The influence of the Ca++ and inhibitor concentrations, pH, and temperature
on the phase behaviour and precipitation yield of a phosphinopolyacrylate
scale inhibitor, PPAA, has been studied. The results are interpreted in ter
ms of the chemical processes governing PPAA-Ca++ complexation, and evidence
for the role of inhibitor molecular weight in determining the degree of pr
ecipitation is produced. Comparative adsorption and precipitation squeezes,
carried out in sandpacks, demonstrate that significant enhancement of the
treatment lifetime can be achieved when conditions giving extensive inhibit
or precipitation are used. The sandpack experiments and dissolution studies
on the precipitated inhibitor both suggest strongly that kinetic phenomena
influence the return level of inhibitor in the field. Together these studi
es point the way to approaches for optimising inhibitor precipitation squee
ze treatments in order to control scale deposition in petroleum reservoirs.