| Popis: |
An extensive research programme was launched with the aim at evaluating the potential of seven different polyamino carboxylic acids (PACAs) using both technical and economic aspects. Dissolving capacity of each compounds was determined under equilibrium conditions as a function of concentration for barite and reservoir rock (sandstone). The absolute and relative selectivity of dissolution, viz. the matrix effect of formation rock were precisely analyzed. Dissolution of barium sulfate, calcium and magnesium carbonate and iron compounds was followed in time, and thus, the kinetic calculation could also be made. Results of the research programme provided reliable data for comparison of dissolution capacities under identical chemical (equilibrium, kinetic, dissociation, etc.) conditions. On the basis of the experimental findings it was concluded that the sequence of dissolution capacity is different if the results were evaluated in technical or economic senses. It was also shown that the preferentially used compounds (e.g. DTPA, and particularly EDTA) are not the best choices when technical considerations are only enforced. The economic grounds, however, may partly justify their application at the expense of poor efficiency. The systematic analysis of the mentioned dissolvers may open new vistas in mitigation of formation damage caused by barite or barium sulfate scales and accelerate the search for more effective mixtures of complex-forming agents to be applied under field conditions. |
