Fluid Phase Equilibria 366 (2014) 117–126 Contents lists available at ScienceDirect Fluid Phase Equilibria jou rn al h om epage: www.elsevier.com/locate/fluid Rigorous modeling for prediction of barium sulfate (barite) deposition in oilfield brines Arash Kamari a , Farhad Gharagheizi a,b , Alireza Bahadori c,∗∗ , Amir H. Mohammadi a,d,∗ a Thermodynamics Research Unit, School of Engineering, University of KwaZulu-Natal, Howard College Campus, King George V Avenue, Durban 4041, South Africa b Department of Chemical Engineering, Buinzahra Branch, Islamic Azad University, Buinzahra, Iran c School of Environment, Science & Engineering, Southern Cross University, Lismore, NSW, Australia d Institut de Recherche en Génie Chimique et Pétrolier (IRGCP), Paris Cedex, France a r t i c l e i n f o Article history: Received 30 August 2013 Received in revised form 20 December 2013 Accepted 24 December 2013 Available online 3 January 2014 Keywords: Barium sulfate deposition Scale deposition Predictive model LSSVM Coupled simulated annealing a b s t r a c t Barium sulfate (barite) has been recognized to be a major operational problem in surface and subsurface oil and gas production operations. Therefore, accurate estimation of this deposition type can result in increasing the efficiency of oil and gas production. In this work, a novel approach is implemented to develop a predictive model for the estimation of solubility product data of barite in oilfield brines. The model is proposed using a robust soft computing approach, namely, least-squares support vec- tor machine (LSSVM) modeling optimized with the coupled simulated annealing (CSA) optimization approach. Our results indicate that there is good agreement between predictions based on the CSA-LSSVM model and literature data on the solubility product of barite in oilfield brines. Furthermore, performance of the developed model is compared with the performance of an artificial neural network, available correlation in the literature and standard software (OLI Scalechem) for predicting barite deposition. The model perfectly fits the literature data with a squared correlation coefficient of 0.999. © 2013 Elsevier B.V. All rights reserved. 1. Introduction To pressure maintenance of petroleum reservoirs, if seawater is applied for injection into sandstone formation containing barium, strontium, or both, sulfate scaling may occur in the near wellbore area [1]. The amount of scale deposited will depend on the ratio of seawater to formation water. This means that it is deposited by reaction between barium ions and sulfate. One of the major recog- nized problems in the oilfield production industry is the deposition of mineral scale on the surface of production equipment and in the pores of rock. In other words, it limits and sometimes blocks oil and gas production by plugging the oil producing formation matrix or fractures and perforated intervals [1]. Experience in oil and gas industry has demonstrated that many oil wells have suffered flow restriction because of scale deposition within the oil-producing formation and the downhole equipment, mostly in types of recovery methods including primary, secondary (such as water injection method) and tertiary oil recovery opera- tion (such as types of EOR methods) [2]. The deposition of various ∗ Corresponding author at: Institut de Recherche en Génie Chimique et Pétrolier (IRGCP), Paris Cedex, France. ∗∗ Corresponding author. E-mail addresses: alireza.bahadori@scu.edu.au (A. Bahadori), a.h.m@irgcp.fr (A.H. Mohammadi). types of scale in oil and gas production operations is very common; these mainly involve barium sulfate (barite), calcium sulfate, cal- cium carbonate, and strontium sulfate [3]. An expensive solution to the problem of scale formation is to decrease the salt concentration in the process water by reverse osmosis prior to injection [4]. How- ever, a far cheaper alternative is to utilize scale control inhibitors, with the objective of either preventing the mineral scale from form- ing, or altering the precipitate to such an extent that it no longer poses a problem [5]. So far, many cases [6–18] of oil well scaling barium sulfate, calcium sulfate, strontium sulfate and calcium carbonate have been reported in the literature. Moghadasi et al. [2] presented the mechanisms of scale deposition by water in oilfields and also suggested an accurate model capable of estimating scaling phenomena in Iranian oilfields operations due to mixing of incom- patible waters and or change in thermodynamics, kinetics and hydrodynamic condition of systems. The results showed that the model can be applied to estimate scale deposition due to com- mingling of chemically incompatible waters as well as changes in physical conditions of the system. In a survey on barium sulfate, Morizot et al. [5] used an electrochemically based technique, in which the scale formed on a rotating disk electrode in conjunction with assessment of bulk precipitation measurement. The results indicated that the action of a commercial polyphosphinocar- boxylic acid inhibitor is different in the bulk solution and at the surface. 0378-3812/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fluid.2013.12.023