Yousef Kazemzadeh

In this work, barium sulfate precipitation was analyzed under ambient and reservoir conditions. The worst scenario for barium sulfate precipitation occurred at a mixing ratio of 40:60 formation and injection waters. This ratio was used in the jar, turbidity, dynamic tube blocking, and coreflood tests. In addition, a critical radius and mass of barite particles were determined at various values of supersaturation ratio and surface tension. For the prevention of barium sulfate precipitation, three well-known industrial scale inhibitors and one recently developed reagent (named DPAAI) were used. Results of static and dynamic tests indicated that DPAAI had the best performance for inhibiting barium sulfate precipitation. Moreover, DPAAI could prevent the heterogeneous nucleation of barium sulfate and was effective in blocking the formation of barite and inhibiting crystal growth. The chances of collisions between the cations and anions in the solution were significantly reduced in the presence of DPAAI. The rock permeability due to barium sulfate was reduced to less than 40% of the initial permeability. After the application of the inhibitors, the formation damage was considerably reduced. Besides, a correlation has been developed to predict the reduction in rock permeability owing to the precipitation of barium sulfate in rock samples. Meanwhile, it was found that data predicted by the model were in good agreement with experimental data. Furthermore, scale inhibitor return concentration was evaluated by modeling and experiments, on the basis of which the protection period of the near-wellbore region and well from barium sulfate was determined. Among the investigated reagents, the longest squeeze lifetime was observed for DPAAI, which was associated with the intensification of adsorption and desorption processes on the rock surface.