Solubility and Phase Transitions of Calcium Sulfate in KCl Solutions between 85 and 100 °C

Yang, Lei; Guan, Baohong; Wu, Zhongbiao; Ma, Xiaoyu

doi:10.1021/ie900372j

Cited by 24 publications

(25 citation statements)

References 19 publications

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“…Injecting low-salinity water or chemically tuned water with high sulfate content into a formation with high calcium content will increase the calcium sulfate precipitation (Vetter and Phillips 1970;Carlberg and Matthews 1973). The same applies for the KCl salt-the higher the KCl concentration, the higher the calcium sulfate solubility in the solution (Yang et al 2009). Adding high-pH EDTA or HEDTA chelating agents to the seawater will sequester the calcium from the solution (which is responsible for the reduction of sulfate solubility) and will not affect the sodiumconcentration content in the seawater and formation brine (which is responsible for increasing the sulfate solubility).…”

Section: Comparison Of Chelating Agent With Low-and High-salinitymentioning

confidence: 93%

“…Additional recovery of 8.6% was also obtained in coreflood experiments when aquifer water was injected after formation brine. Yousef et al (2010) investigated the effect of injecting diluted seawater on the oil recovery from carbonate cores. The increase in oil recovery was 18 to 19% more than seawater flooding obtained from coreflood experiments as a result of the stepwise dilution of the seawater up to a 20-fold dilution.…”

Section: Introductionmentioning

confidence: 99%

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Chelating-Agent Enhanced Oil Recovery for Sandstone and Carbonate Reservoirs

Mahmoud

Abdelgawad

2015

SPE Journal

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Recently low-salinity waterflooding was introduced as an effective enhanced-oil-recovery (EOR) method in sandstone and carbonate reservoirs. The recovery mechanisms that use low-salinitywater injection are still debatable. The suggested possible mechanisms are: wettability alteration, interfacial-tension (IFT) reduction, multi-ion exchange, and rock dissolution. In this paper, we introduce a new chemical EOR method for sandstone and carbonate reservoirs that will give better recovery than the low-salinitywater injection without treating or diluting seawater.In this study, we introduce a new chemical EOR method that uses chelating agents such as ethylenediaminetetraacetic acid (EDTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), and diethylenetriaminepentaacetic acid (DTPA) at high pH values. This is the first time for use of chelating agents as standalone EOR fluids. Coreflood experiments, interfacial and surface tensions, and zeta-potential measurements are performed with DTPA, EDTA, and HEDTA chelating agents. The chelating-agent concentrations used in the study were prepared by diluting the initial concentration of 40 wt% with seawater and injecting it into Berea-sandstone and Indiana-limestone cores of a 6-in. length and a 1.5-in. diameter saturated with crude oil. The coreflooding experiments were performed at 100 C and a 1,000-psi backpressure. Low-salinity-water and seawater injections caused damage to the reservoir because of the calcium sulfate scale deposition during the flooding process. The newly introduced EOR method did not cause calcium sulfate precipitation, and the core permeability was not affected. The core permeability was measured after the flooding process, and the final permeability was higher than the initial permeability in the case of chelating-agent injection. The coreflooding effluent was analyzed for cations with the inductively coupled plasma (ICP) spectroscopy to explain the dissolution-recovery mechanism. The effect of iron minerals on the rock-surface charge was investigated through the measurements of zeta potential for different rocks containing different iron minerals.HEDTA and EDTA chelating agents at 5 wt% concentration prepared in seawater were able to recover more than 20% oil from the initial oil in place from sandstone and carbonate cores. ICP measurements supported the rock-dissolution mechanism because the calcium, magnesium, and iron concentrations in the effluent samples were more than those in the injected fluids. The IFTreduction mechanism was confirmed by the low IFT values obtained in the case of chelating agents. The type and concentration of chelating agents affected the IFT value. Higher concentrations yielded lower IFT values because of the increase in carboxylic-group concentration. We found that the high-pH chelating agents increased the negative value of zeta potential, which will change the rock toward more water-wet.

