NONLINEAR REGULARITIES OF INDICATOR CURVES ADJUSTED FOR RESERVOIR DAMAGE EFFECT
M.I. Epov1, N.N. Mikhailov2,3,4, V.N. Sokotuschenko2, O.M. Ermilov2,5
1Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
2Gubkin Russian State University of Oil and Gas, Moscow, Russia
3Institute of Oil and Gas Problems, Russian Academy of Sciences, Moscow, Russia
4M.V. Lomonosov Moscow State University, Moscow, Russia
5OOO Gazprom Dobycha Nadym, Nadym, Russia
Keywords: Hard-to-recover reserves, low permeability reservoirs, nonlinear filtration, well flowrate, drawdown, skin factor, formation damage, indicator curves, hysteresis, power-law filtration
Abstract
We comprehensively analyzed the influence of nonlinear reservoir processes on well flowrate vs. drawdown for low permeability reservoirs with hard-to-recover (HTR) hydrocarbon reserves. New nonlinear relationships between the flowrate of low permeability reservoirs and reservoir drawdown (indicator curves) were identified. The nonlinearity of the indicator curves is due to the combined effects of nonlinear filtration, technogenic reservoir change, and the dependence of formation damage parameters on drawdown. The applied approach allowed us to find out qualitatively new regularities in the relationship between flowrate and drawdown in low permeability reservoirs. A well productivity analysis revealed hysteresis in the indicator curves and a shift in critical drawdown values when considering both formation damage and filtration nonlinearity. It has been found that the combined effects of nonlinear filtration and damage effects lead to an additional flowrate decline of 25-40%, as compared to separately considering each of these effects. The obtained results are of practical importance for optimizing the development of low permeability reservoirs with HTR reserves and for predicting their productivity.
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