EFFECT OF PH ON INITIATION OF FINES MIGRATION: DLVO MODELING AND EXPERIMENTAL VALIDATION

Abstract

THE INTERACTION OF ROCK AND FLUID ELEMENTS DURING PRODUCTION STARTS FORMATION DAMAGE, WHICH REDUCES PERMEABILITY AND DECREASES HYDROCARBON EXTRACTION. IN SANDSTONE RESERVOIRS, SMALL SOLID PARTICLES CALLED FINE PARTICLES START TO RELEASE AND MOVE DURING THE INVASION OF DIFFERENT FLUIDS DURING PRODUCTION OR OIL RECOVERY RELATED OPERATIONS. THIS PROCESS IS CALLED FINES MIGRATION, A TYPE OF FORMATION DAMAGE IN SANDSTONE RESERVOIRS. FINES MIGRATION CAN AFFECT OIL PRODUCTION. SINCE FINES WERE RELEASED AND STARTED TO MIGRATE THROUGH THE RESERVOIR, THEY BLOCKED SOME OF THE OPEN HOLES, WHICH MAY COMPLICATE THE FLUID FLOW IN POROUS MEDIA AND REDUCE THE PERMEABILITY. SEVERAL FACTORS AFFECT THE FINES MIGRATION INITIATION. TO REDUCE THE FINES MIGRATION IMPACT ON FORMATION DAMAGE, PARAMETERS SUCH AS PH, FLOW RATE, AND IONIC STRENGTH WERE ANALYZED TO PREDICT AT WHICH CONDITIONS FINES START TO MOVE IN A SAND-FINE-BRINE SYSTEM. FOR THIS PURPOSE, TERMS SUCH AS CRITICAL PH AND CRITICAL FLOW RATE ARE DEFINED. CRITICAL PH SHOWS AT WHICH PH LEVEL MIGRATION STARTS, WHEREAS CRITICAL FLOW RATE SHOWS THE LOWEST FLOW RATE AT WHICH MIGRATION DOES NOT OCCUR. ENHANCED OIL RECOVERY METHODS, SUCH AS INJECTION OF LOW-SALINITY WATER AND ALKALINE FLOODING, ALTER THE SALINITY AND PH INSIDE THE FORMATION, WHICH AFFECTS THE ELECTROSTATIC INTERACTION FORCES BETWEEN FINES AND THE ROCK SURFACE. THERE ARE ALSO HYDRODYNAMIC FORCES THAT IMPACT THE RELEASE OF THE FINES. HENCE, TO PREDICT THE FINES MIGRATION INITIATION, ALL THESE FORCES SHOULD BE CONSIDERED AND ANALYZED. IN THIS WORK, A MODIFIED METHOD BASED ON DLVO (DERJAGUIN, LANDAU, VERWEY, AND OVERBEEK) THEORY WAS USED TO PREDICT THE CRITICAL PH TO RELEASE THE FINES. ANALYSIS OF REPULSIVE AND ATTRACTIVE FORCES RESULTED IN THE PREDICTION OF CRITICAL PH IN DIFFERENT CONDITIONS. THE MODEL PREDICTS THAT THE INITIATION OF FINES MIGRATION OCCURS AS A FUNCTION OF PH AND SALINITY AND PREDICTS CRITICAL PH VALUES OF 8 AND 10 (FOR 0.2 M NACL AND 0.25 M NACL, RESPECTIVELY). FURTHERMORE, THE MODEL WAS VALIDATED, WHERE CRITICAL FLOW RATES AT A PH OF 8 AND A 0.25 M NACL CONCENTRATION CAN BE PREDICTED, WITH A CALCULATED ERROR OF 13%. SEVERAL COREFLOODING EXPERIMENTS WERE CONDUCTED TO VERIFY OUR DEVELOPED MODEL AND METHODOLOGY. HENCE, THE VERIFIED MODEL CONSIDERED ELECTROSTATIC, GRAVITATIONAL, AND HYDRODYNAMIC FORCES THAT AFFECT FINES MIGRATION. TO CONCLUDE, DLVO MODELING IS ONE OF THE WAYS TO PREDICT PARAMETERS THAT AFFECT THE FINES RELEASE AND FURTHER MIGRATION BY CALCULATING THE FORCES THAT ARE INFLUENCING THE SAND-FINE-ROCK SYSTEM. THIS METHOD MAY REDUCE THE EXPERIMENTAL WORK TYPICALLY NECESSARY FOR DESIGNING OPERATIONS SUCH AS EOR.