页岩气储层充填天然裂缝渗透率特征实验研究

Experimental Study on Permeability Characteristics of filled natural fractures in Shale Gas Reservoir

为了解页岩储层充填天然裂缝开启前、后的渗透率特征,利用四川盆地充填裂缝的不同页岩,结合裂缝面形貌测试,实验对比分析了天然裂缝原位闭合、剪切错位及酸处理后的渗透率特征。实验结果表明:混合充填裂缝矿物颗粒大,硬度高,渗透率应力敏感程度低于方解石充填裂缝。当剪切裂缝错位位移大于0.15mm时,渗透率大小主要受控于裂缝断面整体粗糙度。当错位位移小于0.15 mm时,充填矿物颗粒类型、大小控制的小尺度形貌更起决定作用。酸液溶蚀胶结物形成不整合面,大幅度提高裂缝导流能力,但也需要考虑酸液弱化页岩强度以及颗粒运移而产生的不利影响。

In order to understand the permeability characteristics of the filled natural fractures in the shale reservoirs before and after o-pening, the permeable characteristics of the closed natural fracture, the natural fracture with shear dislocation and the natural fracturetreated by acidizing are comparatively analyzed by the experimental testing cff the surface morphology of the filled fracture in the shalereservoirs of Sichuan Basin. The experimental results show that the stress sensitivity of the permeability of the natural fracture filled bythe mixed mineral particles with large size and high hardness is lower than that of the natural fracture filled by calcite. When the sheardisplacement of the fracture is larger than 0.15 mm, its permeability is mainly controlled by the overall roughness of the fracture sur-face, and when the shear displacement is less than 0. 15 mm, the type and the size of the mineral particles control the permeability of thefilled fracture. Acid solution dissolves cement to form an unconformity surface, which greatly improves the seepage capacity of the frac-ture, but the unfavorable effects of the shale strength weakening of and the particle migration caused by the acid solution need to be con-sidered.