Steamflooding can be an efficient and economically viable recovery technique for light oils. under the right conditions. This paper includes a thorough review of the current state of steamflood technology as applied to light and moderately viscous oil reservoirs, including a description of the mechanisms involved in the steamflood recovery process. The paper also gives the results of selected scaled model studies of a light oil steamflood, showing the type of drive to expect in the field.
An elementary numerical simulator, employing the Mandl-Volek method, was developed to examine the potential for light oil steamflooding in Alberta. One hundred and fifteen reservoirs in Alberta were examined and it was found that at least ten of Alberta's light oil reservoirs are suitable for steamflooding. These reservoirs are listed, and predicted steamflood recoveries and oil-steam ratios are given. Criteria for steamflooding a light oil reservoir are suggested in light of the results obtained.
The chief concerns in light oil steamfloods are (i) the initial oil saturation, (ii) the formation porosity, and (iii) the formation thickness. It is concluded that the porosity-oil saturation product should be at least 0.1 and that minimum formation thickness should be about six metres. Other factors to consider include depth, reservoir pressure, and steam injectivity.
Steam injection is a proven method of oil recovery which has been widely successful in recovery operations around the world. It currently accounts for over 80 % of all oil produced in the world by enhanced recovery methods. Of the two steam injection methods being employed, viz. cyclic steam stimulation and steamflooding, we shall consider only the latter, because cyclic steaming is only appropriate for heavy oils.
The efficiency of steamflooding is evident in California heavy oil reservoirs where steamflooding has resulted 1n oil recoveries of as much as 77 %(San Ardo) with 55–60 % being commonplace. There is a growing belief that this heavy oil steamflood technology can be applied with similar success to 1ight oil reservoirs to recover waterflood residual oil.
Following primary production, light oil reservoirs are typically waterflooded to increase the ultimate oil recovery. However, such waterflooding operations still leave a considerablevolume of unrecovered oil. Waterflood residual oil saturations are generally in the range of 40 to 50 % and may be much greater.
Several methods have been proposed to recover waterflood residual oil. These include micellar/ polymer flooding, alkaline flooding, microbial techniques, and miscible' and immiscible gas injection. However, in many instances, the incremental recoveries from such operation are not economical.
A number of field tests have been conducted (listed later in the paper), where a steamflood was carried out in a light oil reservoir. Several of hese have been successful. Unlike heavy oils where oil viscosity is of primary concern, light oil ecovery by steamflooding is strongly dependent on the steam distillation effect, which results in extremely low residual oil saturations in the steamed out zone, Studies have shown that the steamflood residual oil saturation approaches zero in the case of a light oil.