复杂断陷盆地深层煤岩气地质特征、有利成藏因素及发育模式——以渤海湾盆地大港探区为例

Geological characteristics， favorable accumulation factors， and developmental models of deep coal-rock gas in complex fault-bounded basins： A case study of the Dagang exploration area in the Bohai Bay Basin

周立宏 陈长伟 韩国猛 李宏军 崔宇 董晓伟 宋舜尧 蒲秀刚 刘国全 甘华军

Lihong ZHOU Changwei CHEN Guomeng HAN Hongjun LI Yu CUI Xiaowei DONG Shunyao SONG Xiugang PU Guoquan LIU Huajun GAN

近年来，深层煤岩气勘探逐渐成为热门的非常规勘探领域，中国深层煤岩气的勘探主要集中在鄂尔多斯盆地，勘探与开发先导试验取得了重要突破，渤海湾盆地深层煤岩气勘探尚处于起步阶段。通过煤层岩心、测井和录井等地质资料，系统分析了大港探区上古生界深层煤层特征和有利成藏因素等，剖析了深层煤层生气、存储和保存机制，明确了上古生界深层煤岩气的发育模式。研究认为：① 大港探区上古生界深层煤岩气发育多套有利的甜点层段，煤层有机质丰度高，演化程度中等，生气强度较大。② 煤层具有多尺度孔缝结构，密集微裂缝规模发育提供了有效的储集空间。③ 煤层顶、底板以泥岩为主，保存条件较好。④ 受多期构造运动影响，煤层两次规模生气，复杂断陷背景下存在煤层风化-降解带、饱和吸附带和构造成藏带，深层煤层具有“超饱和”含气特征，煤层吸附气与游离气并存。据此建立了复杂断陷盆地深层煤岩气复式聚集发育模式，大港探区上古生界深层煤岩气理论研究与勘探实践对于渤海湾盆地深层煤岩气的勘探开发具有重要的指导与借鉴意义。

In recent years， deep coal-rock gas has gradually become a popular target for the exploration of unconventional hydrocarbons. In China， the deep coal-rock gas exploration is concentrated in the Ordos Basin， where breakthroughs in the exploration and production pilot tests have been achieved. In contrast， the exploration of deep coal-rock gas in the Bohai Bay Basin remains in its initial stage. Using geologic data of coal seams obtained from core observations and well logging， we systematically analyze the characteristics and favorable accumulation factors of the deep Upper Paleozoic coal seams in the Dagang exploration area. Furthermore， the mechanisms underlying the gas generation， storage， and preservation in deep coal seams are explored and the developmental model of the deep Upper Paleozoic coal-rock gas is thereby clarified. The results indicate that the Dagang exploration area contains multiple favorable sweet spot intervals for the deep Upper Paleozoic coal-rock gas occurrence， where the coal seams exhibit high organic matter abundance， moderate thermal maturity， and high gas-generating intensity. In terms of pore structure， these coal seams manifest multi-scale pores and fractures， with the large-scale， intensively distributed microfractures providing effective storage spaces. The roofs and floors of the coal seams are composed predominately of mudstones， creating favorable preservation conditions. The coal seams experienced two large-scale gas-generating processes under the influence of multistage tectonic movements. Against the backdrop of complex fault-bounded depressions， the coal seams exhibit weathering-degradation zones， saturated adsorption zones， and structural hydrocarbon accumulation zones， with its deep parts characterized by supersaturated gas-bearing properties and coexistence of adsorbed and free gas. Based on these findings， we establish a developmental model for the complex accumulation of deep coal-rock gas in a complex fault-bounded basin. The theoretical research and exploration practices of the deep Upper Paleozoic coal-rock gas in the Dagang exploration area serve as a significant guide and reference for the exploration and development of deep coal-rock gas in the Bohai Bay Basin.

10.11743/ogg20240613