Gas migration and gathering characteristics and accumulation mechanism in upper paleozoic Shiguhao area

Through the research on gas composition,isotope characteristics and gas accumulation conditions,it is believed that natural gas lateral migration with long distance does exist in lower Shihezi formation of Shiguhao area.Meanwhile,its characteristics of gas reservoir are similar to Boerjianghaizi fault in the south of the area,the mixed gas reservoirs of parallel migration with long distance plus in-place migration.Gas accumulation mechanism shall have two patterns,one of which is strata uplift,pressure reduction,drop of temperature and degasification accumulation pattern,and the other of which is water-soluble gas bedding and parallel migration,pressure reduction,and degasification accumulation pattern.The water-soluble gas by degasification is the prime accumulation mechanism in mass area of lithology reservoir development and scale gas gathering in He-2+3 of Shiguhao area.It also explains the reasons why He-1 of Xaishihezi formation,Shiguhao widely contains water,and why the relation between gas and water is complicated,and why large scale gas gathering is formed in He-2+3 though the source rock in the north is poorly developed.