A thermodynamic model for the prediction of phase equilibria and speciation in the H2O–CO2–NaCl–CaCO3–CaSO4 system from 0 to 250°C, 1 to 1000 bar with NaCl concentrations up to halite saturation

Li, Jun; Duan, Zhenhao

doi:10.1016/j.gca.2011.05.019

Cited by 59 publications

(38 citation statements)

References 55 publications

(86 reference statements)

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“…The influence of salinity on solubility is higher for low temperatures and decreases slightly at high temperatures. Solubilities displayed in Figure 4 are in good agreement with the batch modelling results of Li and Duan [47] and experimental data by Kushnir [48]. The Ca concentration of fluids released by gypsum dehydration therefore depends on temperature and salinity during the conversion into anhydrite.…”

Section: Approachsupporting

confidence: 84%

“…This is equal to an overall volume increase of about 10%. The solubility of anhydrite in water mainly depends on salinity and temperature and to a lesser degree on pressure [47]. A simple PHREEQC batch model, where anhydrite is brought into solution at different temperatures (10 ∘ C-70 ∘ C) and different salinities (0.0 moles/kgw-7.0 moles/kgw), shows that an increase in temperature decreases the solubility of anhydrite and that an increase in salinity increases the solubility of anhydrite (Figure 4).…”

Section: Approachmentioning

confidence: 99%

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Dedolomitization Potential of Fluids from Gypsum-to-Anhydrite Conversion: Mass Balance Constraints from the Late Permian Zechstein-2-Carbonates in NW Germany

2018

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The Zechstein-2-Carbonates represent one of the most prolific hydrocarbon systems of Central Europe. Carbonate reservoir quality is primarily controlled by mineralogy, with dolomite representing moderate-to-good porosities and calcite commonly representing low porosities. Current models suggest that this calcite is the result of a basin-wide phase of dedolomitization. The calcium (Ca) source for the dedolomites is thought to be derived from the fluids liberated during gypsum-to-anhydrite conversion. We present an easy-to-use and generally applicable template to estimate the dedolomitization potential of these fluids. Depending on reaction stoichiometry, salinity, and temperature, we estimate that between 2.8 * 10 −3 m 3 and 6.2 * 10 −3 m 3 of calcite may replace dolomite for each m 3 of anhydrite created. Within the constraints dictated by the environment of the late Permian Zechstein basin, we estimate that about 5 * 10 −3 m 3 of dedolomite is created for each m 3 of anhydrite. Mass balance constraints indicate that fluids derived from gypsum-to-anhydrite conversion account for less than 1% of the observed dedolomite in most of the studied industry wells from northern Germany.

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Section: Approachsupporting

confidence: 84%

Section: Approachmentioning

confidence: 99%

Dedolomitization Potential of Fluids from Gypsum-to-Anhydrite Conversion: Mass Balance Constraints from the Late Permian Zechstein-2-Carbonates in NW Germany

2018

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“…The chemical reactions for these different soluble rocks in an aqueous solution can be described through the following set of reactions (e.g. Duan & Li 2008;Li & Duan 2011):…”

Section: Chemical Propertiesmentioning

confidence: 99%

Fracture evolution in soluble rocks: From single-material fractures towards multi-material fractures

