基于修正幂律指数递减的致密气井产能评价新方法

A new method for productivity evaluation of tight gas well based on modified power law exponential decline

致密气是我国天然气勘探开发的重要新领域之一,目前已经有许多致密气井投产,并积累了大量的气井试采动态数据。本文以有效分析致密气井现场试采数据进而指导气井下一步的生产为目标,研究气井不同渗流阶段瞬时递减率的变化规律,对常规气井幂律指数递减模型进行分段修正,引入直线段特征线分析方法,并给出了这种分析方法在致密气藏多段压裂水平井中应用的理论依据,将原来毫无章法的散点拟合求参变为直线拟合求参。研究表明,通过对产量的分阶段评价,降低了原有方法进行产能预测时极易出现的多解性问题;致密气井前期产量递减规律为修正幂律递减模式,后期为双曲递减模式。

Tight gas is a new and important type of energy in China.Nowadays many tight gas wells have been put into production,and lots of production data has been accumulated in the field.In order to analyze these data effectively and provide some guidance for the following production,change law of instantaneous decline rate has been put forward.On the basis of power law exponential decline model,some modifications have been made periodically and beeline analysis method has been introduced.The theoretical foundation has also been studied.Research shows that the method changes the previous method of striving parameters by unstructured scatter fitting into the new method by linear fitting,which will improve the accuracy of fitting and also will help to solve the problem of multiple solutions.And for tight gas well,the decline law is conforms to modified power law exponential decline mode in the early stage,lately,the hyperbolic decline maybe more reliable.