Study of Carbonatic Scale in Completion Tools Through Modeling and Simulation Techniques

Abstract

Scale prediction in downhole scenarios is somewhat complex due to the large range of variables that drive inorganic precipitation. While the reservoir fluid flow ascendant into the wellbore it passes through many different completion equipments such as downhole valves. In the scope of oilwell completion design, a typical wellbore configuration takes into account two or three intervals, so a selective completion is required. In this way, Sliding Sleeve Valves (SSV) are normally employed together with packers to allow the production selectivity. Despite the positive aspects of this arrangement, the turbulence, the change in the flow trajectory into the valves and the considerable pressure drop can generate a friendly environment for the occurrence of calcium carbonate (CaCO3) scale. The pressure drop in this tool induces the flash liberation of CO2 from the aqueous solution and consequently, the chemical equilibrium, which controls the precipitation of CaCO3, is displaced towards the direction of precipitation of this solid in the flowing stream. Through the computational fluid dynamics technique (CFD), this work aims to study the effect of geometric variables of a generic downhole valve and the effect of the influx flow rate and fluid properties on the minimization of the overall pressure differential in the valve. Through the discrete phase modeling (DPM), the effect of the flow intensity on the transport of the solids to the internal adhesion surfaces is verified, and which of these surfaces are more favorable to the scaling phenomenon. By comparative analysis, it is shown that the volumetric influx rate is the most significant factor in the pressure drop (response variable). For the geometric factors, the effect of the number of connections between the annular outer region and internal tube presented a greater relevance compared to the chamfer angulation effect considered at the inlet of these connections.