Abstract: The BZ-A oil reservoir in the Bohai Sea is a rare highly volatile metamorphic rock buried hill reservoir.The reservoir is characterized by thick layers,low porosity and permeability,strong heterogeneity,randomly distributed fractures, and large fracture dip angles.The deployment of injection and production well networks is an important issue that needs to be urgently addressed for the efficient development of the oil field.To this end,a dual-medium reservoir compositional model was established based on the fluid and reservoir development characteristics of the BZ-A oil reservoir.A study on the deployment strategy of three-dimensional well networks for gas injection development was conducted,and a quantitative analysis of the key influencing factors of gas injection development well networks and their coupling relationship with fracture development was performed.The results show that the BZ-A oil reservoir is suitable for development with associated gas reinjection to supplement energy,making full use of the structural position and gravity-assisted oil displacement mechanism for the deployment of injection and production well networks.Gas is injected at the top of the high structural positions, while oil is produced from the middle and lower parts of the low structural positions,forming a spatial three-dimensional well network.The development method using highly-deviated wells with a 45° angle to the fracture direction is adopted, which increases the oil drainage area and enhances the single-well production capacity.The optimal injection-production well spacing along the fracture direction is approximately 1 000 m,and the reasonable well spacing perpendicular to the fracture direction is approximately 800 m.The oil production rate during the peak period is 3%, and the recovery rate for gas injection development is 28.4%.The research findings have been applied to the development practice of the BZ-A buried hill oilfield,where the initial production capacity of oil wells ranges from 132 to 340 m³/d,achieving good development results.The research results are of reference significance for the preparation of development plans and efficient gas injection development of buried hill oil and gas fields.

Key words: buried hill, fracture, highly volatile reservoir, gas injection development, well network, injection-production well spacing