The Integrative Evaluation Of Petro-geologic Condition And Forming Mechanism Of Jixi Basin

Jixi Basin is the Mesozoic rift Basin and which is one of the important contained coalbasins.It is located in the south of Pre-Mesozoic Jiamusi massif, Northeast China. It is on theNorth part of Dunmi Fault. The basin formed in the early Early Cretaceous and closed in the earlyLate Cretaceous period,which experienced many tectonic movements. We study on the basicpetro-geologic conditions and the accumulation mechanisms of petroleum based on logging data,seismic data, and sample testing data before collecting predecessor’s experiences.First,we study on the basic petro-geologic conditions such as source rocks, reservoirs and sealrocks. The results show that the basin mainly developed two sets of good source rocks–Chengzihe Formation and Muling Formation. The source rocks of Chengzihe Formation havegood organic enrichment, the Kerogen is dominated Ⅲ type, the evolution level of mosthydrocarbon source rocks is mature and the part is high maturity; The source rocks of MulingFormation also have good organic enrichment, the Kerogen is mainly dominated Ⅲ type and thepart dominated Ⅱ, the evolution level of hydrocarbon source rocks is mature-low mature. Thereservoirs are mainly made up of fan-delta sand body and underwater fan sand body is the secondary,and the rock types are mainly medium-fine grain arkoses and lithic arkosics. the pore types aremainly primary pores such as intergranular pores and micropores and the secondary pores such asdissolved pores and fracture pores. The diagenetic stage of reservoirs of K1ch and K1m havebeen in stage A of middle diagenetic stage, and it is low porosity and low permeability、 ultra-lowpermeability reservoirs. The reservoir performance of K1ch is better than K1m’s, The cap rocks ofK1ch and K1m is mainly mudstone and tuff is the secondary. The thickness of mudstone is largeand the mudstone distributed widely. The displacement pressure of the cap rocks is high and theSealing ability of cap rocks is strong. According to the disposalrelationsh ip of source rocks,reservoir rock s and cap rocks of Lishuzheng Depresion, three types of basic assemblage can bedivided. The first associations is usually of the type with source rocks in the upper and reservoirsbelow, the second one with source rocks below and reservoirs in the upper, the third one is “self-generation and self-accumulation”.Secondly, the type of Jixi Basin reservoirs, oil and gas distribution and Controlling factors ofhydrocarbon accumulation were studied. The type of Lishuzheng Depression of Jixi Basinreservoirs mainly faulted anticline, fault block reservoir, lenticular-tongue lithologic reservoirs,fault block structure-lithologic reservoirs based. Oil and gas accumulation is mainly affected bytectonic activity, sedimentary environment, diagenesis, reservoir-cap oil and gas transportingsystem and other factors.Furthermore, The study selected Jican1well as research goals and used basin modelingtechnology, which to analyze its burial history, thermal history, maturity history. The resultsshowed that the eroded strata thickness of Muling Formation is1700m,Jican1well. The paleo--geothermal gradient is large and it gradually reduced after experiencing a brief warming duringChengzihe Formation.The source rocks of Chengzihe Formation began generate oil at125Ma andgas at120Ma,while generate oil at120Ma of Muling Formation. As a whole, they had entered theoil generation period at120Ma. On this basis, wo summarized hydrocarbon accumulation stages inChengzihe Formation and Muling Formation by fluid inclusion study.The results indicates thatthere were three oil-gas filling:first period is82-76Ma,second period is68-64Ma,third prriod is46-39Ma.Finally,we summarixed the hydrocarbon accumulation model of LishuzhengDepression.,which developed source rocks and delta plain, delta front, and other underwater fansandstone reservoirs in Chengzihe Formation and Muling Formation. Because the study area hadexperienced multiple stage of tectonic activity structure and developed series of faults, folds, etc,which provided a driving force for the oil and gas migration and configured to form a effectiverelationship in time and space for the storage for oil and gas. The oil-gas migrated into thereservoir by faults and other grooming system after generated and gathered in the traps and formeddifferent types of oil and gas reservoirs.