莺歌海盆地乐东10区新近系黄流组储层天然气充注与超压演化史

Gas charging and overpressure evolution history of the Neogene Huangliu Formation reservoir in Ledong 10 area， Yinggehai Basin

范彩伟 刘爱群 吴云鹏 侯静娴

Caiwei Fan Aiqun Liu Yunpeng Wu Jingxian Hou

莺歌海盆地乐东10区新近系黄流组储层异常高压极其发育，压力系数最高可达2.3，超压的发育和演化与天然气成藏关系密切。基于流体包裹体岩相学观察，通过流体包裹体显微测温和激光拉曼光谱分析恢复黄流组储层气包裹体捕获压力，研究储层天然气充注和压力演化的关系。莺歌海盆地乐东10区黄流组储层发育纯CO气包裹体、富CH气包裹体、CO-CH混合气包裹体，对应两期CO和两期烃类气体充注。两期CO充注时间分别在2.0 Ma和1.0 Ma，包裹体中碳同位素显示两期CO为无机成因。两期烃类气体充注时间均晚于两期CO充注时间，分别是在1.8 Ma和0.4 Ma。黄流组储层超压经历了先增后降的过程。在2.0～1.0 Ma，两期CO和一期天然气的充注使黄流组储层压力逐渐升高，第二期CO充注到黄流组储层中之后，最大压力系数达到2.43。第二期烃类气体充注对应的黄流组储层剩余压力和压力系数都低于第二期CO充注时期，可能指示了在第二期CO充注之后，存在天然气泄漏的现象，使储层压力在1.0～0.4 Ma降低。莺歌海盆地乐东10区黄流组储层天然气充注与压力演化的关系对认识天然气成藏规律具有重要意义。

The abnormal high pressure of the Huangliu Formation reservoir in the Yinggehai Basin is quite common with a pressure coefficient reaching up to 2.3. The development and evolution of overpressure are closely related to natural gas accumulation. This study focuses on the relationship between gas accumulation and reservoir pressure evolution， based on the petrographic observation of fluid inclusions， coupled with the trapping pressure of gas inclusions in the Huangliu Formation reservoir revealed by microscopic temperature measurement of fluid inclusions and Laser Raman spectrometry. The reservoir of Huangliu Formation in Ledong 10 area of Yinggehai Basin develops pure-CO gas inclusions， CH-rich gas inclusions， as well as mixed CO and CH gas inclusions， corresponding to CO and hydrocarbon gas charging of two stages respectively. The two-stage CO charging occurred 2.0 Ma and 1.0 Ma ago from now， respectively， and the CO is of inorganic origin as shown by the carbon isotopes in the inclusions. The two-stage hydrocarbon gas charging occurred 1.8 Ma and 0.4 Ma ago from now， later compared with the CO charging. The overpressure of Huangliu Formation reservoir experienced a process of increasing first and then decreasing. From 2.0 Ma to 1.0 Ma， the two-stage CO and one-stage natural gas charging gradually increased the reservoir pressure of the study area. As the second-stage CO charging occurred in the formation， the maximum pressure coefficient reached 2.43. The residual pressure and pressure coefficient in the reservoir during the second-stage hydrocarbon gas charging are lower than the second-stage CO charging， which may indicate that natural gas leak might happen after the second-stage CO charging， which functions to reduce the reservoir pressure around 1.0 Ma to 0.4 Ma. The relationship between natural gas charging and pressure evolution of the Huangliu Formation reservoir in Ledong 10 area of Yinggehai Basin is of great significance to understanding the pattern of natural gas accumulation.

10.11743/ogg20220608