3种常用页岩气井经验递减方法——以四川盆地威远区块为例

页岩气井的递减规律与常规气井有一定的区别，分析页岩气井递减规律对准确评价页岩气井储量至关重要。经验递减法因为操作简单、有效而被广泛使用，但每种方法都有自身的缺陷及适用性，笼统的使用难免会造成很大的误差。分析了页岩气井的递减规律及SEPD法、Duong法及WK法这3种最为常用方法的特点，发现SEPD法是Arps指数递减的延伸，WK法是Duong法的延伸；并详细地给出了这些方法的应用步骤，结合四川威远区块的大量页岩气井得到了这3种方法的适用条件：①SEPD法不适用于页岩气井；②只有当气井进入边界流后，才可使用Duong法或WK法准确预测估算最终储量(EUR)；③数据波动对传统Duong法、WK法影响非常大。最后改进了Duong法中参数q1的获取途径，消除了数据波动对Duong法的影响，避免了Duong法多解性的问题；与WK法的对比，改进Duong法要优于WK法。

Research on three widely-used empirical decline methods for shale gas wells in Weiyuan block of the Sichuan Basin

The diminishing law of shale gas well is different from that of conventional gas well，thus to analyze the diminishing law of shale gas well is important for shale gas well in accurate reserves evaluation.Empirical methods have been widely introduced in the industry owing to their simplicity and efficiency，but each method has its own disadvantages and applicability，and general use of them without pertinence will inevitably cause a big error.The diminishing law of shale gas well has been discussed，and three most widely used empirical methods，including SEPD，Duong’s method and WK’s method，have also been analyzed with their characteristics and application steps.Further research of the three methods revealed that SEPD is the improvement of Arps’s exponential decline and WK’s method is the improvement of Duong’s method.Examples have been implemented to find out the application condition：(1)SEPD is not suitable for shale gas wells；(2)Only when the well is in boundary flow can use Duong’s method or WK’ method to predict EUR；(3)The fluctuation of production will make big errors in reserves evaluation by Duong’s method or WK’ method.At last improvement in obtaining the parameter q1 of Duong’s method has been proposed to eliminate the big errors caused by production fluctuation and avoid the problem of the multiple solutions in Duong’s method successfully，application results have shown that the improved Duong’s method is better than Wk’s method in production and EUR estimation.