A composite model of multi-stage fractured horizontal well with secondary fracture by high-precision boundary element method

Horizontal well volume fracturing plays an important role on enhancing gas recovery. Microseismic map indicates that the secondary fracture has been observed obviously and irregular stimulated reservoir volume (SRV) region created. In order to simulate pressure response of this phenomenon, the aim of this paper presented the semi -analytical model of multi -stage fractured horizontal well with secondary fracture and SRV region. Composite model is used to describe irregular SRV, and high -precision boundary element method and coupling method are employed to solve the semi -analytical mathematical model. Compared with conventional fractured horizontal well model, pressure transient behavior of multi -stage fractured horizontal well with secondary fracture and irregular SRV region has unique flow regime. The supply regime from secondary fracture to hydraulic fracture, second bilinear flow regime. Pressure derivative curve shows obvious 'dip' for supply regime from secondary fracture to hydraulic fracture, and 1/2 slope line for second bilinear flow regime reflecting formation gas flow towards hydraulic fractures and secondary fractures. Fracture parameter (such as conductivity, length and number) have an obvious influence on pressure transient curve of early and middle flow regime, and they can cover up some flow regime of early flow regime. SRV parameter and shape have an obvious influence on pressure transient curve of late and middle flow regime, and they can cover up some flow regime of late and middle flow regime. Model verification indicates that semi -analytical solving method combining with high -precision boundary element method can enhance calculation accuracy of early flow regime.