Prediction of Permeability Reduction Rate Due to Calcium Sulfate Scale Formation in Porous Media

Abstract

Water injection is usually associated with various types of mineral scale formation and deposition which significantly undermine the performance of the injection by changing some reservoir properties such as permeability and porosity. Mineral scale deposition in surface and subsurface petroleum streams is one of the main concerns affecting the economy and safety of any production scenarios. Among various types of mineral scales, calcium sulfate is one of major scales in petroleum industry that can cause sever flow assurance and formation damage issues. Many parameters are affecting this problem. Temperature, pressure, fluid concentration, ratio of brine to hydrocarbon, fluid dynamic and type of porous media are among these parameters. Interpretation and prediction of permeability reduction in such complicated system is very complex. In this work an experimental and theoretical study has been conducted to investigate the permeability reduction due to CaSO4scale formation. For this purpose, brine solutions containing calcium and sulfate ions were injected in a packed glass beads porous media at elevated temperatures and various flow rate and brine concentrations. The pressure decline and permeability changes were measured in all the conducted tests. It was found that the permeability reduction by calcium sulfate scale formation follows a systematic trend considering various above mentioned important parameters. Hence, a novel empirical equation has been suggested, which can predict permeability reduction rate with high accuracy to experimental data. Introduction The formation of mineral scale due to flowing of fluid containing saline solutions in porous media is a common problem in many industries, such as oil and gas production, geothermal and membrane separation 1–6. Reliable prediction of calcium sulphate scale in production from oil and gas fields is a challenging and complex issue. This issue has been investigated and addressed by numbers of researchers in open literature. Among them, Vetter and Phillips2 described a thermodynamic model to predict the equilibrium condition of CaSO4 scale formation under down hole condition. Shen and Crosby4 investigated the mechanisms of CaSO4 scale deposition in oil producing wells. Villafafia Garica et all.5 presented a sulphate scale prediction method based on the extended UNIQUAC model. Hennessy and Graham7 reported the effect of additives on co-crystallisation of calcium with barium sulphate scale deposition. Almost in all available works in open literature, the complexity of prediction of various scale formation has been described and addressed. From the reservoir and downhole to surface conditions there are wide ranges of temperature, pressure and fluid compositions. The formation of various calcium sulphate crystalline forms including the anhydrite (CaSO4), dehydrate or gypsum (CaSO4, 2H2O), hemihydrates (a-CaSO4,½H2O or ß-CaSO4,.½H2O) are affected by changes in temperature and pressure and ionic strength, however, it is more sensitive to temperature rather than pressure 2,8. The solubility and formation of various crystalline forms has been schematically shown in Fig. 1. Yuan and Tood6 investigated the effect of brine ion concentrations and temperature and pressure on sulphate based scales precipitation. The formation of scales can cause many problems such as, plugging of equipment and producing formation pores. The prediction of the scale formation in well production path and the associated permeability and porosity reduction rate, therefore, are necessary for the success of the operation. For better understanding the permeability reduction mechanism due to calcium sulphate mineral scale formation, various important parameters need to be taken into account. These parameters can include the kinetic of precipitation reaction, morphology of crystalline form and transformation from one to another, the rate of calcium sulphate crystal growth, surface properties of porous media, the effect of pressure and temperature, the role of flow dynamic to entrainment of fine particles and the interactions of ions, fluid-fluid and fluid-rock interactions1,5,8,10. Interpretation and prediction of permeability reduction in such complicated system is very complex, as, the role of these important parameters needs to be considered. In this work, some of these parameters have been experimentally and/or theoretically studied. In the first part of the work, the carried out experimental tests have been described. The development of a novel empirical correlation for prediction of permeability reduction due to calcium sulfate scale formation based on the experimental work is then explained.

Effect of temperature and calcium ion concentration on permeability reduction due to composite barium and calcium sulfate precipitation in porous media

“…According to literature (Moghadasi et al, 2002(Moghadasi et al, , 2004AbuKhamsin and Ahmad, 2005;Tahmasebi et al, 2007) permeability reduction of porous media due to CaSO 4 deposition, increases with rising temperature and calcium ion concentration. Calcium ion concentrations which were selected for this study were so small and the permeability reduction of porous media due to them could not be severe, so the worst case of CaSO 4 formation experiments ([Ca 2þ ] ¼ 0.672 g/L, temperature ¼ 70 C) was performed and no CaSO 4 deposition was observed during 300 min experiment.…”

“…Permeability reduction of porous media due to formation and deposition of these scales has been studied for many years. Several experimental studies were conducted using either pack of glass beads/sands (Read and Ringen, 1982;Wat et al, 1992;Moghadasi et al, 2002Moghadasi et al, , 2004Tahmasebi et al, 2007) or core plugs (McElhiney et al, 2001;Abu-Khamsin and Ahmad, 2005;BinMerdhah et al, 2010;Mahmoud, and Gadallah, 2013) to determine the scaling tendency and potential of BaSO 4 and CaSO 4 precipitation. Most of these studies focused on single scale deposition.…”

Dimensionless correlation for the prediction of permeability reduction rate due to calcium sulphate scale deposition in carbonate grain packed column

“…Because of the lack of suitable and usable reaction and crystallization rate of calcium sulphate, scale deposition in porous media is necessary. Based on the results of this experimental work, theoretical studies conducted on solubility, thermodynamics of ionic solution; kinetic of precipitation reaction and crystallization of calcium sulphate precipitation rate, the reaction rate is presented (Tahmasebi et al, 2007). Precipitation and crystallization reaction of calcium sulphate is considered as function of super saturation index of calcium sulphate (SS Anhy ) and dimensionless temperature ratio (T/40) 1/2 as shown in Eq.…”

“…However, it is more sensitive to temperature rather than pressure (Firas et al, 2005;Hennessy and Graham, 2002;Vetter and Philips, 1970). The solubility and formation of various crystalline forms of calcium sulphate has been schematically shown in literatures (Tahmasebi et al, 2007;Villafafia Garica et al, 2005). The mechanism of scale deposition in low permeability reservoir was premeditated by Ren Xiaojuan et al (2006).…”

“…Among various types of mineral scales, calcium sulphate is one of the major scales in petroleum industry that can cause severe flow assurance and formation damage issues. The following parameters were described by different authors (Ahmed, 2004;Firas et al, 2005;Hennessy and Graham, 2002;Tahmasebi et al, 2007;Villafafia Garica et al, 2005) in which scaling was affected by:…”