川东南丁山地区龙马溪组富有机质页岩脆性评价

Brittleness Evaluation of Organic-Rich Shale in Longmaxi Formation in Dingshan Area,Southeastern Sichuan

开展页岩储层的脆性评价对优选页岩气藏有利层段具有重要意义。综合利用岩心、测井、X射线衍射、岩石力学实验等资料,采用岩石矿物组分法和弹性参数法对丁山地区龙马溪组页岩脆性特征进行了综合研究,进而开展了页岩储层可压裂性评价。结果表明:研究区龙马溪组页岩矿物脆性主要受石英、长石、黄铁矿等矿物的影响,矿物脆性指数为36.2%~62.7%,平均48.1%;不同围压条件下,页岩受力破坏主要有劈裂型、双剪切型、单剪切型3种模式,力学脆性指数为40.7%~61.6%,平均52.6%。与国内外其他页岩产气区相比,研究区页岩脆性指数级别为中等偏上,脆性矿物、脆性指数与TOC含量具有较好的相关性,岩石可压裂性较好。DY1井龙马溪组脆性较强井段位于2 027.0~2 054.2m,脆性指数均超过50%,可实施压裂求取产能,与实际生产情况匹配性较好。

The brittleness evaluation of shale reservoirs is of great significance for determining the favorable stratigraphic zone of shale gas reservoirs.Comprehensive utilization of core data,logging data,X-ray diffraction data,rock mechanics experiments data and other data is adopted to study the brittleness characteristics of shale in Longmaxi Formation in Dingshan area together with rock mineral composition method and elastic parameter method,before the evaluation of shale reservoir′s fracture property.The results show that the brittleness of the shale in the study area is mainly affected by brittle minerals such as quartz,feldspar and pyrite,and the mineral brittleness index is 36.2%-62.7%,with an average of 48.1%.Under different confining pressure conditions,shale failure mode is mainly split type,double shear type,single shear type,while the elastic brittleness index is 40.7%-61.6%,with an average of 52.6%.Compared with other shale gas production zones at home and abroad,the shale index level of the study area is medium.The brittle minerals,the brittleness index and the TOC content have good correlation,and the fracture property is better.The brittleness of the Wufeng Formation-Longmaxi Formation is located at 2 027.0-2 054.2 min Well DY1,and the brittleness index is more than 50%.The production capacity of fracturing can be obtained,and this matches well with the actual production.