Geochemical Characteristics And Petroleum-gas Geological Gignificance Of The Jurassic Source Rocks In The Xorkol Basin,Western China

Qaidam basin basin has kept a set of Jurassic source rocks. The thickness of the Jurassic source rocks is 300 m and it's distribution area is about 3875.5km2. The study of geochemistry characteristics and biomarker features, which is of guiding significance to hydrocarbon potential evaluation and the oil-gas reserves in Qaidam Basin. This thesis collect Jurassic source rocks in Xorkol basin, ranging from Sonam profile, Qingshuigou profile and mangbei profile. This paper has also carried out many experiments, such as, analyzing rock pyrolysis, microscopic examination of kerogen, composition and biomarker features. Discussing kerogen type of source rock, depositional environment and thermal evolution degree. Evaluating hydrocarbon potential and oil and gas resources is to discuss the prospections of the Jurassic oil and gas resources in Xorkol. The main conclusions are listed below:1 The TOC distribution of Jurassic source rocks in Xorkol basin is 0.22%-16.10%, with distribution of total hydrocarbon content is 6.3-263.1ppm. The hydrocarbon latent amount distribution of S1 + S2 is 0.00-0.71mg/g; with distribution of pyrolysis kerogen type parameter S2 / S3 is 0.01-0.45, Source rocks saturated / aromatic ratio is 5.4, the distribution of kerogen type is 41.26- 73.38%, so it belongs to ?1kerogen. Pyrolysis peak temperature(Tmax) is 227-520?.2 Xorkol Basin source rocks n-alkanes of carbon number is between of C11-C33, with a single peak.The main peak carbon numbers are C20, C21, C22 and C23,?C21-/?C22+ is low;most source rocks OEP value is greater than 1, showing a slight advantage of odd carbon and C23, C24 tetracyclic diterpenoids / C26 tricyclic diterpane mean of 0.76, C24 tetracyclic diterpenoids content lower than C26 tricyclic diterpane.3 Xorkol Basin source rocks are mainly belong to sapropel mixed parent materials, partial samples are humic materials. Source rocks Pr/Ph is less than 1. r-/0.5C31 in average number is 0.34,with a distribution range of 0.14-0.64. So the main characteristics of Xorkol basin sedimentary environment is Weak reduction circumstance of brackish water and salt water.4 Non-hydrocarbon source rocks of Xorkol basin Jurassic in 17%, poor source rocks 13%,moderate 25% of hydrocarbon source rocks, good source rocks accounted for 45%.Ro average is 1.28%, C31??22S/22(S+R) and C32??22S/22(S+R) in average are 0.56 and 0.57, respectively. Xorkol Basin source rocks is in the mature stage.5 The original hydrocarbon generation quantity of Jurassic source rocks in Xorkol Basin is 886.84 million tons, with a residual hydrocarbon generation quantity is 9.21 million tons. Hydrocarbon expulsion amount is 877.63 million tons. The aggregate amount is 87.763 million tons.