断洞体:非碳酸盐岩区油气大规模运聚的可能空间

Fault-cavity bodies: probable spaces for large-scale hydrocarbon migration and accumulation in non-carbonate rock areas

罗群 王千军 桂诗琦 贺小标 胡婉婧 张曰静 汪亮 曹旭明

LUO Qun WANG Qianjun GUI Shiqi HE Xiaobiao HU Wanjing ZHANG Yuejing WANG Liang CAO Xuming

1. 油气资源与工程全国重点实验室, 北京 102200; 2. 中国石油大学, 北京 102200; 3. 中国石化 胜利油田分公司, 山东 东营 257001

1. State Key Laboratory of Petroleum Resources and Engineering, Beijing 102200, China; 2. China University of Petroleum (Beijing), Beijing 102200, China; 3. SINOPEC Shengli Oilfield Company, Dongying, Shandong 257001, China

碳酸盐岩沿断裂发育溶洞形成断溶体是很好理解的，毕竟碳酸盐岩容易被沿断裂活动的流体溶蚀，但在非碳酸盐岩区，流体对非碳酸盐岩的溶蚀作用有限，是否也能形成沿断裂发育的洞穴并能运聚和富集油气？为了证明在非碳酸盐岩区沿断裂也存在大型的洞穴，能形成油气运聚的重要空间，以准噶尔盆地西部车排子隆起为例，通过野外考察、岩心观察、钻井分析、地震解释和物理模拟实验等途径和手段，开展了断裂内部结构、洞穴分布发育特征及油气差异运聚的研究，提出了在非碳酸盐岩区沿断裂的核部能够发育大型洞穴地质体即断洞体的观点。断裂活动中因断裂两盘活动而产生相对位移形成的空洞空间，即断洞体，它可以是断层两盘沿起伏的断层面(带)错动而产生，也可以是两盘沿断裂的倾向拉分而产生。断洞体的形成与溶蚀无关，与断裂面(带)起伏、走向断距或倾向断距、断裂产状及断裂两盘的运动方向有关。断洞体规模可能很大，主要分布于走滑断裂产状发生变化的部位或不同断裂的交叉部位，也可以发育在伸展或张扭应力集中且倾向断距明显的部位，断洞体能够聚集油气形成断洞体油气藏。断洞体的提出有利于解放思想，即在广大的碎屑岩、火山岩、变质岩等溶蚀作用不发育的非碳酸盐岩区，同样可以找到像塔河、顺北(富满)碳酸盐岩地区油气丰富的大型断层体油气藏。

In carbonate rocks, it is easy to understand that fault-cavity bodies form because they dissolve easily when fluids flow along faults, creating caves. However, non-carbonate rocks are not as easily dissolved by fluids. This raises the question of whether caves still develop along faults in such areas, and if so, whether they can facilitate the migration, accumulation, and enrichment of hydrocarbons. The study aims to demonstrate the existence of large caves along faults in non-carbonate rock areas, which are key spaces for hydrocarbon migration and accumulation. Taking the Chepaizi Uplift in the western Junggar Basin as an example, the internal structures in fault rocks, the distribution and development characteristics of caves, and differential hydrocarbon migration and accumulation were studied through field investigation, core observation, drilling analysis, seismic interpretation, and physical simulation experiments. This study suggests that large cave-like geological bodies, such as fault-cavity bodies, can form along fault cores in non-carbonate rock areas. The void space, formed by the relative displacement of two fault blocks during fault activity, is defined as a fault-cavity body. It can either form as the two fault blocks move along an undulating fault plane (zone), or they separate along the dip direction of the fault. The formation of fault-cavity bodies is not related to dissolution but is instead controlled by fault surface (zone) undulations, strike or dip separation, fault occurrence, and the movement direction of two fault blocks. fault-cavity bodies can be massive in scale and are often found where strike-slip fault occurrence changes, at the intersections of different faults, or in areas of concentrated extensional or transtensional stress with significant dip separation. These fault-cavity bodies can trap hydrocarbons, forming fault-cavity type hydrocarbon reservoirs. The concept of fault-cavity bodies challenges traditional perspectives, suggesting that in extensive non-carbonate rock areas, such as clastic, volcanic or metamorphic rock areas where dissolution effect is minimal, hydrocarbon-rich, large-scale fault-related hydrocarbon reservoirs, similar to those in carbonate rock regions of the Tahe and Shunbei (Fuman) oilfields can exist.

中国石化胜利油田技术项目(30200018-22-ZC0613-0123，30200018-20-ZC0613-0104)资助。

https://doi.org/10.11781/sysydz2025020248