库车坳陷现今构造应力场与天然气分布关系

摘要

The present plane and sectional tectonic stresses were recovered by finite element numerical simulation,their distribution characteristics were summarized,and the relationship between the tectonic stress and the natural gas distribution was analyzed.The results show that in plane,the distribution of maximum principal stress of the sub-salt reservoir in different structural zones is not uniform and characterized by bigger stress in the north than in the south,roughly band-distributing toward near E-W,in the northern part with serious structural compression formed many low-stress areas;in cross section,the maximum principal stress is smaller at the territorial gypsum-salt caprock and its overlying strata,and bigger at the sub-salt strata;and the maximum principal stresses of the Triassic and Jurassic source rocks are generally bigger than that of overlying Cretaceous reservoir.The relative low-stress areas are formed in Kela faulted anticlines and fault blocks in Kelasu structural belt with strong tectonic compression,anticlinal apex and the side of faulted anticline in the upper close to the fault of Keshen zone.The natural gas pools discovered in Kuqa depression up to now are located at the relatively low areas of maximum principal stress.%运用有限元数值模拟,确定库车坳陷现今平面和剖面的构造应力,总结其分布特征,并对构造应力与天然气分布的关系进行分析。盐下储集层在不同构造带最大主压应力分布不均,呈现出北部大,南部相对小,且大致呈近东西向条带状展布的分布格局,构造挤压强烈的北部区带内形成了诸多相对低应力区;区域性膏盐岩盖层及以上岩层最大主压应力较小,盐下岩层最大主压应力普遍较大,且埋深较大的三叠系、侏罗系烃源岩层最大主压应力较白垩系储集层普遍大,构造挤压强烈的克拉苏构造带北部克拉区带断背斜和断块、南部克深区带背斜顶部和断背斜靠近断层一侧上部均形成了相对低应力区。目前已发现天然气藏大都位于现今最大主压应力的相对低值区。