The Relationship Between Features Of Jurassic Faults And Hydrocarbon Accumulation In Middle 4 Block Of Jungar Basin

Middle 4 block of Jungar Basin located in the east of Fukang sag.The Jurassic oil and gas resources are abundant in this area.There are lithological traps and tectonic-lithologic traps in the Toutunhe Formation and the Qigu Formation,which have huge exploration potential.However,the fault is a necessary condition of oil and gas accumulations in the traps,which causes the oil and gas generated in the deep source rocks to accumulate in the Toutunhe Formation and the Qigu Formation.Another key factor of oil and gas accumulation in the traps is the Lateral Seal of faults.However,the current research shows that the faults in the study area are more complex and the causes are not yet clear.And the relationships between oil and gas migration,accumulation and accumulation still need further study.Based on the study of fault genesis,types,and tectonic styles,the dissertation uses the balanced section technology to carry out the study of fault activity.Based on the geochemical data of the sample,this paper analyzes the hydrocarbon generation potential and the source of oil and gas,and analyzes the fluorescent thin section,defining the hydrocarbon charging period in the region,starts from the characteristics of single well formation pressure,analyzes the relationship between stratigraphic overpressure distribution and hydrocarbon accumulation,and determines the control effect of faults on hydrocarbon reservoirs through the study of fault sealability.The results and understanding are as follows:(1)The formation of faults in the study area is related to the strike-slip effect of Phase of Yanshan.The faults are mainly strike-slip faults,and the geometric patterns of the sections mainly show flower-like structural patterns.Positive flower-like structural styles are mainly distributed in the Dong 2-Dong 7-Dong 1-Dong 101 line,faults strike E-W.The negative flower-like structures are mainly distributed near the Dong 8 well,and faults strike the S-N direction.In terms of sub-division,the Jurassic faults in the Dong1-West of Dong1 industrial area are dominated by reversed faults.They are compression and scissor fault,showing flower-like and en-echelon patterns,some of which have large hade.The Jurassic faults in the North of Dong 2 area are affected by the Baijiahai strike-slip fault and the thrust belt of the Bogeda Mountain.They have both normal faults and reverse faults.They are negative flower-like structures.The normal faults are distributed in the north and strike N-S.The reversed faults are distributed in the south and strike E-W.The Jurassic faults in the Dong 6 area were affected by the Bogeda Mountain,all of which are normal faults.The faults in east of Dong 6 well strike E-W,and in west of Dong 6 well strike N-SW and N-WS.(2)Based on the analysis of zonal fractures,combined with the fault activity rate,the structural evolution characteristics of the middle 4 block are analyzed.The Dong 1 – West of Dong 1 area reversed faults are dominated by isolated or en-echelon and medium hade.Partially are Flower structure.Tectonic background of the zone is early extension,mid-late pressure and twist;North of Dong 2 area is dominated by negative flower structure,form in Tensional-Shear background;Dong 6 area is dominated by faults which are upright and lack of branch and negative flower structure.The tectonic setting is early extension and late twisting.North of Dong 2 area had the highest average rate of fault activity in the early-middle Jurassic period,and was weaker than Dong 1-West of Dong 1 area in the late Jurassic period.Dong 6 area had the weakest average rate of fault activity during the Jurassic period.(3)The content of organic carbon in Xishanyao Formation and Badaowan Formation are the highest,and they are good hydrocarbon source stratum.The kerogen type is dominated by type III,followed by type II2,and source rocks buried below 4800 m have basically entered the hydrocarbon generation threshold.Comparing the characteristics of terpane and sterane,the oil sands of the Toutunhe Formation and the source rocks of the Xishanyao Formation are well comparable.In addition to the source rocks of the Badaowan Formation in the middle 4 Block,the Xishanyao Formation also provide important sources of oil and gas to the Toutunhe Formation and Qigu Formation.(4)Three sets of overpressure systems in the Jurassic Formation,Bayaowan-Sangonghe,Xishanyao-Toutunhe-Qingshuihe,and Xishanyao have been established,and there are relatively independent pressure systems in different overpressure systems.Two kinds of different accumulation modes have been created,inside of the overpressure system and outside of the overpressure system(atmospheric pressure system).(5)There are three acts of hydrocarbon charging in the Jurassic in the study area,and the main accumulation time of the Sangonghe Formation was in the Cretaceous,and the composition of the Toutunhe was in the Neogene.The residual pressure difference formed in the high-pressure source stratigraphy and reservoirs of the Xishanyao Formation and Badaowan Formation is the main driving force of oil and gas transmission in the overpressure system.The late fault activity provides migration paths for the upward flow of overpressure fluids.Based on this,the control of faults on hydrocarbon accumulation is proposed: 1.The development of oil source faults is the primary condition for oil and gas enrichment;2.The types of traps associated with faults are the main sites for oil and gas enrichment;3.The fault sealability affect the accumulation of oil and gas within the trap.