碎软低渗煤层顶板水平井分段压裂煤层气高效抽采模式
|
摘要
碎软低渗煤层的煤层气高效抽采一直是制约我国煤层气产业化发展和煤矿瓦斯灾害防治的技术瓶颈。以安徽淮北矿区芦岭煤矿8号碎软低渗煤层为研究对象,通过开展现场调研、分析测试、理论分析、水力压裂物理模拟和数值模拟等工作,提出了碎软低渗煤层的煤层气顶板岩层水平井分段压裂高效抽采模式,揭示了该模式下水力压裂裂缝的扩展延伸规律及控制机理,构建了该模式实施的主要工艺流程。研究结果表明:顶板岩层相对脆性、裂缝扩展压力较高,碎软煤层相对塑性、裂缝扩展压力低。在顶板岩层水平井进行套管射孔和水力压裂,顶板岩层中产生的压裂裂缝,在垂向上向下扩展伸延并穿入碎软煤层;同时在水平方向上也快速扩展延伸,由此产生的牵引作用撕裂下部碎软煤层形成较长的压裂裂缝。数值模拟结果显示,在给定的压裂施工参数条件下,顶板岩层中压裂在碎软煤层中形成的压裂裂缝长度,是直接在碎软煤层中压裂形成的压裂裂缝长度的6.7倍。碎软煤层和顶板岩层中形成的这些压裂裂缝在后续加砂压裂过程中被充填,成为煤层气从下部煤层向顶板岩层水平井运移的导流通道。显然,采用这种抽采模式,碎软低渗煤层可以获得良好的压裂改造效果。研究成果应用于淮北矿区芦岭煤矿煤层气顶板岩层水平井抽采示范工程,取得了很好的产气效果,水平井单井曾连续3,6,12个月平均日产气量分别为10 358,9 039,7 921 m~3,截至2017-11-16,已累计产气500万m~3,日产气量仍在3 200 m~3以上,创造了我国碎软低渗煤层的煤层气水平井气产量的新记录。
Coalbed methane high efficiency production from broken soft and low permeable coal seams has been being a technical bottleneck of restricting coalbed methane industrialization development and coal mine gas control for many years.This paper has investigated the No.8 broken soft and low permeable coal seam in Lulling coal mine of Huaibei mining area in Anhui Province,China.Site investigation,sampling and testing,theoretical analysis,hydraulic fracture physical and numerical simulation have been performed.As a result,a new model of coalbed methane high efficiency production from broken soft and low permeable coal seam by roof strata-in horizontal well and staged hydraulic fracture has been presented,the hydraulic fracture extension and control mechanism under this model have been revealed,and the main technological processes of the model implementation have been given.The results show that the roof strata are relatively brittle and have high propagation pressures,while the broken soft coal seam is relatively plastic and has a low propagation pressure.When case perforation and hydraulic fracture are performed in horizontal well of the roof strata,the hydraulic fractures in roof strata,on the vertical,extend downward and penetrate the broken soft coal seam.At the same time,the hydraulic fractures also get rapid horizontal extension,and the traction engendered by this rapid horizontal extension rips the coal seam to form long hydraulic fractures in the coal seam.Numerical simulation results show that the hydraulic fracture length formed in the broken soft and low permeable coal seam when fracturing in roof strata is long as 6.7 times as that when fracturing directly in the coal seam.Those hydraulic fractures formed in the roof strata and the broken soft coal seam are filled with sand proppant in follow-up adding-sand fracturing,and come into being a coalbed methane migration pathway from the underlying coal seam to the roof strata-in horizontal well.It can be seen that broken soft coal seam can get a good fracturing stimulation effect in this new model.The results of this study are applied to the coalbed methane development demonstration project by roof strata-in horizontal well and staged hydraulic fracture in Luling coal mine of Huaibei mining area in Anhui province,China and have obtained a good gas production effect.The average daily gas production rate of the single coalbed methane horizontal well was respectively10 358 m~3,9 039 m~3,7 921 m~3 in three,six and twelve consecutive months.As of November,16,2017,this horizontal well already produced 5 million cubic meters of coalbed methane gas,and its daily gas production rate was still over 3 200 m~3.This has created a new record of gas production of a single coalbed methane horizontal well from broken soft and low permeable coal seam in China.
