渤海海域蓬莱9-1大型复合油田潜山发育演化及其控藏作用

Tectonic Origin and Evolution and Their Controls on Accumulation of Penglai 9-1 Large Composite Oilfield Buried Hill in Bohai Sea

蓬莱9-1大型复合油田是国内目前已发现的规模最大的中生界花岗岩潜山油田。本文立足渤海海域宏观构造演化，结合油气钻探实践结果，应用地质、地球物理和地球化学相结合的分析方法，阐述了蓬莱9-1花岗岩潜山形成的地质背景，探讨了该潜山构造成因演化及其对油藏形成的控制作用。结果表明，蓬莱9-1潜山花岗岩为受深大断裂诱导作用下主动构造侵位形成，其侵入时期为侏罗纪（160～170 Ma）中燕山构造幕，之后又经历了晚燕山运动和渤海湾升降运动两期构造抬升。蓬莱9-1花岗岩潜山构造演化可划分为四个阶段：岩浆侵入形成期、风化剥蚀夷平期、差异风化定型期和整体埋藏期。中生代以来，受到持续的走滑活动和构造应力叠加改造作用，蓬莱9-1潜山三面发育3条NW向及NE向深大断裂，同时使花岗岩潜山内幕形成大量不同规模的断裂和裂缝，极大改善了花岗岩储层的储集性能。另一方面两期适度的构造抬升进一步强化了花岗岩差异风化作用，形成南、北山头、中间鞍部的宏观古地貌，使得潜山花岗岩风化壳储层物性条件得以良好保存。综合蓬莱9-1花岗岩构造成因、演化阶段及成藏响应，蓬莱9-1潜山规模大、埋深浅，构造稳定，储集条件好、油源充足，是蓬莱9-1亿吨级潜山油田形成的关键因素。

The Penglai 9-1 large compoun d oilfield is the largest buried-hill granite oilfield related to the Mesozoic granite found recently in China. Based upon macroscopic geological background of the Bohai Sea area and drilling results, we discuss the geological background of the Penglai 9-1 granite buried-hill, its tectonic origin and evolution, and its controls on the hydrocarbon accumulation. The results show that the Penglai 9-1 buried-hill granite intruded during the Jurassic, i.e., the middle Yanshan tectonic episode （160-170 Ma）. The intrusion of the granite was affected by deep active faults and the granite buried hill experienced late Yanshan movement and Bohai lifting movement. Tectonic evolution of the Penglai 9-1 buried-hill can be divided into four phases： intrusion of granites, planation by weathering and erosion, stereotype by different weathering and integral burial. Since the Mesozoic time, affected by strike-slip movement and overlay tectonic stress, the Penglai 9-1 buried-hill developed three north-west and north-east deep faults. Meanwhile, a large number of faults and fractures of different sizes developed on the granite inner buried hills, which greatly improved the granite reservoir properties. On the other hand, two stages of appropriate tectonic uplift strengthened the granite weathering differences and formed a paleo-geomorphic with hilltop in the north and south, saddle in the middle which conducive to the preservation of weathering crust reservoir. Comprehensive analysis of the influence of the tectonic origin and evolution on the hydrocarbon accumulation shows that the Penglai 9-1 buried hill is a large scale, shallow burial, stable structure and excellent reservoir, so it is a key factor controlling the formation of the Penglai 9-1 large compound oilfield.