Study On Gas Tracer Interpretation Method Of Gas Flooding In Fractured Vuggy Reservoir

Development of EOR by gas injection is an important part of tertiary oil recovery in fractured-vuggy carbonate reservoir.In the process of gas injection,the tracer can be used to identify the trend of gas flow and determine the reservoir connectivity.The application of tracer in water flooding process of sandstone reservoir is more mature,but in the aspect of gas tracer monitoring,especially in Carbonate Reservoir is almost blank.At present,most of the tracer interpretation methods for fractured-vuggy carbonate reservoir are mainly to explain the connectivity between wells and the types of fractures and cavities,meanwhile,there are few reports on the interpretation of reservoir volume.The difference of fluid flow patterns in the fracture and vug,the diversify and the complexity of fracture and vug combination are the difficult points in the research of tracer flow in fractured-vuggy carbonate reservoir.Based on the tracer flow law of fractured-vuggy carbonate reservoir,further research on the establishment of the flow model and interpretation method of tracer in process of gas injection for fractured-vuggy carbonate reservoir is done,which can be used to explain the reservoir volume parameters.The achievements are listed as below:(1)A lot of survey on the flow pattern and gas tracer monitoring in fractured-vuggy carbonate reservoir is done.The migration,dispersion and retention of gas tracer are analyzed.By introducing the partition coefficient and the apparent moving velocity of tracer,a mathematical model for the one-dimensional flow of the tracer is established.(2)The numerical simulation model of tracer flow in fractured vuggy reservoir is established by using Fluent software.Fluent software is also used to simulate the flow process of the gas tracer in fractured-vuggy carbonate reservoir during the process of continuous injection,slug injection and static diffusion.(3)Slug injection mode response of tracer fracture cave is more obvious.When the holes are connected in series,the larger the total volume of the cave is,the later the production time of the tracer is,the longer the residence time of the tracer is,and the lower the peak value is.The output concentration curve of the tracer at the outlet of the parallel channel exhibits the characteristics of multi peaks when the multi holes are connected in parallel.(4)Based on tracer flow theory,combined with simulation results,using multi channel superposition principle and point source superposition principle,the tracer flow model of different gas injection way and different vuggy connectivity in fractured-vuggy reservoir is established and solved innovatively.(5)The interpretation method of gas injection tracer in fractured-vuggy reservoir is established innovatively,including the simplified calculation method of reservoir volume and genetic fitting method.Through the simulation results,the simulation model parameters are obtained.The calculated results are in good agreement with the actual parameters,which shows that the method is reasonable and effective.