论文详情
在寻找页岩气有利区域时,页岩的脆性预测是非常重要的一个环节。传统的脆性指数预测方法是叠前三参数反演,即通过反演纵波速度、横波速度和密度等参数计算页岩脆性指数。但受入射角度或偏移距的限制,叠前反演得到的密度误差较大,根据以上参数计算的页岩脆性指数累积误差更大。以四川盆地焦石坝页岩气区块为例,探讨了应用叠后地震波形指示反演预测页岩地层脆性的方法。在页岩脆性矿物定量评价的基础上,依据测井资料计算出单井脆性矿物含量曲线,综合利用测井、地震、地质等资料,通过叠后地震波形指示反演得到脆性矿物含量数据体,进而求取页岩地层脆性的空间分布,提高页岩脆性预测精度。焦石坝工区页岩脆性波形指示反演结果显示,目的层五峰组和龙马溪组的①、③小层脆性指数较高,与岩心测试数据和实钻压裂结果吻合,为该区页岩气田的开发和井位部署提供了依据。
Shale brittleness is an important factor in finding favorable areas for shale gas.The traditional method for predicting the brittleness index relies on a prestack three-parameter inversion,which evaluates the shale brittleness index by inverting the compressional wave velocity,the shear wave velocity,and the density.The density error of the pre-stack inversion is large due to limitations in the incident angle (or offset).Consequently the cumulative error in the evaluated shale brittleness index is also large.In this paper,the shale gas block in the Jiaoshiba area in the Sichuan basin is taken as a case study,and its shale brittleness is predicted through a poststack inversion of the seismic waveform.Based on the quantitative evaluation of the brittle minerals in shale,the distribution of brittle minerals in a single well is calculated from logging data,and data on brittle mineral contents are also obtained through the post-stack seismic waveform inversion using logging,seismic and geological data comprehensively.The predicted brittleness index of the layers ① and ③ of the target layers,which include the Wufeng Formation and the Longmaxi Formation,is higher than that in other layers,which is consistent with logging data and with the actual drilling fracturing effect.The good agreement between measured and predicted values provides a technical support for shale gas field development and well location deployment.
国家自然科学基金委员会中国石油化工股份有限公司石油化工联合基金资助项目(U1663207)、国家重点基础研究发展计划(973计划)项目(2014CB239104)与国家科技重大专项(2017ZX05049-002)共同资助。