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Section: Comparison Of Chelating Agent With Low-and High-salinitymentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Chelating-Agent Enhanced Oil Recovery for Sandstone and Carbonate Reservoirs

Mahmoud

Abdelgawad

2015

SPE Journal

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“…Mg 2+ ions went against the formation of α-CSH, because of the association effect formed by stable MgSO 4 0 in 4.50 M magnesium chloride solution [34]. Yang et al [35] researched that when the potassium chloride concentration is up to 18.0 wt. %, pure calcium sulfate phase is difficult to obtain, due to the formation of syngenite or gorgeyite.…”

Section: Introductionmentioning

confidence: 99%

Calcium Sulfate Hemihydrate Whiskers Obtained from Flue Gas Desulfurization Gypsum and Used for the Adsorption Removal of Lead

Wang

et al. 2017

Crystals

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As a recycled material, flue gas desulfurization gypsum has been used to prepare calcium sulfate hemihydrate whisker (CSHW) through hydrothermal synthesis for several decades. However, the subsequent utilization of this resultant material has not yet received considerable attention. In the present research, CSHW was successfully synthesized at a certain region, and was used for the adsorption of lead ions from aqueous solutions, thereby broadening the research field for the practical application of CSHW. Its adsorption capacity was significantly influenced by various parameters, particularly, the pH level and initial lead concentration. The pH value highly affected the hydrolysis degree of lead ions and dominated the adsorption of lead. The equilibrium isotherms under two different temperatures were simulated using Langmuir, Freundlich, and Temkin models. Both Langmuir and Temkin models showed a good fit to the data. Combined with the well-fitted pseudo-second-order model, the adsorption mechanism was thought to be a chemisorption process that was enforced by the ion exchange reaction. In addition, the specific crystal structure of CSHW revealed that ion exchange reaction occurred on the (010) and (100) facets due to their preferential growth and negatively charged property. The residual solid phase after adsorption was collected and detected using X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy. Results revealed that PbSO 4 was formed on the surface of CSHW. The alkaline condition introduced the tribasic lead sulfate, and thus reduced the stability of the adsorption system.

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“…Moreover, a foreign ion‐free crystallization surrounding provided by such solutions seems attractive for α‐HH preparation with higher purity than that produced through the salt solution method. It is due to the fact that substituted phases and certain double salts of α‐HH are easy to form in the salt solutions containing the foreign electrolytes, such as Na 2 SO 4 , K 2 SO 4 , MgSO 4 , and SrSO 4 15–17 …”

Section: Introductionmentioning

confidence: 99%

Preparation of α‐Calcium Sulfate Hemihydrate from Calcium Sulfate Dihydrate in Methanol–Water Solution under Mild Conditions

Guan

Jiang

et al. 2011

Journal of the American Ceramic Society

Self Cite

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For the first time, a-calcium sulfate hemihydrate (a-HH) was successfully prepared from calcium sulfate dihydrate (DH) in methanol-water solution under atmospheric pressure. The effect of methanol concentrations (40-73 mol%) on the transition from DH to a-HH were investigated at temperatures (601-751C) within a reaction time of 36 h. The results showed that an increase in methanol concentration could lower the transition temperature. The transition was speeded up by increasing methanol concentration from 47 to 57 mol% at 751C. When the temperature dropped to 701C, the transition rate firstly increased with the methanol concentration until it reached 69 mol% and then exhibited a reverse trend with increasing methanol concentration from 71 to 73 mol%. The accelerating effect, involved during the nucleation of a-HH, attributes to the elevated supersaturation due to the fall in the water activity resulting from the increasing methanol concentration. The retarding effect, involved during the crystal growth of a-HH, was likely derived from the specific adsorption of methanol molecules onto the surfaces of a-HH crystals. Overall, the aqueous solution of methanol could act as a novel category of medium suitable for the a-HH preparation from DH. D. Viehland-contributing editor

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Solubility and Phase Transitions of Calcium Sulfate in KCl Solutions between 85 and 100 °C

Abstract: Morphology of DH, α-HH, and AH that were used for the solubility determination 2. Morphology of the conversion products of DH and α-HH during the phase transition.

Cited by 24 publications

References 19 publications

Chelating-Agent Enhanced Oil Recovery for Sandstone and Carbonate Reservoirs

Chelating-Agent Enhanced Oil Recovery for Sandstone and Carbonate Reservoirs

Calcium Sulfate Hemihydrate Whiskers Obtained from Flue Gas Desulfurization Gypsum and Used for the Adsorption Removal of Lead

Preparation of α‐Calcium Sulfate Hemihydrate from Calcium Sulfate Dihydrate in Methanol–Water Solution under Mild Conditions

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