Formation Fines Stabilization Using Surface Adsorption Polimerization: Field Application of an Emerging Technology

Abstract

Abstract Wells in a field offshore South East Sumatra, Indonesia, produce oil at very high rates and water cut. Under these conditions the reservoir is susceptible to fines migration with the associated pore plugging and production decline. Conventional acid treatments to dissolve fines in the near well bore have been effective for limited periods. However after some days or weeks of production, rates have been observed to fall as fines once again migrate, accumulate and plug the formation and gravel pack. Retarded mud acid formulations -that claim fines stabilization- have also been put into practice in an attempt to solve the problem. These formulations have also been ineffective and fines migration remained an unsolved problem. A novel technique to inhibit fines migration through the "Surface Adsorption Polymerization" technique has been used to stabilize the fines around the borehole. The technique is a three-stage process that results in fines being coated with a solid thin polymer film that is stable at high flow (shear) rate locking the fines in place. The validity of the approach has been confirmed with flow tests in cores from the field under study, and has been validated by field results. This paper presents the process followed to implement this technique in the field, case histories and production data of the treated wells. Introduction Formation fines, in general comprised of aluminosilicate particles a few microns in diameter, are found in the majority of oil and gas producing sandstones. Fines become a problem when they swell or detach from the pore wall and migrate through rock matrix with produced fluids. These mobile fines eventually clog in pore throats, plugging the pores and causing a reduction of rock permeability. Factors contributing to the production of fines include exposure to high pH fluids, exposure to fresh (low salinity) water, wettability and high fluid velocity1,2. Quaternary ammonium salts, sulfonated polymers, hydrolyzable metal ions and organosilane products have been used to mitigate fines migration. These chemicals are adsorbed on the rock surface and prevent detachment of fines by forming a protective shield around negatively charged clay particles. These additives have often been termed permanent clay stabilizers, and when compared to inorganic salt stabilizers such as KCl or NH4Cl, they can provide longer-term protection. The fact is that these stabilizers are far from being permanent since they still rely on charge neutralization. The limitations of these treatments are:Charge neutralization does not prevent mechanical dislodgment of particles subjected to high fluid velocity3.Fines with low charge density (feldspars) are not controlled effectively by charge neutralization.Only temporary control is obtained because the polyvalent ions tend to desorb over time as large volumes of fluid are produced. Points 1) and 3) are particularly true in the field of the study, where producing rates of 10,000 to 30,000 BFPD at 90–98% water cut promote mechanical dislodgment of particles and ion desorption.