Interpretation Method Research For Well-Group Tracer Production Curves

Most of the water-flood reservoirs have been in the late development stage, of which the water cut is more than 90%. Dominant channels may formulate after long-term water flooding, which will contribute to the inefficiency of injected water circulation and lower sweep efficiency, so that the utilization of the injected water is seriously affected. To achieve the ultimate objective of improving oil recovery by carrying out measures which will advance the sweep efficiency of injected fluid, it has become extremely important to identify the heterogeneity of reservoirs. As one of the most common methods used in oil fields, tracer testing technology has played a more and more important role in characterizing reservoir heterogeneity.Based on the description of the existing interpretation methods of tracer production curves, the well group tracer production curve interpretation methods are established in this paper: combination interpretation model and allegiance interpretation method for well-group tracer production curves. A combination mathematical model, one injection well is related to multiple wells and production curves, is established in the former. As it is disharmonious for the parameters and difficult to obtain partial derivative by last square fitting method, genetic algorithm is used to match the production curves to avoid this intricate problem. And parameters of dominant channels can be got for every well at the same time. The numerical methord for tracer production curve is improved in the latter. The reservoir is assumed to be composed of two media: the normal formation and the high permeability zone which is formed for the water injection. High permeability zones are generated randomly between the injector and the producer by statistical methods. Two mathematical models are established and solved for the two formations, respectively. The tracer concentration of production well is obtained by weighting the two concentrations according to water production. The cumbersome process of parameter adjustment is eliminated by genetic algorithm. The parameters like permeability, thickness of dominant channels and the distribution of pressure and saturattion can be obtained.Based on these theories, the well group tracer production curve interpretation program is developed, which is used to explain a well group tracer production curve.