Abstract: Wushi oilfield is a Cenozoic complex fault block oilfield developed in the eastern part of Wushi sag in Beibuwan Basin. It is also the third largest oil production base in the western part of the South China Sea, with the total proven reserves of 100 million tons and daily production of more than 1 000 m³. By reviewing the exploration and development history of Wushi oilfield, this paper systematically summarizes the geological conditions and characteristics for hydrocarbon accumulation, and key exploration and development technologies of the oilfield. On this basis, the following achievements and understandings are obtained. (1)The organic-rich lacustrine shale and oil shale of Liushagang Formation, which are widely distributed in the eastern part of Wushi sag, have laid a good material foundation for the formation of oil field. (2)Owing to the multi-source, multi-period and multi-stage tectonic-sedimentary evolution, many sets of favorable reservoir-cap assemblages are formed in the sag. (3)Several sets of regional stable mudstone caprocks were developed in the whole area during the lacustrine transgression period, providing favorable conditions for oil and gas preservation. (4)Multi-level oil source faults, sand body, structural ridges and unconformity surface constitute favorable hydrocarbon migration pathways. (5)Based on the dynamic and static accumulation factors, three typical hydrocarbon accumultion patterns are clarified in Wushi oilfield, including the lateral step-type in slope zone, three-dimensional composite type in uplift zone of the sag, and pumping type with fault-sand coupling in steep slope zone. (6)A series of supporting technologies with a focus on the high-resolution seismic data acquisition and processing technology, fine interpretation and evaluation technology for complex fault blocks, fine carving technology for large-scale reservoirs, and water flooding compatibility evaluation technology for offshore waterflooding oil fields have been established, which provide a technical guarantee for efficient exploration and production as well as capacity construction in Wushi oilfield. The research results are expected to provide some guidance and reference for the exploration and development of similar reservoirs in other basins at home and abroad.

Key words: complex fault block, low permeability reservoir, accumulation condition, key exploration and development technology, Wushi oilfield, Beibuwan Basin

摘要： 乌石油田是发育在北部湾盆地乌石凹陷东区的新生代复杂断块油田,也是南海西部第3大产油基地,累计探明储量达亿吨级,目前产油量超1 000 m³/d。通过回顾乌石油田的勘探开发历程,系统总结了油田的成藏地质条件、油气成藏特征及勘探开发关键技术,取得如下成果和认识:①乌石凹陷东区广覆式展布的流沙港组湖相富有机质泥页岩和油页岩为油田的形成奠定了良好的物质基础;②多物源、多期次、多阶段的构造-沉积演化在凹陷内形成了多套有利储-盖组合;③湖侵期在全区范围内发育的多套稳定分布的区域性泥岩盖层为油气的保存创造了有利条件;④多级油源断层与骨架砂体、构造脊及不整合面构成了有利的油气运移通道;⑤基于动、静态成藏要素分析,乌石油田可归纳出"斜坡带侧向阶梯式"、"洼中隆起带立体复式"和"陡坡带断裂-砂体耦合抽吸式"3种典型成藏模式;⑥以高分辨率地震资料采集与处理技术、复杂断块精细解释与评价技术、大型储集体精细雕刻技术及海上注水开发油田水驱配伍性评价技术等为核心的配套技术系列为乌石油田高效勘探开发和产能建设提供了技术保障。研究成果以期对国内外其他盆地同类型油藏的勘探开发起到一定的指导和借鉴作用。

关键词: 复杂断块, 低渗储层, 成藏条件, 勘探开发关键技术, 乌石油田, 北部湾盆地