Understanding the features of apertures of hydraulically conductive fractures occurring in the subsurface is vitally important in tight-gas reservoirs. The Cretaceous Bashijiqike Formation in the Kelasu Belt, Tarim Basin, is a gas enrichment reservoir at depths greater than 6,500 m. The matrix permeability is less than 0.1 mD, and generally decreases by one to two orders of magnitude under the reservoir conditions. Core analyses and image logs indicate that one type of natural fractures, which were assumed to have minor contributions to fluid flow in the subsurface, are pervasively developed with barren features and appear as conjugate fracture patterns with en-echelon steps occurring on the fracture surfaces. The hydraulic apertures of these fractures were determined based on core-image calibration and overburden pressure testing on the fractured cores under reservoir conditions, and suggests that they have hydraulic apertures ranging between 2.54 μm and 5.62 μm. The hydraulic fracture apertures could gradually decrease in size with burial depth. The fractures are hydraulically open implied by the presence of asperities generated by certain amounts of shearing displacement along the fracture surface and the abnormally high formation pressure of the Bashijiqike Formation. The results also imply that all of the fractures are able to enhance the reservoir permeability in the tight-gas sandstones, but affected by present horizontal stress.

在致密气藏中，了解地下发生的导水裂缝的孔隙特征至关重要。塔里木盆地克拉苏带的白垩纪巴什基奇克组是一个天然气富集层，其深度大于6,500 m。基质渗透率小于0.1 mD，在储层条件下通常降低1-2个数量级。岩心分析和图像测井表明，一种天然裂缝被普遍认为具有贫瘠特征，被认为对地下流体流动的贡献很小，并表现为共轭裂缝形态，并在裂缝表面形成梯级台阶。这些裂缝的液压孔是基于岩心图像校准和在储层条件下对裂隙岩心的上覆压力测试确定的，表明它们的液压孔在2.54μm和5.62μm之间。水力压裂孔的尺寸可以随着埋深的增加而逐渐减小。沿裂缝表面一定程度的剪切位移和巴什基奇克组异常高的地层压力产生的凹凸不平，暗示着裂缝是水力开放的。结果还暗示，所有裂缝都能够提高致密气砂岩中的储层渗透率，但受到当前水平应力的影响。水力压裂孔的尺寸可以随着埋深的增加而逐渐减小。沿裂缝表面一定程度的剪切位移和巴什基奇克组异常高的地层压力产生的凹凸不平，暗示着裂缝是水力开放的。结果还暗示，所有裂缝都能够提高致密气砂岩中的储层渗透率，但受到当前水平应力的影响。水力压裂孔的尺寸可以随着埋深的增加而逐渐减小。沿裂缝表面一定程度的剪切位移和巴什基奇克组异常高的地层压力产生的凹凸不平，暗示着裂缝是水力开放的。结果还暗示，所有裂缝都能够提高致密气砂岩中的储层渗透率，但受到当前水平应力的影响。