Study On Petroleum Geology And Geochemistry In The Puwei-wenliu Part Of Dongpu Depression

The exploration and development of oil and gas in Dongpu depression has entered the middle and late stage,and the exploration difficulty is increasing day by day.Many years of exploration and development research have shown that its geological structure is relatively complex,the number of faults is numerous and staggered,the reservoir sand-body has strong heterogeneity,resulting in different oil and gas distribution characteristics of each layer section,which greatly increases the difficulty of oil and gas exploration in the future..In view of this situation in the study area,we plan to select Wenliu area and Puwei area in Dongpu depression as the main research target area,fully absorb the previous research results on petroleum geology,and systematically analyze the molecular composition of crude oil,especially the composition characteristics of biomarkers in each layer of the target area,so as to reveal the different genetic types,distribution characteristics and maturity variation law of crude oil.Go further to explore the law of oil and gas accumulation in the study area and provide geochemical basis for further exploration of oil and gas.Mainly achieved the following understanding:(1)The preservation conditions of the oil samples in the study area are good,and there is no obvious secondary microbial alteration.The sedimentary environment of oil source has the characteristics of strong reducibility,which is the salt lake facies with stratified water body and high salinity.Generally speaking,the highest evolutionary maturity has not reached the main peak stage of oil generation.(2)Based on the type and maturity distribution of crude oil,there are two periods of crude oil in Puwei-Wenliu area: the first is the early crude oil with relatively low maturity,which is distributed in Wenliu and Hubuzhai area;the second is the late crude oil with relatively high maturity,which is distributed in Pucheng and Weicheng area.The late mature crude oil has the characteristics of southward migration,and there are different degrees of mixing with the early crude oil.However,the eastern part of Wenliu is short of high maturity crude oil.The oil maturity of well Wei 79-7 in Weicheng area is the highest,and there should be good oil and gas resources nearby,which can be used as a future exploration direction.(3)The reservoirs in Puwei and Wenliu areas have good lateral connectivity,and there should be oil and gas distribution along the drilling line.In Wenliu area,the vertical connectivity of the reservoir is good,and the caprock is located above the lower sub section of Sha2;in Puwei area,there are two regional caprocks,respectively,above the lower sub section of Sha2 and between the lower sub sections of Sha2 and Sha3,which block the oil-gas migration between the lower sub section of Sha2 and Sha3,and the oil-gas under the caprock is the most abundant,which is a good exploration direction.(4)Through the study of the geochemical characteristics of well wengu2 near well wen101 in Wenliu area,it is clear that the oil source of well wengu2 is different from that of the crude oil in the study area,which has no impact on the oil and gas in the nearby well wen101 area.It is said that the oil and gas filling capacity of well wengu2 is insufficient or there is structural shielding between well wen101 and well wengu2 is not a good oil and gas exploration direction.