一种页岩气远井地层可压性简易评价方法及其应用

可压性是页岩体积压裂设计和效果评价的关键参数,反映了在现有工艺技术条件下,页岩气储层能够被压开并形成具有一定规模的复杂网络裂缝的能力。现有可压性指数评价方法主要以实验数据或测井评价等静态资料为依据,考虑的可压性影响因素各有差异,导致评价效果不理想。通过对施工参数进行等效折算、归一化处理后,建立了远井地层可压性指数的计算方法;将远井可压性指数计算结果与远井脆性指数计算结果,与无量纲归一化处理后的自然伽马和密度进行交汇,实现了对页岩的可压性参数条件的定量化评价。应用结果表明,远井可压性指数、脆性指数与停泵压力具有负相关性;同时具备较高的远井脆性和可压性的参数条件为:自然伽马值216~303API、密度值2.56~2.61 g/cm3。根据此条件评价的压裂段可压性指数越高,对应的微地震监测解释裂缝体积越大,改造效果越好。由此说明方法方便、准确,可为后续压裂井选段分簇和工艺参数设计提供指导。

Simple Evaluation Method for Far-Field Shale Fracability Index and Its Application

Fracability is the key to fracturing design and effectiveness evaluation, which reflects the capability of shale gas reservoir can be fractured and formed with a certain scale of complex network fracture under the existing conditions. The existing fracability index evaluation method is based on the static data, such as the experimental data or well logging evaluation, and the influence factors of the compressibility are different, the evaluation result is unsatisfactory. By means of equivalent conversion and normalization of pumping parameters, the calculation method of the fracability index of the far-field formation is established. Furthermore, combined the fracability index and brittleness index of far-field shale with the dimensionless normalized natural gamma ray and density, it achieved the goal of quantitative evaluation of the shale fracability condition. The results show that the far-field shale fracability index and brittleness index have negative correlation with the ISIP .Meanwhile, the conditions with good fracability and brittleness are: gamma ray is 216-303API and shale density is 2.56-2.61g/cm₃. According to this condition, fracturing stage with the higher fracability index can get the larger stimulated reservoir volume ( SRV) , and the better effect. Therefore, it implies the fracability index evaluation method is convenient and accurate, which provides the guidance for stage optimization, clustering and fracturing parameters design of the subsequent fracturing wells.