Measurement of iron and lead sulfide solubility below 100 °C

Murcia, Diana Carolina Figueroa; Fosbøl, Philip Loldrup; Stenby, Erling Halfdan; Thomsen, Kaj

doi:10.1016/j.fluid.2018.07.033

Cited by 3 publications

(1 citation statement)

References 20 publications

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“…42 The solubility product for crystalline forms, obtained by ageing the precipitate in the solution, is smaller; 8 the solubility product increases with increasing temperature. 43 Under the solution conditions used here, therefore, precipitation of ferrous sulfide would require concentrations of Fe 2+ on the mM scale. Hence the experiment probes a very particular case of very small H 2 S concentration, close to or below the limit for precipitation of ferrous sulfide near the electrode surface.…”

Section: Methodsmentioning

confidence: 99%

Effect of Trace H₂S on the Scale Formation Behavior in a Predominant CO₂ Environment under Hydrodynamic Control: Role of Cr/Mo Micro-Alloying in Plain Carbon Steel

Abdullah

et al. 2019

J. Electrochem. Soc.

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The effects of the presence of trace H 2 S (∼ 0.5 μM total dissolved H 2 S) on the electrocrystallization of siderite on plain carbon steel and its various micro-alloyed counterparts are explored. This small concentration of H 2 S in a CO 2 saturated (sweet) brine (0.5 M NaCl), at 80°C, in a slightly acidic environment (pH 6.6) at the elevated temperature was found to increase the anodic dissolution rate of the plain carbon steel and inhibit the electrocrystallization of carbonate scale. Highly porous surface scales resulted that contained sulfide uniformly distributed through the thickness through which anodic dissolution of the steel proceeded. There was a strong dependence on both electrode rotation rate and on micro-alloying (Cr, Mo) of the scale formation kinetics, morphology and eventual scale protectiveness. For the 1Cr steel, the electrocrystallization of carbonate was inhibited but was still observable electrochemically. The resultant scale was highly porous but contained little sulfur. With sufficient Mo (0.7 wt%) in the 1Cr steel, a two-layer scale was formed, with the inner layer coherent but not containing appreciable sulfur: it was probably a carbonate. With sufficient Cr (3.5 wt%) a coherent and protective layer, presumed to be a chromium oxide or oxyhydroxide that also contained Fe, 200-600 nm thick, protected the steel from the anodic activation by H 2 S. The results contrast with literature results for similar H 2 S concentrations at room temperature or for higher concentrations at elevated temperature, where passivating films of iron sulfide have been reported. The effect of trace H 2 S on the formation of protective, crystalline siderite scales at elevated temperature is a possible mechanism for initiation of corrosion of pipeline steels in operational conditions in nominally 'sweet' fields.

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Section: Methodsmentioning

confidence: 99%

Effect of Trace H₂S on the Scale Formation Behavior in a Predominant CO₂ Environment under Hydrodynamic Control: Role of Cr/Mo Micro-Alloying in Plain Carbon Steel

Abdullah

et al. 2019

J. Electrochem. Soc.

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Mineral Scales in Oil and Gas Fields

Hussein¹

2023

Essentials of Flow Assurance Solids in Oil and Gas Operations

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New Insights into the Dissolution of Iron Sulfide Using Chelating Agents

