NORTHWEST TURKEY

This study investigates gas reservoirs using AVO modeling and analysis for 3D pre-stack seismic data acquired by Turkish Petroleum Corporation in the Thrace Basin located in the northwest part of Turkey. The Thrace Basin is Turkey’s the most productive onshore gas province, and is the largest and thickest sedimentary basin in Turkey. The Thrace basin is basically a vertical stack of sand-shale-silt sequences with no complex structures or salt domes. In such sedimentary stacks, rock properties such as density and velocity to calculate Poisson’s Ratio and preserving amplitude are very significant in order to obtain a successful AVO result. These features can help determining reservoir locations and increasing gas productivity. The main objective of this thesis is to understand rock properties at the possible reservoir zone, to do AVO (Amplitude Versus Offset) modeling, and to test the effectiveness of AVO modeling and analysis on the pre-stack seismic reflection data acquired over the Thrace Basin to identify new reservoirs. In this study, several processing steps were applied to our data, including true amplitude recovery, normal move out correction, pre-stack time migration, correlation of log and seismic data, and well log interpretation. Synthetic data were generated and elastic parameters obtained on synthetic and real data. Conventional AVO analysis techniques were applied; however, the effects of the hydrocarbon saturation to the amplitude could not be highlighted in the reservoir zone. Therefore, three different inversion techniques were performed to obtain an accurate reservoir signature. The inversion techniques could help to map the reservoir zone in a better way by increasing the vertical resolution.