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Scale formation in upstream oil operations may cause lower production rate, higher operational costs and detrimental environmental impacts when hazardous chemical inhibitors should be used to combat scaling. Green scale inhibitors (SI) are also gaining increased attention but their utilization is still a matter of much debate with many open questions to be addressed. In this study, green SIs, i.e., folic acid and inulin were investigated from experimental and theoretical perspectives. In the experimental part, two brines were mixed incompatibly through standard high-temperature static tests i) to examine the performance of green SIs and also ii) to discern their optimum concentrations and pH. Furthermore, SEM (Scanning Electron Microscopy) and EDX (Energy Dispersive X-ray) analyses were carried out to identify mechanisms under which the mitigation of scale precipitation would take place. The results revealed that folic acid and inulin could optimally be applied with concentrations of 450 mg/L (pH = 4) and 600 mg/L (pH = 6), respectively. SEM analyses also showed that the dominant inhibition mechanism for folic acid was crystal modification whereas it was threshold inhibition for inulin. Moreover, based on the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, the work of cohesion was calculated which confirmed that folic acid and inulin retarded calcite from getting precipitated almost %65 and 54%, respectively. Finally, the performance of a commercial phosphonated SI was also investigated for the sake of comparison with the green SIs which confirmed their comparable efficacy. |
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