莺歌海—琼东南盆地超压层系油气聚散机理浅析  

Mechanisms of natural gas accumulation and leakage in the overpressured sequences in the Yinggehai and Qiongdongnan basins,offshore South China Sea

作　　者：郝芳[1,2] 刘建章[1] 邹华耀[2] 李平平[2] 

机构地区：[1]中国地质大学(武汉)构造与油气资源教育部重点实验室,湖北武汉430074 [2]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249

出　　处：《地学前缘》2015年第1期169-180,共12页Earth Science Frontiers

基　　金：国家油气重大专项(2011ZX05023-006-07);国家自然科学基金项目(90914006)

摘　　要：文中讨论了超压层系天然气成藏的特殊性、超压圈闭油气聚散机理和油气成藏的超压强度上限。根据压力、应力状态和含油气性,将超压圈闭划分为充满型、部分充注型、未聚集型或油气散失型。通过钻孔证实,莺歌海、琼东南盆地的天然气聚散过程和含气性均与超压密切相关,其中DF13-1气田为充满型超压气藏,而YA21-1构造的储层水相压力已达到盖层破裂压力,盖层发生了周期性破裂并引起了明显的地球化学异常,属于未聚集或天然气散失型。超压圈闭天然气的聚散受最小水平应力、水相超压强度和盖层岩石力学性质等因素的控制。由于封闭性断层的开启压力低于地层的破裂压力,断层和底辟控制的砂体中天然气更易于散失。砂岩上倾尖灭点(岩性圈闭的顶点)的埋深对储层的压力状态和含气性具有重要控制作用。有效的压力、应力预测和盖层岩石力学性质研究是降低深层超压层系天然气勘探风险的重要途径之一。This article discusses the specific characteristics and mechanisms of natural gas accumulation and leakage in overpressured sequences.Based on the pressure,stress regimes and the petroleum-bearing properties,three types of overpressured reservoirs（filled,underfilled,unfilled or drained）are recognized.The charging history and gas-bearing properties of all drilled traps in the Yinggehai and Qiongdongnan basins are closely related to overpressure.The newly discovered DF13-1gas field is a filled overpressured gas reservoir,whereas the YA21-1structure represents unfilled or drained overpressured trap with water-phase pressure close to the fracture pressure of the top seal.The accumulation or leakage of natural gas in overpressured traps is controlled by the minimum horizontal stress,the intensities of water-phase pressure relative to seal fracture pressure,and the geomechanical properties of top seals.In the Yinggehai and Qiongdongnan basins,fault-and diaper-controlled overpressured traps may contain relatively short gas columns compared to lithologic traps with similar burial depth and water-phase excess pressure.The depth to the crest of lithologic traps played an important role in determining the pressure state and gas-bearing properties of the reservoirs.Effective prediction of the pressure and stress combined with the analysis of the geomechanical properties of the seals is an important way to reduce exploration risk.

关 键 词：超压 压力-应力耦合 盖层破裂 聚散机理 封闭潜力 莺琼盆地 

分 类 号：P618.13[天文地球—矿床学]