Prediction method of production performance of modified water drive in sandstone reservoirs

In order to increase the reliability of the modified water drive development plan, a general method for calculating the recovery factor of modified water drive is established based on the basic principles of reservoir engineering. Reservoir subdivision is carried out with the aid of the differential thought, and in some grids the relationship among the recovery factor, the recovery degree and the recovery speed of the reservoir is established. The change law of the production rate and the production decline rate index of modified water drive and the reservoir of modified water drive are derived. The definition and engineering algorithm of production increase multiple of modified water drive are put forward. It is clear that the production increase multiple of modified water drive is determined by the ratio of the initial displacement efficiency of modified water and conventional water and the recovery degree of generalized recoverable reserves when driving. The research results provide the necessary reservoir engineering basis for the prediction of the production performance of the modified water drive, and have a guiding significance for the formulation of the development plan of the modified water drive and the evaluation of the production effect.