Coalbed methane high efficiency production from broken soft and low permeable coal seams has been being a technical bottleneck of restricting coalbed methane industrialization development and coal mine gas control for many years.This paper has investigated the No.8 broken soft and low permeable coal seam in Lulling coal mine of Huaibei mining area in Anhui Province,China.Site investigation,sampling and testing,theoretical analysis,hydraulic fracture physical and numerical simulation have been performed.As a result,a new model of coalbed methane high efficiency production from broken soft and low permeable coal seam by roof strata-in horizontal well and staged hydraulic fracture has been presented,the hydraulic fracture extension and control mechanism under this model have been revealed,and the main technological processes of the model implementation have been given.The results show that the roof strata are relatively brittle and have high propagation pressures,while the broken soft coal seam is relatively plastic and has a low propagation pressure.When case perforation and hydraulic fracture are performed in horizontal well of the roof strata,the hydraulic fractures in roof strata,on the vertical,extend downward and penetrate the broken soft coal seam.At the same time,the hydraulic fractures also get rapid horizontal extension,and the traction engendered by this rapid horizontal extension rips the coal seam to form long hydraulic fractures in the coal seam.Numerical simulation results show that the hydraulic fracture length formed in the broken soft and low permeable coal seam when fracturing in roof strata is long as 6.7 times as that when fracturing directly in the coal seam.Those hydraulic fractures formed in the roof strata and the broken soft coal seam are filled with sand proppant in follow-up adding-sand fracturing,and come into being a coalbed methane migration pathway from the underlying coal seam to the roof strata-in horizontal well.It can be seen that broken soft coal seam can get a good fracturing stimulation effect in this new model.The results of this study are applied to the coalbed methane development demonstration project by roof strata-in horizontal well and staged hydraulic fracture in Luling coal mine of Huaibei mining area in Anhui province,China and have obtained a good gas production effect.The average daily gas production rate of the single coalbed methane horizontal well was respectively10 358 m~3,9 039 m~3,7 921 m~3 in three,six and twelve consecutive months.As of November,16,2017,this horizontal well already produced 5 million cubic meters of coalbed methane gas,and its daily gas production rate was still over 3 200 m~3.This has created a new record of gas production of a single coalbed methane horizontal well from broken soft and low permeable coal seam in China.
引文
[1]张新民,庄军,张遂安.中国煤层气地质与资源评价[M].北京:科学出版社,2002.
[2]SCHRAUFNAGEL R A,HILL D G,MCBANE R A.Coalbed methane-a decade of success[A].Paper SPE28581,presented by at the60th Annual Technical Conference&Exhibition[C].New Orleans,1994:161-173.
[3]张群,冯三利,杨锡禄.试论我国煤层气的基本储层特点及开发策略[J].煤炭学报,2001,26(3):230-235.ZHANG Qun,FENG Sanli,YANG Xilu.Basic reservoir characteristics and development strategy of coalbed methane resource in China[J].Journal of China Coal Society,2001,26(3):230-235.
[4]叶建平,陆小霞.我国煤层气产业发展现状和技术进展[J].煤炭科学技术,2016,44(1):24-28,46.YE Jianping,LU Xiaoxia.Development status and technical progress of China coalbed methane industry[J].Coal Science and Technology,2016,44(1):24-28,46.
[5]张群.关于我国煤矿区煤层气开发的战略思考[J].中国煤层气,2007,4(4):3-5.ZHANG Qun.Strategic thinking on coal mine methane development in China[J].China Coalbed Methane,2007,4(4):3-5.
[6]尹清奎,焦中华.焦作某煤层气井田低产原因分析[J].中国煤层气,2012,9(3):16-19.YIN Qingkui,JIAO Zhonghua.Analysis of reasons for low yield of certain CBM well in Jiaozuo[J].China Coalbed Methane,2012,9(3):16-19.
[7]王鸿勋.水力压裂原理[M].北京:石油工业出版社,1987.
[8]李年银,赵立强,张倩,等.裂缝高度延伸诊断与控制技术[J].大庆石油地质与开发,2008,27(5):81-84.LI Nianyin,ZHAO Liqiang,ZHANG Qian,et al.Diagnosis method of artificial fracture vertical extension and the control technique of fracture height in fracturing or acid fracturing[J].Petroleum Geology and Oilfield Development in Daqing,2008,27(5):81-84.
[9]GIDLEY Johnl L.水力压裂技术新进展[M].北京:石油工业出版社,1995.
[10]HUBBERT M K,WILLIS D G W.Mechanics of hydraulic fracturing[J].Developments in Petroleum Science,1957,210(7):369-390.
