Identification Of Ineffective Water Injection Cycle And Quantitative Characterization Of Predominant Percolation Channels

After long-term waterflood development,most of China's oil fields have entered the high water cut period and even the extremely high water cut period.Especially in the highly water-bearing oil reservoirs,the comprehensive water cut is as high as 95%,the remaining oil is highly dispersed.The dominant percolation channels are widely developed,and the ineffective injection and production cycle is severe,which seriously restricts the economic benefits of oilfield waterflooding development.The recognition of invalid waterflood cycles and the management of dominant seepage channels have become the focus of oilfield work,so it is necessary to carry out relevant research.This paper first summarizes the research course,research methods,and main understanding and achievements of invalid water injection cycle identification methods and dominant percolation channel characterization methods at home and abroad,analyzes the weak links in the research process,and clarifies the research direction and research of this paper.The experimental study of oil-water two-phase flow law was conducted,revealing that the inherent permeability of the core is the root cause of the difference in oil-water two-phase flow.At the same time,the difference in the two-phase flow caused by the difference in the intrinsic permeability will also enhance the fluid flow capacity and aggravate the ineffective cycle.Through indoor sand-filling pipe experiments,we have a deeper understanding of the injection-production dynamics during the ineffective cycle,laying the foundation for the identification of subsequent water-flooding cycles.Numerical simulation of streamline model reveals the characteristics of the development and evolution of dominant percolation channels,and it is believed that the high permeability of the reservoir is the main site for the development of dominant channels.Utilizing the dynamic characteristics of injection and production in oil and water wells,a water-invalid loop-recognition well was selected;based on economic benefits,a single well economic limit moisture ratio model considering oil price,ton liquid cost and other factors was established;Distribute flow,displacement efficiency,and abundance of surplus reserves,and use the comprehensive evaluation parameters to divide the reservoir into three regions: water injection effective area,inefficient recycling area,and invalid recycling area.Using the data of injection and production dynamics in oil and water wells,the correlation coefficients of different oil and water well combinations are calculated by the correlation coefficient method to determine the turbulence direction between wells.In consideration of the relationship between oil and water two-phase flow,"viscosity" is introduced to correct various small wells between wells.The percolation resistance coefficient of the two-phase seepage flow;the water injection volume and the connected volume between wells in the injection wells were quantitatively calculated to characterize the size of the turbulent flow in the dominant percolation channel.The research results of this paper further improve the identification system of invalid water injection cycles and the quantitative characterization methods of the dominant percolation channels.It has certain guiding significance for adopting governance measures in the later stage of special high-water-bearing reservoirs to improve the economic benefits of oilfield development.