摘要
中国西南地区煤层气资源量十分丰富,且主要赋存于上二叠统煤系薄—中厚煤层群中,贵州地区虽然有近10年的煤层气规模化试采与探采工程实践,但仍存在低产井、低效井比例偏高的问题。为了推进贵州地区薄—中厚煤层群煤层气高效探采工作,在系统梳理织纳煤田文家坝区块地质条件、煤储层特征、开发工艺与开发效果基础上,分析了煤层气井高产及井间产气差异的地质控制因素,探讨了地质适配性分层压裂与合层排采技术。研究结果表明:①薄—中厚煤层群具有埋藏浅、含气性好、渗透率较高、储层压力欠压—正常的特征;②煤层气井高产既受阿弓向斜轴部构造应力集中、水力封堵作用下煤层气富集影响,同时也与浅埋藏条件下煤储层原始渗透性较高有密切关系,区内断裂构造与水文地质条件共同导致了丛式井组内井间产气效果差异;③应根据丛式井压裂煤层靶点间距及导水断层距离合理控制水力压裂施工规模,注前置液造缝阶段快速提升注入排量并非连续段塞增大裂缝延伸长度,注携砂液支撑阶段阶梯式连续加砂有效支撑裂缝;(4)长期维持小于0.5 MPa的低套压合层排采条件,缩短憋压持续时间,延长提产持续时间以提高稳产前的压裂液返排率,保证排采过程连续性以避免储层伤害,产气量提升阶段主动缓慢暴露上部产层。结论认为,文家坝区块具备煤层气探采的有利储层条件,浅埋藏背景下的煤储层特征及井区构造、水文条件共同影响到煤层气井的产气表现,选择与煤储层特征相匹配的分层水力压裂、合层排采工艺对提高煤层气采收率具有促进作用。
Abundant CBM resources are hosted in southwest China and mainly occur in the thin–medium-thick coal seams in the Upper Permian coal measure.Large-scale CBM trial production and exploration engineering have been operated in Guizhou for nearly 10 years,but there is still a high proportion of low production wells and low efficiency wells.To promote highly efficient CBM exploration and production in the thin–medium-thick coal seams in Guizhou,this paper systematically reviews the geological conditions,coal bed properties and development technology/effects of the Wenjiaba block in the Zhina coalfield.On this basis,the geological factors controlling high production and production differences between CBM wells were are analyzed,and the technologies of geological adaptive layered fracturing and commingled drainage and production were are discussed.The results are obtained as follows.First,the thin–medium-thick coal seams in the Wenjiaba block are characterized by shallow burial,good gas gas-bearing property,high permeability,and reservoirs with under-pressure and normal pressure.Second,the high production of CBM wells is affected by tectonic stress concentration in the axial of Agong syncline and CBM enrichment under the action of hydraulic plugging and is also closely related to the high original permeability of coal seam under shallow burial conditions.The fault structure and hydrogeological conditions in the area lead to the difference of production between wells in clusters.Third,the hydraulic fracturing scale should be optimized according to the spacing of fractured coal seam targets in the clusters.The technique of rapid increase of injection rate in the pre-pad stage but continuous fluid slug to increase the fracture length,and the stepped continuous sand adding in the sand carrying fluid stage to realize effective fracture propping should be implemented.Fourth,the commingled drainage and production conditions of low casing pressure less than 0.5 MPa are maintained for a long time,and the duration of pressure buildup is reduced,the duration of production increase is extended to improve the backflow rate of fracturing fluid before stable production,which ensures continuous drainage and production and avoids reservoir damage.The upper production beds should be exposed actively and slowly during the gas production increase phase.It is concluded that there is favorable reservoir conditions for CBM exploration and production in the Wenjiaba block.The coal bed properties,well block structures and hydrological conditions under shallow burial affect the production of CBM wells.The technique of layered fracturing and commingled drainage and production compatible with the coal bed properties enhances CBM recovery.
作者
陈畅然
周效志
赵福平
孟海涛
朱世良
赵有州
魏元龙
CHEN Changran;ZHOU Xiaozhi;ZHAO Fuping;MENG Haitao;ZHU Shiliang;ZHAO Youzhou;WEI Yuanlong(Key Laboratory of Coalbed Methane Resources&Reservoir Formation Process,Ministry of Education,Xuzhou,Jiangsu 221008,China;School of Resources and Geosciences,China University of Mining and Technology,Xuzhou,Jiangsu 221116,China;Key Laboratory of Unconventional Natural Gas Evaluation and Development in Complex Tectonic Areas,Ministry of Natural Resources,Guiyang,Guizhou 550009,China;Guizhou Engineering Research Institute of Oil&Gas Exploration and Development,Guiyang,Guizhou 550009,China;Guizhou Aoruian Clean Energy Co.,Ltd.of Shuicheng Mining Group,Bijie,Guizhou 552100,China)
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2023年第1期55-64,共10页
Natural Gas Industry
基金
国家自然科学基金项目“煤系气高效勘探开发的岩石力学地层理论方法体系研究”(编号:42030810)
贵州省地质勘查资金项目“贵州上二叠统龙潭组煤层气重点层段优选和丛式井完井及压裂技术研究与示范”(编号:208-9912-JBN-UTS0)
“毕节试验区煤层气资源调查评价与开发技术研究实施方案”(编号:52000021MGQSE7S7K6PRP)。
关键词
织纳煤田
文家坝区块
上二叠统
煤层气高产井
地质因素
工程因素
协同控制
水力压裂
合层排采
Zhina coalfield
Wenjiaba block
Upper Permian
High-production CBM wells
Geological factor
Engineering factor
Collaborative control
Hydraulic fracturing
Commingled drainage and production
