Propane-Gas-Water Miscible Floods In Watered-Out Areas of the Adena Field, Colorado
Authors: Holm L.W. 
Published: December 2007

Results of the field tests described here showed that within the contacted pore volume the injected propane mobilized essentially all the oil left pore volume the injected propane mobilized essentially all the oil left behind by the waterflood. This residual oil was recovered profitably in the ratio of more than two barrels of reservoir oil for each barrel of propane.

Introduction
The Adena reservoir (Fig. 1), Colorado's second largest field and the largest in the Denver-Julesburg basin, was produced by gas-cap expansion, solution-gas drive, and waterflooding. The waterflood was conducted early in the primary life of the field by injecting water into wells just above the gas-oil contact in a line drive pattern (see Fig. 1). Details of this flood are given by Weyler and Sayre. The important reservoir, rock, and fluid properties for the Adena reservoir are listed here in Table 1. Although the waterflood-pressure maintenance program had been highly successful in recovering oil program had been highly successful in recovering oil from the Adena reservoir, it was estimated that half the original oil in place would remain when the economic limit of the waterflood was reached. A literature search and laboratory study of tertiary recovery methods were made to determine the one process best suited to recover additional oil at the reservoir conditions that were found at the time of the study - 1961. Solubility data for propane, methane, and recombined Adena reservoir oil showed that miscible displacement of the oil by propane and gas could be achieved at pressures above 1,000 psi at reservoir temperature (180 degrees F). The mobility ratio in the reservoir between oil and propane was calculated to be 6.4, and that between propane and gas was 4. Miscible floods conducted in 8-ft-long Berea sandstone cores at these conditions recovered more than 90 percent of the oil left after a waterflood. A detailed economic study of such a tertiary recovery program indicated that with propane available at 4.5 cents gal, the profitability prospects of the program warranted pilot testing of the miscible displacement process. Two separate field tests of the propane-gas-water process. Two separate field tests of the propane-gas-water recovery process were conducted from 1962 to 1965. This paper presents the results of those tests. paper presents the results of those tests.

Clar A Test
Fig. 2 shows the portion of the Adena reservoir in which the first pilot test of the propane-gas miscible flood was conducted. Table 2 gives pertinent reservoir properties for this area. The waterflood front had moved past the Clar A lease and Clar A-5 had been shut in; Clar A-2 was expected to be watered out and shut in when the test flood started. A potentiometric model study of the proposed potentiometric model study of the proposed propane-gas-water flood was made to determine the propane-gas-water flood was made to determine the total pore volume that would be swept by a 5 percent PV slug of propane followed by alternate gas and water PV slug of propane followed by alternate gas and water injection (see Fig, 2). The model study showed that to achieve the swept areas shown in this figure, it would be necessary to reduce injection of water into Injection Wells W-17, W-18, W-19, W-20, and W-44 from about 1,000 B,/D each to the rates shown, The cross-hatched area in Fig. 2, denoted as 1, was the area expected to be contacted at the time of propane breakthrough in Clar A-2; Area II is the additional area to be contacted by propane at the time of breakthrough in the second location, Crone 1. (Also see Table 2.)
JPT
P. 1264