库车坳陷致密裂缝孔隙型砂岩储层评价的物性界限探讨

Discussion on Evaluation Scheme of Physical Property Boun-dary for Tight Fractured Porous Sandstone Reservoirs in Kuqa Depression

摘要: 塔里木盆地库车前陆盆地冲断带经历强烈构造应力作用，勘探目的层古近系–白垩系埋藏超深，储层致密，基质物性非常差，但构造裂缝相对比较发育，为具有双孔双渗特征的致密裂缝孔隙型砂岩储层。储层产能大小主要与地层渗透率有关，而与孔隙度关系不明显。大量未充填–半充填构造裂缝是这类致密储层总渗透率的主要贡献因素。基于单井测试资料讨论了不同产能对应地层渗透率的界限。对构造裂缝的贡献按照四个层次进行评价。建立了适合库车坳陷致密裂缝性砂岩天然气勘探的储层物性综合评价方案。

Abstract: Experienced a strong tectonic stress, the main exploration layers of Cretaceous-Paleogene in thrust belt of Kuqa foreland basinofTarimbasin buried deeply and were very tight. The reservoirs were characteristic of very poor physical property about the matrix but with abundant tectonic fractures. They were tight fractured porous sandstone reservoirs with dual-porosity and dual-permeability. Reservoirs productivity of the studied area were controlled defini- tively by the total stratum permeability and have no obvious relation with the porosity. Unfilled and semi-filled struc- tural fractures are the main contributing factors for the total permeability of the tight reservoirs. Boundaries of stratum permeability for different reservoirs productivity were proposed based on well testing data. Tectonic fractures were evaluated in four types according to their contribution for the stratum permeability. A scheme of evaluation parameters about the tight fractured porous sandstone reservoirs adapting to the natural gas exploration in Kuqa depression was established.