Study On Interwell Tracer Monitoring Interpretation Model In Oil Field

Oil is a non-renewable resource,so how to improve oil recovery is of great significance to the development of petroleum industry.Oilfield tracer technology is to inject tracer into injection wells and dynamically monitor the tracer in the surrounding producing Wells.According to the production concentration of the tracer,the formation parameters between injection and production wells can be deduced,so as to make a reasonable plan for the later production of the oilfield and improve the oil recovery.In this process,the interpretation method of tracer production curve becomes particularly important,and the accuracy and completeness of the interpretation method of tracer production curve are also regarded as an important standard to judge whether the interwell tracer detection technology is mature.In this paper,based on the ideal convection-diffusion equation,the tracer monitoringmathematical model is established by analyzing the tracer migration law under the reservoir.At the same time,combining with the heterogeneity factor,the tracer monitoring mathematical model is deduced.In cooperation with Zhong Yuan Oilfield,the tracer monitoring was carried out for Hu136 well group,and the tracer production concentration was obtained by relying on China's first single-stage electrostatic ¹⁴C special accelerator mass spectrometer(GXNU-AMS)jointly developed by Guangxi Normal University and China Institute of Atomic Energy.The established mathematical model can be used to invert the tracer production curve,and the dilution coefficient,tracer dispersion coefficient,average flow velocity and reservoir heterogeneity factors can be obtained simultaneously.On the basis of static reservoir data,the tracer flow state,average pore throat radius and heterogeneity in the reservoir are obtained by analyzing the four parameters.Specific work includes the following:1.Establishment of inter-well tracer mathematical model:The tracer seepage and diffusion mechanism was analyzed,and the ideal convection-diffusion equation was derived.Based on this,the inter-well tracer mathematical model for typical regular well pattern was established.At the same time,the heterogeneity factor was considered to establish the inter-well tracer mathematical model for heterogeneous multilayer.2.Study on the interpretative model of tracer monitoring between(heterogeneous)multilayer Wells:the tracer concentration output curve was fitted with the objective function,and the program was programmed with MATLAB.Four formation parameters,such as wellbore dilution coefficient,tracer dispersion coefficient,reservoir average flow velocity and heterogeneity factors,which affect the tracer concentration production curve were analyzed for parameter sensitivity.Based on this,the relationship between the tracer concentration production curve and the tracer flow state below the reservoir was understood.3.Data processing,model interpretation and analysis were carried out on the tracer detection results of Hu-136 well group in Zhong Yuan Oilfield:¹⁴C-AMS technology was used to measure the abundance ratio of ¹⁴C to ¹²C in the produced well samples,and the results were converted into the common unit for environmental monitoring of nuclides:¹⁴C radioactive activity concentration,and the abnormal pseudo data were processed by the method of amplitude limit and recursive average filtration.The processed data were then incorporated into the tracer monitoring interpretation model to obtain the water flooding rate,injection water distribution,flow paths of injection and production Wells,reservoir heterogeneity and pore-throat radius.The characteristics of the work in this paper are as follows:the method of interwell tracer monitoring interpretation model is reliable,it can be used in actual oil fields and get basic oil field parameters,and it has the characteristics of high efficiency,less pollution and short time.The heterogeneity factor can be used to describe the complexity of heterogeneous multilayer reservoirs with complex stratigraphic composition,which provides a basis for understanding the specific stratigraphic information in heterogeneous reservoirs.The application of ¹⁴C-AMS technology in oil field tracer monitoring is relatively rare,which has the characteristics of shorter time,higher sensitivity and less consumption compared with the commonly used liquid scinthe method.