Screening Estimation Of Recovery Efficiency And Chemical Requirements For Chemical Flooding
Authors: Lake L.W. , Stock L.G. , Lawson J.B. 
Published: December 2007

This paper introduces a graphical procedure that incorporates reservoir heterogeneity into a screening estimation of chemical flood recovery efficiency. Such an estimate would be useful in a preliminary evaluation of the expected oil preliminary evaluation of the expected oil production, chemical requirements, and project life of production, chemical requirements, and project life of a designated candidate reservoir. The graphical procedure augments the usual chemical flooding procedure augments the usual chemical flooding screening procedures based on average permeability, oil viscosity, reservoir temperature, waterflood residual oil saturation, waterflood sweep efficiency, and remaining oil values.

We also describe screening techniques for geological characterization of a candidate reservoir and demonstrate the adjustment of reservoir volumetrics to calculate chemical flood target oil. This calculation indicates the sensitivity of the target oil to uncertainties in waterflood residual oil saturation, original oil in place, and the degree of resaturation of oil in primary-depleted areas. Finally, we describe and present screening estimates of well spacing/permeability/project life relationships and a sample production function for a candidate reservoir using a dimensionless production function developed from a numerical simulation.

Introduction

Before starting a chemical flood research program and before large expenditures are required program and before large expenditures are required to coordinate a field-scale test, an estimate of the large-scale ultimate profitability of the project will be needed. Such an estimate will, in turn, require estimates of ultimate recovery and chemical requirements. Early in the design there may not exist sufficient data about either the reservoir or the process to justify an elaborate estimate of these quantities, so that recourse to screening techniques to estimate chemical flood recovery efficiency and chemical requirements is usually necessary. The objective of this paper is to describe such a screening procedure and to illustrate its use on an extended example referred to hereafter as the candidate reservoir.

The general scheme of the screening procedure is similar to that which would be used in an elaborate study of the chemical flood process, namely, development of a geological model and then use of this model and a calculational model to estimate recovery efficiency. of course, since this study is intended to be primarily a gross screen of the reservoir's (or production area's) chemical flooding potential, both the geological model and the calculational model used here are superficial treatments of the many complexities involved in actual reservoirs and in chemical flooding. However, such an approach will provide a rough estimate of chemical flooding potential and could allow for optimal ranking of various candidate reservoirs. The main thrust of this paper is, then, toward geological characterization and calculational techniques which will yield a satisfactory screening estimate of chemical flood recovery efficiency and chemical requirements.

APPROACH

In the sections that follow we first introduce geological and petrophysical concepts so that the distribution of porosity, permeability and residual oil saturation can be graphically portrayed. Then, beginning with an initial data base, we determine the volume of target oil and the dependence of target oil upon 1) swept zone residual oil saturation, 2) unswept zone oil resaturation, and 3) original oil in place. Finally, the target oil volumes are reduced to account for the presence of bottom water. We then apply a simplified graphical procedure for calculating chemical flood recovery procedure for calculating chemical flood recovery efficiency to the reservoir model and its target oil to obtain the chemical flood reserves (CFR). Permeability/spacing and project life relationships Permeability/spacing and project life relationships are developed which can be subsequently coupled with a dimensionless production function, determined from a computer simulation, to give a production function. The recovery efficiency, chemical requirement and production function thus developed can form a basis for a subsequent economic analysis.