RESEARCH ON THE DYNAMIC PREDICTION MODEL OF HORIZONTAL WELL PRODUCTIVITY IN THE LOW-PERMEABILITY GAS RESERVOIR

The production process of gas reservoirs usually consists of two stages: pressure drop at constant rate and production decline at constant pressure, and the real gas PVT parameters change with pressure changes. In view of the production characteristics of the gas reservoirs, based on the steady seepage theory, considering the real gas PVT parameters with pressure changes, combining the material balance equation, a dynamic prediction model of the horizontal well productivity was established for the low-permeability gas reservoirs which considering the influence of the start-up pressure gradient, slippage effect and stress sensitivity, and the productivity characteristic was discussed by analyzing and calculating examples. The results showed that the bigger the start-up pressure gradient and deformation coefficient of permeability, the more decreasing extent of the stable production period, while the more slippage effect, the more increasing extent of the stable production period, and considering the high speed non-Darcy, the stable production period would decrease. The bigger the heterogeneity, the more decreasing extent of the stable production period, while the more length of the horizontal well, the more increasing extent of the stable production period. The bigger the gas production rate and bottom hole pressure, the more decreasing extent of the stable production period.