页岩含气量现场测试中损失气量的计算方法对比分析

Comparative analysis of calculation methods for lost gas in the field-test of shale gas content

作为一种直接测试方法,页岩气现场含气量测试技术已得到广泛应用,但其中损失气量的计算方法却各有不同。本研究对昭通示范区4口深度不同的页岩气井进行现场含气量测试,并对比3种常用的损失气量计算方法。分析表明:USBM方法计算的损失气量最小,平均值为2.51m3/t,占总含气量的50.31%～80.58%;采用Amoco曲线拟合法计算的损失气量最大,平均值为7.81m3/t,占总含气量的45.43%～96.06%;采用多项式拟合的结果居中,平均值为4.45m3/t,占总含气量的58.94%～89.35%。损失气量的计算结果主要受损失时间和计算方法的影响。虽然Amoco曲线拟合法的理论基础更清楚,但是对于长损失时间的样品,其计算结果明显偏大;USBM方法的理论基础虽然简单,但其适用性更强,计算结果更为合理。

As a direct method,the gas content test in field has been widely applied in shale gas industry,but various techniques were used to calculate the lost gas content.The field test of gas content is conducted in four shale gas wells in the Zhaotong area,and three methods were compared commonly used for calculating the lost gas amount.The analysis results show that the minimum lost gas is calculated by the USBM method.The average value is about 2.51 m3/t,accounting for 50.31%-80.58% of the total gas content. The maximum lost gas is calculated by the Amoco curve fitting method,with the average value about 7.81 m3/t, accounting for 45.43%-96.06% of the total gas content.And the median lost gas is calculated by the polynomial fitting method,with an average value of 4.45 m3/t,accounting for 58.94%-89.35% of the total gas content.It is considered that the calculation results of lost gas content are mainly affected by the lost time and calculation method.The theoretical basis of the Amoco curve fitting is clearer,but the calculation results are obviously larger for the samples with longer lost time.Although the theoretical basis of the USBM method is simple,its applicability is stronger and calculation results are more reasonable.