地应力-岩石力学分析在东海低渗透致密砂岩气藏水平井压裂中的应用

In-situ stress and rock mechanics analysis in the application of hydraulic fracturing for horizontal wells in the low-permeability and tight sandstone gas reservoirs of the East China Sea

明确现今地应力分布规律和岩石力学特征是提高水力压裂效果的重要基础。目前海上低渗透致密砂岩气藏地应力分布及岩石力学参数研究尚不充分,且海上测井存在声波时差曲线缺失及密度曲线易失真等问题。因此,采用东海西湖凹陷A区已压裂井Well-1和Well-A2的测井、地震及水力压裂技术资料,通过声波时差及密度测井曲线重构方法形成了井筒地应力及岩石力学参数分析技术,结合建立的地震驱动的构造应力场及三维脆性指数预测技术,形成了适合东海西湖凹陷低渗透致密砂岩气藏的地应力及岩石力学研究技术体系,并以东海西湖凹陷第1口多级压裂水平井Well-A4H作为应用对象,从钻井及水力压裂等方面对该技术体系进行了应用评价。研究表明,该技术体系可用于对东海西湖凹陷低渗透致密砂岩气藏多级压裂水平井进行钻前井位优化、钻后分析,以及指导压裂方案设计、优化及压后效果评价,保障东海西湖凹陷低渗透致密砂岩气藏多级压裂水平井顺利开展地质工程一体化施工。

It is an important basis for improving hydraulic fracturing effect to make clear the distribution law present in-situ stress and rock mechanics characteristics.At present,the in-situ stress distribution and rock mechanics parameters of offshore low permeability and tight sandstone gas reservoirs are not fully studied,and offshore logging will miss the acoustic lag curve and the density curve is easy to distort.Therefore,the well logging,seismic and hydraulic fracturing technical data of two fractured wells including Well-1 and Well-A2 in Xihu Sag in the East China Sea are used to establish wellbore in-situ stress and rock mechanics parameter analysis techniques by constructing acoustic time difference and density logging reconstruction methods,combined with the established seismic driven tectonic stress field and three-dimensional brittleness index prediction technology to form the research technology system of in-situ stress and rock mechanics suitable for low permeability and tight sandstone gas reservoir in Xihu Sag in the East China Sea.The application evaluation of this technology system is carried out from the aspects of drilling and hydraulic fracturing by Taking Well-A4H as the application object,which is the first multistage fractured horizontal well in the East China Sea.The research shows that this technology system has good guiding significance for pre-drilling well location optimization,post-drilling analysis,fracturing plan design,optimization and post-drilling effect evaluation of offshore multi-fractured horizontal Wells,and can provide strong technical support for integrated geological engineering construction of multi-fractured horizontal wells in Xihu sag in the East China Sea.