The Fine Reservoir Description On First Segment Of Shuangyang Formation In Laomoliqing Area, Yitong Basin

Laomoliqing area is located at southeastern Moliqing fault depression, Yitong Basin. It has been finished drilling 37 wells and among these wells there are 8 wells which obtain oil and gas in the Shuangyang formation at Laomoliqing area. Based on available information, the cause factor of sand bodies in Moliqing fault depression may be complex, not only developed sand body of the fan delta which cause of tractional current water system, but also developed sand body of exogenous sublacustrine fan with waterfall style and authigenic slump sublacustrine fan, which cause of gravity flow. In this area, a lot of different contributing factors gravity flow sand bodies are developed, and cause the sand body change fast in longitudinal direction and transverse direction. This situation make it very difficult to predict favorable reservoir.According to the characteristics mentioned above in Laomoliqing area, In this paper, based on the stratigraphic correlation, combined with drill cores, well logs and seismic sections, studied the characteristics and distributive rules about the sedimentary micro-facies of the first segment of Shuangyang formation in Laomoliqing area, analyzed characteristics of reservoir space types, reservoir physical properties and heterogeneity, summarized the spatial variation of reservoir physical properties and their relationship with hydrocarbon accumulation, to provide the scientific basis for oil and gas exploration and development.The first segment of Shuangyang formation in Laomoliqing area mainly make up of dark mudstone in the upper section, glutenite, sandstone and siltstone in the middle and lower section, its bounded up theâ…¤sand group in second segment of Shuangyang formation and bounded down the base rock with high resistance, and it like mud neck in the form compared with the upper and lower strata. Based on sedimentary cycle of Yi-18 well, we divided the first segment of Shuangyang formation into six sand groups and divided sand groupâ…¢,â…£,â…¤,â…¥into 12 thin layer. According to the comprehensive analysis such as drill cores, well logs, seismic sections and granularity distribution, the first segment of Shuangyang formation in Laomoliqing area developed lacustrine facies, fan delta facies and sublacustrine fan facies. Based on these information we restored distribution characteristics of sedimentary micro-facies about the first segment,â…¢~â…¥sand groups and thin layers of Shuangyang formation. Overall, the fan delta in southeast study area is the key sedimentation, small-scale fan delta also developed in the southern Laomoliqing area and in the north-west of study area developed the small-scale sublacustrine fan. Besides, sedimentation of underwater distributary channel and sublacustrine fan mainly developed in the middle area, it composed the overall sedimentary system of lacustrine-fan delta-sublacustrine fan.The main porosity style of Laomoliqing area reservoir can be divided into intergranular porosity, intergranular dissolution porosity and intra-filling disslution porosity. The main level of porosity type in the underwater distributary channel of fan delta front zone isâ…¡A ,where developed reservoir with mesoporosity and high permeability; the level of porosity type in the middle-fan of sublacustrine fan zone mostly distribute fromâ…¡B toâ…¢A, where developed reservoir with low-porosity and low permeability, and compared with the former, it with poor physical property.The relativity analysis between sedimentary facies and hydrocarbon accumulation show that oil and gas mostly accumulate at the underwater distributary channel of fan delta front facies and the middle-fan of sublacustrine fan facies, and less accumulate at the sheet sand and mouth bar of fan delta front facies, besides, the hydrocarbon oil and gas distribute along shore-shallow lacustrine facies in edge of basin .The main genetic type of reservoir in first segment of Shuangyang formation is underwater distributary channel, sheet sand, mouth bar of fan delta front facies and middle-fan of sublacustrine fan facies. The sand body mainly develop at lower section in first segment of Shuangyang formation, is a type of water-transgression sand body. The source rocks of semi-deep lacustrine facies in highstand above these sand bodies. This area also developed high quility covers as well as source-reservoir-cap assemblage, hydrocarbon in source rocks can accumulate in the reservoir directly and further turned into lenticular lithologic hydrocarbon reservoir, or forming fault-lithologic hydrocarbon reservoir when it combine with fault in the study area.