库车前陆盆地秋里塔格构造带东、西段构造变形与储层物性的差异性

Difference of Structural Deformation and Reservoirs Physical Property in Qiulitage Structural Belt of Kuqa Foreland Basin

根据地震剖面解释和平衡剖面分析,库车前陆盆地秋里塔格构造带东段盐下地层的构造变形强度大于西段,东段的构造变形缩短率为13%~25%,形成了断层相关褶皱、叠瓦构造、双重逆冲构造等构造样式;西段的构造变形缩短率小于10%,形成了背冲构造、台阶状构造等断块构造。利用回剥原理,采用盆地模拟技术分析表明,东段的沉降速率大于西段。构造变形和沉降速率的差异性对储层成岩作用和物性产生了重要影响。东段的构造变形强,沉降速率大,储层的深埋时间长,导致储层的成岩作用强,处于中成岩A2—B期,储层的视压实率为37%~64%,储层物性较差;但强烈的构造作用造成裂缝发育,裂缝的存在提高了低渗透储层的渗透性能。西段的构造变形相对较弱,沉降速率较小,储层的浅埋时间较长,造成储层的成岩压实作用较弱,处于中成岩A1—A2期,储层的视压实率为24%~55%,储层物性相对较好。构造—成岩作用是影响库车前陆盆地秋里塔格构造带低渗透储层物性差异的关键地质因素。

According to the analyses of the seismic sections and balanced sections,subsalt structural deformation strength in the east is higher than that in the west of Qiulitage structural belt of Kuqa foreland basin. Structural shortening rate in the east part ranges from 13%to 25%and subsalt structures mainly include fault-related folds,imbricated thrust and duplex in the east.Structural shortening rate is below 10% and structural styles are a series of fault blocks in the west,such as back thrust and step thrust.Using the principle of back stripping and basin modeling technology,the result suggests subsidence rate is higher in the east than that in the west.The differences in structural deformation and subsidence rate have influence on reservoir diagenesis and physical property.In the east,structural deformation is intensive.Subsidence rate is higher and deep burial time is longer.The compaction is strong and reservoir diagenesis stage is in middle diagenesis A2-B period.Visual compaction rate ranges from 37%to 64%and reservoir physical property is bad.Intense tectonism leads to development of the fractures which greatly improve reservoir permeability. On the contrary,structural deformation is faint and subsidence rate is lower in the west.Shallow burial time is longer.Visual compaction rate is between 24%and 55%,reflecting the compaction is weaker.Reservoir diagenesis stage is in middle diagenesis A1-A2period.Reservoir physical property is better in the west.Tectonic-diagenesis is a crucial geological factor causing the inferior physical property of the reservoir in Qiulitage structural belt of Kuqa foreland basin.