Experimental Basis for Extending the Oil Recovery/Volume Burned Method to Wet and Superwet Combustion
Authors: Moore R.G. , Bennion D.W. , Ursenbach M. , Gie D. , Millour J.P. 
Published: March 2010

C.G. Gates and H.J. Ramey comparing combustion tube results and field data from the South Belridge in situ combustion pilot developed an engineering correlation for predicting oil recovery as a function of volume burned.

The University of Calgary has conducted 32 air combustion tube tests on Athabasca bitumen under various conditions of packing procedures, pressures, air fluxes and water/air ratios.

The liquid production histories of these tests provide an extension of the oil-recovery/volume burned method to wet and superwet conditions. In addition to the burned volume, the volume swept by the steam bank is taken into consideration.

It is shown that for wet and super wet burns, the total production of fluids (oil and water) provides valuable information. This information is further enhanced by the presentation of the residual saturations in the core after the burn.

To complete the data bank for an engineering approach, curves of the cumulative air injected/oil produced ratios vs the volume burned are presented. This allows a comparison of economics and operating procedures under different combustion types.

Introduction

Prediction of oil recovery as a function of time is a very important aspect of the economic evaluation of in situ combustion projects. Oil recovery during in situ combustion is influenced by gas drive due to injected nitrogen and generated product gases, by steam and hot water drive, by miscible displacement resulting from the thermally upgraded hydrocarbons which are displaced by the high temperature combustion zone and by gravity drainage. Based on field and combustion tube data, Gates and Ramey(l) developed the oil-recovery/volume-burned method for predicting the oil recovery curve for fields similar to South Belridge. Fassihi et al'(2), using combustion tube data, extended the Gates and Ramey curves to account for varying initial gas saturations. An algorithm for predicting oil recovery performance during in situ combustion has been developed by Fassihi et al.(3).

The purpose of this paper is to illustrate how variations in the water/air ratio effect the performance of a laboratory in situ combustion test. A number of previous articles (Dietz(4), Parrish and Craig(5), Burger(6), Garon and Wygal(7), Bennion et al.(8), Ejiogu et al.(9) have presented over-all air and fuel requirements and ultimate recoveries as functions of the water/air ratio, however, very little information has been provided as to the relationship between fluid production rates and the movement of the combustion and steam fronts. This is not surprising as the traditional role of the combustion tube was strictly the determination of air and fuel requirement parameters (Showalter(10), Martin el al.(11)).

In recent years, combustion tube tests have been used for extending the oil recovered/burn volume curves of Gates and Ramey (Fassihi et al.(2)) and as reference sources for the tuning of numerical models. The validity of this type of use of the laboratory combustion tube test is further justified by the good correlation shown by Moore et al.(12) between field and laboratory derived produced fluid properties. Trends observed in the laboratory were generally displayed in the corresponding field application.