Research On Water Flooding Laws Of Ordinary Heavy Oil Reservoirs With Strong Bottom Water On The Sea

Offshore sandstone heavy oil reservoirs with huge bottom and edge water generally adapts the development modes of horizontal well and high flow rate.After a strong wash by formation water,formation properties including mineral composition,pore and throat structure,and wettability are altered,which further influence oil-water relative permeability,displacement efficiency,and residual oil saturation.Therefore,the highintensitive flooding characteristics for such reservoirs is obviously different from routine waterfooding.To provide technical basis for EOR of such reservoirs,it is necessary to study its high-incensitive waterflooding characteristics.Based on the production dynamic data of oilfield,displacement velocity and flooding pore volume of the horizontal well in different place of the reservoir are calculated by reservoir engineering method.The conventional waterflooding experiment procedures are modified,and wettability alteration of the core during high-incensitive waterflooding process is evaluated by measuring contact angle.Then,oil-water relative permeability curves are measured by J.B.N method,and based on experimental data displacement efficiency,residual oil saturation and dimensionless fluid-water index are also analyzed.Besides,the influence of oil viscosity,permeability,and displacement velocity on flooding characteristic and wettability are also investigated.In the end,XRD experiment,SEM,SARA,and molecular dynamics simulation are conducted to study the mechanisms of wettability alteration of heavy oil reservoirs in a microscopic view.The research results reveals that,after high-intensitive waterflooding core wettability has a tendency to be more water wet,and among all the viscosities 150 m Pa·s is the most potential.The decrease of clay content and desorption of asphaltene are the two main reasons for core's wettability alteration.Oil viscosity has a great influence on the wettability and flooding characteristics,displacement velocity plays a role on water cut increasing rate,and core permeability seems not to be a key factor affecting the development of such reservoirs.The research outcomes can be meaningful to the EOR methods and development adjustment of offshore sandstone heavy oil reservoirs.