塔里木盆地雅克拉断凸中生界底界不整合及其油气勘探意义

雅克拉断凸中生界底界是一个长期发育的重要不整合面,其上、下地层差异变形很大。通过解释雅克拉断凸三维地震资料,并结合钻井、区域地质资料以及该地区地层展布特征,依据不整合的成因机制及其形态的主控因素,将与该反射界面有关的不整合类型划分为非整合、削截、超覆和岩溶不整合。非整合主要分布在东、西部,其所在地区中生界下伏地层被全部剥蚀,分布最广;削截不整合的单斜区、皱褶区和断皱区从西至东依次分布于中、西部区域;超覆不整合沿雅克拉断凸南翼分布;岩溶不整合主要分布在上古生界被全部剥蚀而出露碳酸盐岩的中、西部区域。不整合对油气成藏有重要意义,既可作为油气运移的良好通道,也可改善储集层条件,还可形成大量圈闭。综合分析各类不整合特征及其分布规律,发现其因该地区"东强西弱"构造变形强度所导致。

Mesozoic bottom boundary unconformity and its significance for hydrocarbon exploration in the Yakela faulted uplift, Tarim Basin

Mesozoic bottom boundary in Yakela Faulted upliftt is an important unconformity developed for a long geologic time,and its overlying and underlying formations are quite different in deformation manner.Based on interpretation of 3D seismic data in the Yakela faulted uplift,combining with well data,regional geology and regional strata distribution characteristics,the types of unconformities related to this reflector can be divided into nonconformity,truncation unconformity,overlap unconformity and karst unconformity according to their formation mechanisms and main factors controlling geometry.The nonconformities mainly occur in the eastern and western parts,where the pre-Mesozoic deposits were denuded completely.The monocline area,fold area and fault-fold area of truncation unconformity exsit in the middle and western parts of the Yakela faulted uplift from west to east.The overlap unconformity distributes along south climb of the Yakela faulted upliftt.The karst unconformity mainly distributes in the central and western parts,where the upper Palaeozoic was eroded completely and carbonates expose.The unconformities are of great significance for hydrocarbon accumulation as they can act as migration pathway,improve reservoir conditions and create lots of traps.Comprehensive analysis of the characteristics and distribution patterns of various unconformities in this area reveals that they are the results of tectonic deformations strong in the east and weak in the west of the Yakela faulted uplift.