Study On High Intensity Water Flooding And Development Countermeasures Of Offshore Gas Cap Water Reservoir

China’s offshore heavy oil reservoir is rich in resources,generally using water injection development,so it is very necessary to understand the characteristics of water drive offshore heavy oil reservoir.This paper focuses on the study of water drive characteristics of strong edge water reservoirs,especially the characteristics of phase permeability curve after high-multiple water drive.The conventional understanding of oil displacement efficiency and residual oil saturation may be different.Firstly,this paper analyzes the dynamic characteristics of the target oilfield and divides the oilfield into the boundary region,the middle region and the gas cap region according to the regional characteristics.Dynamic analysis was carried out on the characteristics of different regions to study the law of water cut increase and yield decline.Then,based on the actual data of CB reservoir,ECLIPSE software was used to study the displacement characteristics and sweep rule of the common heavy oil reservoir with strong edge and bottom water in the offshore through numerical simulation,and the eor development model of this type of reservoir was discussed.Finally,the relationship between the oil displacement efficiency and the water displacement multiple was studied by combining the high-multiple water displacement physical experiment,and the next step to improve the recovery factor and the space amplitude were given.The results show that the main oil-producing contribution of heavy oil reservoir is concentrated in the stage of high water cut.It is the key to improve sweep in the later period of the edge region and the key to improve oil displacement efficiency in the later period of the middle region.In the early stage of the development of the target oilfield,the water drive mode is marginal water drive,but after many years of development,the water drive development mode begins to change from the original marginal water drive to secondary bottom water drive,and later to bottom water drive.The change of water flooding model is related to permeability range,formation dip Angle and crude oil viscosity.The smaller the permeability range,the faster the displacement mode changes.The higher the dip Angle,the faster the displacement mode changes.The lower the viscosity of crude oil,the faster the displacement mode changes.For the target reservoir,the displacement to 30 pv,core average oil displacement efficiency is 63%,the average residual oil saturation is 25%,the displacement 2000 pv,core average oil displacement efficiency is 72%,the average residual oil saturation is 20%,30 pv-2000 pv displacement,the displacement efficiency increased by 9%,8% lower residual oil saturation,showed the high water flooding to CB oilfield reduce residual oil saturation effect is obvious.