国内埋深大于2 000 m的深层煤层气资源丰富，但整体勘探开发程度低，尚未有明确的开发规律认识和系统的开发地质理论。对比分析了鄂东缘大吉地区埋深大于2 000 m的深部煤层与1 000~1 500 m中深部煤层20项地质参数，对深部煤层单斜构造上的微幅构造区进行了精细刻画和分类，通过深部煤层气井生产特征规律、测井、工程改造参数及压裂曲线特征研究，发现煤层微幅构造差异对深部煤层气井高产控制作用明显，并从现象入手，深入剖析了深部煤层气赋存机理、开发机理及高产主控因素，预测了深部煤层气理想排采曲线，提出了与浅层煤层气排采曲线的异同之处。研究表明:① 深部煤层整体上展现了“高含气、高饱和”的优势和“煤体结构好、特低渗”的特征，生产井具有“见气时间短、见气时压力高、见气后产液量少”的特点;② 精细划分出斜坡构造上的5类微构造区，深部煤层气高产井主要分布在顶板封盖较好的正向微幅构造和平缓构造区，该区渗透性相对较好、易于加砂，生产井压裂施工压力相对低、稳产能力好，且稳产气量与施工排量、总加砂量呈现出明显的正相关;在中高加砂规模的前提下，位于正向微构造部位直井平均稳产水平为5 000 m3/d、平缓构造部位井3 500 m3/d;位于其他部位井试验了不同的工艺、施工排量、酸量、加砂规模，稳产水平1 500 m3/d;③ 不同于浅层开发机理“排水诱导解吸”，深部煤层气是“产气诱导解吸”;在一定深度高温状态对解吸占主导作用时，部分解吸出来的煤层气会以“游离态”赋存于煤层，开发初期表现为以“游离气”为主，生产特征类似页岩气;④ 认为深层煤层的致密性是制约深部资源能否开采出来的最关键因素，深部煤层具有原生结构煤的优势和特低渗的劣势，微幅构造在深部高压状态下对煤层渗透性有“放大”的效果，或者改善、或有较大影响，故除了压裂能改善有限的范围外，寻找渗透性相对较好、天然裂隙更发育的正向或平缓微构造部位，不仅有助于压裂改造效果，还有助于高产;⑤ 由于背斜构造比例少，建议将深部煤层的精细微幅构造研究，作为突破深部煤层气勘探开发的重要方向，可将正向微构造和平缓构造部位作为优选“地质-工程”双甜点部位;负向微构造和水平向挤压部位的压裂改造技术攻关，将是关系到未来深部煤层气是否能开拓更大战略场面必须要攻克的难题。研究为深部煤层气勘探开发方向、深部煤层甜点评价、针对性地开展工程技术对策攻关及深部煤层气井曲线合理生产制度的制定，提供了借鉴。

There are abundant deep coalbed methane (CBM) resources over 2 000 m deep in China,but the overall exploration and development level is low,and there is no clear understanding of development laws and systematic development geological theory.Based on the comparative analysis of 20 geological parameters between the deep coal seam with a buried depth of more than 2 000 m and the middle deep coal seam with a buried depth of 1 000-1 500 m in Daji area,the detailed description and classification of microstructural areas on monoclinic structure of deep coal seam are carried out.From the study of production characteristics,logging,fracturing parameters and fracturing curve characteristics of deep CBM wells,it is found that the difference of coal seam microstructure has obvious control effect on the high yield of deep CBM wells.From the phenomenon,the occurrence mechanism,development mechanism and main control factors of high yield of deep CBM are analyzed in depth,and the ideal production curve of deep CBM is predicted.Finally,the similarities and differences between deep and shallow CBM drainage curves are put forward.Research shows that ① the deep coal seam shows the advantages of “high gas content and high saturation” and the characteristics of “good coal structure and ultra-low permeability”.Deep CBM wells show the characteristics of “short time before gas breakthrough,high gas pressure at gas breakthrough,and little liquid production after gas breakthrough”.② Five types of micro structural areas on the slope structure are finely depicted.Deep CBM high-yield wells are mainly distributed in the positive microstructure and gentle zone of coal seam under good roof sealing,with relatively good permeability,easy sand addition,relatively low fracturing pressure and good stable production capacity.A stable gas production is significantly positively correlated with construction displacement and total sand addition.On the premise of medium high sand adding scale,the daily stable production of vertical wells in positive microstructure is 5 000 m3/d,and that of wells in gentle structure is 3 500 m3/d.The wells located in other parts are tested with different technologies,construction displacement,acid amount and sand adding scale,and the stable production level is 1 500 m3/d.③ Different from shallow CBM development mechanism “drainage induced desorption”,deep CBM development is “gas production induced desorption”.At a certain depth,when high temperature plays a dominant role in desorption,part of the desorbed CBM will exist in the coal seam as “free state”,and the “free gas” is the main form in the initial stage of development,in which the production characteristics are similar to shale gas.④ It is considered that the compactness of deep coal seam is the most critical factor to restrict the exploitation of deep resources.Deep coal seam has the advantages of primary structure coal and the disadvantages of ultra-low permeability.Under the condition of deep high pressure,the microstructure has “amplification” effect on the permeability of coal seam,or improves or has great influence.Therefore,in addition to the limited range of fracturing,the positive or gentle microstructure areas with relatively good permeability and more developed natural fractures should be targeted,which can not only help the fracturing effect,but also contribute to high production.⑤ Due to the low proportion of anticline structure,it is suggested that the fine microstructure research of deep coal seam be considered as an important direction to achieve a breakthrough in the exploration and development of deep CBM,and the positive and gentle structural parts can be regarded as the preferred “geological engineering” double dessert location.To tackle the key problems of fracturing technology in the negative microstructure and horizontal compression position will be a difficult problem that must be solved,which is related to whether the deep CBM can achieve a larger strategic development in the future.This study provides a strong theoretical basis for the exploration and development direction of deep CBM,the deep CBM desserts evaluation,the engineering and technical countermeasures and the reasonable production system establishment of deep CBM wells.

1 深部煤层与中深部煤层地质特征对比

   1.1 区块概况

   1.2 深部与中深部煤层地质特征对比

2 深部煤层产气特征规律

   2.1 深部煤层气井的产气特征

   2.2 深部煤层的微构造特征

   2.3 深部煤层气井生产认识

3 深部煤层气高产主控因素与开发机理剖析

   3.1 影响深部煤层气高产的因素

   3.2 深部煤层正向微构造对高产主控作用的发现与启示

   3.3 深部煤层气开发机理、理想排采曲线模式与启示

4 结论