Field Demonstration of Steam Drive With Ancillary Materials

Abstract

Summary CLD Group Inc. and the U.S. DOE are conducting field demonstration tests. on the use of ancillary materials to improve the efficiency of conventional steam drive. During the first year of this multiyear contract, laboratory tests were conducted to identify surfactants with the best foam-blocking potential, as well as optimal techniques for injecting the foaming materials. The first field test of foam injection with a five-spot pattern in the Midway-Sunset field was conducted the second year. Radioactive tracers were used to determine the extent of the thief zone before surfactant was injected. The year-long injection of foam with steam resulted in a significant improvement in the recovery of oil, estimated at 30,000 bbl from the pattern wells and 50,000 bbl from the wells outside the pattern. Introduction The recovery efficiency and effectiveness of conventional steam drive often are limited by premature breakthrough of steam to the producing well because of gravity segregation or fingering of steam. The resulting steam channels serve as conduits for subsequent volumes of steam and inhibit it from dispersing uniformly throughout the reservoir. The objective of this U.S. DOE cost-shared demonstration is to evaluate the potential of chemical-blocking foams for increasing efficiency of steam drive operations, particularly in heavy-oil reservoirs. The contract is being conducted in four phases. Phase 1 - Preparation, Laboratory Work, and Pretesting. During this initial phase, laboratory and coref lood tests were carried out on chemical selection and foam development. Phase 2 - Pilot Tests. A series of short-duration pilot tests on alternative uses of the foam-blocking process will be conducted during Phase 2. Phase 3 - Verification Field Test. A longer verification field test, incorporating the experience gained from the pilot tests, will be conducted during Phase 3. Phase 4 - Data Collection and Analyses. Data collection and analyses of the laboratory and field results will be performed on an ongoing basis. Phase 1 - Laboratory Testing The initial task under this contract consisted of screening foaming materials. Before this, the state of the art was surveyed through a literature review, and meetings were held with universities and private companies to discuss equipment, data, and alternative chemicals for use in foam generation. The testing consisted of five steps. Step 1 - Static Foam Testing. This was an initial screening test to evaluate the foaming ability of various chemicals with Chevron's high-speed stirrer test (HSST) and Stanford U. Petroleum Research Inst.'s refluxing test (RT). Step 2 - Laboratory Sand pack Tests. The most promising chemicals from Step 1 then were tested in a short sand pack at ambient temperature for their effectiveness at reducing permeabilities. Step 3 - Corrosion-inhibitor Studies. Chevron-type stirrer tests were undertaken to determine the effects of corrosion inhibitors when used in conjunction with air and foaming materials. Step 4 - Laboratory-Scale Steam Sand pack Tests. A high-temperature Sand pack was used to examine the effectiveness of foaming agents in the presence of steam and noncondensable gas. Step 5 - Long Sand pack Tests. A 16-ft core was constructed to test foam-blocking ability over longer distances and to examine the most efficient method for injecting surfactant.