Sha Tin Ping Carboniferous Low Permeability Gas Reservoir Production Decline Law Research

Caroniferous Gas Reservoir in East Sichuan have been recovered for many years, some of them were recovered for more than15years, which were in the middle&later period of developing.The pressure of reservoir is dropping fast, the production is declining quickly, The decline Law is not clear.So it’s very importanrt to study on the decline law of low permeaility reservoir and its impact factors.This paper summarized Geological and developping Characteristics of Shaguanping Gas reservoir.And calculated the productivity base on the imformation from productivity well testing and production data.The rational working system is determined through different method which are experienced method, gas-recovering curve, node analytical method and liquid carrying flow method.The results will be very useful for determine the impact factors of production decline. This paper summarized a variety of production decline analysing methods often-used.There are many method of analysing production decline, it could be summatized as traditional decline curves and modein typical curves.Elabolated the gas well productivity decreasing curve fitting method systemly. Analyzed the fitting condition and steps of using each curve method.And these method were used to analyse the productiion decline of gas resevior and its wells.The most suitable model for Gas resevior is Matthews—Leficovits model, and The most suitable model for most Gas wells is Logistic model.The recoverable reserves got form both traditional decline curves and modein typical curves are approximate.Moreover, this paper presents a new method of production prediction, which applise to the well its production is rising.It shows a good match when it was used to a Horizontal well. The main impact factors of gas well’s production decline are Physical Properties and the Formation pressure. The Formation pressure is unavoidable as the development proceeding, and it is more difficlut for Law permeaility reservoir to keep a stable production. And the production will drop fast when the well product beyond its productivity.Tihs is the main reason of formation pressure dropping fast at the early time.