Recovery of Lloydminster And Morichal Crudes By Caustic, Acid And Emulsion Floods
Authors: Ali S.M. Farouq , Figueroa J.M. , Azuaje E.A. , Farquharson R.G. 
Published: March 2010

Non-thermal oil recovery methods, such as caustic, acid and emulsion flooding. Hold promise for 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 techniques. The first part of the study was concerned with a systematic examination of the emulsification of each crude with aqueous solutions, having pH's ranging from acid to basic. The Lloydminster 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, utilizingselected emulsions,acid solutions andcaustic 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 88% greater than that obtainable by a woterflood. The type and size of the slug were the critical factors in determining recovery. The oil recovery in the case of the Morichal 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 formations have received a great deal of attention, and hold considerable promise for the recovery of moderately viscous oils. The status of these processes was recently reviewed by Johnson(l). He discussed four principal mechanisms for caustic flooding: emulsification and entrapment, 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. In a water-wet porous medium, the emulsion droplets 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, which 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 present. Ehrlich, Hasiba and Raimondi(3)describe an efficient screening method for this purpose. Cooke, Williams and Kolodzie(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 cannot be fanned in situ.

A number of laboratory studies of caustic flooding have been reported. Jennings(5) gives caustic solution – crude oil interfacial measurements for 164 crude oils from 78 fields. Almost all crude oils with API gravities of 20 ° or lower exhibited an interfacial tension lower than 0.01 dyne/cm.