煤层气采收率预测技术

煤层气预测采收率准确与否，直接影响着可采储量的计算精度。实际情况表明，按气藏分别赋予采收率值与采用综合平均采收率相比，可采储量计算结果有差异，而且地质储量越大差异也就越大。在对煤层气采收率预测方法评述的基础上，借助于已提交探明储量报告的研究成果，提出了使用数值模拟法和等温吸附曲线法综合求取采收率的方法：储量计算区内按气藏分别赋予采收率值，以达到提高可采储量的合理性、科学性和准确性的目的。陕西韩城煤层气田的探明储量采用综合法求取采收率，并获得了国土资源部的批准。该气田的3号、5号和11号煤层气藏采收率分别取值45.8%、53.1%和 48.3%。

METHODS OF PREDICTING CBM RECOVERY FACTOR

The accuracy of CBM recovery factor prediction will directly influence the calculation of recoverable reserves. The recoverable reserves calculated by assigning a recovery factor value to each gas reservoir are different from that calculated by using composite average recovery factor, and the difference between them enlarges along with the increasing geologic reserves of CBM. Based on an assessment of the prediction methods of CBM recovery factor and a study of the proved CBM reserve reports, it is proposed to calculate recovery factor of CBM by integrating numerical simulation method with isothermal adsorption curve method. A recovery factor value should be assigned to each CBM reservoir, so as to improve both rationality and accuracy. The integrated synthesis method is used to calculate the recovery factor of the proved CBM reserves in the Hancheng CBM field in Shaanxi province and the obtained recovery factors have been ratified by the Ministry of Land and Resources P. R. C. The No. 3, 5 and 11 CBM reservoirs of this field are assigned a recovery factor of 45.8%, 53.1% and 48.3% respectively.