Kaufmann

Romanov

Gabrovšek

2017

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IzvlečekUDK 551.435.8 Georg Kaufmann, Franci Gabrovšek & Douchko Romanov: Odvisnost kraškega razvoja razpoke od vrste in zaporedja vodotopnih kamnin, skozi katere poteka Z numeričnim modelom smo raziskovali razvoj sekundarne poroznosti v enodimenzionalni razpoki v apnencu, sadri in anhidridu. Cilji raziskav so bili: 1) ugotoviti razlike med razvojem plitvih in globokih razpok v različnih kamninah; 2) oceniti učinek morebitnega izločanja enega od mineralov v razpoki in 3) dinamika rasti razpoke, ki gre skozi plasti različnih kamnin. Rezultati kažejo na primerljiv razvoj razpok v apnencu in sadri, pri čemer je čas razvoja v obeh kamninah precej različen. V anhidridu je zaradi drugačne kinetike raztapljanja razvoj še hitrejši. Izločanje ob spreminjajočih se geokemičnih pogojih lahko hitro zamaši razpoke in posebej v večjih globinah spremeni poti razvoja mreže kraških prevodnikov. V primeru, ko so razpoke v apnencu prekrite s plastjo sadre, kar v naravi pogosto opažamo, je hitrost širjenja najhitrejša, kar daje vodnim potem vzdolž takih razpok izrazito primerjalno prednost pri zajemanju razpoložljivega toka. Ključne besede: vodotopne kamnine, enostavna razpoka, raztapljanje in izločanje, incepcijski horizont. We employ a numerical model describing the evolution of secondary porosity in a single fracture embedded in soluble rock (limestone, gypsum, and anhydrite) to study the evolution of isolated fractures in different rock types. Our main focus is three-fold: The identification of shallow versus deep flow paths and their evolution for different rock types; the effect of precipitation of the dissolved material in the fracture; and finally the complication of fracture enlargement in fractures composed of several different soluble materials. Our results show that the evolution of fractures composed of limestone and gypsum is comparable, but the evolution time scale is drastically different. For anhydrite, owing to its difference from calcite in the kinetical rate law describing the removal of soluble rock, the evolution is even faster. Precipitation of the dissolved rock due to changes in the hydrochemical conditions can clog fractures fairly fast, thus changing the pattern of preferential pathways in the soluble aquifer, especially with depth. Finally, limestone fractures coated with gypsum, as occasionally observed in caves, will result in a substantial increase in fracture enlargement with time, thus giving these fractures a hydraulic advantage over pure limestone fractures in their competition for capturing flow.

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“…These large chambers might have been generated due to the presence of deep saline waters that mixed with the sulfate waters, tripling the solubility of the gypsum up to 7 g/L (Blount & Dickson, 1973;Li & Duan, 2011;Acero et al, 2013) and due to the common-ion effect by precipitation of carbonates forming huge flowstones on the shaft walls ( Fig. 6.4).…”

Section: áGuila Sinkhole: Halokinesis Diapirism and Gypsum Cavesmentioning

confidence: 99%

Gypsum speleogenesis: a hydrogeological classification of gypsum caves

Calaforra¹,

Gázquez²

2017

IJS

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Abstract:This article reviews the state of the art of speleogenetic investigations in gypsum karsts from numerous studies carried out over the past 50 years in Spain. A classification of gypsum karsts is proposed based on the hydrogeological, tectonic and stratigraphic criteria that decisively control the evolution of gypsum karsts. In this respect, lithological aspects of Messinian and Triassic-Permian gypsum series in south-eastern Spain are considered, such as the alternation of rhythmic levels of marl and gypsum, as well as geodynamic aspects. The influence of the hydrogeological characteristics of evaporite aquifers on gypsum cave speleogenesis is discussed; this includes speleogenetic processes in confined, semi-confined or free aquifers controlled by regional and local base levels. Also, the importance of intense saline diapiric uplift is examined. To illustrate our classification, examples of gypsum caves developed in Spain are presented. Their similarities and differences with gypsum karsts in other regions (Italy, Ukraine, and USA) are discussed. A first general division addresses: (1) caves controlled by stratigraphic factors and (2) caves controlled by tectonic factors. Several typologies can be described, including (A) multilayer caves with confined hydrogeological origin, (B) confined hypophreatic caves with linear or maze configurations, (C) caves controlled by the variation or remanence of regional or local base-levels, and (D) caves controlled by the halokinetic evolution of salt/gypsum diapirs. The proposed classification is flexible and adaptable to each case, because different genetic mechanisms can coincide in time and space. Likewise, most considerations stated in this work about gypsum karst are valid for speleogenesis in other rock types.caves, gypsum, karst, speleogenesis

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A thermodynamic model for the prediction of phase equilibria and speciation in the H2O–CO2–NaCl–CaCO3–CaSO4 system from 0 to 250°C, 1 to 1000 bar with NaCl concentrations up to halite saturation

Cited by 59 publications

References 55 publications

Dedolomitization Potential of Fluids from Gypsum-to-Anhydrite Conversion: Mass Balance Constraints from the Late Permian Zechstein-2-Carbonates in NW Germany

Dedolomitization Potential of Fluids from Gypsum-to-Anhydrite Conversion: Mass Balance Constraints from the Late Permian Zechstein-2-Carbonates in NW Germany

Fracture evolution in soluble rocks: From single-material fractures towards multi-material fractures

Gypsum speleogenesis: a hydrogeological classification of gypsum caves

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