Geochemical Characteristics Of Source Rocks In Nanhu 1 Well In Hami Depression Of The Tuha Basin

Petroleum geochemistry is based on the principle of organic chemistry and theviewpoint of organic chemistry to help oil and gas exploration and development,which is an in-depth exploration of the source and composition,nature and evolution of organic matter in oil and gas,also in-depth discussion the process and mechanism of the conversion of organic matter into oil and gas.At the same time,the effective application of biomarkers in the oil and gas geochemistry has made the oil and gas exploration more advanced.The study area is located in the southern margin of hami depression in Tuha basin.The landform in the region is mainly the gobi desert,the topography is relatively flat,and the general trend is low in the north and high in the south.It is formed late Paleozoic-Mesozoic residue depressions in carboniferous fold basement or more ancient devonian base.The upper surface of the depression is abundant,and the secondary and carboniferous source rocks are found in the outcrop.This paper is based on extensive research on the literature and regional geological background of the source rocks of hami depression,to systematic sampling of three potential sources rocks in Nanhu 1 well,a total of 165 samples were collected.Three sets of potential source rocks are the middle Jurassic Xi Shanyao group?J₂x?,the Permian Tao Donggou formation?P₂td?and the middle carboniferous Di Kaner group?C₂d?.Based on the organic geochemistry analysis,this paper detailed analysis of source of organic matter and Sedimentary environment of the source rocks,more comprehensive evaluation of the basic geochemical characteristics of organic matter abundance,type and maturity in Nanhu 1 well.The abundance of rock samples in Xi Shanyao group in the study area is high.The content of TOC in the coal rock was 6.87%²8.7%,while the PG value was between13.65mg/g¹00.31mg/g and the content of chloroform asphalt was 0.12%⁰.69%.The average content of TOC in carbonaceous mudstone was 26%,and the PG value was27.16mg/g⁵1.97mg/g,and the content of"A"of chloroform asphalt was 0.28%⁰.67%.The content of TOC in the mudstone sample was 0.72%¹1.8%,the PG value was0.29mg/g²1.65mg/g,and the average value of chloroform asphalt"A"was 0.09%.Coal and carbonaceous mudstone in Xi Shanyao group is given priority to with?type,organic matter type mudstone is given priority to with?type,coal and carbonaceous mudstone HI average 341 mg/g respectively and 223 mg/g,mudstone samples HI average of 219 mg/g.Xi Shanyao group samples embedded depth of 728.83 m to827.42 m,measured Ro is 0.46%⁰.51%,the sample is mainly between immature,low mature,in the coal and rock Tmax value is 423?⁴29?,carbonaceous mudstone Tmax value is 421⁴21?,mudstone samples Tmax value distribution between 416?⁴31?.The comprehensive evaluation is medium-good hydrocarbon source rock.The average content of TOC in the Tao Donggou group of Permian is 3.03%,the content range is 0.44%¹6.7%,PG average is 3.91mg/g,and the average content of chloroform asphalt"A"is 0.06%.HI average of 118 mg/g,mainly for?2 and?type organic matter;Tmax average of 436.71?,distribution between 422?⁴50?,the sample 842 m to 1240.33 m depth,the measured Ro is 0.48%⁰.73%,mainly in the range of low mature and mature.The comprehensive evaluation is medium hydrocarbon source rock.The average content of TOC in the Di Kaner group of carboniferous is 0.34%,the content range is 0.07%¹.18%,the average of PG is 0.1mg/g,and the average content of chloroform asphalt"A"is 0.01%.For organic matter types for?,HI average 52mg/g;Tmax average of 452.75?,the range between 368?⁵34?,most of the hydrocarbon source rocks in the mature stage.The comprehensive evaluation is medium hydrocarbon source rock.The geochemical characteristics of saturated hydrocarbons in nanhu 1 well source rocks are as follows:In the middle Jurassic,the normal alkanes in the Xi Shanyao group were dominated by the weak bimodal,and the mudstone samples in the Tao Donggou group of formation and the Di Kaner group of carboniferous were mostly the former peak type.In the hopane series,C₂₃TT is the quasi-normal distribution of the main peak,and mudstone samples from carboniferous to Jurassic,C₂₄Te/C₂₆TT ratio has an increasing trend.In the sterane series,the sample of the study area is mostly anti-"L",which reflects the outstanding contribution of the terrestrial higher plants,and the contribution of mudstone samples from the carboniferous to the Jurassic terrestrial biological contribution increased.Sample in the study area has a certain phytane advantages,characterization of reduction environment,different mudstone Pr/Ph differences characteristics,reveals the south lake 1 well hydrocarbon source rocks from the carboniferous to Jurassic sedimentary environment is reducing the characteristics of the transition to a partial oxidation.The hydrocarbon source rocks in the study area are less than 0.2,indicating that the sedimentary environment of nanhu lake is fresh water deposit.