This paper was prepared for the Second Midwest Oil and Gas Industry Symposium of the Society of Petroleum Engineers of AIME, to be held in Indianapolis, Ind., March 28–29, 1974. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract

Heavy oil of 20 degrees - 29 degrees API gravity occurs in a number of reservoirs in the Illinois and Michigan Basins. These deposits represent an important hydrocarbon resource, and in some cases occur under conditions that are favorable from the standpoint of the application of thermal recovery methods. Previous attempts at thermal oil recovery in these areas were unsuccessful - with the important exception of the Fry in situ combustion project - principally because of two factors. First, the thermal methods used were not properly applied, and second, the economics were unfavorable in view of low oil prices and a lack of demand for heavy oils. This has changed, now, and conditions are just right, since the oil prices are going up, and at the same time, a great deal of experience with thermal oil recovery methods has been gained in the last 10 years when these methods were first tried in the Illinois oilfields.

This article examines the suitability of selected reservoirs in Illinois from the standpoint of cyclic steam stimulation, steamflooding, and in situ combustion. It is concluded that steamflooding and wet combustion have the best chance of success in the Illinois-Michigan oilfields. The two methods are considered for two heavy oil reservoirs in Illinois. Oil recovery as well as the overall economics are examined as functions of spacing.

The heavy oil deposits of Indiana, Kentucky, and Michigan are smaller and less attractive from the standpoint of thermal oil recovery. Heavy oil in Michigan occurs in limestone formations. Application of thermal methods in these reservoirs would yield valuable new knowledge. It is concluded that until more detailed information on the heavy oil reservoirs in the Illinois and Michigan basins is obtained, the full potential of thermal recovery in those areas cannot be assessed.

Introduction

Heavy oil (API gravity of 25 degrees or less) occurs in 22 states in the U. S. A comprehensive heavy oil survey, conducted by the U. S. Bureau of Mines in 1967 (1), estimated the total heavy oil resource as 106.8 billion STB, of which 45.9 billion STB is in reservoirs having characteristics most favorable for thermal recovery operations. According to this survey, the heavy oil resource of the Illinois and Michigan basins is between 60 and 70 million barrels.

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