Abstract
Calcium carbonate scale is formed during oil and gas production. Tube-blocking tests (TBTs) are used to define the minimum inhibitory concentration (MIC) in order to prevent scale adhesion in the petroleum production system equipment. However, non-adhered crystals may favor heterogeneous nucleation to other deposits such as calcium naphthenates, causing a more severe scale problem, increasing production losses and treatment costs. The objective of the present work was to develop a new dynamic test methodology to determine the MIC for CaCO3 using a sintered metal filter. Organophosphorus inhibitors were selected for comparison with the conventional dynamic tube-blocking system. The results demonstrated that the use of the filter allowed an MIC of the inhibitors to be obtained considering the precipitation prevention. The inhibitor concentration in the conventional tube-blocking system does not prevent precipitation, acting only on adhesion and crystal growth on the capillary wall. Tests to evaluate the potential of calcium naphthenates formation in a naphthenate flow rig dynamic system demonstrated the influence of heterogeneous nucleation from non-adhered carbonate crystals, potentially aggravating deposition problems in oil and gas production systems.
Highlights
Calcium carbonate scale is one of the main flow assurance problems encountered during oilfield operations
Tube-blocking tests (TBTs) used to evaluate the effectiveness of calcium carbonate inhibitor in the
The use of a sintered metal filter allowed the presence of calcium carbonate crystals in suspension to be evaluated, making the determination of the inhibition efficiency of carbonate precipitation possible
Summary
Calcium carbonate scale is one of the main flow assurance problems encountered during oilfield operations. This salt can agglomerate at different points in the production system, resulting in a partial or even total loss of production and additional operational costs for cleaning [1,2]. The general equilibrium involved in calcium carbonate precipitation [3,4] is defined as: Ca2+ (aq) + HCO−. Supersaturation is the boundary to trigger precipitation or crystallization processes. The saturation ratio (SR) of a solution is defined as: SR2 = aCa2+ CO3 2− /kpsCaCO3 (2). When SR > 1, the solution is supersaturated, and the precipitation process is spontaneous.
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