裂缝型储层复杂人工裂缝压后定量诊断方法研究

Research of quantitative diagnosis of complex hydraulic fractures for fractured reservoirs

沟通天然裂缝并形成复杂人工裂缝网络对裂缝型储层高效压裂改造具有重要意义,通过压后诊断准确获取复杂人工裂缝特征有利于针对性地优化压裂设计,从而提高该类储层开发效果。针对目前常规压后诊断方法仅可对复杂人工裂缝做定性识别,无法对其裂缝条数、主裂缝及各分支缝缝长、施工滤失量等参数做定量诊断的问题,首先建立了压后渗流流态诊断曲线,通过识别线性流特征对施工形成的裂缝条数及各条裂缝闭合时间、闭合压力做准确判断;在此基础上结合G函数进一步开展了复杂人工裂缝压后滤失动态分析,获取不同裂缝开启状态下的滤失变化特征并推导了复杂人工裂缝滤失方程,从而实现对复杂裂缝缝长、滤失量、液体效率的定量求解;最后通过应用实例,验证了本文方法在裂缝型储层复杂人工裂缝压后诊断中的适用性及可靠性。本文研究成果可为人工裂缝优化设计提供参考。

The propagation of natural fractures and the generation of complex hydraulic fracture networks are significant for stimulation of fractured reservoirs.Accurate diagnosis of the hydraulic fracture characters is of great importance to optimize fracturing design pertinently and improve the development effect of fractured reservoirs.The usual fracturing diagnosis method can only identify the complex hydraulic fractures roughly but the specific data such as fracture number,fracture lengths of main and branch fractures,and filtration loss can’t be acquired quantitatively.Therefore the flow pattern diagnosis curve is established to get the fracture number and the closure time and closure pressure of each fracture by identifying the characteristic line of linear flow.On this basis,the filtration loss dynamics after fracturing is analyzed in combination with G function to acquire filtration loss coefficient at different states of complex fractures and the filtration loss equation of complex fractures is derived to calculate the fracture length,filtrate volume and liquid efficiency.At last,a case is analyzed with the new diagnostic method and the results verify this method’s applicability and reliability.The research results of this paper can provide reference for optimizing design of the complex hydraulic fractures.