| Unconventional resources such as shale gas has become the focus of the oil and gas resources development in the world. Shale gas development has entered a high-speed development stage in recent years. However, at present both study for shale gas reservoir percolation mechanism and shale gas well production prediction at home and abroad is insufficient, which fail to predict rate decline for shale gas well accurately.Based on a large number of research literature at home and abroad, a method for rate decline analysis on multi-fractured horizontal well was presented which is more suitable for shale gas well, and a software names "shale gas productivity prediction and production dynamic analysis for multi-fractured horizontal well" was developed, which provides theoretical basis for shale gas development. The main research content are as follows:(1) Microscopic pore structure, the seepage and storage characteristics in shale gas reservoir was analyzed based on research literature.(2) A basic seepage model in finite shale gas reservoir is established considering seepage, desorption and diffusion effect. The seepage differential equation in integrated system in shale gas reservoir was derivated under steady and unsteady condition.(3) A muti-fractrured horizontal well in shale gas reservoir was simplified as five-linear-flow model based on the analysis of strorage, flow mechanism and microseismic monitoring of shale gas. Using methods in seepage mechanics, a mathematical five-linear-flow model of fractured horizontal well in dual-porosity formation was established considering shale gas desorption/adsorption and unsteady diffusion effect. Laplace’s transformation was used to solve the mathematical model and rate decline curve was drew in dimensionless coordinate. Then the parameters that may have influenced the curves were analyzed.(4) The asymptotic solution in real space on linear flow and double-linear flow stage was obtained through the analysis of characteristics of the rate decline curves. A method to analysis production data on linear and double-linear stage was presented.(5) A software names "shale gas productivity prediction and production dynamic analysis for multi-fractured horizontal well" was developed using VS2008based on the research results obtained. The software was compared with the commercial software in the case of well production prediction to validate the rationality of the model. The key factors affecting well production was investigated using the software. The actual production data was analyzed and horizontal well’s fracturing and formation parameter was interpretated. The results show that the established five-linear model and the software can be applied to the production prediction and dynamic analysis for multi-fractured horizontal wells of shale gas. |
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