The Research Of Low Permeability Gas Reservoir Gas Well Production Decline Analysis And Prediction Methods

The diminishing of low permeability gas reservoir is of great significance for dynamic prediction of gas reservoir and the production planning work,aiming at production decline type understanding unclear or inaccurate result in diminishing of low permeability gas reservoir gas well,this article mainly study from the traditional type of Arps decline,decline rate and gas production of the following:The first is the method research of determining decreasing type.For traditional Arps method through the linear correlation coefficient to determine decreasing type of gas wells caused decreasing type difficult to determine,put forward by modern production instability analysis method to evaluate dynamic reserves as the standard,diminishing by comparing different types of gas well to optimization of technical recoverable reserves decline type;From the perspective of Arps hyperbolic decline general formula,derive and draw the different n values chart of dimensionless decline rate and recovery degree,engraving method and instability analysis dynamic reserves evaluation results are basically identical.The second is the research of declining rate influence factor.Gas well decrease along with the production time is changing,and related to reservoir,the working system,a typical low permeability gas well single-well numerical model is established,using the single factor analysis method,the decline rate change rule and the main influencing factors.The results show that the gas well decline rate is fast and slow decline in two stages,gas well into the decline rate decline period 2～3 years later become stable;Lapse rate as the permeability,gas saturation,increase with the increase of the wellhead pressure,along with the porosity,and decreases with the increase of well control reserves;The late production decline rate is not with the reservoir thickness,initial proration,formation pressure change and change.By orthogonal experiment design method,to determine the permeability for well control reserves and the master control factors influencing the low permeability gas well production decline.And then is the research of declining rate model.For well control reserves,permeability,formation pressure and gas production and other four major influence factors,using the response surface design,the decline rate and the factor of nonlinear regression model,in order to rapidly and accurately predict the decline rate.According to the prediction model,the well control reserves,the greater the permeability is smaller,the smaller decline rate.To reduce the gas well production decline rate in the process of production,it is suggested that to comprehensively consider the effect of various parameters on the decline rate,improve the well control reserves of gas well,as far as possible choose low permeability zone drilling Wells.Production decline model research of low permeability gas reservoir gas well.For low permeability gas well production decline after the first fast slow characteristics,such as the power law model for production decline is improved and examples of gas Wells both at home and abroad show that the improved model is higher than power law model fitting accuracy;Aimed at decreasing index changing in the process of decreasing,the new production decline analysis model is deduced,the instance analysis shows that the new model of low permeability gas reservoir production decline analysis has a good applicability.