Abstract
Oilfield mineral scale deposition can become severe flow assurance challenge especially for offshore deepwater productions. Hazards arising from scale formation and subsequent deposition include production system throughput reduction and eventually blockage. Among various types of scales, carbonates are among the most frequently observed scales in oilfield operations. Similar to many natural and industrial processes, co-precipitation of multiple scales can commonly be observed in oilfield operations. Although extensive research efforts have been made in the domain of understanding the thermodynamics of scale formation, there are limited studies to investigate the kinetic aspect of scale formation, particularly the kinetics of co-precipitation of multiple scales. In this study, the kinetic characteristics of CaCO3/BaCO3co-precipitation have been experimentally investigated at representative oilfield conditions of 80 °C and 1 M NaCl condition. The focus was given to the investigation of the impact of different brine chemistry conditions such as mineral saturation level and Ca to Ba molar ratio. The experimental results suggest that CaCO3saturation level, substrate material and molar ratio can impact the nature and morphology of the carbonate scales formed. An elevation of CaCO3saturation index from 0.6 to 2 will change the formed carbonate solids from calcite to aragonite. In addition, at a Ca:Ba molar ratio of 1:15 with an excessive aqueous Ba species available, Ba species can partition into CaCO3crystal lattice to distort CaCO3lattice, resulting in almost 2-fold increase in aqueous Ca concentration. The results and conclusions from this study have the potential to benefit oilfield scale control strategy development, particularly the one related to carbonate scale formation control.
Highlights
The focus was given to evaluate the impact of different brine chemistry conditions on precipitation kinetics, mineral nature and characteristics
Both beaker test setup and flow-through tube reactor were adopted to examine the impact of various physiochemical factors, such as Saturation Index (SI), substrate material and Molar Ratio (MR)
It is difficult for Ba species to partition into CaCO3 lattice, which is presumed due to Ca/Ba ionic radius difference
Summary
Massive scale formation and subsequent precipitation can lead to throughput reduction and eventually pipe/conduit blockage in various industrial processes (Bukuaghangin et al, 2016; Ghaderi et al, 2009; Jordan et al, 2012; Kan and Tomson, 2012; Lecerf et al, 2005; Rostami et al, 2019; Vazquez et al, 2016; Zhang et al, 2018b). The combination of Ca ion, which is abundant in oilfield produced water, with the formed carbonate species can lead to CaCO3 precipitation. The water cut will normally increase considerably towards the end of the field life (Fink, 2011). This suggests that the amount of scale formation can markedly rise together with produced water. Barium species is commonly present in oilfield produced water with an aqueous concentration ranging from less than 0.1 mg LÀ1 to over 2000 mg LÀ1 (Neff and Sauer, 1995)
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