Research On Influence Factors And Effects Of The Adjustment And Development Of Strata In Ultra-high Water-cut Oilfield

Ultra-high water-cut stage is an inevitable stage after a long period of water drive development.It is one of the most concerned problems for reservoir engineers to effectively recover the highly dispersed remaining oil in the reservoir during this period.Under the current injection and production well pattern conditions,it is difficult to improve the development effect only by conventional adjustment and exploitation measures,so it is of great significance to study the overall exchange of the two layers' well patterns.Based on theoretical analysis,this paper summarizes the seepage mechanism of improving water flooding development through layer adjustment.Combined with the reservoir physical properties and seepage parameters of Ng3-4unit in Zhongyi area of Gudao Oilfield,Eclipse software is used to analyze and characterize the influencing factors of layer interchange by means of variable flow line numerical simulation.Combined with some influencing factors,the technical circles of interchange flow lines of layers are illustrated and analyzed.The research results of this paper are as follows:(1)The seepage mechanism of improving water drive development through layer adjustment is analyzed and summarized,which mainly includes three aspects: reducing the influence of dominant channels,changing volume sweep coefficient and changing fluid flow direction.(2)By means of numerical simulation,the factors influencing the effect of strata interchange and variable flow line are analyzed.When the water cut is 97%,the strata well pattern is interchanged and produced to 99% water cut.The following conclusions are drawn:(1)With the increase of the number of small layers,the degree of recovery first increases and then decreases.(2)The recovery degree increases first and then decreases with the increase of the thickness of the small layer.When the thickness of the small layer is 4 meters,the recovery degree reaches the maximum.(3)The recovery degree increases with the permeability range and decreases gradually.When the permeability range is 1,the recovery degree reaches the maximum.(4)The recovery degree increases gradually with the decrease of oil viscosity,and the recovery degree reaches the maximum when the oil viscosity is 30 c P;(5)The recovery degree decreases gradually with the increase of the injection-production ratio.When the injection-production ratio is 1.0,the recovery degree reaches the maximum.(3)According to the simulation results of each influencing factor and combined with the data,the effect evaluation of the recovery improvement after the interchange of the upper and lower layers is given,that is,when the water content reaches 99% after the interchange of the upper and lower layers,the recovery degree of the original well pattern is 66.94%,the recovery degree of the replacement well pattern is 67.57%,and the recovery rate is increased by 0.63%.(4)Combined with some influencing factors,according to the numerical simulation of the reservoir flow line distribution and the degree of recovery,the technical boundaries of the parameters are as follows:(1)When the water cut is less than 97%,the well pattern exchange is carried out,the recovery rate is positive,and the well pattern exchange measures achieve good results;(2)When the number of small layers is greater than 3,the recovery rate after well pattern adjustment increases by more than 1%,and the well pattern adjustment measures are good;(3)The larger the permeability range is,the better the potential exploitation effect of remaining oil will be.When the permeability range is 9,the recovery efficiency increases the most after the interchange of well pattern;(4)Among the five different well pattern adjustment schemes,the plan of interchange of layers well pattern increases the recovery degree the most;(5)When the injection-production ratio is 0.9 and 1.0,the recovery degree is improved after interchanging well pattern.When the injection-production ratio is 1,that is,when the injection-production ratio is balanced,the recovery degree is increased by 1.10%,and the effect of interchanging well pattern is the best.