摘要
在煤层气开发过程中,地质条件不仅是煤层气开采的先决条件和地质保障,也直接影响了水力压裂施工,从而影响煤层气井的产能。以沁水盆地柿庄南区块施工参数相近的34口煤层气井为例,从地应力条件、煤体结构和煤层顶底板岩性组合3个方面具体分析了地质因素对煤层气井水力压裂效果的影响,进而对研究区压裂效果进行评价。结果表明:三向地应力的大小关系控制裂缝的延伸方向和缝长,煤体结构类型决定能否形成有效裂缝,煤层顶底板砂岩、泥岩厚度及比例影响裂缝能否穿透隔水层。应力比越小、水平主应力差系数越大、煤层中原生结构煤比例越高、煤层顶底板的泥岩隔水层厚度及比例越大,水力压裂效果越好,煤层气井的平均日产气量也越高。综合上述3方面地质因素,研究区中部地区具有易发育垂直裂缝的地应力特征,且煤层的原生结构煤比例和顶底板泥岩比例高,最有利于水力压裂裂缝的形成与延伸,该区域为水力压裂的优选区域。其次为南部及西南部地区,地应力和顶底板条件较好,但煤体结构破坏程度相对较大。研究区北部、东北部及东南部区域由于煤体结构破坏程度大、顶底板封闭性差等因素,在进行水力压裂时应尽量规避。建议在对煤层气井进行水力压裂时应根据煤层气井的地质条件进行压裂方案设计。
Geological conditions are predominant factors for developing the coalbed methane(CBM),and directly affect the hydraulic fracturing process,which results in the varying performance of coalbed methane wells.In this study,a total of 34 CBM wells with similar construction parameters were selected to analyze the effect of geological factors on the hydraulic-fracturing performance.Geological factors including crustal stress,coal texture and the lithological signature of roof and floor bed were analyzed and the fracturing effect were then evaluated.Results show that the magnitude of three-direction crustal stress controls the direction and the length of extended fractures.The type of coal texture determines whether effective fractures can be formed.The roof and floor of coal seam are mostly sandstones and mudstones,and their relative thicknesses affect whether the fractures can penetrate the aquifer.Better fracturing performance was found in the areas with smaller stress ratio,larger horizontal principal stress difference coefficient,higher proportion of the primary coal and larger thickness and proportion of the aquifer roof and floor.The production of CBM wells were recognized to be higher at such areas.The central part of the study area was characterized to develop vertical fractures,and to have a high proportion of the primary coal and high mudstone proportion in the top and floor,which makes it to be the primary area for hydraulic fracturing.The secondary targets for hydraulic fracturing are located in the south and southwest of the study area,where good crustal stress and roof-floor conditions could be found.In the north,northeast and southeast of the study area,however,the hydraulic fracturing should be avoided due to the large destruction of coal structure and poor sealing condition of roof and floor.It is suggested that the hydraulic fracturing scheme should be designed based on the geological conditions of coalbed methane wells.
作者
张迁
王凯峰
周淑林
唐书恒
张松航
闫欣璐
伊永祥
党枫
朱卫平
ZHNAG Qian;WANG Kaifeng;ZHOU Shulin;TANG Shuheng;ZHANG Songhang;YAN Xinlu;YI Yongxiang;DANG Feng;ZHU Weiping(School of Energy and Resources,China University of Geoscience(Beijing),Beijing 100083,China;MOE Key Lab of Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism,China University of Geoscience,Beijing 100083,China;Beijing Key Laboratory of Unconventional Natural Gas Geological Evaluation and Development Engineering,Beijing 100083,China;Coal Geological of Inner Mongolia Autonomous Region,Hohhot 010010,China;Unconventional Natural Gas Engineering Technology Research Center of Inner Mongolia Autonomous Region,Hohhot 010010,China;Zhejiang Normal University,Jinhua 321004,China;Exploration & Development Research Institute,Tuha Oilfield Company,Hami 839000,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2020年第7期2636-2645,共10页
Journal of China Coal Society
基金
国家自然科学基金资助项目(U1910205,41772159,41872178)。
关键词
水力压裂
煤层气井
地质因素
柿庄南区块
沁水盆地
hydraulic fracturing
CBM
geological factor
Shizhuangnan Block
Qinshui Basin
