摘要
我国煤储层地质条件复杂,煤矿瓦斯灾害严重,煤层气井产量普遍偏低,高效抽采技术是我国煤层气行业和煤矿安全生产迫切需要解决的瓶颈技术难题。以山西大宁井田低渗低压的3号煤层为对象,研发了水平井密集多簇压裂高效开发技术,并进行了工程试验,获得了高产开发效果。结果表明:①试验井LDP-02所在区段煤层的平均渗透率0.112×10-15 m^2,储层压力梯度3.7 kPa/m,多分支水平井平均日产量800~1000 m^3,直井平均日产362 m^3左右,具有典型的低渗低压低产储层特征。②产能模拟预测表明,采用15~25 m的簇间距,经过3.85~5.95 a排采,两簇裂缝末端中间位置煤层瓦斯含量可降低至8 m^3/t,满足煤矿生产要求;单段压裂可形成4簇有效裂缝,在液量1000 m^3、砂量50 m^3、排量10 m^3/min的条件下,单簇裂缝半长为64.1 m。③LDP-02井为一组U型水平井,水平井煤层段长920 m,分10段38簇压裂,每段3~4簇,簇间距11~23 m。④排采生产893 d,其中产气687 d,气产量长期稳定16000 m^3/d,已累计产气890×104 m^3,平均日产12955 m^3,日产量是同区段直井的20~36倍,是同井场多分支水平井的10倍以上。
Coal reservoirs are geologically complex and gas-related coal mine incidents and disasters are getting worse in China.as Also,some underperformance coalbed methane(CBM)wells are widely distributed.Effective gas production rate enhancement from low permeability and low pressure CBM seams is one of the key technical challenges for the CBM industry and coal mine safety.In this study,a novel technology was developed and high gas production rate was achieved in No.3 coal seam of Shanxi Formation in Daning coal mine,Qinshui basin,Shanxi Province.The outcomes of this study include four key points.Firstly,the No.3 coal seam is recognized as a typical low permeability and low pressure reservoir with low production in the studied coal field.Based on the observed data from six testing wells,the average permeability was estimated only 0.112×10-15 m^2 and the reservoir pressure gradient was 3.7 kPa/m.Average gas production rate was 362 m^3/d from 120 vertical wells,and average gas production rate was only 800-1000 m^3/d from a multi-lateral horizontal wells.Secondly,the horizontal well with multi-clusters fracturing technology was recommended for increasing gas production in this area.The key technical parameters were numerically optimized through a numerical modeling using COMET3.The optimized cluster spacing was found to be 15-25 m,and four clusters in a single stage fracturing were recommended.Fractures with 64.1 m semi-length can be effectively induced through pumping the well(in one stage)fluid of 1000 m^3,sand of 50 m^3 with an injection rate 10 m^3/min.Thus,the coal seam gas content can be reduced to 8 m^3/t at the middle of two clusters fractures end after 3.85-5.95 years production.Thirdly,a U-shape horizontal wells named LDP-02 was completed for a pilot trail.The pilot horizontal well with total length of 1445.6 m connected with a directional well.The horizontal section in coal seam was 920 m and was fully cased and cemented.The hydraulic fracturing was completed for the coal seam section of 920 m with 38 clusters in 10 stages.Each stage was designed as 3-4 clusters and cluster spacing was as close as about 11-23 m.Finally,this pilot well reached a continually stable daily gas production rate as high as 16000 m^3/d and an average of 12955 m^3/d depending a drainage period of 893 days and gas production period of 687 days.The cumulative gas production was 890×104 m^3.This production was 20-36 folds of vertical wells and 10 times of the multiple lateral horizontal wells in the same area.
作者
曹运兴
石玢
田林
李丰亮
曹永恒
董轼
周丹
CAO Yunxing;SHI Bin;TIAN Lin;LI Fengliang;CAO Yongheng;DONG Shi;ZHOU Dan(Institute of Resource and Environment,Henan Polytechnic University,Jiaozuo 454000,China;Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains Economic Region,Henan Province,Jiaozuo 454000,China;Henan International Joint Laboratory for Unconventional Energy Geology and Development,Jiaozuo 454000,China;Gas Geology and Engineering Research Center,Henan Polytechnic University,Jiaozuo 454000,China;Shanxi Lanhua Coal Mining Co.,Ltd.,Jincheng 048002,China;Henan Arks New Energy Co.,Ltd.,Jiaozuo 454000,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2020年第10期3512-3521,共10页
Journal of China Coal Society
基金
山西省科技重大专项资助项目(20111101003)。
关键词
低渗低压
煤层气
水平井
多簇压裂
高效抽采
大宁井田
low permeability and low pressure
coalbed methane
horizontal wells
multi-cluster fracturing
effective gas drainage
Daning coal mine
作者简介
曹运兴(1955—),男,河南鲁山人,教授,博士生导师,E-mail:yxcao17@126.com。