[11]黄荣撙.水力压裂裂缝的起裂和扩展[J].石油勘探与开发,1981,27(5):62-74.HUANG Rongzun.Initiation and propagation of fractures in hydraulic fracturing[J].Petroleum Exploration and Development,1981,27(5):62-74.
[12]SIMONSON E R,ABOU-SAYED A S,CLIFTON R J.Containment of massive hydraulic fracture[J].Society of Petroleum Engineering Journal,1978,38(1):27-32.
[13]HANSON M E,SHAFFER R J.Some results from continuum mechanics analyses of hydraulic fracturing process[J].Society of Petroleum Engineering Journal,1980,20(2):86-94.
[14]万军凤,肖阳,王明.大牛地气田泥砂岩间互层穿层压裂影响因素分析[J].石油化工高等学校学报,2017,30(3):32-38.WAN Junfeng,XIAO Yang,WANG Ming.Effect factors for layer penetration fracturing of thin interbeds in Daniudi gas field[J].Journal of Petrochemical Universities,2017,30(3):32-38.
[15]吴奇,于去宏.水平井分段压裂优化设计技术[M].北京:石油工业出版社,2013.
[2]SCHRAUFNAGEL R A,HILL D G,MCBANE R A.Coalbed methane-a decade of success[A].Paper SPE28581,presented by at the60th Annual Technical Conference&Exhibition[C].New Orleans,1994:161-173.
[3]张群,冯三利,杨锡禄.试论我国煤层气的基本储层特点及开发策略[J].煤炭学报,2001,26(3):230-235.ZHANG Qun,FENG Sanli,YANG Xilu.Basic reservoir characteristics and development strategy of coalbed methane resource in China[J].Journal of China Coal Society,2001,26(3):230-235.
[4]叶建平,陆小霞.我国煤层气产业发展现状和技术进展[J].煤炭科学技术,2016,44(1):24-28,46.YE Jianping,LU Xiaoxia.Development status and technical progress of China coalbed methane industry[J].Coal Science and Technology,2016,44(1):24-28,46.
[5]张群.关于我国煤矿区煤层气开发的战略思考[J].中国煤层气,2007,4(4):3-5.ZHANG Qun.Strategic thinking on coal mine methane development in China[J].China Coalbed Methane,2007,4(4):3-5.
[6]尹清奎,焦中华.焦作某煤层气井田低产原因分析[J].中国煤层气,2012,9(3):16-19.YIN Qingkui,JIAO Zhonghua.Analysis of reasons for low yield of certain CBM well in Jiaozuo[J].China Coalbed Methane,2012,9(3):16-19.
[7]王鸿勋.水力压裂原理[M].北京:石油工业出版社,1987.
[8]李年银,赵立强,张倩,等.裂缝高度延伸诊断与控制技术[J].大庆石油地质与开发,2008,27(5):81-84.LI Nianyin,ZHAO Liqiang,ZHANG Qian,et al.Diagnosis method of artificial fracture vertical extension and the control technique of fracture height in fracturing or acid fracturing[J].Petroleum Geology and Oilfield Development in Daqing,2008,27(5):81-84.
[9]GIDLEY Johnl L.水力压裂技术新进展[M].北京:石油工业出版社,1995.
[10]HUBBERT M K,WILLIS D G W.Mechanics of hydraulic fracturing[J].Developments in Petroleum Science,1957,210(7):369-390.
[11]黄荣撙.水力压裂裂缝的起裂和扩展[J].石油勘探与开发,1981,27(5):62-74.HUANG Rongzun.Initiation and propagation of fractures in hydraulic fracturing[J].Petroleum Exploration and Development,1981,27(5):62-74.
[12]SIMONSON E R,ABOU-SAYED A S,CLIFTON R J.Containment of massive hydraulic fracture[J].Society of Petroleum Engineering Journal,1978,38(1):27-32.
[13]HANSON M E,SHAFFER R J.Some results from continuum mechanics analyses of hydraulic fracturing process[J].Society of Petroleum Engineering Journal,1980,20(2):86-94.
[14]万军凤,肖阳,王明.大牛地气田泥砂岩间互层穿层压裂影响因素分析[J].石油化工高等学校学报,2017,30(3):32-38.WAN Junfeng,XIAO Yang,WANG Ming.Effect factors for layer penetration fracturing of thin interbeds in Daniudi gas field[J].Journal of Petrochemical Universities,2017,30(3):32-38.
[15]吴奇,于去宏.水平井分段压裂优化设计技术[M].北京:石油工业出版社,2013.