Abstract
A scale inhibitors evaluation study was conducted to minimize the possibility of scaling tendencies when Effluent water, with or without Zubair Aquifer water, is injected into the reservoir of West Kuwait oil fields. A static autoclave jar test and a dynamic scaling rig were used to screen and evaluate six commercially available products under different reservoir conditions. Results obtained indicate that Zubair Aquifer water showed no tendency to scale by itself under reservoir conditions while Effluent water showed significant scaling under all down-hole conditions and a tendency to scale, although not as rapidly, at surface conditions. Evaluation of 60:40 and 50:50 mixtures of Aquifer and Effluent water showed no scaling tendency at the surface conditions of 150°F (65.6°C) and 380psi (2.6Mpa). Scale type observed for the Effluent water was CaSO4 in the bassanite form [Ca2 (SO4)2H2O] in all cases. Based on the observed results, phosphonate based scale inhibitor at 20 ppm would prevent scaling by the Effluent water under both surface and down-hole conditions with 100% Effluent water. An organic phosphate ester was found to prevent down-hole scaling at 20 ppm in the Effluent water, but failed to prevent slow scale deposition in dynamic tests at 60 ppm under surface conditions. Results indicate that a scale inhibitor will need to be applied early upon use of the Effluent water to prevent scaling in the surface equipment as well as upon reinjection, if injected by itself. Blending and dilution with other water sources may limit or prevent scaling and should be considered as an alternative. Any such blending should be conducted before storage in surface tanks.
