This paper provides an overview of current steam injection technology. The emphasis is on steamflooding with some data on cyclic steam stimulation. subjects discussed include oil recovery and sweep latest trends in steam injection operations and equipment, operating problems, and special conditions encountered in steamflooding such as gas cap and bottom water.
The purpose of this paper is to help petroleum engineers keep up with emerging steamflood technology including both reservoir and operating experience.
Steam injection is the principal enhanced oil recovery method today, accounting for 90% of all oil produced by such methods. Prats estimates the produced by such methods. Prats estimates the total worldwide oil production rate due to steam is now 405,200 B/D. Production in the U.S. is about 240,000 B/D, Venezuela 148,000 B/D, and Canada 9,000 B/D. It is the most important recovery method for the oil sands of Alberta and Orinoco (Venezuela), where several large projects are in the planning and construction stages.
There has been a significant advance in steam injection technology since the principal author reviewed the status of steam injection at the CIM meeting five years ago. The Oil and Gas Journal's annual review for 1978 lists 99 active steam injection projects for the United States, 41 for Venezuela, and 14 for Canada. In addition, petroleum engineers have published a number of technical papers which describe field projects and provide greater understanding on how the process can best be applied in the future.
The most notable development in steam injection over the past five years is the overwhelming shift to steamflooding, with cyclic steam stimulation becoming an important adjunct, rather than a separate oil recovery precess. This is attributed to the relatively low ultimate oil recovery attainable by cyclic steam stimulation on the one hand, and to higher oil prices on the other, which have served to make the considerably lower oil-steam ratios, characteristic of steamfloods, economically attractive.
Tables 1(a) and 1(b) list the principal statistics for 12 selected steam injection field tests. These represent the major steam injection projects except for-those already reported earlier in References 2 and 3. All, except Test 6, are steamfloods. Test 6, a commercial cyclic steam stimulation project in Indonesia, is included here because of project in Indonesia, is included here because of its size and the high oil-steam ratio achieved.
Unfortunately, several large projects are not listed in Table 1 because sufficient data were not available. These include: Imperial's Cold Lake Lemming project (5000 B/D: cyclic stimulation), Chanslor-Western's Midway-Sunset, California project (23,000 B/D: steamflood), Texaco's San Ardo project, California, and several projects in Venezuela.
Table 1(a) gives the formation characteristics for the tests cited, while Table 1(b) lists some of the test results for the same. It is notable that the formation thickness in most cases is 100 ft. or less. There is a wide variation in reservoir pressures and oil viscosities. Tests 7 and 12 are pressures and oil viscosities. Tests 7 and 12 are essentially in the start-up stage; the data given are based upon scaled model studies. The only projects repeated from the previous survey are Tests 10 and 11, which have undergone major expansions.
Table 1(b) shows that oil recoveries up to 73% have been attained in steamfloods conducted to-date, and are much higher than previously reported. Consequently, the oil-steam ratios average 0.20 bbl/bbl, or better.
Test 4, Charco Redondo, was cited in Table 1 primarily because of its unique features. It was a primarily because of its unique features. It was a highly instrumented steam pilot in a waterflooded reservoir; following the steamflood, and was successfully subjected to in situ combustion.