The deposition of scale salts, particularly calcium carbonates (CaCO3), on production equipment is a very challenging problem for the oil and gas industry. The process of deposition of scaling salts is often an intrinsic problem, occurring as a consequence of the physicochemical conditions in oil wells. In order to remedy the oil industries use chemical species called scale inhibitors to prevent the deposition process. The understanding of the molecular mechanism of action of inhibitors is not completely understood. Then, computational studies were carried out to calculate the electronic and structural properties of the interaction between scale inhibitors and calcium cations (Ca2+), in order to provide details at the molecular level about the mechanistic action of anti-scalants. For these studies, the approach of density functional methods combined with the implicit solvation model for the quantum electronic structure calculations was used. The thesis was divided into three distinct studies, involving the calculation of the binding energy between the Ca2+ ion(s) and inhibitory species, namely: (i) sodium hexametaphosphate, (NaPO3)6 – HMP; (ii) copolymer monomer poly(4-styrene-sulfonic acid-co-maleic acid) [P(SS-MA)] and anionic surfactant sodium dodecyl sulfate (SDS); and (iii) carboxymethylcellulose (CMC) and hydroxyethylcellulose (HEC) polymer monomers. For the species HMP, the pKa values of the (de)protonation process of the species (HPO3)6 were estimated, namely: pKa1 = –1.2; pKa2 = -0.98; pKa3 = +3.7; pKa4 = +5.6; pKa5 = +10.4; and pKa6 = +12.0. The values obtained by the theoretical calculations show good agreement with values of +6.2 (pKa4) and +9.2 (pKa5) obtained experimentally. In all cases the binding energies between the inhibitor species and the Ca2+  ion were compared with the binding energies of Ca2+···HCO3–  and Ca2+···CO32–. In (i) the complexes formed by the interaction between Ca2+  ions at each HMP coordination site, in their anionic forms H4(PO3)62− and H2(PO3)64−, are thermodynamically favorable. In (ii) the theoretical results suggest that the binding energies between the monomeric species of P(SS-MA) and Ca2+ ions are thermodynamically favorable if the coordination occurs through the carboxylate groups. However, the binding energy between the SDS and the Ca2+ ion is unfavorable in terms of the Gibbs energy. Furthermore, the cooperative interaction of the surfactant SDS and P(SS-MA) with the Ca2+ ion(s) can result in an exergonic complex. Finally, in (iii) the results of binding energy calculations between Ca2+ and CMC and HEC monomers suggest that the Ca2+ cation interacts more strongly with CMC than with HEC. This is because while the CMC monomer has carboxylate groups to interact with the cation, the HEC has only polar (non-anionic) groups. Furthermore, for this system, the interaction energy of the monomers with a cluster of [CaCO3]5 was calculated. Theoretical results suggest that the CMC monomer can replace the position of a CO32– ion in the cluster, but the HEC monomer does not have this ability.