琼东南盆地乐东-陵水凹陷中新统储层流体包裹体特征及成藏期研究

Characteristics of Fluid Inclusions and Accumulation Period of Miocene Reservoir in Ledong-Lingshui Sag of Qiongdongnan Basin

通过流体包裹体的镜下观察及均一温度测定,对琼东南盆地乐东—陵水凹陷中新统储层流体包裹体特征及成藏期进行了研究。研究表明:流体包裹体主要沿石英愈合裂隙呈带状分布,部分在石英颗粒边部分布或切穿多个碎屑颗粒;主要包括盐水包裹体、液烃包裹体、气烃包裹体和气液烃包裹体四种类型,其中烃类包裹体呈三期发育,荧光下多为黄色—蓝白色,有机质成熟度较高;流体包裹体的均一温度呈不连续分布,峰值主要集中在130~150℃范围内。根据流体包裹体的特征、产状及均一温度,综合分析认为,中新统储层主要发育三期烃类流体充注和一期CO2流体充注,其中第二、第三期烃类流体充注为主要成藏期,CO2流体充注发生在天然气充注晚期。结合埋藏史与热演化史可知主要成藏期为1.9 Ma^1 Ma,对应新近纪上新世莺歌海末期—第四纪更新世乐东期。

Based on the observation of microscope and the measurement of homogenization temperature of fluid inclusions, the characteristics of fluid inclusions and the accumulation period of Miocene reservoir in Ledong-Lingshui Sag of Qiongdongnan Basin are discussed. The results indicate that the fluid inclusions are mainly distributed along the healing fissures in quartz, partly distributed in the side of quartz granules or through multiple clastic particles. The types of fluid inclusions mainly include brine inclusions, liquid hydrocarbon inclusions, gaseous hydrocarbon inclusions and gas-liquid hydrocarbon inclusions. The hydrocarbon inclusions are developed in three phases, which present yellow and blue-white fluorescence with high organic maturity. The distribution of homogenization temperatures is discontinuous and concentrates in the range of 130℃ to 150℃ .According to the comprehensive analysis of characteristics and occurrence of fluid inclusions, and homogenization temperatures, it is determined that the Miocene reservoir experienced three phases of hydrocarbon filling and one phase of CO2 filling, which happened in the late stage of natural gas injection, and the second and third phase of hydrocarbon filling are the main period of hydrocarbon accumulation. Combined with the burial history and thermal evolution, it can be concluded that the main period of hydrocarbon accumulation is 1.9Ma-1Ma.