Abstract

This paper deals with the influence of oil viscosity, water influx and production rate on WOR in a hypothetical heterogeneous and anisotropic reservoir. We show that for the case examined, the amount of water influx is only important because viscosity of oil depends upon pressure. For a constant viscosity oil the amount of water influx has very little effect on the WOR of the well. Results are also presented for two different production rates. As expected the higher production rate will result in higher WOR but this is not necessarily detrimental to ultimate recovery at economic abandonment.

In the last part of this paper we compare some of our computer results with some coning correlations It is shown that available correlations are not reliable.

Introduction

Oil bearing formations are often underlaid by a water zone. An oil well completed in such a formation will initially produce essentially water free hydrocarbons. However, as the production is continued water saturation around the well increases and finally bottom water finds its way into the well. In some reservoirs it is possible to handle large quantities of water along with the oil before reaching the economic abandonment conditions.

In a previous paper by Aziz, Kaneko, Mungan and Settari (1973) results of coning simulation were presented. In one example considered in that paper it was found that the WOR at the producing well was lower for the higher water influx rate. A careful examination of the results showed this to be due to the decrease of oil viscosity with increase in pressure below the bubble point. Using a numerical coning model, Byrne and Morse (1973) studied the influence of several parameters on WOR. They did not, however, consider the normal variation of Viscosity with pressure. In this paper we consider a hypothetical reservoir and show the influence of production rate and oil viscosity on WOR. In addition we also compare our model predictions with the correlations of Sobocinski and Cornelius (1965) and Bournazel and Jeanson (1971).

The coning model used for our study has been adequately described elsewhere (Settari and Aziz, 1973) and will not be discussed here.

Reservoir Data And Model Parameters

Computations were performed to predict the behavior of a well in the center of a cylindrical drain age volume. The outer boundary of the drainage volume was at 1500 ft while the well radius was assumed to be 1 ft. The oil in place within the drainage volume is 3,671,800 STB.

For simulation purposes the equations for multi phase flow in porous media are solved at the nodal points of a grid network. The grid used for this study is shown in Figure 1. We have used 7 grid points in the radial direction and 17 in the vertical direction. The grid points are distributed in a non-uniform fashion in both directions. The distribution of grid paints in the radial direction is selected to provide greater detail near the well than near the outer boundary.

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