煤层气储层应力敏感性定量表征及影响因素研究
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摘要
煤层气储层应力敏感性较强,对煤层气开发具有重要影响。采用不同区块天然煤样开展应力敏感性室内实验,应用应力敏感性系数和渗透率伤害系数2个参数评价了各煤样应力敏感性程度,并研究了煤阶、渗透率和储层气体压力等参数对煤岩应力敏感性的影响。结果表明:镜质组反射率R_o<1.7%时,煤阶越低,应力敏感性程度越大,渗透率伤害程度越高;而镜质组反射率R_o>1.7%时,煤阶越高,应力敏感性程度越大,渗透率损害程度越高;煤岩初始渗透率越高,应力敏感性系数越低,应力敏感性越弱,利用初始渗透率与其应力敏感性系数之间的经验公式可以估算煤岩应力敏感性,方便现场应用;储层气体压力越低,渗透率越高,越有利于煤层气开发,而煤岩应力敏感性系数和渗透率伤害系数也略高,需预防应力敏感性造成的渗透率伤害。
The stress sensitivity of coalbed methane reservoirs is strong, which has an important influence on the development of coalbed methane. Natural coal samples from different blocks were used to carry out stress sensitivity experiments, and two parameters, stress sensitivity coefficient and permeability damage coefficient were applied to evaluate the degree of stress sensitivity of coal samples. The stress sensitivity effects of coal rank, permeability and the gas pressure of a coal reservoir were studied. The results showed that when R_o is lower than 1.7%, the lower the coal rank is, the greater the degree of stress sensitivity is and the higher the extent of the permeability damage. When R_o is higher than 1.7%, the higher the coal rank is, the greater the degree of stress sensitivity is and the higher the permeability damage is. The empirical formula, put forward by this paper, between initial permeability and stress sensitivity coefficient can be used to predict the stress sensitivity coefficient of coal samples, which is convenient for pilot application. The lower the pressure of a gas reservoir is, the higher the permeability, which is advantageous for CBM development. However, lower gas pressure results in a slightly higher stress sensitivity coefficient and permeability damage coefficient, so avoiding stress sensitivity is important.
The stress sensitivity of coalbed methane reservoirs is strong, which has an important influence on the development of coalbed methane. Natural coal samples from different blocks were used to carry out stress sensitivity experiments, and two parameters, stress sensitivity coefficient and permeability damage coefficient were applied to evaluate the degree of stress sensitivity of coal samples. The stress sensitivity effects of coal rank, permeability and the gas pressure of a coal reservoir were studied. The results showed that when R_o is lower than 1.7%, the lower the coal rank is, the greater the degree of stress sensitivity is and the higher the extent of the permeability damage. When R_o is higher than 1.7%, the higher the coal rank is, the greater the degree of stress sensitivity is and the higher the permeability damage is. The empirical formula, put forward by this paper, between initial permeability and stress sensitivity coefficient can be used to predict the stress sensitivity coefficient of coal samples, which is convenient for pilot application. The lower the pressure of a gas reservoir is, the higher the permeability, which is advantageous for CBM development. However, lower gas pressure results in a slightly higher stress sensitivity coefficient and permeability damage coefficient, so avoiding stress sensitivity is important.
引文
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[16] 孟雅,李治平.覆压下煤的孔渗性实验及其应力敏感性研究[J].煤炭学报,2015,40(1):154-159. MENG Ya,LI Zhiping.Experimental study on the porosity and permeability of coal in net confining stress and its stress sensiti-vity[J].Journal of China Coal Society,2015,40(1):154-159.
[17] 陈振宏,王一兵,郭凯,等.高煤阶煤层气藏储层应力敏感性研究[J].地质学报,2008,82(10):1390-1395. CHEN Zhenhong,WANG Yibing,GUO Kai,et al.Stress sensitivity of high-rank coalbed methane reservoir[J].Acta Geolo-gica Sinica,2008,82(10):1390-1395.
[2] 熊波,刘坤,郭凯,等.基于X-CT技术对黔西滇东区域煤储层物性特征的研究[J].石油实验地质,2016,38(3):407-412. XIONG Bo,LIU Kun,GUO Kai,et al.Characterization of the physical properties of coal reservoirs in the western Guizhou and eastern Yunnan by X-ray computed tomography[J].Petroleum Geology & Experiment,2016,38(3):407-412.
[3] 陈振宏,陈艳鹏,杨焦生,等.高煤阶煤层气储层动态渗透率特征及其对煤层气产量的影响[J].石油学报,2010,31(6):966-969. CHEN Zhenhong,CHEN Yanpeng,YANG Jiaosheng,et al.Reser-voir dynamic permeability of high rank coalbed methane and its effect on the coalbed methane output[J].Acta Petrolei Sinica,2010,31(6):966-969.
