The major objective of this study was to evaluate a new fluid injection scheme for recovering tertiary oil. These fluids, developed by the Molecular Energy Research Company (MERCO), appear to be composed primarily of sodium silicate and ammonia as well as other undisclosed, unidentified additives.

In particular, a series of core flood experiments were conducted along with various fluid property measurements. Two of the MERCO fluids were tested with Delaware–Childers crude oil (35°API), two others with Bakersfield crude oil (15°API). Prior to tertiary flooding the cores were water-flooded with sodium chloride brine.

Recoveries for the Delaware–Childers floods using a continuous injection of Merco of Si-Na (NH2CONH2) fluids recovered from 3.9 to 35.4% of the tertiary oil. Oil response increased as the flooding rate increased from 1 to 5 ft/d. Much of this recovery could be credited to the gas drive created when the hydrogen peroxide used in the tertiary fluid decomposed in the core. Floods utilizing hydrogen peroxide alone recovered 6.4 to 20.5% of the tertiary oil and showed the same rate dependence .

The core floods conducted with Bakersfield crude oil and slugs of C–4–L and C–8–5 test fluids chased by polymer had recoveries ranging from 14.3 to 18.8% of the tertiary oil in place. Recoveries with C–4–L increased as slug size was increased from 1.6 to 10.0% of the pore volume, while C–8–5 flooded cores showed no change in recovery. Most of this recovery was attributable to the polymer buffer used for mobility control. Polymer injection alone recovered 14.1% of the tertiary oil.

Crude oil – aqueous phase interfacial tensions were reduced 58 to 92 percent with the MERCO fluids. This is not enough to significantly alter recovery. The MERCO type fluids were also able to break water–oil emulsions more quickly than gravity alone. However, a commercial demulsifier was much more efficient than any of the MERCO fluids tested for this oil–water system.

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