煤层气井低产原因及二次改造技术应用分析

我国多数煤层气储层低孔低渗、构造煤发育，储层改造效果难以保障，单井产气量和采收率低。选择高效的储层改造和增产技术，提高低效井产量，是当前煤层气产业发展的关键任务。本文系统剖析“地质储层条件、工程施工改造和排采管理控制”影响的低产原因，分析煤层气井二次改造相关技术及应用效果，为不同类型低效井针对性改造提供建议。煤层气井可二次改造的低产原因主要包括压裂裂缝扩展不足、裂缝/管柱煤粉堵塞和压降面积受限等，改造中需考虑煤体结构分布、初次裂缝形态、储层渗透性、产气产水量变化、排采及控制设备适用性等因素。二次改造技术分为物理法、化学法、微生物法和其他方法，物理法中二次水力压裂、间接压裂和无水压裂技术以及化学法中酸化增透和泡沫酸洗技术运用较广泛。二次改造应根据地质条件、初次改造效果、工程排采情况选择针对性技术，避免储层再次伤害，以实现有效改造，提高煤层气单井和井网产气量。

Analysis of low production coalbed methane wells and application of secondary reconstruction technologies

Most coalbed methane reservoirs in China are of low porosity, low permeability and with extensive structural coals, which is difficult to be reformed, resulting in low single well gas production and recovery rates.It is the the key target for the development of coalbed methane industry to choose high efficiency reservoir and well reconstruction technology to effectively improve low efficiency wells.This paper systematically dissects the reasons for low production under the influence of "geological reservoir conditions, engineering construction reforms and drainage management control", summarizes the related technologies and application effects of the secondary reconstruction of coalbed methane wells, and provides suggestions for targeted reforms of different types of low-efficiency wells.The secodary reconstructable low-yield factors in coalbed methane wells include insufficient fractures propagation, fractures/pipe coal fines blockage, and limited pressure drop area.During secondary reconstruction, the distribution of coal structure, primary fracture morphology, reservoir permeability, variations of gas and water production, and applicability of drainage equipment need to be considered.The secondary reconstruction technology covers physical, chemical, microbial, and other methods.Secondary hydraulic fracturing, indirect fracturing, and anhydrous fracturing in physical methods, as well as acidification and permeability increasing technology and foam acidification in chemical methods are widely used.In secondary reconstruction, the reservoir adaptability of the reconstruction technology should be analyzed based on the geological conditions, primary reconstruction results, engineering and drainage status, and the purpose of secondary reconstruction should be determined based on the engineering drainage situation.In the secondary reconstruction, re-damage of the reservoir should be avoided to achieve effective transformation and improve the coalbed methane production from single well and well patterns.