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中南大学学报(自然科学版)

Journal of Central South University

第51卷    第2期    总第306期    2020年2月

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文章编号:1672-7207(2020)02-0385-14
复杂地质条件区页岩气聚集差异性及其意义:以湘西北古生界为例
李智文1,郭建华1,秦明阳1,黄俨然1, 2,曹铮3

(1. 中南大学 地球科学与信息物理学院,湖南 长沙,410083;
2. 湖南科技大学 页岩气资源利用湖南省重点实验室,湖南 湘潭,411201;
3. 重庆科技学院 石油与天然气工程学院,重庆,401331
)

摘 要: 针对湘西北地区寒武系牛蹄塘组和奥陶系五峰组—志留系龙马溪组富有机质海相页岩勘探效果巨大差异,比较复杂地质条件区聚集特征,分析差异性原因,指出未来勘探方向。研究结果表明:1) 牛蹄塘组页岩有机质质量分数w(TOC)及厚度异常高,明显比五峰组—龙马溪组的高;2) 牛蹄塘组以热水沉积作用下的硅质页岩为主,黏土矿物以伊利石为主,而五峰组—龙马溪组以生物作用下的硅质页岩和硅质岩为主,黏土矿物主要为伊/蒙混层;3) 牛蹄塘组储层中孔(孔径为2~50 nm)和小孔(孔径<2 nm)更加发育,吸附能力比五峰组—龙马溪组的强;4) 牛蹄塘组热演化程度高,主要生气期与燕山—喜山期构造运动时期相一致;5) 牛蹄塘组含气量低,甲烷体积分数低,残余气体积分数超过65%;而五峰组—龙马溪组含气性较好,甲烷体积分数超过90%,解吸气体积分数超过50%。产生这种差异性的原因在于:不同的沉积环境影响页岩品质,尤其是w(TOC)及厚度;牛蹄塘组顶底板条件较差,影响页岩气保存;燕山—喜山期断裂与滑脱双重作用导致牛蹄塘组含气性较差。复杂地质条件区页岩气聚集的关键因素为:沉积条件控制页岩气聚集的物质基础,保存条件控制页岩气富集程度。未来牛蹄塘组勘探应该重视寻找“外源供给型”气藏,五峰组—龙马溪组应重视残留向斜内滑脱作用形成的“甜点区”。

 

关键词: 古生界;页岩气;聚集条件;差异性;滑脱层;外源供给型

Differences and significance of shale gas accumulation in complex geological condition area:a case of Paleozoic in northwestern Hunan
LI Zhiwen1, GUO Jianhua1, QIN Mingyang1, HUANG Yanran1, 2, CAO Zheng3

1. School of Geosciences and Info-Physics Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Shale Gas Resource Utilization of Hunan Province,
Hunan University of Science and Technology, Xiangtan 411201, China;
3. School of Petroleum Engineering, Chongqing University of Science and Technology,
Chongqing 401331, China

Abstract:Organic-rich marine shales are developed in the Cambrian Niutitang Formation(∈1n) and the Ordovician Wufeng Formation—Silurian Longmaxi Formation(O3w—S1l) in the northwest of Hunan Province, but exploration results are quietly different in the complex geological condition area, the differences in shale gas accumulation condition were compared, the reasons from multiple aspects were analyzed, and the exploration direction in the future was pointed out. The results show as follows. 1) The organic matter mass fraction and thickness of ∈1n are extremely high, which are obviously superior to those of O3w—S1l. 2) The lithology of ∈1n is dominantly composed of siliceous shale, which is affected during hydrothermal sedimentary. The clay mineral is dominated by illite. However, the lithology of O3w—S1l is dominated by siliceous shale and siliceous rock, which are closely related to biological action. The clay mineral is mainly I/S(illite-montmorillonite). 3) Mesopores (2-50 nm) and micropores (<2 nm) of ∈1n are more developed, and reservoir adsorption capacity of ∈1n is stronger than that of O3w—S1l. 4) Thermal evolution of organic matter is higher and tectonic movements from Yanshan to Xishan period are consistent with the main gas generation period of ∈1n.5) ∈1n has lower content of shale gas, lower volume fraction of methane(CH4) and more than 65% of residual gas. O3w—S1l has higher volume fraction of shale gas, more than 90% of CH4 and more than 50% of residual gas. The reasons for the difference are as follows. Different sedimentary environments affect characteristics of organic-rich shale, especially w(TOC) and thickness. Bad roof and floor conditions of ∈1n affect shale gas preservation. The double actions of fracture and detachment cause the high content of ∈1n. Therefore, the key factors of shale gas accumulation in complex geological condition area are proposed, i.e., sedimentary condition controls the material basis of shale gas accumulation, and preservation condition controls the degree of shale gas enrichment. In the future, the exploration of ∈1n should be focused on the search for “exogenous type” shale gas, while the exploration of O3w-S1l should be focused on “sweet spots area” created by detachment.

 

Key words: Paleozoic; shale gas; accumulation condition; detachment; difference; exogenous type

中南大学学报(自然科学版)
  ISSN 1672-7207
CN 43-1426/N
ZDXZAC
中南大学学报(英文版)
  ISSN 2095-2899
CN 43-1516/TB
JCSTFT
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