Two-Phase Flow Model and Well Testing Analysis for Multi-Stage Fractured Horizontal Well in Shale Gas Reservoirs

Abstract

Two-phase flow in shale gas reservoirs is caused by water flowback after multi-stage fractured, this paper presents a two-phase pressure transient analysis model of multi-stage fractured horizontal well in shale gas reservoirs. With the new mathematics model, the two-phase flow characteristics and well testing analysis for early production period can be described. The two-phase flow model is established by material balance law, Langmuir isotherm law and Fick diffusion law. Accurate solution to this flow model is obtained by source function theory, Laplace transform, three-dimensional eigenvalue method and orthogonal transformation. According to the solution, bilogarithmic type curve of the two-phase flow model is illustrated, the pressure transient performance under the effects of hydraulic fractures and shale gas reservoir properties are discussed. It is found that there are seven different flow regimes which have been identified on the type curve of two-phase flow model, initial gas-water saturation, storage ratio and fractured stages have deeply impacted the type curve; absorption index, skin factor and interporosity flow coefficient have lower influence to the curve shape. According to the research results and field data of Lower Paleozoic shale in China, improved well testing analysis and dynamic monitoring have been provided. The research of this paper can make optimization design for the parameters selection of drilling and hydrofracture in shale gas reservoir.