Study On Evaluation Index And Method Of Intelligent Separate Injection And Production Effect In Bohai Oilfield

Bohai oilfield is one of the main offshore development oilfields in China.Its oil and gas reserves and production play a very important role in ensuring the safe supply of domestic energy.Affected by reservoir geology and development conditions,Bohai oilfield has the characteristics of high crude oil viscosity,large reservoir thickness,strong heterogeneity,low rock cementation strength,large injection production well spacing,high injection production intensity of single well and multi-layer combined production.At present,it is in the stage of medium and high water cut development,and it is urgent to further strengthen the effect of separate injection and production measures.In recent years,the research and application of intelligent separate injection and production technology have been highly valued by petroleum scientists and technicians.Because this technology has the characteristics of adjusting while measuring,short allocation cycle,low construction cost and high success rate of measurement and adjustment,it can greatly reduce the workload of separate injection and production measures in offshore oil fields and improve the efficiency of measurement and adjustment.Now it has become one of the important ways to improve the effect of reservoir water flooding development.The existing test data show that the field application of intelligent separate injection and production technology in Bohai oilfield has achieved good results in stabilizing oil and controlling water.However,with the gradual expansion of the application scale of separate injection and production technology,it is urgent to establish a unified evaluation index and method.Therefore,under the theoretical guidance of reservoir engineering,seepage mechanics and mathematical statistics,taking Bohai oilfield as the research object,and taking data analysis and numerical simulation as the research means,this paper has carried out the research on the evaluation index and method of intelligent separate injection and production effect in Bohai oilfield.The main research results and understanding are as follows:(1)According to the effect characteristics of oil wells after intelligent separate injection,three effect types of oil wells are divided: liquid increasing and efficiency increasing,oil increasing and precipitation and oil stabilizing and water controlling.52 intelligent separate injection well groups in Bohai oilfield are counted.The results show that the effect types of well groups are mainly liquid increasing and efficiency increasing,followed by oil stabilizing and water controlling,and less oil increasing and precipitation.(2)The commonly used development effect evaluation indexes of the oilfield are systematically counted and classified,and then the practical significance and scope of application of each evaluation index are analyzed from the perspective of reservoir engineering.Based on the methods of logical analysis and principal component analysis,9 evaluation indexes for the application effect of intelligent separate injection and production technology in Bohai oilfield are selected.At the same time,from the perspective of single index evaluation,the water flooding development effects before and after the application of intelligent separate injection and production technology in different well groups in BZ28-2S,SZ36-1,LD10-1 and LD5-2 oilfields are compared and analyzed.The results show that except for individual evaluation indexes,the changes of most evaluation index values of each well group reflect the improvement of water flooding development effect.(3)Combined with grey relational analysis and analytic hierarchy process,a calculation method of objective weight of evaluation index is established;At the same time,according to the existing development level classification of Bohai oilfield and other industry standards,a grading system scoring standard considering oilfield fluid physical properties and development performance is established.(4)Considering the factors of reservoir physical properties,fluid properties and development performance,a set of comprehensive evaluation method that can quantify the application effect of intelligent separate injection and production technology is established.Firstly,based on the theory of reservoir engineering,nine evaluation index values of oil fields,blocks or well groups to be evaluated are calculated;Secondly,according to the corresponding grading system scoring standards and the principle of linear interpolation,the scores of each evaluation index before and after the application of intelligent separate injection and production technology are calculated;Finally,based on the weighted summation idea,the comprehensive score before and after the application of intelligent separate injection and production technology in the oilfield,block or well group to be evaluated is obtained.The comprehensive score reflects the overall effect of water flooding development,and the difference of comprehensive score before and after intelligent separate injection and production measures reflects the improvement degree of water flooding development effect.(5)The comparison between evaluation results and numerical simulation results shows that the greater the comprehensive score difference of well group,the higher the oil increase.It can be seen that the well group with low comprehensive score should be the key candidate well for the application of this technology.This paper provides theoretical guidance for the intelligent separate injection and production technology in Bohai oilfield to improve the evaluation method of water flooding development effect and well selection,which is of great significance.