塔里木盆地北缘库拜煤田陡倾斜煤储层纳米孔隙特征及其地质控制

贺小标¹　李　鑫¹　魏永恒¹　田继军¹　琚宜文^2,3

杨曙光⁴王文峰¹　吴　斌⁵　王　猛¹

（1.新疆大学地质与矿业工程学院 乌鲁木齐 830047；2.中国科学院计算地球动力学重点实验室 北京 100049；3.中国科学院大学地球与行星科学学院 北京 100049；4.新疆维吾尔自治区煤田地质局煤层气研究开发中心 乌鲁木齐 830091；5.新疆维吾尔自治区煤田地质局一六一地质勘探队 乌鲁木齐 830009）

摘　要　近年来新疆塔里木盆地北缘库拜煤田陡倾斜煤储层成为我国煤层气勘探开发新热点，部分煤层气井相继取得高产。本次采集了库拜煤田陡倾斜储层不同深度及煤体结构共61块煤样，通过煤岩组分与成熟度、低温液氮吸附、等温吸附等实验，分析了陡倾斜煤储层纳米孔隙结构特征及其地质控制。结果表明：受控于南天山山前冲断带内部不同部位剪切及挤压强度的非均质性，库拜煤田陡倾斜储层纳米孔隙体积随深度增加先增大后减小；随煤体破坏程度的增大，煤岩纳米孔隙体积相应增加且其孔隙结构复杂程度趋于复杂；陡倾斜储层倒转位置煤体变形相对增强，构造煤发育程度较高，煤岩纳米孔隙体积以及比表面积相应增大，甲烷吸附能力强、含气性较好。研究成果对陡倾斜储层煤层气勘探和开发具有重要指导意义。

关键词　煤层气　孔隙结构　吸附孔隙　煤体结构　库拜煤田

Nano-pore characteristics and their geological control of the steeply inclined coal reservoir in the Cubey coalfield, the northern Tarim Basin

He Xiaobiao¹　Li Xin¹　Wei Yongheng¹　Tian Jijun¹

Ju Yiwen²　Yang Shuguang³　Wang Wenfeng¹，Wu Bin⁴　Wang Meng¹

(1. School of Geological and Mining Engineering, Xinjiang University, Urumqi 830047; 2. College of Earth and Planetary Sciences，University of Chinese Academy of Sciences，Beijing 100049; 3. CBM Research and Development Center of Xinjiang Coal Geological Bureau, Urumqi 830091; 4. No.161 Geological Exploration Team, Bureau of Xinjiang Coalfield Geology, Urumqi 830009)

Abstract：In recent years, the steeply inclined coal reservoir in Cubey coalfield, northern margin of Tarim Basin, Xinjiang, has become a new hot spot for CBM exploration and development in China, and some CBM wells have achieved high production. In this paper, 61 coal samples were collected from different depths and coal structure of steeply inclined coal reservoirs in Cubey coalfield. Through the experiments of coal rock composition and maturity, low temperature liquid nitrogen adsorption and isothermal adsorption, the characteristics of nano-pore structure and geological control of steeply inclined coal reservoirs were analyzed. The results shows that: Controlled by the heterogeneity of shear and compression strength in different parts of the piedmont thrust belt in South Tianshan, the nano-pore volume of steeply inclined reservoir in Cubey coalfield increases first and then decreases with the increase of depth; With the increase of coal failure degree, the nano-pore volume of coal rock increases and the complexity of pore structure tends to be complex; The deformation of coal body at the inversion position of steeply inclined reservoir is relatively enhanced, and the development degree of tectonic coal is relatively high. The nano-pore volume and specific surface area of coal rock increase accordingly, and the methane adsorption ability is strong and the gas content is good. Results of this work can provide instructions on CBM exploration and development of the steep inclined coal reservoir.

Keywords　Coalbed methane,  Pore structure,  Adsorption pores,  Coal structure,  The Cubey coalfield

煤是一种具有复杂孔隙结构的多孔介质。煤中纳米孔隙（孔径＜100 nm）（琚宜文等，2018），主要包括微孔（孔径<10 nm）和过渡孔（10 nm<孔径<100 nm）（孔径划分据Xoдот（1966）），是煤层气的主要吸附空间（傅雪海等，2007；解得录等，2014；徐海飞等，2015）。揭示纳米孔隙在形貌、类型、结构复杂度、孔径分布、连通性等方面的特征有助于加深对煤微观储集空间的理解，对矿井瓦斯防治、煤层气资源评价与开发有重要意义（赵迪斐等，2017；聂百胜等，2018）。

国内外学者开展了大量煤纳米孔隙的相关研究，Hainbuchner et al.（2004）、琚宜文等（2005）分别通过小角度中子散射与小角度X射线散射等方法对煤微孔在变质环境中的显微变形过程、微孔分布及其表面特征进行了研究；范俊佳等（2013）利用低温氮气吸附等实验手段对不同煤储层条件下煤岩微孔结构进行了研究；姜玮等（2015）分析了煤储层孔隙特征对多煤层区煤层气开采的影响；高为等（2017）探讨了分形几何参数与煤储层孔渗性的关系；Lu et al.（2017）运用沉积学、煤岩显微组分、地层学来构建了新的沉积模型以揭示煤岩微观特征。新疆煤层气资源量占全国的26%，是中国未来重要的煤层气产能来源。与我国其它地区煤储层地质条件不同，新疆库拜煤田大部分地区煤储层倾角达到50°以上（张洲，2016），特别是库拜煤田铁列克东区煤储层倾角可达80°以上，部分煤层近乎直立甚至倒转，这种地质条件下煤储层的孔隙结构特征研究较薄弱。

鉴于此，本文针对新疆南天山山前冲断带内部不同部位剪切及挤压作用影响的塔里木盆地库车坳陷北缘库拜煤田陡倾斜煤储层不同深度的61件煤样，开展了煤岩组分与成熟度、低温液氮、等温吸附等实验，旨在探讨库拜煤田陡倾斜煤储层纳米孔隙特征及其地质控制因素。由此这项研究成果对我国陡倾斜储层煤层气勘探和开发具有指导意义。

图1　研究区位置及采样点分布图

Fig. 1　Location and sampling point distributions of the study area

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