A One-Dimensional Analytical Technique for Predicting Oil Recovery by Steamflooding

Abstract

Abstract This paper describes a graphical method for calculating oil recovery by steamflooding that permits accurate prediction of fluid saturation permits accurate prediction of fluid saturation profiles and oil bank formation. profiles and oil bank formation. The oil displacement calculation is based on the Buckley-Leverett method for isothermal, two-phase flow in porous media. The fluid-flow theory is used with the Marx and Langenheim method to predict the size of a steam zone from energy balance and beat transfer considerations. The method is more complex than previous simplified methods, but permits band calculations of fluid saturation profiles and the delay of oil bank, arrival in producing wells for partially depleted oil reservoirs. These computations are in excellent agreement with those calculated numerically. Since uniform vertical displacement is assumed this method is suggested for use only for thin sands. Introduction The model for steamflooding described in this paper is based on the physical system illustrated paper is based on the physical system illustrated in Fig. 1. The reservoir is considered in vertical cross-section and is bounded above and below by impermeable strata. Heat losses to adjacent strata are accounted for by the method of Marx and Langenheim to describe the rate of steam front advance. This paper is concerned primarily with the prediction of linear fluid-flow behavior in the presence of temperature distributions that are time presence of temperature distributions that are time and distance dependent. The method may also be applied m hot waterflooding. In order to use the isothermal two-phase flow theory of Buckley and Leverett, the temperature distribution T(x, t) is represented by a series of n + 1 moving isothermal zones separated by discontinuities or "shocks" in temperature (Fig. 2a). The Marx-Langenheim method assumes only two isothermal zones (n = 1 in Fig. 2) -- one at injection temperature and the other at initial reservoir temperature - separated by a single shock. Since piston-like flow through the reservoir is assumed, the Marx-Langenheim method is not recommended for thick sands where gravity segregation would greatly reduce vertical sweep. A two-dimensional numerical method as described in Ref. 10 should be used in such a case. SPEJ P. 489