The Evaluation Of Hydrocarbon Source Rocks And Oil-gas Resource Of Chagan Depression In Yin-e Basin

On the basis of the study of basic geological data of Chagan depression in Yin’ebasin, the principle and methods such as oil and gas geochemistry, petroleum geology,principles of sedimentology, well logging and drilling are comprehensive applied, it isconsidered that the main source rock in Chagan depression is k₁b²segment andsecondary source rock are k1b1segment and k1s1segment. Laterally，the condition ofsub-depression source rocks in western Chagan depression is better than eastern onthe abundance of organic matter, organic matter maturity,evolution characteristicsand amount of resource.By researching sedimentary facies of the three sets of source rocks, it can be seenthat k₁b²segment contains a large set of dark-gray, black-gray claystone, dolomiticclaystone, claystone and gray sandstone, siltstone are interbedded with unequalthickness, the maximum thickness is1000m,and it belongs to shallow-deep lake; k1b1segment contains mainly a set of underwater-fan, shallow-lake gray, dark-gray muddysiltstone and dark-gray claystone, the maximum thickness is500m; k1s1segmentcontains dark-gray, gray and black-gray claystone and silty mudstone, the maximumthickness is400m, it belongs to Shallow lake.k₁b²segment has higher abundance oforganic matter, better type of organic matter, that is Ⅱ1, it is in the mature–highmature stage as the main source rocks;k1b1segment is about the same k₁b²in theabundance of organic matter, type, maturity; In contrast, k1s1segment is lower on theabundance of organic matter, II₂is main type, it is in a low mature-mature stage as asecondary source rocks.The distribution of oil and gas in the Chagan depression is complex, the result oftesting for oil in Chacan1well, Mao1well shows that vertical main oil layer is k1yformation, k1s1segment and k₁b²segment. On the premise of the analysis of thechromatograms of crude oil and source rocks, using of biomarker distribution featuresand content shows that the crude oil is light, mature and low-sulfur. Stable carbon isotope and sterane and terpane distribution characteristics show that the variouslayers of the source of crude oil present a great comparability to each other. Parentmaterial from crude oil and hydrocarbon organic matter are mixed type. By usingoil-source correlation indicators to analyse the relationship of crude oil and sourcerocks in the Chagan Sag, the following conclusion has been come that crude oil islikely to come from k₁b²segment, particularly affinity with the dolomitic claystone ofk₁b²segment, while there is a poor correlation with the k1s1segment.This study uses Cause and basin modeling to calculate the amount of resourcesin the Chagan sag. According to experimental data obtained from BaiyinChagandepression by the simulation of kerogen and pyrolysis simulation, this study obtainshydrocarbon generation curves after correcting in Chagan sag, then comes to get theexpulsion coefficient of the various source rocks. Combining type of structure，resources structure and petroleum geology background, the geological analogymethod is used to determine the clustering coefficient of each source rocks. Finally,the hydrocarbon generating quantity and resource quantity are obtained.According tothe currently new achievement, it can be predict that the percentage of oil and gasresources is82%in western sub-depression, and18%in eastern sub-depression.Therefore，it is considered that the eastern sub-depression has also some of resourcepotential. Meanwhile, calculation results using basin model method is similar to that.