Oilfield production chemistry is the subject to study the impact on production fluid flow due to physicochemical changes in the production system. Together with material corrosion and gas hydrate blockage, mineral scale deposition is one of the top three water-related oilfield production chemistry threats. Mineral scale is the hard crystalline inorganic solid precipitated from the water phase due to local oversaturation. The formation and deposition of scale solids can lead to a considerable reduction in pipeline throughput and reservoir formation damage. Extensive studies have been carried out to evaluate the thermodynamics of scale deposition, including calculation of scale saturation ratio and prediction of the mass of deposited scale solids. However, these studies are predominately thermodynamic in nature and typically take no account of scale formation kinetics, i.e., the rate of scale deposition. Compared to the existing thermodynamics study of scale deposition, scale kinetics studies are considerably limited and the models predicting scale kinetics are less reliable due to insufficient kinetic studies. In this presentation, a plug-flow type tube reactor will be reported for the experimental investigation of deposition kinetics of one of the most commonly encountered oilfield scale, calcium carbonate (CaCO3). Compared with the conventional apparatus, such as beaker and rotating disc, the introduced tube reactor is able to maintain a constant experimental condition of solution pH and surface area and a controlled saturation ratio during the experimental study. This presentation will elaborate the obtained scale deposition kinetics of CaCO3 solid onto a CaCO3-free surface and also a surface pre-coated with CaCO3. It shows that the CaCO3 deposition process can be segmented into multiple sub-stages with varying deposition kinetics and different solid morphologies. Moreover, experimental conditions including flow rate, temperature and solution chemistry can have a substantial influence on the deposition kinetics of CaCO3. The presented studies provide an in-depth understanding of the kinetics of CaCO3 deposition onto the surface of a pipe material. This introduced tube reactor apparatus can expand our capability in investigating mineral scale deposition kinetics and the influences of different experimental factors on scale deposition.

Laboratory investigation of mineral scale deposition kinetics by adopting a plug-flow tube reactor in oilfield chemistry conditions

2019 Fall National Meeting

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