焦石坝地区页岩储层可压裂性影响因素及计算方法

Influence factors and evaluation methods for shale reservoir fracability in Jiaoshiba Area

页岩储层具有低孔、低渗的特点,大规模压裂改造后才能形成商业产能,所以可压裂性是页岩气开发中最关键的评价因素之一。文中研究采用分析化验资料与测井资料结合的方法,分析页岩储层可压裂性的影响因素,影响因素主要包括脆性指数、天然裂缝、水平应力差异系数、Ⅰ型和Ⅱ型断裂韧性以及成岩作用等。根据各种影响因素与地层可压裂性的相关关系,对其进行归一化处理,采用层次分析法确定每种影响因素的权重,从而提出一种定量评价页岩储层可压裂性的方法。运用此方法,依据可压裂性评价系数,将页岩储层的可压裂性划分为3个级别：可压裂性评价系数大于0.7的储层,可压裂性好;可压裂性评价系数介于0.6-0.7的储层,可压裂性较好;可压裂性评价系数在0.6以下的储层,可压裂性较差。

Shale reservoir has the characteristics of low porosity and low permeability.It could form business capacity only after massive hydraulic fracturing.So the fracability is one of the most important parameters in the development of shale gas.This study uses a method combining the core analysis data and logging data to analyze the influence factors of shale reservoir fracability,including brittleness index,natural fracture,horizontal stress coefficient,fracture toughness,and diagenesis.Normalized processing of each factors,analytic hierarchy process is adopted to determine the weight coefficient.A new quantitative evaluation method of shale reservoir fracability is put forward.Shale fracability can be divided into three levels according to the fracability evaluation coefficient.The shale with high fracability evaluation coefficient greater than 0.7 is the best interval to be fractured.When the fracability evaluation coefficient is between 0.6 and 0.7,the shale can be fractured effectively.And when the fracability evaluation coefficient is less than 0.6,the shale could not be fractured effectively.