[4] 贾慧敏,孙世轩,毛崇昊,等.基于煤岩应力敏感性的煤层气井单相流产水规律研究[J].煤炭科学技术,2017,45(12):189-193. JIA Huimin,SUN Shixuan,MAO Chonghao,et al.Study on single-phase flow water production law of coalbed methane well based on coal and rock stress sensitivity[J].Coal Science and Technology,2017,45(12):189-193.
[5] 田永东,武杰.沁水盆地南部高煤阶煤储层敏感性[J].煤炭学报,2014,39(9):1835-1839. TIAN Yongdong,WU Jie.Sensitivity of high-rank coal-bed methane reservoir in the southern Qinshui Basin[J].Journal of China Coal Society,2014,39(9):1835-1839.
[6] 杨延辉,陈彦君,郭希波,等.沁水盆地南部高煤阶煤岩渗透率压敏效应分析[J].煤炭科学技术,2015,43(12):152-156. YANG Yanhui,CHEN Yanjun,GUO Xibo,et al.Analasis on effect of stress sensitivity on permeability of high-rank coal in southern Qinshui Basin[J].Coal Science and Technology,2015,43(12):152-156.
[7] 陈刚,秦勇,杨青,等.不同煤阶煤储层应力敏感性差异及其对煤层气产出的影响[J].煤炭学报,2014,39(3):504-509. CHEN Gang,QIN Yong,YANG Qing,et al.Different stress sensitivity of different coal rank reservoir permeability and its effect on the coalbed methane output[J].Journal of China Coal Society,2014,39(3):504-509.
[8] 鲍清英,东振,张义,等.低煤阶应力敏感性机理及其对产气的影响:以二连盆地为例[J].煤炭学报,2017,42(3):671-679. BAO Qingying,DONG Zhen,ZHANG Yi,et al.Stress sensitivity mechanism of low-rank coal and its influence on gas production:a case study from Erlian Basin[J].Journal of China Coal Society,2017,42(3):671-679.
[9] 陈术源,秦勇,申建,等.高阶煤渗透率温度应力敏感性试验研究[J].煤炭学报,2014,39(9):1845-1851. CHEN Shuyuan,QIN Yong,SHEN Jian,et al.Temperature-stress sensitivity of high-rank coal permeability[J].Journal of China Coal Society,2014,39(9):1845-1851.
[10] 薛培,高潮.有效应力对保德区块煤储层渗透率影响研究[J].地质与勘探,2016,52(2):334-339. XUE Pei,GAO Chao.Study on influence of effective stress on coal reservoir permeability in the Baode block[J].Geology and Exploration,2016,52(2):334-339.
[11] 张羽,张遂安,杨立源,等.煤样三维渗透率应力敏感性试验研究[J].煤田地质与勘探,2016,44(3):51-56. ZHANG Yu,ZHANG Suian,YANG Liyuan,et al.The experimental study on stress sensitivity of three dimensional permeability of coal[J].Coal Geology & Exploration,2016,44(3):51-56.
[12] 贾慧敏,胡秋嘉,刘忠,等.缝应力敏感性对煤层气井单相流段产水影响及排采对策[J].中国煤层气,2017,14(5):31-34. JIA Huimin,HU Qiujia,LIU Zhong,et al.Influence of fractures stress sensitivity on water production law for the single-phase flow of CBM wells and drainage countermeasures[J].China Coalbed Methane,2017,14(5):31-34.
[13] 魏建平,李明助,王登科,等.煤样渗透率围压敏感性试验研究[J].煤炭科学技术,2014,42(6):76-80. WEI Jianping,LI Mingzhu,WANG Dengke,et al.Experimental research on sensibility of coal samples permeability under confining pressure[J].Coal Science and Technology,2014,42(6):76-80.
[14] 毕建军,苏现波,韩德馨,等.煤层割理与煤级的关系[J].煤炭学报,2001,26(4):346-349. BI Jianjun,SU Xianbo,HAN Dexin,et al.The relation between cleat frequency and coal rank[J].Journal of China Coal Society,2001,26(4):346-349.
[15] 陈世达,汤达祯,高丽军,等.有效应力对高煤级煤储层渗透率的控制作用[J].煤田地质与勘探,2017,45(4):76-80. CHEN Shida,TANG Dazhen,GAO Lijun,et al.Control of effective stress on permeability in high-rank coal reservoirs[J].Coal Geology & Exploration,2017,45(4):76-80.
[16] 孟雅,李治平.覆压下煤的孔渗性实验及其应力敏感性研究[J].煤炭学报,2015,40(1):154-159. MENG Ya,LI Zhiping.Experimental study on the porosity and permeability of coal in net confining stress and its stress sensiti-vity[J].Journal of China Coal Society,2015,40(1):154-159.
[17] 陈振宏,王一兵,郭凯,等.高煤阶煤层气藏储层应力敏感性研究[J].地质学报,2008,82(10):1390-1395. CHEN Zhenhong,WANG Yibing,GUO Kai,et al.Stress sensitivity of high-rank coalbed methane reservoir[J].Acta Geolo-gica Sinica,2008,82(10):1390-1395.