The Use of Special Coring and Logging Procedures for Defining Reservoir Residual Oil Saturations

One of the factors influencing the potential applicability of a tertiary recovery program to a specific reservoir is the amount and distribution of oil remaining in the reservoir. Experience has demonstrated that predictions for determining the yet-to-be-recovered oil saturation are frequently optimistic. More positive means for accurately assessing the reservoir oil saturation are needed. Two procedures have recently been used in Amoco's operations in an effort to better define reservoir oil saturation prior to the planning of a tertiary recovery program. These procedures were the use of: 1) Esso's pressure core barrel, and 2) a log-inject-log technique. Pressure cores were obtained in watered-out locations in three different reservoirs. One of the reservoirs was very loosely consolidated, highly permeable sandstone, and the oil saturations found in the cores were considered to be lower than actually existed in the reservoir. Possible factors contributing to the low oil saturations are discussed. Pressure cores from the other reservoirs, both dense carbonates, contained oil saturations in the range expected on the basis of laboratory flow tests on native-state cores.