长岭断陷CO2气藏与烃类气藏成藏特征

以长岭断陷中部隆起区有机成因烃类气藏和无机成因CO2气藏的成藏条件与分布规律研究为基础,应用储集层流体包裹体分析技术,结合构造演化史分析,研究两种气藏的形成时间、期次和序次,并建立两种气藏的成藏模式.综合研究表明:长岭断陷有机成因气为过成熟煤成气,来自营城组、沙河子组及火石岭组烃源岩;无机成因CO2气以幔源成因为主、火山岩自身脱气成因为辅,气源断裂体系的展布与幔源火山活动脱气是无机CO2气藏富集和运聚的两大主控因素.长岭断陷烃类气体先期成藏(成藏时间为距今81～86 Ma,姚家组沉积期一嫩江组沉积早期),CO2气后期成藏(成藏时间为距今约28 Ma,古近纪末);CO2气藏主要赋存于营城组火山岩中,单独存在或与烃类气体混合存在,且烃类气藏位于混合气藏的上部.

Formation of carbon dioxide and hydrocarbon gas reservoirs of the Changling fault depression, Songliao basin

On the basis of the research on the forming conditions and distribution of inorganic CO2 gas reservoirs and organic hydrocarbon gas reservoirs in the central uplift area of the Changling fault depression, the forming time, stage and sequence of the two gas reservoirs were studied and the pool-forming patterns were established by analyzing fluid inclusions and structural evolution. The organic gas is over-mature coal-derived gas, mainly from source rocks of the Yingcheng Formation, Shahezi Formation and Huoshiling Formation. Inorganic CO2 gas is mainly from mantle, secondarily from the degassing of volcanics. The distribution of gas-source fault systems and the degassing of mantle volcanos are the two main factors controlling the enrichment, migration and accumulation of inorganic CO2 gas reservoirs. The formation of hydrocarbon gas reservoirs is earlier than that of inorganic CO2 gas reservoirs, the former is 86Ma~81Ma at the early depositional period of the Yaojia and Nenjiang Formations, the latter is 28Ma in the late Paleogene. CO2 gas reservoirs mainly exist, alone or mixed with hydrocarbon gas, in the Yingcheng Formation volcanics, and the hydrocarbon gas reservoirs are on the top of the mixed gas reservoirs.