Abstract: Marine carbonate hydrocarbon reservoirs in Tarim Basin are characterized by deep burial, considerable thickness, and substantial resource potential. The discovery of medium- to small-scale strike-slip fault-controlled fracture-vuggy hydrocarbon reservoirs has stimulated extensive exploration of deep and ultra-deep hydrocarbon resources, resulting in the identification of two billion-ton-level oilfields, namely the Shunbei oil-gas field and Fuman oilfield, in the Shuntuoguole low-uplift (Shunbei area) and its adjacent regions. Nevertheless, as exploration targets have progressively extended toward smaller-scale faults, such as secondary and lower-order faults, the increasing structural heterogeneity of fault-controlled reservoirs, the occurrence of abnormally high reservoir pressures, and elevated drilling risks have severely constrained the efficient exploration and development of fault-controlled hydrocarbon reservoirs. To elucidate the genetic mechanisms of abnormal formation pressure in fault-controlled hydrocarbon reservoirs, this study focuses on the fault zones of different orders in Shunbei area. Based on detailed characterization of these fault zones, integrated techniques including calcite U-Pb dating and microscopic analysis of hydrocarbon inclusions are employed to conduct a dynamic three- dimensional analysis of the fault-reservoir-trap-hydrocarbon accumulation system across different fault orders, thereby revealing the differential hydrocarbon accumulation processes and genetic mechanisms of abnormal formation pressure in fault-controlled fracture-vuggy reservoirs. The results indicate that reservoirs controlled by major and secondary fault zones are dominated by fracture-vuggy reservoirs. These two types of fault zones experienced sustained late-stage activity, significantly modifying the reservoir systems. In contrast, late-stage en echelon normal faults may have caused temporary trap breaching during their active periods, facilitating the upward migration of minor amounts of hydrocarbons and providing pathways for pressure dissipation. The formation pressure of these reservoirs has undergone an evolutionary process characterized by “normal pressure during early-stage hydrocarbon charging, weak pressure anomalies caused by hydrocarbon dissipation during multi-stage charging, and normal pressure maintained during late-stage charging”. By contrast, low-order fault zones are dominated by fracture-type reservoirs. These fault zones exhibit weak late-stage activity and favorable preservation conditions for fault-controlled traps. Due to the low storage space of fracture-network reservoirs, hydrocarbons tend to form relatively constant-volume reservoirs after charging. Under late-stage high-temperature conditions, in situ cracking of early-stage crude oil generates high-pressure or overpressure constant-volume hydrocarbon reservoirs. The formation pressure evolves through a process characterized by “normal pressure during early-stage charging, weak overpressure anomalies resulting from multi-stage charging, and high-pressure or strong overpressure anomalies induced by late-stage self-sealing cracking”. These findings further elucidate the distribution patterns of abnormal formation pressure in fault-controlled reservoirs and provide theoretical support for the efficient exploration and development of reservoirs controlled by faults of different orders.

Key words: fault-controlled fracture-vuggy reservoir, accumulation process, abnormal formation pressure, genetic mechanism, Shunbei oil-gas field, Tarim Basin

摘要： 塔里木盆地海相碳酸盐岩油气藏具有埋藏深、厚度大、资源潜力大的特征。中—小尺度走滑断控缝洞型油气藏的发现掀起了深层—超深层油气勘探的热潮，并在顺托果勒低隆起（顺北地区）及邻区发现了顺北油气田、富满油田2个十亿吨级大油田。但随着勘探对象逐渐向次级断裂、低序级断裂等更小尺度断裂拓展，断控储集体的结构非均质性变强、油气藏存在异常高压、钻井风险高等问题严重制约了断控油气藏的高效勘探开发。针对断控油气藏异常地层压力的成因机制问题，选取顺北地区不同序级断裂带作为研究对象，基于对不同序级断裂带的精细解析，利用方解石U-Pb定年、油气包裹体微观分析等技术手段，开展不同序级“断裂-储层-圈闭-油藏”动态立体解析，探索断控缝洞型油气藏的差异成藏过程与异常地层压力的成因机制。研究结果表明：主干断裂带和次级断裂带控制的储层以缝洞型储集体为主，这2类断裂带在晚期持续活动，对储层具有显著的改造作用，而晚期的雁列式正断层在活动期会导致圈闭短暂失封，为少量油气的向上运移、泄压提供了可能，其地层压力经历了“早期充注形成常压—多期充注的逸散形成弱压异常—晚期充注保持常压”的演化过程；低序级断裂带储层以裂缝型储集体为主，该类断裂带在晚期活动弱，断控圈闭保存条件好，缝网型储集体的储集空间有限，油气在充注后易形成相对定容的油藏，并在晚期高温条件下由早期原油的原位裂解形成高压或超压定容油气藏，其地层压力经历了“早期充注形成常压—多期充注形成弱高压异常—晚期自封闭裂解形成高压或强超压异常”的演化过程。研究结果进一步阐明了断控油气藏异常地层压力的分布规律，为不同序级断控油气藏的高效勘探开发提供了理论支撑。

关键词: 断控缝洞型油气藏, 成藏过程, 异常地层压力, 成因机制, 顺北油气田, 塔里木盆地