In many mature offshore fields, high water cuts and potential scale deposition are some of the toughest challenges operators need to face. Two common practices used to deal with these challenges are relative permeability modifiers (RPM) polymer injection and scale inhibitor squeeze treatments. Even though many fields face these two challenges simultaneously, little is known about concomitant application of these treatments. In this paper, the effect of applying RPM polymers prior to inhibitor squeeze in the effectiveness of the last treatment is evaluated for sandstone rocks of Campos Basin, Brazil. Sequential laboratory injections in Campos Basin rocks of commercial cationic and anionic polyacrylamide and polyaluminum chloride (PAC) as cross-linking agent were employed prior to the injection of a commercial organophosphonic acid type inhibitor for barium sulfate scale. It was found that the polymers employed are capable of reducing the permeability of porous media to water and increasing the retention time of the scale inhibitor simultaneously. The tests also indicated that the inhibitor's longer retention time is associated with the interaction with an outer cationic layer of the cross-linking agent. The adsorption isotherms were calculated and compared with Langmuir, Freundlich, Sips, and Toth models, the last two being the most accurate in representing the adsorption system for these tests.

No abstract

During reactive flows in porous media with precipitation of a solid chemical reaction product, the permeability reduction occurs. The mathematical model for reactive flow in porous media formulated contains two empirical parameters – the kinetics rate coefficient, determining the reaction rate along with reagent's concentrations, and the formation damage coefficient, reflecting the permeability reduction due to the solid precipitation. These parameters are determined from the laboratory coreflood tests with commingled injection of reacting fluids. A routine laboratory method determines the kinetics rate coefficient from expensive and cumbersome reagent concentration at the core effluent; then, the formation damage coefficient is calculated from inexpensive and simple pressure drop measurements. In the current paper, a laboratory method for determining both coefficients from pressure measurements only is developed. The method utilises pressure measurements at the core inlet, effluent and some intermediate core port during commingled quasi steady state flow of incompatible fluids. The data treatment is based on the analytical model for one-dimensional commingled flow of reacting fluids. The formulae for determining the model coefficients from pressure measurements are derived. The intervals for inverse solution existence, uniqueness and stability are established. Good agreement between the model constants as determined by the routine and three-point-pressure methods validates the proposed method.

No abstract