水平井体积压裂缝网表征及流动耦合模型

针对岩石脆性系数高且发育天然裂缝的储层,提出表征水平井体积压裂形成裂缝网络的三种基本模式,并将渗流过程划分为油藏流动和缝网内部流动.在此基础上,利用势叠加原理导出油藏流动控制方程,利用有限差分方法建立缝网内部有限导流等式;其次,采用星三角变换法处理人工缝与天然缝的交汇流动;最后,耦合两部分流动矩阵方程得到水平井体积压裂缝网渗流数学模型.该模型表明:当水平井改造段长度一定时,压裂段数与段内分簇数是决定产能的最主要因素,其次是人工裂缝半长和人工缝导流能力,而天然裂缝密度和导流能力对产量影响较小.实例应用表明,实际产油量与模型计算值一致,误差较小.

Characterization of Fracture Network by Volume Fracturing in Horizontal Wells and Coupled Flow Model

For reservoirs with high rock brittleness coefficient and uniform development of natural fractures, three basic modes are developed to characterize fracture network created by volume fracturing in horizontal wells. Flow from reservoir to wellbore is divided to two parts:reservoir flow and network flow. Principle of potential superposition is used to derive reservoir flow equation. Finitedifference method is adopted to establish flow equation within finite conductivity network. Star-Delta transformation is used to tackle interplay of flow between hydraulic and natural fractures. A comprehensive flow model is presented by coupling matrix equations of two flows. It indicates that as stimulated horizontal length is kept constant, effect of quantity of fracture stages and perforation clusters in each stage on production is more significant than that of half-length and flow conductivity of hydraulic fracture, which is, in turn, more dominant than that of density and flow conductivity of natural fractures. Finally, a field example shows that little difference exists between measured and calculated results.