2020

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Summary Iron sulfide (FeS) scales create well deliverability and integrity problems such as decreased production rates and damage to well tubulars. The application of chelating agents for production enhancement has been successful because of its high-temperature stability and its clean characteristic nature without the need for expensive additives. However, chelating agents have not been studied adequately for FeS dissolution. This paper investigates ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacteic acid (DTPA), and N-(2-hydroxyethyl) ethylenediamine-N,N′,N′-triacetic acid (HEDTA) for their FeS dissolution capacities and kinetics at 150°F and 300°F. Chelating agents are expensive chemicals and must be investigated carefully to determine the optimum concentration, pH, treatment time, and dissolver/scale ratio. FeS (0.1 g) composed of mainly troilite was used as the scale. EDTA, DTPA, and HEDTA solutions (10 cm3) were prepared at different concentrations ranging from 0.05 to 0.4 mol/L using deionized water with a resistivity of 18.2 MΩ-cm. The pH of the dissolvers was dependent on the concentration and the degree of neutralization. The ligands were deprotonated at higher pH using sodium hydroxide or potassium hydroxide. A comparative study of the chelating agents with a low pH (3 to 5), moderate pH (5 to 9), and high pH (10 to 14) determined the optimum pH for the scale treatment. The sampling time of the dissolution process set at 1, 2, 4, 8, 20, 30, and 72 hours determined the kinetics of the scale-dissolution process and helped optimize the treatment time. A dissolver/scale ratio of 100:1, 50:1, and 20:1 cm3/g were tested. The iron concentration in the dissolver was quantified using inductively coupled plasma-optical emission spectroscopy (ICP-OES). Two calculated parameters, dissolution capacity and dissolver consumption, determined the effectiveness of the chelating agent in dissolving FeS sulfide. From the bottle tests at 150°F, lower pH solutions were more effective. One hundred percent of the iron from FeS was complexed by 0.3 mol/L dipotassium DTPA (K2-DTPA) after 20 hours of soaking; 0.2 mol/L disodium EDTA (Na2-EDTA) and 0.3 mol/L potassium HEDTA (K-HEDTA) were able to remove, respectively, 69 and 96% of the initial iron present in 0.1 g FeS. The mechanism of dissolution at pH < 5 was determined to be hydrogen ion (H+) attack with surface complexation. At alkaline conditions (pH > 10), the dissolution of the scale was negligible and was a result of solution complexation after FeS dissociation. The order of the chelating agents in terms of dissolution capacity was DTPA > HEDTA > EDTA at all pH conditions. The kinetics study showed that the optimum treatment depended on the pH of the chelating agent. For pH < 5 dissolvers, 16 to 20 hours was sufficient to obtain the maximum dissolution capacity. For dissolvers with a pH greater than 10, the dissolution continued for more than 72 hours and was minimal. Increasing the concentration of the chelating agent aided the solubility of the scale only at pH < 5. At 300°F and pH > 5, there was an improvement in the effectiveness of the ligands because of the increase in the system energy and increased activity of the chelating agent. A scanning electron microscopy (SEM) study showed the changes in the morphology of the FeS particles after dissolution with low- and high-pH solutions of the chelating agent. The role of chelating agents in FeS dissolution has not been thoroughly investigated. No study reports the optimum treatment time and dissolver/scale ratio. The role of the pH of the dissolver also needs more attention. This paper fills these gaps in the literature and provides the optimum dissolver composition and treatment time for field operations.

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Measurement of iron and lead sulfide solubility below 100 °C

Cited by 3 publications

References 20 publications

Effect of Trace H₂S on the Scale Formation Behavior in a Predominant CO₂ Environment under Hydrodynamic Control: Role of Cr/Mo Micro-Alloying in Plain Carbon Steel

Effect of Trace H₂S on the Scale Formation Behavior in a Predominant CO₂ Environment under Hydrodynamic Control: Role of Cr/Mo Micro-Alloying in Plain Carbon Steel

Mineral Scales in Oil and Gas Fields

New Insights into the Dissolution of Iron Sulfide Using Chelating Agents

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Measurement of iron and lead sulfide solubility below 100 °C

Cited by 3 publications

References 20 publications

Effect of Trace H2S on the Scale Formation Behavior in a Predominant CO2 Environment under Hydrodynamic Control: Role of Cr/Mo Micro-Alloying in Plain Carbon Steel

Effect of Trace H2S on the Scale Formation Behavior in a Predominant CO2 Environment under Hydrodynamic Control: Role of Cr/Mo Micro-Alloying in Plain Carbon Steel

Mineral Scales in Oil and Gas Fields

New Insights into the Dissolution of Iron Sulfide Using Chelating Agents

Contact Info

Product

Resources

About

Measurement of iron and lead sulfide solubility below 100 °C

Effect of Trace H₂S on the Scale Formation Behavior in a Predominant CO₂ Environment under Hydrodynamic Control: Role of Cr/Mo Micro-Alloying in Plain Carbon Steel

Effect of Trace H₂S on the Scale Formation Behavior in a Predominant CO₂ Environment under Hydrodynamic Control: Role of Cr/Mo Micro-Alloying in Plain Carbon Steel