煤层割理结构及其对井壁稳定的影响研究

doi:10.13809/j.cnki.cn32-1825/te.2020.04.007

摘要/Abstract

摘要：

为了阐明地应力非均质性和割理角度对煤层井壁稳定的影响,参考某地区基础物性、煤岩力学参数、割理宏微观结构及地应力状态,基于离散元数值模拟手段并结合最大位移和归一化塑性区域半径两种评价方法综合评价分析了地应力非均质性和割理角度对煤层井壁稳定的影响。数值模拟研究结果显示,在各向同性地应力条件下,割理角度对煤岩井壁稳定性的影响不大,随着地应力非均质性增大,割理角度对煤岩井壁稳定性的影响逐渐明显。随着割理角度的增加,井周最大位移有先增加后减小趋势。随着地应力非均质性的增加,由割理角度的变化产生的井周塑性区域半径各向异性越明显。因此在地应力差异较大的煤岩地层,不可忽视割理角度对井壁稳定的影响。研究成果可为研究区煤层直井及水平井的钻井方案设计提供参考。

关键词: 煤层, 井壁稳定, 地应力, 非均质性, 割理角度

Abstract:

In order to illustrate the influences of the in-situ stress heterogeneity and cleat angle on wellbore stability of coal seam, the following researches have been done. The basic physical properties, mechanical parameters, macro and micro structure of cleats and in-situ stress states of coal and rock in an area have been acquired. Based on the discrete element numerical simulation method, comprehensive evaluation and analysis of the in-situ stress heterogeneity and cleat angles on wellbore stability in coal seam has been conducted by two kinds of evaluation method i.e. the maximal displacement and normalized the plastic area radius. The results of the numerical simulation show that under the condition of isotropic in-situ stress, cleat angle has little influence on the borehole stability. With the increases of the heterogeneity of in-situ stress, the influence of cleat angle on borehole stability is becoming more and more obvious. The maximum displacement around the well increases first and then decreases with the increase of the cleat angle from 0° to 90°. Meanwhile, with the increase of in-situ stress heterogeneity, the anisotropy of the radius of the circumferential plastic area caused by the change of cleat angle becomes more obvious. Therefore, the influence of cleat angle on wellbore stability should not be ignored in coal and rock strata with great difference in in-situ stress. The research results can provide reference for the drilling plan design of vertical and horizontal wells of coal seam in the study area.

Key words: coal seams, borehole stability, in-situ stress, heterogeneity, cleat angle

中图分类号:

TE122

王跃鹏,孙正财,刘向君,梁利喜. 煤层割理结构及其对井壁稳定的影响研究[J]. 油气藏评价与开发, 2020, 10(4): 45-52.

WANG Yuepeng,SUN Zhengcai,LIU Xiangjun,LIANG Lixi. Study on cleat structure and its influence on wellbore stability in coal seams[J]. Reservoir Evaluation and Development, 2020, 10(4): 45-52.

图/表 8

图1

图2

表1

煤岩力学强度参数"

模拟参数	煤岩	面割理	端割理
密度 $ρ$ /（kg·m^-3）	1.36×10³
体积模量 $K$ /MPa	5.11×10³
剪切模量 $G$ /MPa	2.36×10³
内聚力 $C$ /MPa	7	0	0
内摩擦角 $?$ /（゜）	29.63	26.00	26.00
抗拉强度 $σ$ /MPa	2.0	0	0
法向刚度/MPa		2.0×10⁴	2.0×10⁴
切向刚度/MPa		1.0×10⁴	1.0×10⁴

