Deep Gas System Of The Northern Songliao Basin And Reservoir Forming Mechanism

By analysing the types of gas reservoirs and their distribution laws, this paper pointethe gas of deep strata in the north of Songliao Basin mainly distributes under K1d2 in verticadirection, and on the Anda-Zhaozhou anticlinal zone in plane. By studying the matching relatiobetween gas distribution and each gas accumulation conditions, this paper considered sourceroccaprock, fault, unconformity interface and acient uplift to be the main factors controllingas accumulation and distribution of deep strata in the north of Songliao Basin. According tthe homogenlization temperature of fluid enclosures and measuring technology of ilite agecombinating with generation and explusion gas history of sourcerock, formation history ocaprock and active history of faults this paper considered main gas accumulation period of deestrata in the north of Songliao Basin to be the end of K1q, secondly gas accumulation perioto be the end of K1qn, the end of K1n, the end of K2m and the end of Paleogene period. Therare four accumulation models of gas migration into bedrock crust of weathering througunconformity interface, gas migrating into volcanic rock in sourcerock through fractures, gamigrating into each type of traps over ancient uplift through unconformity interface osandstone and fault and gas migration into stratigrphic overlop through sandstone. Accordinto sourcerock and caprock that determine the formation of gas system, this paper divided deestrata in the north of Songliao Basin into three gas systems of K1sh+yc-K1d2, K1d2~K1q1+2 anK1sh+yc~K1q1+2. According to partition traugh of fluid potenial field, this paper futher dividethe three gas systems into seven, seven and fourteen sub-gas systems partly According to thmotionless and development condition of gas accumulation, this paper comprehensively evaluatethe sub-gas systems, considered Zhaoyuan ~ Zhaozhou, Andanan ~ Changwu and Chaochang ~Zhaodongnan sub-gas systems to be best sub gas systems of K1sh+yc~K1d2 gas system. There arbetter~middle sub-gas systems in K1d2~K1q1+2 gas system. There are better, middle and bad sub-gasystems in K1sh+yc~K1q1+2 gas system. Due to active and open of faults, the three gas systemhave Changed since they formed, expanded upward and made their space increase. It played fou:roles in gas accumulation and distribution: a, In different evolution stages, gas came frodifferent sourceroks, caused the phenomenon of "the gas from different sourcerockaccumulating in the same position " ; b In different evolution stages, gas from the samsourcerock accumulated in different positions, caused the phenomenon of "the gas from the samsourcerock accumulating in different positions " ; c. In different evolution stages, there ardifferent gas accumulation models; d In different evolution stages, the space scope of gasaccumulation increases. Finally, based on comprehensive evaluation of sub-gas systems ancstudying evolution of gas systems, this paper forecast the favourable gas prospeting areas ofdeep strata in the north of Songliao Basin. Pointed out Anda-Zhaozhou anticline zone and thewest of Yingshan depression to be the favorable gas prospect area in K1sh+yc~K1d2 gas system.Anda-Zhaozhou anticline and its north to be the favourable gas prospecting arras in K,d2~K1q1+2 gas system. Anda and Lindian depressions to be the favorable gas prospect area in K1sh+yc-K1q1+2 gas system.