THE AIM OF THIS PROJECT IS TO GATHER A NUMBER OF EXPERIMENTAL DATA WHICH WILL ALLOW AN ATTEMPT TO BE MADE TO QUANTITATIVELY DESCRIBE THE OIL DISPLACEMENT BY WATER IN POROUS MEDIA, BOTH IN THE DRAINING AND IN THE SOAKING MODES.
Comparison between the local measurements of saturation and pressure in oil and in water along the porous medium on the one hand, and the numerical simulation results on the other, resulted in the following conclusions in the case of forced displacement of oil by water and in the case of spontaneous imbibition of oil by water.
Concerning polyphasic flow laws:
the dynamic capillary pressures were higher than the static capillary pressures whether the flow was forced or spontaneous;
a complete matrix of relative permeabilities took into account the viscous coupling between each of the 2 phases (the corresponding mobility matrix was symmetrical and the relative countercurrent permeabilities were lower than the relative cocurrent permeabilities and this was confirmed by experimental results);
the residual oil saturation was higher at the end of a countercurrent imbibition than at the end of a cocurrent imbitions;
the water oil front had a smoother slope in a countercurrent flow than in a cocurrent flow and the heterogeneity effects were more stressed in countercurrent flow than in a cocurrent flow;
relative permeability to oil at irreducible saturation in water may be higher than monophasic permeability;
during spontaneous imbibition, local heterogeneities have a considerable effect on flow (this is more stressed in countercurrent flows).
Concerning the laboratory procedures:
the forced injection procedure, including inversions of the flow direction, constituted a satisfactory solution for obtaining a uniform initial oil saturation;
brine circulation on the ends of a sample submitted to spontaneous imbibition kept a maximum water saturation on each end and did not disturb spontaneous imbibition;
during a forced displacement, the sweep efficiency was better in the fluid injection zone than in the remaining part of the sample;
the sample length has little effect on the drainage or imbibition fluid displacement.
THE FORECASTS OF OIL RECOVERY FROM DEPLETED RESERVOIRS BY WATER INJECTION ARE STILL BASED ON THE DARCY LAW, WHOSE VALIDITY IS OFTEN OPEN TO CRITICISM. NEW TECHNIQUES ARE NOW AVAILABLE WHICH ALLOW A LESSER DEGREE OF COMPROMISE IN THE "IN SITU" DETERMINATION OF THE EXPERIMENTAL DATA NEEDED FOR A QUANTITATIVE DESCRIPTION OF THE PHENOMENA BOTH IN THE DRAINING AND IN THE SOAKING MODES.
IN THE FIRST PHASE OF THE RESEARCH, THE DISPLACEMENT IMPOSED FROM OUTSIDE WILL BE STUDIED (POROUS-ROCK RESERVOIR CASE). A LATERALLY IMPERMEABILIZED HOMOGENEOUS ROCK SAMPLE 2X6X50:60 CM OF POROSITY > 20% AND PERMEABILITY INFERIOR OR EQUAL TO 200 MD, WILL BE USED. SPECIAL WATER-PERMEABLE AND OIL-PERMEABLE SEPTA WILL BE APPLIED ON ITS SURFACE FOR CAPILLARY PRESSURE DETERMINATIONS OF EACH FLUID.
BRINE AND WHITE OIL SHALL BE USED THROUGHOUT. AN ULTRASONIC METHOD, SET UP BY IFP, WILL PERMIT SATURATION DETERMINATIONS AT ANY SPOT. ON THE SAMPLE, CONTAINING "IRREDUCIBLE" WATER AND OIL, SEVERAL EXPERIMENTS WILL BE PERFORMED WITH BRINE FORCED FLOW AIMED AT EVALUATING THE INFLUENCES OF: THE SAMPLE LENGTH ON THE FLUID DISPLACEMENT, THE AVERAGE FLUID DISPLACEMENT VELOCITY ON THE CAPILLARY PRESSURES, THE BRINE FLOWRATE AND PRESSURE GRADIENT ON THE OIL RECOVERY. THE SECOND PHASE SHALL BE CONCERNED WITH THE FRACTURED-ROCK RESERVOIR CASE. SOAKING RUNS SHALL BE EFFECTED AT ROOM TEMPERATURE AND PRESSURE ON POROUS ROCK SAMPLES OF LOW PERMEABILITY (1 TO 100 MD), LARGE POROSITY, CLAYLESS AND HIGHLY HOMOGENEOUS (CHALK). THE SAMPLE ARRANGED AS IN THE PREVIOUS PHASE SHALL BE INITIALLY SATURATED WITH OIL AND "IRREDUCIBLE" WATER PREFERABLY BY BRINE CAPILLARY DESORPTION, THUS ACHIEVING A MORE CORRECT SATURATION PROFILE. THE ABSORPTION OF BRINE THROUGH ITS END SURFACES WILL BE FOLLOWED BY DETERMINATION OF CAPILLARY PRESSURES, LOCAL SATURATIONS (BY ABSORPTION OF =40 KEV PHOTONS) AS WELL AS BY OIL AND WATER FLOWS.
COUNTERCURRENT AND COCURRENT FLOWS POSSIBLY OCCURING NEAR THE WORKING SURFACES AS A FUNCTION OF THE HYDRAULIC POTENTIAL OF THE BRINE WILL BE STUDIED. FINALLY, THE HETEROGENEITY INFLUENCE ON THE DISPLACEMENT FRONT WILL BE EXAMINED, POSSIBLY ON SAMPLES MADE UP OF TWO LAYERS OF DIFFERENT POROSITY. AN EXACT PICTURE OF THE SOAKING PHENOMENA WILL RESULT WHICH WOULD ENABLE AN ATTEMPT AT MODELLING TO BE MADE.