张聪,李可心,贾慧敏,等. 郑庄北中深部煤层气水平井产能影响因素及开发技术优化[J]. 煤田地质与勘探,2024,52(6):21−32. DOI: 10.12363/issn.1001-1986.23.09.0594
引用本文: 张聪,李可心,贾慧敏,等. 郑庄北中深部煤层气水平井产能影响因素及开发技术优化[J]. 煤田地质与勘探,2024,52(6):21−32. DOI: 10.12363/issn.1001-1986.23.09.0594
ZHANG Cong,LI Kexin,JIA Huimin,et al. Factors influencing the productivity and technology optimization of horizontal wells for moderately deep coalbed methane in the northern Zhengzhuang block[J]. Coal Geology & Exploration,2024,52(6):21−32. DOI: 10.12363/issn.1001-1986.23.09.0594
Citation: ZHANG Cong,LI Kexin,JIA Huimin,et al. Factors influencing the productivity and technology optimization of horizontal wells for moderately deep coalbed methane in the northern Zhengzhuang block[J]. Coal Geology & Exploration,2024,52(6):21−32. DOI: 10.12363/issn.1001-1986.23.09.0594

郑庄北中深部煤层气水平井产能影响因素及开发技术优化

Factors influencing the productivity and technology optimization of horizontal wells for moderately deep coalbed methane in the northern Zhengzhuang block

  • 摘要: 【目的】沁水盆地郑庄北中深部煤层气早期采用压裂直井开发,整体表现为低产低效。采用单支套管压裂水平井开发后,单井产量达到直井的10~50倍,目前已成为主体开发井型,但各井产量差异较大。为明确郑庄北中深部煤层气分段压裂水平井产能影响因素,改善开发效果。【方法】基于郑庄北部水平井开发实践,结合地质特征与工程参数,分析了中深部煤层气水平井产能的主控因素,并针对性提出实现中深部水平井高效开发的建议。【结果和结论】结果表明: 单支套管压裂水平井产能受地质和工程因素综合影响。地质条件下,中深部储层含气饱和度明显高于浅部储层,整体资源富集;高产井主要分布在构造曲率较小的平缓区域内;原生煤层射孔段数与水平井产气效果呈正相关关系;研究区水平主应力差介于8~16 MPa,且随埋深增加而增大,无法形成复杂缝网是导致前期产气效果差的原因。工程条件上,当井眼轨迹方位与最大水平主应力方位夹角为60°~90°时产气效果最好,井平均稳产气量可达到9 700 m3/d;水平段越长,煤层稳产气量越高;采用泵送桥塞射孔压裂方式的水平井产气效果明显优于油管压裂方式,稳产气量随压裂规模增加而显著提高,压裂参数中施工排量对改造效果的控制作用显著,当排量<7 m3/min时,水平井稳产气量整体小于2 000 m3/d;当排量增大到8~10 m3/min时,稳产气量逐渐增高;当排量保持在10~12 m3/min,稳产气量持续稳定在10 000~12 000 m3/d;当排量提高到16~18 m3/min时,稳产气量突破18 000 m3/d。最后,优选含气性、构造曲率、煤体结构、地应力等地质参数与水平段长度、压裂段数、单段压裂液量、单段压裂砂量、施工排量、砂比等工程参数,通过灰色关联法分析了中深部水平井产能主控因素。结果表明煤体结构和压裂规模是影响水平井产能的主要因素。提高原生煤层钻遇率与选点效率以及进一步提升施工排量及压裂规模是实现研究区中深部煤层压裂水平井更高产能的主要途径。

     

    Abstract: Objective Hydraulic fracturing of vertical wells was adopted during the early production of moderately deep coalbed methane (CBM) of the northern Zhengzhuang block in the Qinshui Basin, generally yielding low productivity and inefficiency. In contrast, single-casing fracturing of horizontal wells has increased the single-well production to 10‒50 times that of vertical wells, establishing horizontal wells as the dominant development well type. However, the horizontal wells differ greatly in CBM production. This study aims to determine the factors influencing the productivity of horizontal wells using staged fracturing for moderately deep CBM in the northern Zhengzhuang block and improve the production performance. Methods To this end, based on the production practice using horizontal wells in the northern Zhengzhuang block, combined with geological characteristics and engineering parameters, this study analyzed the dominant factors governing the productivity of horizontal wells for moderately deep CBM and proposed targeted suggestions for efficient production of horizontal wells. The results indicate that the productivity of horizontal wells using single-casing fracturing is influenced by both geological and engineering factors. Results and Conclusions The effects of geological conditions are as follows: (1) Moderately deep reservoirs exhibit significantly higher gas saturation than shallow reservoirs, generally boasting high resource enrichment. (2) Horizontal wells with high productivity are primarily distributed in gentle areas with low structural curvature. (3) There is a positive correlation between the number of perforation sections in primary coal seams and the gas production performance of horizontal wells. (4) The horizontal principal stress differences in the study area range from 8 to 16 MPa and increase with burial depth, posing challenges in the formation of complex fracture networks. This is the cause of the low gas production performance in the early stage. The effects of engineering conditions on the productivity of horizontal wells include: (1) The optimal gas production performance occurred when the included angle between the orientation of the wellbore trajectory and the azimuth of the maximum horizontal principal stress varied from 60° to 90°, with the average stable gas production rate of horizontal wells reaching up to 9700 m3/d. (2) Longer horizontal sections of horizontal wells were associated with higher stable gas production of coal seams. (3) The pumping bridge plug and clustering perforation fracturing technology yielded significantly higher gas production performance of horizontal wells than tubing fracturing, with the stable gas production increasing significantly with the fracturing scale. Among fracturing parameters, the fracturing fluid injection rate produced more significant controlling effects on fracture stimulation. Specifically, the stable gas production rate of a horizontal well was less than 2000 m3/d when the injection rate was less than 7 m3/min, increased gradually when the injection rate increased to 8‒10 m3/min, remained stably between 10000 and 12000 m3/d when the injection rate remained at 10‒12 m3/min, and exceeded 18000 m3/d when the injection rate increased to 16‒18 m3/min. Finally, based on optimal geological parameters such as gas-bearing properties, structural curvature, coal structure, and in-situ stress, along with optimal engineering parameters like horizontal section length, fracturing section number, the fracturing fluid volume and proppant volume for single-stage fracturing, fracturing fluid injection rate, and proppant concentration, this study analyzed the dominant factors influencing the productivity of horizontal wells for moderately deep CBM using grey relational analysis. The results indicate that coal structure and fracturing scale are the primary factors influencing the productivity of horizontal wells. Therefore, the principal methods for enhancing the productivity of horizontal wells through hydraulic fracturing for moderately deep coal seams in the study area include increasing the drilling rate and placement efficiency of primary coal seams, as well as further enhancing the fracturing fluid injection rate and fracturing scale.

     

/

返回文章
返回