Effect of Thermal Fluid Activity on Reservoirs in W16 Structure of Laizhou Bay Sag, Bohai Bay Basin

Genetic mechanism of the high-quality reservoirs developed by the Paleogene Shahejie Formation mixed rock in the Laizhouwan Sag, Bohai Bay Basin is still unclear. Based on fluid inclusion, vitrinite reflectance and petrological observation, combined with measured physical properties, it studies the effects of thermal fluid activities on reservoir under the complex mixing background of lacustrine carbonate rocks, terrigenous clastic rocks and volcanic rocks in the Shahejie Formation. The high homogenization temperatures of fluid inclusions, vitrinite reflectance, and paleo-salinity of fluid inclusions indicate the activity of deep hot brines. Acid dissolution exists widely in the reservoir: There are a large number of secondary dissolution pores in tuff, micrite dolomite interstitials and feldspar grains, and the common grain margin fractures, which may be caused by the intrusion of high pressure acid hydrothermal solution driven by magmatic activity. As the fluid temperature pressure drops, hydrothermal mineral precipitation also resulted in a strong and dense reservoir. In general, hydrothermal can produce both constructive and destructive effects on the reservoir, which strengthens the spatial differentiation of reservoir physical properties to a certain extent.