The deposition and subsequent growth of inorganic scale on completion equipment is a major problem within the oil and gas industry. An in-situ flow cell was designed to investigate barium sulphate surface fouling on stainless steel. The set-up allows realtime analysis of the formation of scale as well as following various scaling parameters such as the surface coverage or number and size of crystals growing on the surface. The experimental results were fitted to a diffusion-controlled crystallisation based model. The effect of PolyPhosphinoCarboxylic Acid (PPCA) scale inhibitor on the growth of crystals was studied and showed that the Minimum Inhibition Concentration (MIC) is different for the surface and bulk solution. The results show that the inhibition mechanism was controlled by the mass transport of scale inhibitor molecules to the active sites of the growing crystals.

Impairment of flow by way of mineral scale formation is a major complication affecting production in the oil and gas industry. Soured reservoirs contain hydrogen sulfide (H 2 S) that can prompt the formation of exotic metal sulfide scales, leading to detrimental fouling that can negatively impact production. The contrast in the mode of precipitation (solid formation from liquid solution) and deposition of both sulfide scale and conventional inorganic carbonate and sulfate scales is herein examined. Design of an experimental rig allowing diffusion of H 2 S gas into the brine phase of a sealed reaction vessel resulted in a realistic representation of scaling processes occurring within sour reservoirs. Multiphase conditions, induced by introduction of a light oil phase to scaling brine within a turbulent regime, aimed to study the effect of oil and water wetting on pipeline fouling. Performance of a range of antifouling surfaces was determined through measurement of scale deposition by gravimetry and microscopy techniques. Under conditions modeled to reflect a typical H 2 S-containing reservoir, the contrasting scaling mechanisms of conventional calcium carbonate (CaCO 3 ) and barium sulfate (BaSO 4 ) scales when compared to lead sulfide (PbS) scale highlighted the critical role of the light oil phase on deposition. While conventional scales showed deposition by both crystallization and adhesion onto surfaces, the thermodynamic driving force for PbS prompted rapid bulk nucleation, with adhesion acting as the overwhelmingly dominant mechanism for deposition. The results showed that the addition of a 5% v/v light oil phase had a profound effect on scale particle behavior and deposition onto antifouling surfaces of varying wettability as a result of two processes. Primarily, the oil wetting of hydrophobic surfaces acted as a barrier to deposition, and second, adsorption of scale crystals at the oil/water interface of oil droplets within a turbulent oil-in-water emulsion resulted in adhesion to hydrophilic surfaces after impaction. It is therefore proposed that sulfide scale, typically deposited in the upper regions of production tubing, is driven by adhesion after formation of a PbS solid-stabilized Pickering emulsion. This contrasts with the commonly held view that metal sulfides precipitate and deposit similarly to conventional scales, whereby salts crystallize both directly upon surfaces and in the aqueous bulk phase as solubility decreases toward the wellhead.

Erosion-corrosion degradation in oil and gas pipelines is a significant problem, and a change in flow geometry can significantly enhance rates of degradation. In this study, a 3D printed 90° elbow, integrated into a flow loop, was developed to evaluate erosioncorrosion of X65 carbon steel along both the inner and outer internal portions of the bend in an aqueous carbon dioxide (CO2)-saturated environment containing sand particles.Designing representative geometries capable of measuring rates of corrosion, erosion and their synergistic interactions, can be challenging and currently no designs have been reported in literature that effectively integrate the required measuring techniques to determine local degradation rates throughout the component. To elucidate the individual contributions to overall erosion-corrosion degradation rates, gravimetric and electrochemical measurement techniques were used to quantify degradation rates at multiple locations in the flow geometry, with the specimen design also enabling the possibility of completing acoustic emission measurements to detect particle impacts. The design of the elbow is presented and erosion-corrosion tests were conducted to determine the magnitude and individual contributions of erosion, corrosion and erosioncorrosion interactions at a flow velocity of 6 m/s in a CO2-saturated, pH 4, 60C, 2 wt.% NaCl solution containing 1000 mg/L of sand particles.

There is a considerable interest to investigate surface crystallization in order to have a full mechanistic understanding of how layers of sparingly soluble salts (scale) build on component surfaces. Despite much recent attention, a suitable methodology to improve on the understanding of the precipitation/deposition systems to enable the construction of an accurate surface deposition kinetic model is still needed. In this work, an experimental flow rig and associated methodology to study mineral scale deposition is developed. The once-through flow rig allows us to follow mineral scale precipitation and surface deposition in situ and in real time. The rig enables us to assess the effects of various parameters such as brine chemistry and scaling indices, temperature, flow rates, and scale inhibitor concentrations on scaling kinetics. Calcium carbonate (CaCO3) scaling at different values of the saturation ratio (SR) is evaluated using image analysis procedures that enable the assessment of surface coverage, nucleation, and growth of the particles with time. The result for turbidity values measured in the flow cell is zero for all the SR considered. The residence time from the mixing point to the sample is shorter than the induction time for bulk precipitation; therefore, there are no crystals in the bulk solution as the flow passes through the sample. The study shows that surface scaling is not always a result of pre-precipitated crystals in the bulk solution. The technique enables both precipitation and surface deposition of scale to be decoupled and for the surface deposition process to be studied in real time and assessed under constant condition.

This paper presents an experimental and theoretical investigation into water condensation and corrosion under non-film forming conditions at the top of line in a static, CO2 environment. An experimental test cell is developed to measure droplet lifetimes, condensation rates and corrosion rates, as a function of the surface and gas temperatures, when the gas flow is dominated by natural convection. Experimental results for non-film-forming conditions show clearly that the water condensation rate becomes increasingly influential on corrosion rate as the surface temperature increases between 10 o C to 40 o C. These findings are summarised in a new empirical correlation for TLC rate as a function of the condensation rate and surface temperature that agrees well with previous, relevant studies. A model for condensation at the top of the line for static, buoyancy-driven conditions is also presented and shown to predict dropwise condensation rates accurately for a range of experimental conditions.