摘要
可压性是表征页岩储层能被有效改造的难易程度。根据页岩储层缝网压裂施工实践,通过具体化页岩储层＂有效压裂＂概念,明确了页岩储层可压性的实际意义,即在相同压裂工艺技术条件下,页岩气储层中形成复杂裂缝网络并获得足够大的储层改造体积的概率以及获取高经济效益的能力。现有评价方法由于分析因素不够全面导致评价效果不理想。通过综合页岩脆性、断裂韧性和天然弱面3个方面特性,提出了能全面、科学表征页岩气可压性的评价方法,摒弃了现有方法的不足。基于储层各参数特征,可将该方法的可压性程度分为三级：可压性系数介于0～0.225之间,可压性程度较低,压裂效果差;可压性系数介于0.225～0.5之间,可压性程度一般,压裂效果较好;可压性系数介于0.5～0.8之间,可压性程度较高,缝网压裂效果理想。采用新的评价方法计算得出四川盆地下志留统龙马溪组页岩可压性系数为0.392 8,可压性程度一般,与该区域页岩气井缝网压裂改造时的微地震监测结果一致,说明新方法计算准确,现场应用方便,可为压裂选井、选层提供前期指导。
Fracability is the capability of the shale that can be fractured effectively during hydraulic fracturing.According to the network fracturing construction practice of shale reservoir,by externalizing shale reservoir＂effective fracturing＂concept,the practical significance of fracability evaluation of shale-gas reservoirs has been clarified.So this can be described as the probability to create a complexity fracture network and large stimulated reservoir volume in shale gas reservoir to obtain high economic benefits under the same condition fracturing technology.The consideration of the existing evaluation methods for many reasons influencing fracability was not quite comprehensive,which leads to the inaccuracy.Proposing a new method to evaluate the fracability of shale-gas reservoirs by taking into consideration of the factors of brittleness,fracture toughness and natural planes of weakness,is more comprehensive and scientific than before.Shale fracability can be divided into three levels according to the reservoir parameters.Shale with low fracability（fracablity index of 0-0.225）couldn′t be stimulated effectively.Shale with medium fracability（fracablity index is 0.225-0.5）could be stimulated effectively but the effect is actually modest.Shale with high fracability（fracablity index of 0.5-0.8）is the best choice to be fractured.It is better to choose shale with fracability index above 0.5.The new method was applied to Longmaxi shale in the Sichuan Basin.The fracability index is 0.392 8and the fracability is modest,which agrees with result of microseismic monitoring.Applications in the Longmaxi shale show that the results of calculation are correct and soundly based and that the suggested method is practicable for use,which can be used in the selection of wells or layers for fracturing.
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2015年第6期1165-1172,共8页
Natural Gas Geoscience
基金
新世纪优秀人才支持计划(编号:NCET-11-1062)
国家重点基础研究发展计划("973")项目(编号:2013CB228004)
四川省杰出青年学术技术带头人资助计划(编号:2012JQ0010)联合资助
关键词
页岩气
可压性评价
脆性
断裂韧性
天然弱面
可压性系数
Shale gas
Fracability
Brittleness
Fracture toughness
Natural planes of weakness
Fracability index
