南海北部陆缘盆地深水区油气勘探新认识及攻关方向

New insights and future research focuses on oil and gas exploration in the continental margin deepwater area of the northern South China Sea

南海北部陆缘盆地深水区已成为我国海洋油气勘探增储上产的重要领域,但由于构造演化史复杂,该区不同凹陷的沉积—构造特征、烃源岩生烃—储层成岩演化和成藏模式均存在明显差异。为准确认识该区油气勘探潜力和方向,基于前人研究成果和勘探实践,在综合分析烃源岩、储层、差异成藏等地质条件的基础上,剖析了南海北部陆缘盆地深水区成藏特征、油气勘探作业面临的挑战,并指出了下一步油气攻关研究方向。研究结果表明:①受地壳拆离作用及强烈薄化影响,该区地层沉积特征特殊,岩石地球物理性质多样;②软流圈差异抬升形成深水区独特的高热流背景,促使区域性湖相、煤型及叠合型等3类烃源灶快速、高强度生烃,生烃门限变浅;③深水盆地群的演化和成盆规模差异大,构造演化控制了盆地几何形态和储集体时空展布,深水区独特的板块构造位置、复杂的构造演化史、温压变化剧烈的地质特征等控制了油气成藏模式。结论认为:①该区油气勘探面临地震资料解析度低、规模有效储层预测困难、勘探成本高等技术与经济的双重挑战;②需要创新形成高地温背景下优质储层差异化分布规律的研究思路;③亟需提升勘探设备能力建设,攻关高效地震采集、“重磁电震”地球物理一体化采集处理、双井架钻探作业、多井段“一趟钻”等勘探关键技术,为我国海洋深水油气勘探开发的高质量发展做好理论和技术支撑。

The Continental margin deepwater area of the northern South China Sea is an important target of offshore oil and gas exploration in China.However,due to the complex tectonic evolution history,sags in this area are significantly different in sedimentary–tectonic characteristics,(source rock)hydrocarbon generation–(reservoir rock)diagenetic evolution process,and hydrocarbon accumulation model.To clarify the potential and direction of oil and gas exploration in the continental margin deepwater area of the northern South China Sea,based on previous studies and exploration practices,the geological conditions such as source rock,reservoir rock and differential hydrocarbon accumulation were analyzed.Then,the hydrocarbon accumulation characteristics and exploration challenges in the study area were dissected.Finally,the future research focuses were proposed.The study results are obtained in three aspects.First,as a result of crustal detachment and intense thinning,the strata in the study area exhibit unique sedimentary characteristics and diverse petrophysical properties.Second,the differential rise of asthenosphere created the special high heat flow setting in the deepwater area,which promoted the rapid and intense hydrocarbon generation of three types of source kitchens(regional lacustrine facies,coal-measure,and superposed),accompanied with shallowing hydrocarbon generation threshold.Third,deepwater basins vary greatly in evolutional and basin-forming scales,and the tectonic evolution has controlled the basin geometry and the spatiotemporal reservoir distribution.Furthermore,the unique plate tectonic location,complex tectonic evolution history,and geological feature of dramatic temperature and pressure change in the deepwater area have dominated the hydrocarbon accumulation model.It is concluded that the exploration in the deepwater area of the northern South China Sea is challenged technically and economically by,for example,low accuracy of seismic data,difficult prediction of effective and large-scale reservoirs,and high costs.Therefore,it is necessary to(1)define an innovative approach for identifying the differential distribution of high-quality reservoirs in high geothermal setting,and(2)upgrade the exploration equipment and develop/improve key exploration technologies including efficient seismic acquisition,gravity-magnetic�electric-seismic-based geophysical acquisition and processing,dual-derrick drilling,and multi-section drilling in one trip,providing theoretical and technical support for the high-quality operations of deepwater oil and gas exploration and development in China.