摘要
页岩储层的"体积压裂",使美国页岩气产业取得巨大成功,有效评价压裂裂缝网络形成的难易程度,是压裂开采的首要目标,目前国内外尚未发现有效的评价方法,为此开发了一种新的测试方法。针对10种岩芯,测试岩石力学参数,并对比分析常用的3种页岩脆性评价方法。采用压后裂隙结构面迹长分布的分维值和面密度对裂缝进行定量表征,并对压后崩落碎块进行对比分析。通过实验认为,杨氏模量和泊松比判别法与塑性系数判别法用于评价岩石脆性,精确度更高;脆性岩石通常表现为高杨氏模量或(和)低泊松比的特征,与单轴抗压强度、抗张强度和压入硬度没有对应关系;压裂裂缝的分布具有统计意义上的分形特征,分维可用于定量评价压后裂缝网络复杂度;硬度越高,压后裂缝密度越小;脆性越强,压后裂缝密度越大。新方法是岩石脆性、硬度和天然裂缝系统(和沉积层理)特征的综合体现,用于评价页岩压后形成缝网的能力,不仅直观可靠,而且简单有效,有利于现场推广应用,对于今后页岩气或致密砂岩气开发的理论研究和现场应用具有一定的指导意义。
Crushability evaluation on shale reservoir is to evaluate the difficult degree of generating fi＇acture network; m other words, is to demonstrate the SRV（stimulated reservoir volume） can whether or not be effectively implemented. It is a key of the whole fracturing work. At present, there is no unified reference standard and evaluation method at home and abroad. A new evaluation method is developed in this paper. For l0 kinds of cores, their rock mechanical parameters are tested firstly; and the commonly used three kinds of shale brittle evaluation methods are comparatively analysed. The fracture is characterized quantitatively by using fractal dimension of trace of fracture structure surface and areal density; and the caving elastic mass after fracturing is analysed. The results show that the accuracy of Young＇s modulus and Poisson＇s ratio discriminance and plastic coefficient discriminance used to evaluate shale brittleness, are higher. The characteristics of high Young＇s modulus, or（and） low Poisson＇s ratio are usually presented for the brittle rock; but there is no corresponding relation between brittleness and uniaxial compressive strength, tensile strength and indentation hardness. Fracture distribution after fracturing has fractal structure with statistical sense of self-similar. The fractal dimension can be used for quantitative evaluation of fracture network complexity. The higher the rock hardness, the smaller the fracture density after fracturing. The stronger the brittleness, the larger the fracture density after fracturing. The new method is the integrated embodiment of characteristics of rock hardness, brittleness and natural fractures system（and sedimentary structure）. It is not only visual and reliable, but also simple and effective to evaluate the ability of forming fracture network after fracturing on shale reservoir; and as a result, it illustrates a good prospect of application and extension in oilfield. This work is very significant for evaluation and development of shale reservoir.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2013年第4期947-954,共8页
Rock and Soil Mechanics
基金
国家科技重大专项"3000型成套压裂装备研制及应用示范工程"资助(No.2011ZX05048-10HZ)
关键词
页岩
可压性
脆性
压入硬度
裂缝密度
分维
shale
crushability
brittleness
indentation hardness
fracture density
fractal dimension
作者简介
郭天魁，男，1984年生，博士研究生，主要从事非常规气藏增产改造研究工作。E—mail：guotiankui@126．com
