LAUSR

ABSTRACT Calcium carbonate (CaCO3) precipitation, due to incompatibility between the injected water (IW) and formation water (FW), is known to be a major operational obstacle during water flooding projects. In this study, initially by using OLI Scale Chem and ScaleSoftPitzer software and static beaker tests, the potentiality of CaCO3 scaling was determined from the given ionic content of incompatible synthetic brines, under different conditions (temperature, pressure, and volume mixing ratio of incompatible brines). The results showed that the maximum amount of CaCO3 salt was formed at a volume mixing ratio of 0.8:0.2 (IW:FW). The simulation results showed that OLI software is more reliable than the ScaleSoftPitzer. In the second stage of this work, the 0.8:0.2 proportion of IW:FW was selected to examine the mechanisms under which the maximum formation damage of the tight carbonate cores occurred through the water injection experiments. In addition, the turbidity of the bulk solution was measured to confirm the core flooding outcomes. Various hydrodynamic parameters (low flow rate, scaling tendency, and the temperature) were evaluated in these experiments. Bulk induction time (tind) and scaling period (ts) were determined from the setup. Either heterogeneous nucleation (i.e. crystallization processes), or both heterogeneous nucleation and adhesion of pre-deposited crystals from the mixed incompatible brines to the pore wall of the cores, were attributed as the principal mechanisms of the formation damage of tight carbonate rocks owing to CaCO3 salt formation. Moreover, a semi-empirical model was established from this laboratory study, which predicts the scaling period (ts) as a function of interfacial energy, temperature, and scaling tendencies.