煤层气与致密气合采敏感性因素的数值模拟

Numerical simulation of sensitive factors of commingled production of coalbed methane and tight gas

 王蕊¹ 石军太¹ 王天驹² 李宝生³ 陈诚⁴ 康晓凤¹

中国石油大学（北京）石油工程教育部重点实验室，北京 102249 中国石油集团工程技术研究院，天津 300450 中国石油集团海洋工程有限公司，天津 300451 中海油能源发展采油服务公司曹妃甸FPSO作业公司，天津 300457）

MOE Key Laboratory of Petroleum Engineering, China University of Petroleum, Beijing 102249, China Research Institute of Engineering Technology, CNPC, Tianjin 300450, China Offshore Engineering Co. Ltd., CNPC, Tianjin 300451, China Caofeidian FPSO Operation Company, Energy Development Production Services Company, CNOOC, Tianjin 300457, China)

 针对煤层气与致密气资源的重叠区，多层合采是提高开发效益的有效手段。综合考虑煤层气和致密气不同的赋存机理及渗流特性，建立一层煤与一致密层合采的数学模型。由该数学模型可知，各储层渗透率、原始地层压力、兰氏常数、临界解吸压力等与煤层气吸附特性相关的参数都是影响合采产能的敏感性因素。利用数值模拟的方法，以不同参考指标（产气贡献率、采出程度、累计产气量）为量度，有针对性地对各因素进行优化分析。结果表明：由于煤层与致密层的渗流机理与压降规律不同，当煤层渗透率大于致密层时合采效果较好；煤层气与致密气合采的合理压力差应小于2.1 MPa，否则，会发生倒灌现象，从而破坏储层，导致地层污染；临界解吸压力越大，兰氏压力越大，兰氏体积越小，则合采效果越好。

 Commingled production is an effective approach for improving development efficiency when coalbed methane and tight gas resources are superimposed. Considering different mechanisms and seepage characteristics, the mathematical model of commingled production is established. The model shows that the permeability, initial formation pressure, Langmuir constants and critical desorption pressure are sensitive factors influencing commingled production. Through numerical simulation, these factors are optimized and analyzed by different reference standards including gas contribution rate, recovery percentage and cumulative gas volume. The analysis result proves that because of the different percolation mechanism of coalbed methane and tight gas, the effect of commingled production is better when the permeability of coal seam is greater than that of tight gas formation; the best pressure difference is less than 2.1 MPa, and fluid will flow backward and cause the formation damage if the pressure difference is out of this range; with greater critical desorption pressure and Langmuir pressure, and less Langmuir volume, the effect of production is better.

10.6056/dkyqt201606027