Prestack three-term seismic inversion for prediction of Carboniferous-lower Permian carbonate reservoir on the Central uplift of South Yellow Sea basin

The Central Uplift of the South Yellow Sea Basin is a stable tectonic unit, of which the Mesozoic- Paleozoic marine deposits are expected as possible oil and gas prospects. However, oil and gas exploration is limited up to date due to complex structure and lack of high quality seismic data. Following the principles of comparative geology, well logging and seismic data from the Sichuan Basin are adopted in this paper as a reference for comparison, where the evolution of depositional environment is similar to the South Yellow Sea Basin to certain extent. We analyzed the logging and seismic responses of the carbonate reservoirs and worked out the seismic facies and reservoir distribution pattern of the Paleozoic marine facies in the South Yellow Sea Basin by application of prestack three-term seismic inversion based on simplified Zoeppritz equation. Extracted are the data of relative density, volume modulus and shear modulus. The three kinds of seismic attributes mentioned above are then extracted from the target layer for 3D clustering analysis, which is used for classification of seismic facies in the seismic profiles. Under the control of different seismic facies, 3D clustering interactions is performed for the three-term seismic parameters, and obtained is the favorable reservoir space. Based on above mentioned analysis, it is found that in the Late Permian and Carboniferous period there mainly developed the four kinds of facies as restricted platform, open platform, platform edge bank and platform edge reefs. And the reservoirs of karstic dolomite, reef and carbonate flat will develop on the Central Uplift of the South Yellow Sea Basin. Sedimentary environment has great impact to reservoir characteristics, but the later tectonic movement will render certain effect on the reservoir pore space.