Non-thermal oil recovery methods, such as caustic, acid and emulsion flooding, hold promisefor certain types of viscous oils under favourable conditions. This investigation was concerned with the recovery of the Lloydminster crude (Saskatchewan) and the Morichal crude (Venezuela) at the respective reservoir temperatures, using these three techni_ ques.Thefirstpartofthestudywascon-cerned with a systematic examination Pf the emulsification of each cru wit@ aqueous solutions, having pH's 1 nging from acid to basic. The Lloydi inster crude yielded both oil-in-water and water-in-oil emulsions, whereas the Morichal crude produced only water-in-oil emulsions, stable at the respective reservoir temperatures. The second part of the study involved core floods, utiliz-ing (I) selected emulsions, (ii) acid solu-tions and (iii) caustic solutions. The oil recovery in the case of the Lloydminster crude was 30 to 46% of the in-place oil, i.e., about 41 to 8801o greater than that obtainable by a waterflood. The type and size of the slug were the criticalfactors in determining recovery. The oil recovery in the case of the Morichat crude was 59 to 65%.In both cases, emulsion slugs were more effective than caustic or acid slugs. The paper discusses the drawbacks of such non-thermal methods, as well as conditions under which such methods are likely to be successful. Introduction & BaCkground In recent years, caustic flooding and emulsion flooding of viscous oil forma-tions have received a great deal of atten-tion, and hold considerable promise for the recovery of moderately viscous oils._ The status of these processes was recent-ly reviewed by Johnson(l). He discussed four principal mechanisms for caustic flooding: emulsification and entrap-ment, wettability reversal from oil-wet to water-wet, or vice versa, and emulsification and entrapment. In the case of viscous oils, it would seem that emulsification and entrapment is the dominant mechaniSM(2). The caustic reacts with the organic acids in the residual oil, leading to the formation of an oil-in-water emulsion in situ. ln a later-wet porous medium, the emulsion ciropiets move downstream with the flowing caustic, and are entrapped again in small pore throats. The over-all effect is a reduction in the water mobility, w'nich is beneficial in improving the volumetric sweep. The crucial factor determining the success of caustic flooding is the crude composition, and the nature of the polar compounds pre-sent. Ehrlich, Hasiba and Raimondi(3) describe an efficient screening method for this purpose. Cooke, Williams and r'ol.odzie(4) also outline guidelines for evaluating potential caustic floods.Emulsion flooding involves the preparation of the crude and water emulsion prior to injection, and offers a possible alternative if an emulsion can_ not be formed in situ.A number of laboratory studies of caustic flooding have been reported. Jennirigs(5) gives caustic solution -crude oil interfacial measurements for 164 crude oils from 78 fields. Almost all crude oils with API gravities of 201 or l...
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe
A comprehensive study was carried out of the in-situ recovery of bitumen from a three-dimensional model, packed with Athabasca Oil Sand, with injection in the centre, near the base and production from the our corner wells, over the entire interval. Five injection-production schemes were tested in a recovery process involving the use of a solvent (Suncor's synthetic crude) with steam. Solvent slug sizes varied from 5to 30% pore volume, with varying amounts of steam injected. Recoveries varied from 5 to 50% of the bitumen in place depending on the slug size, rate of solvent injection and steam volume. It was found that both large and small solvent slugs are less effective than an "optimal" slug size. Of the injection strategies tested, solvent injection into the production wells was found to be most effective, with steam injection into the injection well. Splitting of the solvent slug among the injection and production wells was the next best choice. Base runs involving steam injection alone facilitated interpretation of results, and showed that on the whole solvent-steam injection is a far more promising technique. Among the variables studied rate of solvent injection appears to be a significant factor in determining bitumen recovery. Implications of the results obtained are considered from the standpoint of field application. Introduction In-situ recovery from the Athabasca Oil Sands poses special problems, in view of the virtually immobile nature of the inplace bitumen. Implementation of a suitable recovery method, usually thermal, requires creation of flow paths for the initial injection of a hot fluid. The present research on the subject, now in its tenth year, proposes the use of a solvent for this purpose which is followed by steam injection. Among other non-thermal schemes for creating initial communication between wells, the most notable are those proposed by Redford(l) and formation fracturing using emulsions or air, as employed by Shell Canada (1961) and Amoco Canada, respectively, in the Athabasca Oil Sands region. Thermal methods include cyclic steam stimulation with air or gas, electrical heating of the formation and combustion under fracture pressures. This paper outlines the principal results of the experimental research conducted during the last four years on the use of solvents and steam for in-situ recovery from the Athabasca Oil Sands, encompassing three separate studies (2,3,4) by the co-authors. The data reported here should be of value in judging the applicability of the processes considered, even though the largely unscaled experiments would preclude direct application of the data to field situations. For complete details of individual experiments, the aforementioned works may be referred to. Background and Objectives Previous work on the use of solvents and steam has been reviewed in Reference (5). It led us to believe that Suncor's synthetic crude holds considerable potential for the Athabasca Oil Sands, as an additive to steam injection, in a carefully planned operating strategy. Apart from the desirable properties of this "solvent" vis-a-vis the Athabasca bitumen, it is readily available and cheaper than any other solvent or comparable refinery stream.
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