Abstract: Overpressured formation is widely developed in Yinggehai Basin. Dongfang and Ledong areas are in the heart of favorable gas accumulation in Yinggehai Basin. The Dongfang area is located in the center of the diapiric zone where the overpressure background formed relatively earlier(9~5 Ma)and the main provenance came from the Kuntum Uplift in the west. The Ledong area is situated in the Yingdong Slope where the overpressure ocurred relatively later(5~2 Ma),and its main provenance was from Hainan Uplift in the east. The comparative analysis of petrology and physical properties,hydrocarbon filling,and diagenetic characteristics of overpressured sandstone reservoirs of Miocene Huangliu Formation in Dongfang and Ledong areas are conducted,based on identification of thin sections under microscope,measurement of fluorescence of hydrocarbon-bearing thin sections and fluid inclusions,scanning electron microscope,electron probe,homogenization temperature of fluid inclusions,X-ray diffraction of clay minerals,etc. The result shows that: (1)Compaction and cementation of the Huangliu Formation in the Dongfang area are relatively weak,which resulted in relatively well physical properties(av. porosity is 17.68% and av. permeability is 11.11×10^-3 μm²)and corresponds to the late mesodiagenetic A. However,the Huangliu Formation in Ledong area is characterized by relatively strong compaction and cementation and lead to poor physical properties(av. porosity is 8.94% and av. permeability is 1.52×10^-3 μm²),corresponding to the diagenetic stage of the mesodiagenetic B. (2)The reservoir physical properties are mainly controlled by the sedimentation,overpressure and the diagenesis. The diagenetic characteristics and diagenetic-pore evolution of reservoirs are jointly affected by the provenance,depositional and subsidence centers,sedimentary facies,the timing of overpressure occurring and the scale of hydrocarbon filling. (3)To some degree,overpressure can minimize the compaction strength,inhibite the cementation and in turn,promote the dissolution.

Key words: formation overpressure, hydrocarbon filling, diagenetic evolution, Huangliu Formation, Yinggehai Basin

摘要： 南海莺歌海盆地内地层普遍发育超压,东方区和乐东区是莺歌海盆地天然气成藏有利区的核心地带。其中,东方区位于底辟带中心,超压形成时间较早(9—5 Ma),主要物源来自西部昆嵩隆起区;乐东区位于莺东斜坡带,超压形成时间较晚(5—2 Ma),主要物源区为东部海南隆起区。本研究通过铸体薄片、荧光薄片、扫描电镜、电子探针、含烃包裹体微束荧光分析、流体包裹体激光拉曼成分与均一温度、X射线衍射黏土矿物等分析测试研究方法,对东方区和乐东区超压背景下黄流组砂岩储集层的岩石学与物性特征、烃类充注与成岩作用特征进行对比分析。结果显示: (1)东方区黄流组砂岩的压实作用、胶结作用较弱,物性较好(平均孔隙度17.68%,平均渗透率11.11×10^-3 μm²),处于中成岩A期晚期;乐东区黄流组砂岩整体压实作用、胶结作用较强,物性较差(平均孔隙度8.94%,平均渗透率1.52×10^-3 μm²),处于中成岩B期。(2)研究区储集层物性主要受沉积作用、超压背景和成岩作用的控制。物源、沉积中心与沉降中心、沉积相类型,超压形成时间和烃类充注规模共同影响了储集层的成岩作用特征及成岩—孔隙演化过程。(3)超压在一定程度上抵抗了压实作用强度,抑制了胶结作用,促进了溶蚀作用。

关键词: 地层超压, 烃类充注, 成岩演化, 黄流组, 莺歌海盆地

CLC Number: 

• TE122.2