Research And Application Of Forecasting Method Of Recoverable Reserves In Late Permeability Oilfield

With the increasing percentage of the oil production of low-permeability oil field over total national petroleum reserves, oilfield exploitation enters its late stage, and the prediction of recoverable reserve of low-permeability oil field reveals its importance at this point. However, most of the current predicting methods are only applicable to middle-or high-permeability oil field, and there are not many prediction techniques for middle-or late-stage recoverable reserve for low-permeability oil field. In need of an integrated and comprehensive prediction for development index of low-permeability oil field, field engineers need to research and propose a better prediction technique urgently.In this article, with combination of rheology theories and factors of starting pressure gradient, the analysis of starting pressure gradient, one of the properties of low-permeability oil reservoir, is used to establish an expression for starting pressure gradient based on current geological parameters. By applying mass of practical data of low-permeability oilfield to Tong’s Chart method, various diminishing method and water drive curve method, the differences in calculation results and development index among prediction techniques are analyzed to choose the method for determining the development index and predicting recoverable reserve for low-permeability oil field. A new Tong’s Chart is established based on the deficiencies of applying the original Tong’s Chart to low-permeability oil field.From theories of permeation mechanics, a water drive curve method considering starting pressure gradient and Arps diminishing method are derived and compared with original water drive curve method and diminishing method according to living examples to analyze the influence of starting pressure gradient on prediction index of oilfields and demonstrates the necessity of considering the gradient while making analysis on diminishing and water drive characteristics of low-permeability oil fields. By the expression of relative permeability curve of prediction models, starting pressure gradient is taken into account to build a prediction model for recoverable reserve of low-permeability oil field. This model obtains satisfactory results after applying to cases.