渤海湾盆地辽河坳陷西部冷家—雷家地区中-深层超压成因及其对油气成藏的影响

Overpressure in moderately deep to deep strata in the Lengjia-Leijia area， western Liaohe Depression， Bohai Bay Basin： Origin and effects on hydrocarbon accumulation

陈昌 邱楠生 高荣锦 周晓龙 孙永河 杨琳琳 付健

Chang CHEN Nansheng QIU Rongjin GAO Xiaolong ZHOU Yonghe SUN Linlin YANG Jian FU

为了研究渤海湾盆地辽河坳陷西部冷家—雷家地区中-深层超压发育形成机制及油气运移和成藏对该地区中-深层油气勘探的意义，基于实测地层压力和温度数据、测井数据及构造分析，对冷家—雷家地区中-深层超压发育特征、成因机制及超压在成藏过程中的作用进行了综合分析。研究表明：①冷家—雷家地区发育超压型、常压型和低压型3类地层温度-压力系统，其超压段主要集中在洼陷带的沙河街组三段（沙三段）和沙河街组四段（沙四段），深度约为2 500～4 000 m；②超压形成机制以欠压实作用为主，伴有生烃增压、成岩作用和构造挤压作用贡献；③冷家—雷家地区主要存在超压带内部的油气自生自储型运聚和油气从超压带向常压/低压带的跨压力系统运聚2种运聚模式，前者主要发生在洼陷带内的沙三段和沙四段超压带内部，后者则为断裂活动期陈家洼陷沙四段烃源岩中的油气在超压驱动下向雷家和高升构造带充注，及冷家地区沙三段下亚段-沙三段中亚段超压带中的油气通过砂体和断裂输导向东部陡坡带和兴隆台潜山运聚。

The moderately deep to deep strata in the Lengjia-Leijia area， western Liaohe Depression exhibit significant overpressure. It’s of great significance to understanding its genetic mechanism and its effects on hydrocarbon migration and accumulation in terms of hydrocarbon exploration therein. Based on measured formation pressure and temperature， log data， and structural analysis， we comprehensively investigate the characteristics and genetic mechanisms of overpressure in these strata and explore its role in hydrocarbon accumulation therein. The results indicate that the Lengjia-Leijia area is characterized by composite thermo-pressure system of the overpressure， normal-pressure， and underpressure types， with the overpressure interval predominantly found in the 3 and 4 members of the Shahejie Formation （also referred to as the Sha 3 Member and the Sha 4 Member， respectively） within the sub-sag zone， at depths ranging from 2 500 to 4 000 m approximately. The overpressure in the area primarily results from undercompaction， followed by a combination of hydrocarbon generation-induced pressurization， diagenesis， and tectonic compression. There exist two major hydrocarbon migration and accumulation modes in the study area： the self-sourced indigenous mode within overpressure zones and the cross-pressure mode from an overpressure zone to a normal-pressure/underpressure zone. The former is predominantly found within the overpressure zones of the Sha 3 and 4 members in the sub-sag zone. In contrast， the latter occurred during the period of faulting， including overpressure-driven hydrocarbon charging into the Leijia and Gaosheng structural zones from source rocks in the Sha 4 Member in the Chenjia sub-sag， and hydrocarbon accumulation in the eastern steep slope area and Xinglongtai buried hill in the Lengjia area after transporting through faults and sand bodies from the overpressure zones in the lower to middle sub-members of the Sha 3 Member.

10.11743/ogg20240109