| Daqing LaSaXing oilfield is China's largest continental multi-layer sandstone reservoir,and it is a typical representative of China's ultra-high water cut oil field,the reservoir is a river-delta facies sandstone deposit,and the plane,interlayer and intra-layer heterogeneity is serious.The recoverable reserves of LaSaXing oilfield account for 95.9% of Changyuan Daqing,and the thickness of oil deposits is large,67.5% of the geological reserves are distributed in thick oil layer of more than 2.0m,the proportion of poor oil reserves is also larger,it is the basis for the continuous stable production of LaSaXing oilfield.LaSaXing oilfield has experienced more than 50 years of long-term water flooding,it has been fully into the "double high" development stage,and integrated moisture content of up to 94.2%.The differences of all kinds of reservoir seepage,the reservoir has a great change by long-term water flooding,especially in the development of ultra-high water cut stage,the three major contradictions are very prominent.On the one hand,long term water injection to scour the formation of dominant channel,a large number of injected water along the preponderance flow path between oil and water wells in part of the storage layer formed a strong ineffective or inefficient circulation,it is difficult to continue to expand and affect the development effect of the oil reservoir,This has become a technical bottleneck of ultra-high water cut stage development stage and which is urgent need to solve;On the other hand,the oil field has entered the development of ultra high water cut stage,the characteristics of reservoir seepage have changed obviously,the dynamic characteristics and development law of water flooding have changed greatly compared with the previous stage,and the liquid / oil ratio has increased sharply,therefore,during development stage of ultra-high water cut stage,the oil field is faced with difficulties such as difficulty to tap,water cut rising speed is accelerating,production decline situation is serious and other unfavorable situation,to maintain LaSaXing oilfield water flooding yield stability,it is necessary to systematically and deeply study the water flooding reservoir in ultra-high water cut stage big channel nonlinear seepage evolution rule and dynamic evaluation method and theory,for the next available water flooding fine tap provide reliable theoretical basis and technical support.In this paper,the following contents are studied by using the methods of laboratory analysis,theoretical study,numerical simulation and field statistics:1.Reservoir pore structure and the evolution law of physical parameters and its influence mechanism after long term water flooding in oil field is studied,and fractal characteristics of reservoir dynamic evolution of long-term water flooding were studied.On this basis,the variable dynamic quantitative evolution model of reservoir system is established.2.The high speed nonlinear seepage coefficient and its influencing factors,and existence of high speed nonlinear seepage of thief zone are analyzed,the microscope mechanism of high speed nonlinear seepage flow in the thief zone is analyzed.Fractal characterization of high speed nonlinear percolation law is carried out,which bases on the theory of fractal porous media,an analytical model for the production and pressure of the high speed nonlinear seepage flow are established,the influence laws of the high speed nonlinear seepage on production and water cut are analyzed.Based on the fractal porous medium theory,a fractal analysis model for the relative permeability curve of the high speed nonlinear seepage is established,and the law of oil-water two-phase flow in the predominant channel is studied.3.The fluid speed nonlinear seepage characteristics in the water flow predominant channel and and Darcy flow in the low velocity zone,and reservoir parameter variable dynamic evolution are considered,a mathematical model of time-dependent nonlinear seepage flow in oil reservoir is established,the influence mechanism of high-speed nonlinear seepage and reservoir dynamic effects on the development of dynamic evolution is analyzed by this model,flow field characteristics and evolution law of thief zone in macro view formation process are revealed.4.The identification method of thief zone in reservoir is studied,a quantitative inversion model of reservoir well dynamic connectivity is established based on the dynamic data of injection and production,the effectiveness of the dynamic connectivity inversion model is verified by using tracer test,water absorption profile and numerical simulation data;A new method for judging the existence and development level of the thief zone is put forward based on cloud model,the parameters calculation method of thief zone is improved,and the practicability,reliability and rationality of new method system are verified using some data.5.A new types of water flooding characteristic curve is improved and established base on the ultra-high water cut stage of oil-water two-phase flow characteristics,the variation law of water drive characteristic in the area of water flooding in the advantage of the ultra-high water cut stage was studied,the other reservoir engineering method is improved based on the new water drive characteristic curve,broadening to the description of the evolution of water flooding in the process of formation of thief zone,enriching the theory of reservoir engineering.6.Effect of thief zone on the development effect is considered,a new index system for the evaluation of water flooding development effect in the ultra-high water cut stage is screened and constructed,the weight of evaluation index is determined by using the combination of subjective and objective weighting method,a new model for evaluating the effect of water flooding development which considers the effect of the thief zone in ultra-high water cut stage oilfield is studied.7.The theory method is applied and studied.The method theory and technology of the dynamic evaluation of water flooding in the ultra-high water cut stage,which is the description of the high speed nonlinear seepage flow,the identification of the thief zone and the influence of the thief zone are established by studying,and it is applied in Daqing LaSaXing oilfield water flooding in tapping the fine work,demonstrated by application,the method theory is established in this paper and it has high theoretical and practical value. |
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