塔里木盆地库车坳陷克深气田构造特征及其对气藏的控制作用

Structural characteristics of Keshen Gasfield in Kuqa Depression of Tarim Basin and their controlling effects on gas reservoirs

塔里木盆地库车坳陷克深盐下构造是该区的重点油气勘探领域。但由于目的层埋藏深,盐下高陡构造地震资料品质差,精确成像困难,构造落实程度不高等问题严重影响了气田勘探开发进度。针对克深高陡复杂构造特点,基于新方法处理的全三维地震解释成果,重新落实了构造细节,研究构造特征及其对气藏的控制作用。研究成果表明:1在北推左旋压扭应力作用下,克深盐下构造发育冲起构造、屋脊构造、变换构造等构造样式,圈闭平面上呈雁列式展布;冲起构造气藏密封性好,利于气藏的保存,屋脊构造中间断裂对气藏起破坏作用。2研究区由西向东可划分为三排圈闭带,圈闭带间以调节断层或褶皱实现构造转换;中带构造幅度大,上覆膏岩厚度大,封堵性好,圈闭最为有利;西带上覆膏岩厚度小,断裂发育,封堵条件差;东带构造位置低,构造幅度小,有效圈闭幅度小,气水关系复杂。3受构造条件控制三排圈闭带呈现由西向东圈闭埋深加大,幅度减小、形态变缓的特点。该认识对克深气田开发方案的调整实施及下一步重点勘探开发方向的确定具有参考价值。

The Keshen subsalt structure in Kuqa Depression, the Tarim Basin, is an important exploration of this area. How- ever, the exploration and development of Tarim Oilfield is intensely impacted by the deep burial depth of target layers, poor seismic data quality of subsalt high and steep structures, difficulties of precise imaging and low confirming level of structures. In view of their complex characteristics, Keshen high and steep structures were ascertained in detail again based on the full 3D seismic interpretation results which were processed by using the new method. Then their characteristics and controlling effects on gas reservoirs were investigated. It is indicated that under the effect of north-nappe left-lateral transpression, multiple tec- tonic styles are developed in Keshen subsalt structures, such as pop-up structure, roof structure and transfer structure, and they distribute in the pattern of en echelon in the plane of traps. Pop-up structure is favorable for the preservation of gas reservoirs, and the sealing capacity of gas reservoirs in pop-up structures is good. The middle faulting of roof structure is destructive to gas reservoirs. The study area is divided into three trap zones from the west to the east, and the structural transition between trap zones are in the forms of adjusting faults or folds. In the middle zone, structural amplitude is large and the overlying gyp- sum rocks are thick with good sealing capacity, so the traps in this zone are the most favorable. In the west zone, the overlying gypsum rocks are thin with developed fractures, so the sealing condition is poor. The east zone is structurally low with small structural amplitude, low effective trap amplitude and complex gas-water relationship. Dominated by tectonic conditions, three trap zones show the characteristics of burial depth increasing, structural amplitude decreasing and structural form flatting from the west to the east. The research results can be used as the reference and determining the important exploration and development targets of for adjusting and implementing the development scheme Keshen Gasfield in the following steps.