长岭复式断陷群构造特征及天然气富集规律

Structure features and natural gas enrichment regularity in Changling fault depression groups

长岭复式断陷群是由多条犁式正断层上盘发育的小型箕状半地堑复合形成的复式断陷,由大安—红岗、乾安、孤店、孤西、伏龙泉、查干花、前神子井、长岭牧场东、长岭牧场西及新安镇等断陷组成,经历了火石岭组沉积时期的初始裂陷、沙河子组沉积时期的强烈裂陷及营城组沉积时期的裂陷萎缩3个演化阶段,不同期次活动的断裂控制着不同时期次级断陷的形成、演化、复合及叠加特征。依据盆地结构特征可以将长岭复式断陷群划分为串联式、并联式、斜列式和相对式4种复合类型和继承型及非继承型(相干型)两种叠加类型。长岭复式断陷控陷主干边界断裂的继承性活动,导致不同期次的断陷在纵向上呈现继承性叠加,控制着优质烃源岩的发育。长岭复式断陷在复合、叠加过程中,在两条或多条控陷主干边界断裂的交会处是应力相对薄弱地带,往往是火山喷发的通道,控制着火山岩地层的发育;控陷主干边界断裂的继承性活动构成气源输导通道,同时诱发大量构造裂缝进一步改善了火山岩储层的储集性能;在长岭复式断陷复合过程中形成的调节带控制碎屑岩储集层砂体的发育;形成的继承性古隆起是长岭复式断陷群深层天然气成藏的有利构造部位。

Changling multiple fault depression groups are formed by many half grabens developed on the hanging walls of listric normal faults.They consist of fault depression in Daan-Honggang,Qianan,Gudian,Guxi,Fulongquan,Chaganhua,Qianshenzijing,Changling farm,and Xinanzhen.They experienced three evolution stages,the initial crack in Huoshiling group sedimentary period,the intensive rift in Shahezi group sedimentary period,and the rift shrink in Yincheng group.The fracture of formation,development,compound and superimposition of secondary fault depressions in different periods are under the control of active faults in each phase.Multiple fault depressions in Changling can be classified as 4types of complex(tandem type,parallel type,inclined column type,and relative type)and 2types of superimposition(inheritance type and non-inheritance type).The inheritance activities of the trunk boundary faults in Changling fault depressions caused fault depressions of various periods in the longitudinal,which controlled the development of high-quality hydrocarbon source rocks.The intersection of two or more boundary faults is a weak stress.It is also the volcanic eruption channel which controlled the development of volcanic strata.The trunk boundary faults in depression constitute gas conducting channels,and induce a large number of structural fractures. Meanwhile they improve the reservoir performance of volcanic reservoir further. Accommodation zones in the process of the compound control the development of sandbody of clastic reservoir.The inherited palaeohigh formed in the same period is the advantageous section of natural gas accumulation in deep multiple fault depression groups in Changling.