煤层气新钻井对老井产能的影响及其控制因素——以沁水盆地柿庄南地区为例

Impact of new coalbed methane wells on old well productivity and its controlling factors: a case study of Shizhuangnan block in Qinshui Basin

韩学婷 孟尚志 刘广景 任镇宇 陶树 门欣阳 韦子扬

HAN Xueting MENG Shangzhi LIU Guangjing REN Zhenyu TAO Shu MEN Xinyang WEI Ziyang

1. 中联煤层气有限责任公司, 北京 100015; 2. 中国地质大学(北京) 能源学院, 北京 100083

1. China United Coalbed Methane Corporation Ltd., Beijing 100015, China; 2. School of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China

针对沁水盆地柿庄南地区产能释放不均衡等问题，通过水平井加密方式调整优化初始井网以提高储量动用程度，但钻井泥浆、压裂液窜流至邻井现象频发，导致老井产能受到不同程度的影响。以柿庄南地区煤层气开发实践为基础，分析了该区井间干扰发生的主要原因及其对产能的响应，从地质和工程角度提出应对方法或新钻井部署建议。新钻水平井分段压裂是影响老井产能的主要方式，钻井影响井占比较低、产能恢复率较差且集中发生于近井地带(最小井距小于120 m)。压裂影响井最小井距普遍介于120～300 m，在550～900 m埋深范围内均有分布。被影响井生产异常主要体现为液柱回升，最小井距小于150 m或构造煤发育的部分老井伴有黑水产出、卡泵停机等现象。卡泵停机或黑水产出井产能恢复效率较低，卡泵停机井人工实时解卡产量可大幅恢复，但解卡失败，检泵作业后产气量降幅明显。受新钻井压裂影响的老井分布在新钻井水平段射孔方向，地质层面主要受控于水平主应力各向异性，不同井距条件下存在水力裂缝沟通和压裂液前缘波及两种方式。柿庄南地区煤储层水平应力差为5.5～13.5 MPa，压裂影响井平均水平主应力差普遍大于10 MPa，高水平应力差条件下水力裂缝的强定向性致使老井流体场受到扰动。新钻井部署应与老井最小井距大于300 m且规避断层，高应力差地带可通过暂堵压裂或缩小簇间距、强化缝间应力干扰以弱化其对老井产能的影响。

To address the issue of uneven productivity release in the Shizhuangnan block of the Qinshui Basin, the initial well pattern is optimized through horizontal well infill to enhance reservoir utilization. However, frequent occurrences of drilling mud and fracturing fluid migration to neighboring wells have resulted in varying degrees of effect to old well productivity. Based on the coalbed methane development in the Shizhuangnan block, the study analyzed the main causes for well-to-well interference and its impact on productivity. From the geological and engineering perspectives, countermeasures and suggestions on well deployment were proposed. The results revealed that staged fracturing of new horizontal wells is the primary cause impairing old well productivity. The proportion of wells affected by drilling is relatively low, with poor productivity recovery efficiency. The impact from fracturing is predominantly concentrated near the wellbore (minimum well spacing <120 m). The minimum well spacing for fracturing-affecting wells generally ranges from 120 to 300 m, with impact observed at burial depth between 550 to 900 m. The abnormal production in affected wells is characterized by the height increase in liquid water column. Some old wells, with a minimum well spacing of less than 150 m or developed tectonic coal, experience black water production and pump shutdowns. Wells with these issues exhibit lower recovery efficiency. While the production can be significantly restored by manual real-time unclogging, failure in unclogging results in a substantial decrease in gas production. Old wells affected by new well fracturing are distributed in the perforation direction of the horizontal section of new wells. Geologically, the distribution is mainly controlled by the anisotropy of horizontal principal stress. There are two propagation mechanisms depending on well spacing: hydraulic fracture communication and fracturing fluid front propagation. The horizontal stress difference in the coal reservoir of the Shizhuangnan block ranges from 5.5 to 13.5 MPa, with the average horizontal stress difference in the fracturing-affected wells greater than 10 MPa. Under high horizontal stress differences, the strong orientation of hydraulic fractures disturbs the fluid field of the old wells. To mitigate the impact, the deployment of new wells should maintain a minimum well spacing of over 300 m to the old wells and avoid faults. In areas with high stress differences, temporary plugging and diverting fracturing, reducing spacing between clusters, and enhancing stress interference between fractures can be employed to mitigate the fracturing impact on old well productivity.

国家自然科学基金面上项目(42272200)资助。

https://doi.org/10.11781/sysydz2025010195