沁水盆地煤储层渗透率实验和模拟研究

Laboratory study and prediction on coal permeability of Qinshui basin

作为中国煤储层开发的一个关键参数,割理的可压缩性一直没有得到充分的研究。在本次研究中,从山西省沁水盆地选取了一些有代表性的煤样,并对这些煤样进行了包括He,N2,CH4和CO2四种气体在不同有效应力和温度下的实验研究。在实验数据的基础上,计算了兰氏常数并绘制出了兰氏曲线,并且也分别绘制了吸附和渗透率的曲线。实验结果表明:有效应力对煤储层的渗透率有重要的影响。在恒温35℃下,对于同一孔隙压力下的四种不同气体,随着有效应力的增加,渗透率是降低的。在实验结果的基础上,通过拟合数据计算出了割理的压缩系数。计算结果显示:对于四种测试气体,在恒温35℃下,随着孔隙压力的增加,割理的压缩系数呈现降低的趋势。此外,随着温度的增加,割理的压缩系数仅仅略微地增长。通过对实验结果的分析和资料研究,有效应力被认为是影响割理压缩性的重要参数。

As one key parameter for combed recovery, cleat compressibility has not been well studied in Chi- na. In this study, a Chinese coal sample from Qinshui Basin, Shanxi province, was measured using different gases, including He, N2, CH4 and CO2 with different effective stresses and temperatures. Based on the experi- mental data, the Langmuir constants were calculated and curves of adsorption and permeability were drawn, respectively. The experimental results show that effective stress has important effect on permeability. Permea- bility decreases with increasing effective stress under the same pore pressure for all four kinds of gases at con- stant temperature of 35 ℃. On the basis of experimental results, cleat compressibility was calculated by fitting data to equations. The calculated results also show that cleat compressibility decreases with increasing pore pressure at 35 ℃ for all four gases. Moreover, with increasing temperature, cleat compressibility increases only a little. Based on the analysis the experimental data and summary of literature, effective stress is considered by the authors as the key.