莺歌海盆地乐东地区中深层储层发育特征及成因机理

为研究莺歌海盆地乐东地区中深层储层发育特征及成因机理，开展了岩石铸体薄片分析、扫描电镜观察、常规物性测试、压汞实验，并结合测井和测试资料、区域埋藏史、油气充注期次、超压成因资料，对其储层低渗成因及“甜点”储层发育机理进行了系统研究。结果表明：①乐东地区中深层储层砂岩以长石岩屑砂岩为主，砂岩成熟度较低。次生溶蚀孔隙发育，孔隙结构以大—中孔细喉型为主，储层物性以低孔低渗、特低孔特低渗型为主。②中深层储层经历了强压实作用，岩石中塑性矿物含量较高，抗压实能力弱，胶结物含量高，晚期形成的超压对储层保护作用有限，共同导致了储层渗透性较低。③“甜点”储层发育主要得益于溶蚀作用产生大量次生溶孔，且溶蚀流体主要为烃类充注携带的有机酸，构造作用以及温压环境对于储层物性的改善也均起到一定的建设性作用。该研究成果为莺歌海盆地中深层寻找次生孔隙发育带具有借鉴意义。

Development characteristics and genetic mechanism of mid-deep reservoirs in Ledong area,Yinggehai Basin

In order to research the development characteristics and genetic mechanism of mid-deep reservoirs in Ledong area of Yinggehai Basin,analysis of casting thin section,scanning electron microscope observation, physical properties test and mercury injection experiment were carried out. Combined with logging,well testing data,regional burial history,hydrocarbon charging time and overpressure genesis,a detailed study was carried out on the origin of low permeability and development mechanism of "sweet spots". The results show that:(1)The mid-deep reservoir sandstone in Ledong area is mainly feldspar debris sandstone with low maturity. The secondary dissolved pore is developed,and the pore texture of sandstone is dominated by large-medium pore and fine throat. The reservoir properties are mainly of low porosity and low permeability,ultra-low porosity and ultra-low permeability.(2)The mid-deep reservoirs have experienced strong compaction,and the high content of plastic minerals leads to weak compaction resistance. Not only that,the content of cement is high,and the overpressure formed in late stage has limited protective effect on the reservoirs,which results in the low permeability of the reservoirs.(3)The development of sweet spot reservoir is mainly due to a large number of secondary dissolved pores produced by dissolution,and the dissolution fluid is mainly organic acid carried by hydrocarbon charging. The structural action and temperature-pressure environment play a constructive role in improving reservoir physical properties. The research results can be used for reference in searching for secondary pore development zones in the mid-deep formation of Yinggehai Basin.