Study On Subdivided Oil Recovery Potential Of Multi-layer Commingled Producing Well

When the oil reservoir in a high water cut stage,the remaining oil is dispersed,the water cut difference between layer system is reduced,and the contradiction of high water cut in the multi-layer has become increasingly prominent.At present,the technology of separate layer recovery in multi-well sections of the same well has been basically consummated,and large-scale promotion has become possible.However,due to the unclear seepage law of interwell after separated layer recovery,there is a lack of theoretical basis for the evaluation of subdivided oil recovery potential.Therefore,in order to correctly evaluate the subdivided oil recovery potential of multi-layer commingled producing well and accurately predict the deliverability,it is necessary to conduct a more thorough and comprehensive study on the subdivided oil recovery potential evaluation.At first,parallel experiment of nine-pipe cores with different permeability is adopted.The effects of different injection speeds and different water cut stages on deliverability interference coefficient are studied.At the injection speeds of 1m L/min,2 m L/min and 4m L/min,the three water cut stages are selected.For example,water free period,the water cut is 80%and the water cut is 95%.The development effects of commingled production and selective mining deliverability of multi-pipe parallel cores at different water cut stages are compared.The changing law between deliverability interference,water cut and injection speed is determined.In water free period,as the injection speed increases,the proportion of reduction in deliverability interference coefficient is 1.54%and 1.56%respectively.When the water cut is 80%,the proportion of reduction in deliverability interference coefficient is 1.33%and 2.70%.When the water cut is 95%,the proportion of reduction in deliverability interference coefficient is 1.20%and 3.66%respectively.This shows that under different water cuts,with the increase of injection speed,the deliverability interference coefficient shows a decreasing trend,but the decreasing range is different.Then,select a typical separate layer recovery test area,collect and organize the dynamic and static data of 211 oil and water wells,and determine the actual parameters of the oil field.Use Eclipse software to establish a conceptual model of a production well in multi-layer.Consider 9 factors,such as permeability ratio,average permeability,formation pressure,formation pressure ratio,thickness ratio,crude oil viscosity,injector producer distance,liquid producing capacity and water cut,etc.Each of these factors contains 8 horizontal variables.Orthogonal test method is used to design42 numerical simulation schemes and carry out numerical simulation calculations.In this way,the relationship data between the degree of deliverability interference and various factors in the case of commingled production and selective mining is obtained,and the deliverability of the commingled producing well is analyzed.The mathematical model of grey correlation method is established.The entropy weight method to calculatethe the degree of association between the degree of deliverability interference and 9 factors is combined.Such as permeability ratio,average permeability,formation pressure,formation pressure ratio,thickness ratio,crude oil viscosity,injector producer distance,liquid producing capacity and water cut,etc.The master control factors for subdivided oil recovery are determined.Finally,based on filtration theory,a mathematical model for the subdivided oil recovery potential evaluation is established.Five typical wells for subdivided oil recovery are selected for calculations.Such as:X-1,X-2,X-3,X-4 and X-5.The calculation accuracy of the development indexes of liquid production,oil production,water cut,fluid productivity index and productivity index are validated.The auxiliary program is established.The subdivided oil recovery schemes of 5 wells are calculated.In the two different situations of commingled production and selective mining,the changes of water cut,daily oil production and productivity index are compared.The subdivided oil recovery potential is evaluated.From that we get,the average oil production of a single well during the model selective mining is6.25 m~3/d,the average water cut is 87.67%,and the average productivity index is 1.46m~3/(MPa·d).The average single-well oil production increases by 3.39 m~3/d,the water cut decreases by 6.82%,the productivity index increases by 0.79 m~3/(MPa·d),and the deliverability increase ratio is 52.22%.