The Prediction Of Stratigraphic-lithologic Trap Of Jurassic-cretaceous In Eastern Yakela Fault Arch

The east part of Yakela fault arch is located in the frontal uplift of Kuche Depression. Jurassic-Cretaceous strata southward onlapped on the pre-Mesozoic uplift basement, so the area has very favorable conditions to form a series of lithologic-stratigraphic traps. A number of wells have good oil and gas shows. However, enrichment patterns of the lithologic stratigraphic oil and gas reservoirs are not clear, the understandings of formation and reservoir pinchout are still inadequate, which restrict the depth of non-structural hydrocarbon reservoirs exploration in the area. Combined with core observation, paleontology, log data, seismic data and other comprehensive information, carried out isochronous stratigraphic division, correlation and seismic reservoir prediction, sedimentary facies analysis of the Jurassic-Cretaceous strata, explored conditions of lithologic-stratigraphic traps formation, predicted favorable traps development areas. The main results and understandings from the research are as follows:The north slope of Yakela fault arch is a onlap slope, Jurassic and Kapushaliang formation onlapped on the slope often with diachronous characteristics when they were contrasted as lithostratigraphic units, Yageliemu formation with the typical phenomenon of "the same facies with different time". Comprehensively used log data and3D seismic data, carryied out fine stratigraphic correlation of the study area, Jurassic was divided into three sequences(Jsel, Jse2, Jse3), Kapushaliang formation was divided into six sequences (Ksel-Kse6).Jurassic is fan delta plain-fan delta front, shore-shallow lacustrine and lacustrine bog deposition. Cretaceous Kapushaliang group is alluvial fan-river deposition, Yageliemu formation is root-middle part of the alluvial fan, Shushanhe formation is fan margine branch river-outer fan mud-rich low-sinuosity river deposition, Baxigai formation is meandering river deposition. In Kapushaliang group some small shallow lakes develop locally. Bashenjiqike formation is braided river deposition. Jurassic and Kapushaliang group in the north slope of the east section of Yakela fault arch is a wedge-shaped pinch-out body, T50and T40unconformities develop, but along these unconformities the upper roof rock and the under bottom plate lack better sealing characteristics, these conditions are not conducive to form stratigraphic traps. Jse3, Kse1and Jsel cycle near well DG2are likely to form appreciable and effective stratigraphic overlap traps. Lithologic traps mainly develop in every layer of the middle-upper Jurassic and Cretaceous.