Ji Changjiang, Song Zhimin, Li Guofu, Hao Haijin, Xin Kai, Guo Dingding, Zhang Jianghua
Henan Polytechnic University, Jiaozuo 454003, China.
State Key Laboratory of Coal and CBM Co-mining, Jincheng 048012, China.
ACS Omega. 2023 May 30;8(23):20810-20822. doi: 10.1021/acsomega.3c01278. eCollection 2023 Jun 13.
With the increase of the burial depth of the no. 3 coal seam in the Zhengzhuang minefield of Qinshui Basin, the production of surface coal bed methane (CBM) vertical wells was low. By means of theoretical analysis and numerical calculation, the causes of low production of CBM vertical wells were studied from the aspects of reservoir physical properties, development technology, stress conditions, and desorption characteristics. It was found that the high in situ stress conditions and stress state changes were the main controlling factors of the low production in the field. On this basis, the mechanism of increasing production and reservoir stimulation was explored. An L-type horizontal well was constructed alternately among the existing vertical wells on the surface to initiate a method to increase the regional production of fish-bone-shaped well groups. This method has the advantages of a large fracture extension range and a wide pressure relief area. It could also effectively connect the pre-existing fracture extension area of surface vertical wells, realizing the overall stimulation of the low-yield area and increasing the regional production. Through the optimization of the favorable stimulation area in the minefield, 8 L-type horizontal wells that adopted this method were constructed in the area with high gas content (greater than 18 m/t), a thick coal seam (thicker than 5 m), and relatively rich groundwater in the north of the minefield. The average production of a single L-type horizontal well reached 6000 m/d, which was about 30 times that of the surrounding vertical wells. The length of the horizontal section and the original gas content of the coal seam had a significant influence on the production of the L-type horizontal wells. This method for increasing the regional production of fish-bone-shaped well groups was an effective and feasible low-yield well stimulation technology, which provided a reference for increasing the production and efficiently developing CBM under the high-stress conditions in mid-deep high-rank coal seams.
随着沁水盆地郑庄井田3号煤层埋藏深度的增加，地面煤层气垂直井产量较低。通过理论分析和数值计算，从储层物性、开发工艺、应力条件和解吸特性等方面研究了煤层气垂直井产量低的原因。研究发现，高原地应力条件及应力状态变化是该井田产量低的主要控制因素。在此基础上，探索了增产增储机理。在地面现有垂直井间交替施工L型水平井，开创了鱼骨状井组区域增产方法。该方法具有裂缝延伸范围大、卸压面积广的优点，还能有效连通地面垂直井已有的裂缝延伸区域，实现低产区整体增产增储。通过对井田有利增产区域进行优化，在井田北部瓦斯含量高（大于18m³/t）、煤层厚度大（大于5m）且地下水相对丰富的区域施工了8口采用该方法的L型水平井。单井平均产量达到6000m³/d，约为周边垂直井的30倍。水平段长度和煤层原始瓦斯含量对L型水平井产量影响显著。这种鱼骨状井组区域增产方法是一种有效可行的低产井增产技术，为中深部高煤阶煤层在高应力条件下增产高效开发煤层气提供了借鉴。