表1

图3

图4

图5

图6

图7

参考文献 23

[1]	侯连浪, 刘向君, 梁利喜 , 等. 割理对煤岩加载过程能量演化特征影响数值模拟[J]. 煤炭学报, 2020,45(3):1061-1069.
	HOU L L, LIU X J, LIANG L L , et al. Numerical simulation of effect of cleats on energy evolution of coal and rock in loading process[J]. Journal of China Coal Society, 2020,45(3):1061-1069.
[2]	陈勉, 赵海峰, 金衍 , 等. 非连续介质力学模型预测煤层井眼稳定性[J]. 石油学报, 2013,34(1):145-150.
	CHEN M, ZHAO H F, JIN Y , et al. A discontinuous medium mechanical model for the sidewall stability prediction of coal beds[J]. Acta Petrolei Sinica, 2013,34(1):145-150.
[3]	刘洪林, 王红岩, 张建博 . 煤储层割理评价方法[J]. 天然气工业, 2000,20(4):27-29.
	LIU H L, WANG H Y, ZHANG J B . Evaluation method of cleats in coal reservoir bed[J]. Natural Gas Industry, 2000,20(4):27-29.
[4]	申瑞臣, 屈平, 杨恒林 . 煤层井壁稳定技术研究进展与发展趋势[J]. 石油钻探技术, 2010,38(3):1-7.
	SHEN R C, QU P, YANG H L . Advancement and development of coal bed wellbore stability technology[J]. Petroleum Drilling Techniques, 2010,38(3):1-7.
[5]	刘向君, 叶仲斌, 陈一健 . 岩石弱面结构对井壁稳定性的影响[J]. 天然气工业, 2002,22(2):41-42.
	LIU X J, YE Z B, CHEN Y J . Influence of rock weak plane texture on sidewall stability[J]. Natural Gas Industry, 2002,22(2):41-42.
[6]	GENTZIS T . A stability analysis of two horizontal CBM wells in the deep Mannville coals, Alberta Basin, Canada. Energy Sources Part A: Recovery Utilization & Environmental Effects[J]. Energy Sources, 2011,33(24):2281-2290.
[7]	屈平, 申瑞臣, 杨恒林 , 等. 节理煤层井壁稳定性的评价模型[J]. 石油学报, 2009,30(3):455-459.
	QU P, SHEN R C, YANG H L , et al. Evaluation model of wellbore stability in coal seam[J]. Acta Petrolei Sinica, 2009,30(3):455-459.
[8]	JING L . A review of techniques, advances and outstanding issues in numerical modeling for rock mechanics and rock engineering[J]. International Journal of Rock Mechanics & Mining Sciences, 2003,40(3):283-353.
[9]	李嗣贵, 邓金根, 李明志 . 节理破碎地层井壁稳定的离散元分析[J]. 岩石力学与工程学报, 2002,21(Z1):2139-2143.
	LI S G, DENG J R, LI M Z . Discrete element analysis on wellbore stability in jointed formation[J]. Chinese Journal of Rock Mechanics and Engineering, 2002,21(z1):2139-2143.
[10]	孙正财, 刘向君, 梁利喜 , 等. 煤层气井割理煤岩井壁稳定性影响因素分析[J]. 煤炭科学技术, 2018,46(4):117-122.
	SUN Z C, LIU X J, LIANG L X , et al. Analysis on impact factors of borehole wall stability of coalbed methane well[J]. Coal Science and Technology, 2018,46(4):117-122.
[11]	尹虎, 李黔, 郭亮 , 等. 离散单元法评价煤层井壁稳定性[J]. 天然气工业, 2012,32(11):59-63.
	YIN H, LI Q, GUO L , et al. Evaluation of wellbore stability in coal seams by use of the universal discrete element code(UDEC) method[J]. Natural Gas Industry, 2012,32(11):59-63.
[12]	屈平, 申瑞臣, 付利 , 等. 三维离散元在煤层水平井井壁稳定中的应用[J]. 石油学报, 2011,32(1):153-157.
	QU P, SHEN R C, FU L , et al. Application of the 3D discrete element method in the wellbore stability of coal-bed horizontal wells[J]. Acta Petrolei Sinica, 2011,32(1):153-157.
[13]	CUNDALL P A . The measurement and analysis of accelerations in rock slopes[D]. London: University of London, 1971.
[14]	KARATELA E, TAHERI A, XU C , et al. Study on effect of in-situ stress ratio and discontinuities orientation on borehole stability in heavily fractured rocks using discrete element method[J]. Journal of Petroleum Science and Engineering, 2016,139:94-103.
[15]	孙正财 . 煤岩力学井壁失稳机理研究[D]. 成都:西南石油大学, 2018.
	SUN Z C . Study on mechanism of mechanical borehole wall instability in coal rock[D]. Chengdu: Southwest Petroleum University, 2018.
[16]	Itasca Consulting Group Inc . UDEC(Universal Distinct Element Code) users manual, version 3. 0[M]. Minneapolis: Itasca Consulting Group, 1996.
[17]	邢纪波, 俞良群, 张瑞丰 , 等. 离散单元法的计算参数和求解方法选择[J]. 计算力学学报, 1999,16(1):47-51.
	XING J B, YU L Q, ZHANG R F , et al. Determination of calculating parameters and solution methods of discrete element method[J]. Chinese Journal of Computational Mechanics, 1999,16(1):47-51.
[18]	朱焕春, PATRICK A, 钟辉亚x . 节理岩体数值计算方法及其应用(二):工程应用[J]. 岩石力学与工程学报, 2005,24(1):89-96.
	ZHU H C, PATRICK A, ZHONG H Y . Numerical modeling methods and application in jointed rock mass, part 2: application in engineering practice[J]. Chinese Journal of Rock Mechanics and Engineering, 2005,24(1):89-96.
[19]	BRACE W F, BYERLEE J D . Recent experimental studies of brittle fracture of rocks[C]// paper ARMA-66-0058 presented at the 8th U. S. Symposium on Rock Mechanics（USRMS）, 15-17 September 1966, Minneapolis, Minnesota, USA.
[20]	李光泉 . 深部地质环境对井壁稳定性的影响[J]. 西南石油大学学报(自然科学版), 2012,34(1):103-107.
	LI G Q . The impact of geological environment on wellhole stability[J]. Journal of Southwest Petroleum University(Science & Technology Edition), 2012,34(1):103-107.
[21]	秦启荣, 邓辉 . 裂缝对石油井壁力学稳定性影响[J]. 西南石油大学学报, 2007,29(4):167-170.
	QIN Q R, DENG H . Influence of rock fractures on mechanical stability of well-wall[J]. Journal of Southwest Petroleum University, 2007,29(4):167-170.
[22]	SALEHI S, HARELAND G, NYGAARD R . Numerical simulations of wellbore stability in under-balanced-drilling wells[J]. Journal of Petroleum Science & Engineering, 2010,72(3-4):229-235.
[23]	HAWKES C . Assessing the mechanical stability of horizontal boreholes in coal[J]. Canadian Geotechnical Journal, 2007,44(7):797-813.