柴达木盆地上石炭统和中侏罗统煤岩气地质特征与勘探方向

doi:10.3969/j.issn.1672-7703.2025.03.006

摘要/Abstract

摘要： 野外露头和钻井揭示柴达木盆地普遍发育古生界—中生界煤岩，具备一定的生烃潜力和良好储集性能，是盆地全新的勘探领域，但研究认识程度较低。通过对柴达木盆地中生界中侏罗统大煤沟组和古生界上石炭统克鲁克组煤岩沉积环境、煤岩分布、煤质特征、煤岩储层特征及煤岩气资源量和富集规律等方面开展系统研究，评价了柴达木盆地的煤岩气资源潜力，提出了勘探部署方向。研究表明：（1）中侏罗统湖沼相煤岩单层厚度为 2～30m，分布面积达11100km²；上石炭统海陆过渡相煤岩单层厚度为1～6m，分布面积为5689km²。（2）中侏罗统和上石炭统煤岩为半光亮—光亮煤，达到中煤阶演化阶段，均具有生气能力；中侏罗统大煤沟组煤岩TOC为32.22%～79.50%，平均为62.85%，R_o为0.77%～1.38%，平均为0.9% ；上石炭统克鲁克组煤岩TOC为35.67%～98.34%，平均为72.40%，R_o为 0.92%～1.82%，平均为1.57%。（3）煤岩储层孔渗性能好，割理密度高，呈网状分布，连通性好；气孔、铸模孔、溶蚀孔、晶间孔和植物组织孔等基质孔隙发育；煤岩实测孔隙度达5.26%～34.01%，平均为15.65% ；渗透率为5.11～12.60mD，平均为8.91mD。（4）纵向上发育5种煤岩气聚散组合，其中广泛分布的煤岩—泥岩与煤岩—石灰岩聚气组合，封闭条件好，录井全烃气测峰值高，是煤岩气富集的最佳组合。（5）优选柴达木盆地北缘圆顶山—九龙山地区中侏罗统和德令哈地区都兰—乌兰地区上石炭统有利区作为首选勘探战略部署区带。上述认识以期指导柴达木盆地煤岩气战略部署，开辟煤岩气勘探新领域，揭开盆地天然气勘探新篇章。

关键词: 柴达木盆地, 煤岩气, 上石炭统, 中侏罗统, 煤岩储层, 富集条件

Abstract: Field outcrops and drilling data reveal that the Paleozoic–Mesozoic coal rocks are widely distributed in Qaidam B asin, with certain hydrocarbon generation potential and good reservoir performance, which is a new exploration field in the basin. However, the level of research and understanding is relatively low. A systematic study on coal rocks in the Middle Jurassic Dameigou Formation and the Upper Carboniferous Keluke Formation in Qaidam Basin is conducted, including sedimentary environment, distribution, coal properties, reservoir characteristics, resource amount, and gas enrichment rules. In addition, gas resource potential in coal rocks is evaluated, and exploration deployment orientations are proposed in Qaidam Basin. The study results show that: (1) The limnic facies coal rocks in the Middle Jurassic have a single layer thickness of 2 – 30 m and a distribution area of 11100 km²; The transitional facies coal rocks in the Upper Carboniferous have a single layer thickness of 1 – 6 m and a distribution area of 5689 km². (2) The coal rocks in the Middle Jurassic and the Upper Carboniferous are semi-bright to bright coals in a middle coal rank stage, all possessing gas generation capacity; TOC of coal rocks in the Middle Jurassic Dameigou Formation is 32.22%–79.50%, with an average of 62.85%, and R_o is 0.77%–1.38%, with an average of 0.9%; TOC of coal rocks in the Upper Carboniferous Keluke Formation is 35.67%–98.34%, with an average of 72.40%, and R_o ranges in 0.92%–1.82%, with an average of 1.57%. (3) The coal rock reservoirs are characterized by good porosity and permeability properties, and the coal cleats have a high density, showing a reticular distribution pattern and good connectivity; The matrix pores such as stomata, mold pores, dissolution pores, intercrystal pores and plant tissue pores are observed; The measured porosity of coal rocks ranges from 5.26% to 34.01%, with an average of 15.65%; The permeability is 5.11–12.60 mD, with an average of 8.91 mD. (4) Five types of gas accumulation and dispersion combinations are classified vertically in coal rocks, among which the widely distributed coalrock–mudstone and coal rock–limestone gas accumulation combinations have good sealing conditions and high peak values of total hydrocarbon gas logging shows, indicating the most favorable combinations for coal rock gas enrichment. (5) The favorable areas of the Middle Jurassic in Yuandingshan–Jiulongshan area in the northern margin of Qaidam Basin and the Upper Carboniferous in Dulan–Wulan in Delingha area are optimally selected for further strategic exploration deployment. The above understanding is expected to guide the strategic deployment of coal rock gas in Qaidam Basin, open up a new field for coal rock gas exploration, and unveil a new chapter in natural gas exploration in the basin.

Key words: Qaidam Basin, coal rock gas, Upper Carboniferous, Middle Jurassic, coal rock reservoir, gas enrichment condition

中图分类号:

TE122.2

刘国勇, 张永庶, 薛建勤, 龙国徽, 马峰, 王波, 王永生, 张长好, 周飞, 田继先, 孙秀建, 吴志雄. 柴达木盆地上石炭统和中侏罗统煤岩气地质特征与勘探方向[J]. 中国石油勘探, 2025, 30(3): 75-88.

Liu Guoyong, Zhang Yongshu, Xue Jianqin, Long Guohui, Ma Feng, Wang Bo, Wang Yongsheng, Zhang Changhao, Zhou Fei, Tian Jixian, Sun Xiujian, Wu Zhixiong. Geological characteristics and exploration orientations of the Upper Carboniferous and Middle Jurassic coal rock gas in Qaidam Basin[J]. China Petroleum Exploration, 2025, 30(3): 75-88.

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