City Research Online

Abstract

The precipitation, crystallisation and aggregation processes in CaC03, BaS04-SrS04-CaC03 and CaS04-CaC03 systems have been studied. For the CaC03 system the effects of applied magnetic fields on the formation of calcium carbonate scale were the subject of a detailed investigation. The study of the BaS04-SrS04-CaC03 and CaS04-CaC03 systems was designed to determine (1) the effects of varying the ion concentrations in simulated offshore oilfield formation and sea waters and (2) the effect of the ratio of mixing the simulated waters on the rate of deposition of scale.

The scale-forming properties of CaC03 are shown to be affected by applied magnetic fields. Propensity to scale data obtained by measuring the back pressure as scale builds up in a microbore tube show that the passage of calcium-containing solutions through a magnetic field prior to CaC03 precipitation delays deposition. The effects of (1) flow rate of both calcium and hydrogen carbonate ion solutions through an electromagnetic field, (2) sodium hydrogen carbonate concentration and (3) temperature on CaC03 deposition are also reported. Heat exchanger experiments show that applied magnetic field treatment causes major differences in the crystal and aggregate sizes of the precipitates and significantly reduces the quantity of scale formed. The results are interpreted in terms of the direct interaction of applied fields on charged species in fluids. The data from the present work taken with the results from previous work show that these field interactions are part of a general phenomenon.

The precipitation and aggregation properties of the solids formed in the BaS04-SrS04-CaC03 and CaS04-CaC03 systems from mixed simulated formation and sea waters are reported. Precipitation tests and scale prediction model data for the BaS04-SrS04-CaC03 system provide information on the amount of each solid formed and explain changes in the propensity to scale. Data for both systems on the changes arising from increasing each significant ion concentration in the simulated offshore oilfield waters are also reported. All the changes in the propensity to scale measurements are related to solubility effects, ion-pair effects and kinetic effects.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > QD Chemistry
Departments:	School of Science & Technology School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

Export

Downloads