Deep Marine Carbonate Reservoir Prediction In South Section Of West Sichuan Foreland Basin

Sichuan basin is one of the main producing gas basins in China, developing twosets of continental and marine sedimentation systems. Marine carbonate hydrocarbonresources are abundant but very low proved reserves rate in west Sichuan basin. Thekey point in marine carbonate hydrocarbon exploration is looking for high qualityreservoirs in west Sichuan basin.Firstly, based on geological data and combined with the seismic responsecharacteristics of marine formation and drilling data, the paper makes syntheticseismogram and calibrates stratigraphic horizon. Because five wells are drilled onlyinto terrestrial formation, not into deep marine strata in Dayi three-dimensional region,horizon calibration is to have an overall grasp for the depth of deep marine strata. It islargely dependent on L2line through LS1well and2582line of two dimensionalsurvey lines to calibrate deep marine stratigraphic formations in Dayi region.According to marine strata characteristics LS1well drilling and seismic responsefeatures of marine strata in the basins, the article calibrates five marine layers,including upper Triassic Ma’antang bottom, lower Triassic the bottom of JialingjiangFormation Section two, lower Triassic the bottom of Feixianguan Formation sectionone, upper Permian, lower Permian, and draws the corresponding T0time structuralmap.Combined with coherent cube attribute calculated, it utilizes foreland basingeological tectonic theory and fault-related folds method to interpret the tectonic style.There are six reverse faults through Ma’antang Formation in central fault blockanticline region. The Dayi fault developed deeply strikes northeast, throughout thework area and marine strata and plays a huge role in studying central fault block anticline in Dayi region, while others mostly belong to local faults and terminate inT1j2Layer (Lower Permian Jialingjiang Formation, Section two).West Sichuan region developed mainly rimmed platform depositional system,including evaporation platform, restricted platform, open platform, platform marginreefs, platform margin shoal, slope and shelf. Combined with sedimentary facies ofbasin marine strata, it utilizes seismic facies analysis to make waveform classificationof T1f1-T1f2layer and T2l4layer to obtain deposition facies diagram of theseformations.Seismic attribute is the comprehensive factor reflections of geological structure,formation lithology and formation containing oil and gas. Time attribute (such ascoherence cube time slices) is often closely linked with the geological structure. Theamplitude attribute of seismic data reflects the stratigraphic and lithologiccharacteristics while frequency and absorption properties often correspond toreservoir fluid nature. The attribute calculation includes amplitude class, complextrace, coherence and energy for divided layers in the study area, a variety of sectionsshowed, as well as the prediction of favorable reservoir region.