Quantitative characterization and influencing factor analysis of coal structure of deep coal reservoirs in Linxing area
GAO Xiangdong;ZHOU Shihao;GUO Hui;SUN Hao;ZHANG Mingda;LUO Chaowei;WANG Yanbin;WU Xiang
煤体结构的定量表征是煤储层研究的热点问题之一。为精细刻画煤体结构的空间分布,查明其差异分布的主控因素,通过煤岩取心观测,借助地质强度因子对煤体结构进行定量表征,结合不同煤体结构的测井响应,构建了基于测井曲线的煤体结构量化表征模型,预测了煤体结构的空间分布,探讨了沉积、构造、地应力、微观力学性能对煤体结构的影响特征。研究结果表明:密度、伽马、声波、井径测井对煤体结构响应灵敏,利用测井多元回归法可以显著提高煤体结构的判识精度。研究区煤体结构以原生−碎裂结构为主,其次为碎裂结构,发育少量的原生结构和碎裂−碎粒结构。整个研究区的煤体结构分布可以归纳为四大类七个小分区。发育在潮道、砂坪、泥坪、三角洲平原、泻湖环境中的煤层,其厚度逐渐变大,但煤体结构与煤层厚度没有明显的关系。然而,灰分含量与煤体结构的完整性呈正相关,研究不同沉积环境中灰分的变化规律是揭示沉积环境对煤体结构控制特征的关键。煤储层变形程度越大,煤体结构越破碎。原生结构煤、原生−碎裂结构煤、碎裂结构煤的平均构造曲率分别为8.4×10−6、18.7×10−6、25.7×10−6 m−1。断层发育区,煤体结构以碎裂结构为主。随着埋深增大,原位地应力增大,煤体结构完整性增强,地应力状态在此基础上进一步分化煤体结构。在浅部伸张−压缩过渡带以碎裂−碎粒结构为主;在深部压缩状态以原生−碎裂结构为主;在深部压缩−伸张过渡带碎裂结构的比例有所增加。煤岩微观力学性能受控于煤基质组分和显微孔隙结构。煤岩无机组分力学强度高于有机组分,且无机组分孔隙孔径比有机组分孔隙孔径小,则无机组分含量越高,煤岩力学强度越高,煤体结构越完整。该研究成果为煤层钻井施工、压裂改造、储层评价提供参考。
The quantitative characterization of coal structure is one of the hot topics in coal reservoir research. To finely characterize the spatial distribution of coal structure and identify the main controlling factors for its differential distribution, through observation and measurement of coal cores, quantitative characterization of coal structure using geological intensity factors, and statistics of logging response of different coal structures, a quantitative characterization model of coal structure based on logging curves was constructed. The spatial distribution of coal structure was predicted, and the influence characteristics of sedimentation, structure, in-situ stress, and micro-mechanical properties on coal structure were explored. The research results indicate that density, gamma-ray, interval transit time, and caliper loggings are sensitive to the coal structure, and the use of logging multiple regression method can significantly improve the accuracy of coal structure identification. The coals in the study area are mainly composed of primary-fragmented coals, followed by cataclastic coals, with a small amount of primary and cataclastic-granulated coals developed. The coal structure of the entire study area can be divided into four categories and seven small areas. The sedimentary environment can affect the coal structure by controlling the thickness of coal seam development. The thickness of coal seams developed in tidal channels, sand flats, mud flats, delta plains, and lagoon environments gradually increases, but there is no obvious relationship between coal structure and coal seam thickness. However, the ash content is positively correlated with the integrity of coal structure, and studying the changes in ash content in different sedimentary environments is the key to revealing the control characteristics of sedimentary environments on coal structure. The average structural curvature of primary structured coals, primary- fragmented structured coals, and cataclastic coals are 8.4×10−6, 18.7×10−6, 25.7×10−6 m−1, respectively. Where faults develop, the coal structure is characterized by cataclastic coals. As the burial depth increases, the in-situ stress increases, and the integrity of the coal structures are enhanced. Based on this, the in-situ stress state further differentiates the coal structures. In the shallow extensional and compression transition zone, the coal structure is mainly fragmented and fragmented; In the deep compression state, the primary fragmented structure is dominant; The proportion of fractured structures in the deep compression and extension transition zone has increased. The micro mechanical properties of coal are controlled by the composition of coal matrix and micro pore structure. The mechanical strength of inorganic components of coal is higher than that of organic components of coal, and the pore size of inorganic components is smaller than that of organic components. The higher the content of inorganic components, the higher the mechanical strength of coal, and the more complete the coal structure. This research achievement provides reference for coal seam drilling construction, fracturing transformation, and reservoir evaluation.
Ordos Basin;Linxing area;deep coal reservoir;coal structure;quantitative characterization
主办单位:煤炭科学研究总院有限公司 中国煤炭学会学术期刊工作委员会