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The thermodynamic and kinetic uncertainities created by the mixing together of various fluids during oil processing and transportation will affect scaling tendency of facilities and the efficiency of inhibitors to combat scaling. The most severe operational challenges with pipeline transportation are flow assurance issues due to scale formation, which often lead to blockage of pipelines, and related to the flow of multiphase fluids. There is therefore the need for an understanding and assessment of the mechanisms and kinetics of scale formation in multiphase systems containing mxture of oil phases. This work studies the mechanisms and behavior of precipitation of calcium carbonate scale in mixed oil fractions. Experiments were conducted in both single and multiphase systems for SR 211 at 30°C and SR 198 at 60°C. The mixed oil fractions include 50ml cyclohexane, 30ml kerosene, 20ml toluene and 0.01% asphaltene, fully dissolved in toluene. Homogeneous dispersion in the two-phase mixture was achieved using the Rotating Cylinder Electrode (RCE) with an overhead impeller blade stirring at 520 rpm to create The fouling process was investigated in the presence of a chemical scale inhibitor, polyphosphinocarboxylic acid (PPCA) at below the Minimum Inhibitor Concentratio (MIC). Samples are collected and analysed using the Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Atomic Absorption Spectroscopy (AAS) techniques to evaluate the morphology, polymorphic transformation and calcium ion concentration respectively at different time intervals. The study shows that the presence of an organic phase has a major effect on CaCO3 polymorphic abundance, slowing down the initial rapid transformation of vaterite to calcite. Injection of inhibitor below MIC combined with the presence of asphaltene do not prevent the bulk scaling but has an effect on the relative distribution as well as stability of the metastable vaterite. This could provide further insights for the development of inhibition and control strategies to deal with CaCO3 scale formation in multiphase systems.

Polymer-induced drag reduction (DR) in fluids was studied using a rotational rheometer with double-gap concentric cylinder geometry. Although both polymers (polyacrylamide (PAM) and 2-acrylamido-2-methylpropane sulfonic acid (SPAM)) had molecular weights of several MDa, the contrasting polymer charge, nonionic and anionic, led to different polymer overlap concentrations (c*), PAM ≫ SPAM, and fluid rheology, with PAM fluids mostly Newtonian and SPAM fluids non-Newtonian (shear-thinning). Based on these differences, it was important to account for the infinite shear viscosity and normalize the polymer concentration by the intrinsic concentration (cint) so that the DR performance of the two polymer fluids could be accurately compared. Both polymers induced DR, and the maximum DR by SPAM (DR% = 28) was slightly higher than that by PAM (DR% = 22) when Rep ∼ 1700. For PAM, the loss of DR with time diminished at higher polymer concentrations (≥100 ppm, at Rep = 3149) but was found to be sensitive to high Rep, with polymer chain scission the likely cause of the reduced performance. For the semi-dilute SPAM fluids, the shear stability contrasted that of PAM, showing negligible dependence on the polymer concentration and Rep. The apparent rapid loss of DR was predominantly attributed to a time-dependent effect and not polymer degradation. In pipe flow, the maximum DR for SPAM was higher than that measured by rheometry and was attributed to differences in the flow conditions. However, changes in the normalized DR/c with polymer concentration were found to be consistent between the two flow geometries. Furthermore, the high fluid stresses in pipe flow (at high Rep) led to drag reduction losses consistent with PAM, as the time-dependent effect was not seen.

This paper outlines the development of an automated underwater abrasion rig to assist in understanding the galvanic interaction induced by surface films when continuous localised mechanical film breakdown is encountered on the surface of carbon steel in CO