Abstract

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 (35API), two others with Bakersfield crude oil (15API).Prior to tertiary flooding the cores were waterflooded Prior to tertiary flooding the cores were waterflooded 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 from14.3 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 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.

Introduction

At the end of 1977, fields had been discovered in the U.S. containing a total of 450 billion barrels of oil originally in place. The ultimate recovery expected from these fields is 33%, which means that two-thirds or 300 billion barrels will be left as residual. In other words, if one-half of the residual oil in this country could be produced, it would equal all the reserves found to date. Obviously this is a vast amount of oil, but in order to exploit its full benefit new methods must be discovered to recover it. New processes and materials such as micellar/polymerflooding, CO2 flooding, miscible gas flooding, in-situ combustion, and stem flooding need to be developed and tested. MERCO oil-recovery fluids are an example of new technology developed to recover tertiary oil. Chemically, they are inorganic polymers which claim to enhance oil mobilization, disperse clay, break water-in-oil emulsions and generate hydrogen which raises the gravity of oil.

The purpose of this study was to examine the ability of these fluids to recover residual oil. In order to evaluate them, the following experiments were conducted.

  1. Berea core floods with a light, Delaware-Childers crude oil (35API).

  2. Berea core floods with a heavy, Bakersfield crude oil (15API).

  3. Tests to determine the emulsion breaking capabilities of the fluids and to compare it to a commercial demulsifier.

  4. Measure the interfacial tension of the fluids with the crude oil they displaced and their conductivity.

IMPROVED WATER FLOODING THEORY

Many methods to improve the recovery of oil during conventional water flooding have been examined by the oil industry. In order to accomplish this goal, two routes became readily apparent.

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