THE AIM OF THIS PROJECT IS TO EVALUATE THE EFFECTIVENESS OF A NUMBER OF WAYS OF REDUCING THE EXTENT OF SURFACTANT RETENTION IN SURFACTANT ASSISTED OIL RECOVERY.
Research on the reduction of surfactant retention took 3 directions. The first resulted in proposing the injection of alkaline carbonates to raise the formation pH to approximately 11 before injection of the surfactants. A mathematical model for alkaline solution propagation in clayey porous media was designed to evaluate the possibilites made available by an alkaline injection in a specific assisted recovery operation. This model satisfactorily takes into account the ion exchange data but problems remain where the dissolution kinetics are concerned involving modelling of the aluminum inhibiting effect on quartz dissolution kinetics and modelling of the dissolution of constituents on argillaceous sandstones other than quartz and kaolinite, such as feldspath or various types of clay.
The second direction dealt with the passing back into solution of the surfactants adsorbed using a desorbing agent. The conducted study showed the efficiency of highly hydrophylic nonionic surfactants. However, such passing back into solution was merely a part of the process and the study should be pursued by evaluating the interfacial efficiency of the micellar plug restored by the desorbed surfactant and the desorbed agent in contact with oil. Lastly, the modification of the surfactant structure did not result in retention levels low enough to allow surfactant implementation without adding an alkaline or desorbing agent.
OIL RECOVERY BY MEANS OF SURFACTANTS IS STILL UNECONOMIC. IT IS BELIEVED THAT THIS ARISES MAINLY FROM THE SURFACTANT RETENTION BY THE COMPONENTS OF THE ROCK IT PASSES THROUGH.
THE PROPOSED RESEARCH WORK DEALS WITH THE STUDY OF THREE WAYS OF REDUCING THE EXTENT OF SUCH A RETENTION.
1.- RAISING THE MEDIUM PH. CAUSTIC SODA ADDITION HAS BEEN ALREADY SHOWN TO BE EFFECTIVE BUT IT ENTAILS SEVERE LOSSES DUE TO ITS DISSOLUTION. BETTER RESULTS WOULD PROBABLY RESULT FROM THE USE OF CARBONATES OR SILICATES. AS TO THE CARBONATES, A PRELIMINARY THEORETICAL APPROACH SHALL BE MADE USING LITERATURE DATA. EXPERIMENTALLY DETERMINED ION-EXCHANGE AND DISSOLUTION PARAMETERS WITH STANDARD SANDS OR CLAYEY SANDS WILL ALLOW A NUMERICAL MODEL TO BE OBTAINED DESCRIBING THE PH FRONT PROPAGATION. FOR SILICATES, KINETIC PARAMETERS SHALL BE OBTAINED BY DYNAMIC EXPERIMENTS FIRST WITH A SAND-KAOLIN MIXTURE, THEN WITH CLAYEY SANDS AS ABOVE. THE EFFECTIVENESS OF THE VARIOUS INJECTION MODES OF THE SURFACTANT/ALKALI COUPLE WILL BE EXPERIMENTALLY EVALUATED AND POSSIBLY MODELLED.
2.- USING ADSORPTION INHIBITORS. ANIONIC POLYELECTROLYTE INHIBITORS ARE PROPOSED (POLYPHOSPHATES, POLYSILICATES, ANIONIC POLYMERS). DYNAMIC EXPERIMENTS WITH A SAND-KAOLIN MIXTURE WILL ALLOW THE MODELLING OF THE INHIBITOR PROPAGATION TO BE ATTEMPTED. THE EFFICIENCY OF THE INHIBITOR ON THE RESIDUAL SURFACTANT ADSORPTION AND ITS INFLUENCE ON THE SURFACTANT PROPAGATION WILL BE EXPERIMENTALLY STUDIED AND POSSIBLY MODELLED.
3.- USING DESORBING AGENTS. PREVIOUS FIELDS TESTS HAVE PROVEN PROMISING. VERY HYDROPHILIC PRODUCTS ARE SUGGESTED FOR THIS PURPOSE. A MIXTURE OF AN ANIONIC AND A NON-ANIONIC SURFACTANT WILL BE INJECTED INTO A POROUS MEDIUM MADE UP OF SAND AND KAOLIN, FOLLOWED BY AN INJECTION OF A SOLUTION AT VARIOUS CONCENTRATIONS OF THE DESORBING AGENT (ETHOXYLATED ALCOHOLS OR PHENOLS) AND THE PROFILE OF THE DESORBED SURFACTANTS IN THE EFFLUENTS WILL BE DETERMINED BY USUAL ANALYTICAL TECHNIQUES. A MODELLING OF THE SOLUTION MIGRATION WILL BE ATTEMPTED. A SEARCH FOR THE BEST DESORBING AGENT WILL BE ATTEMPTED BY A CORRELATION OF ITS PERFORMANCE VS MOLECULAR WEIGHT. AN EXPERIMENTAL EVALUATION OF THE EFFECTIVENESS OF THE VARIOUS INJECTION MODES WILL BE EFFECTED. AS TO THE RELATIONSHIP BETWEEN SURFACTANT STRUCTURE AND ITS RETENTION, ANIONIC PRODUCTS WILL BE EXAMINED UNDER CONDITIONS DEFINED BY PRELIMINARY TESTS.