Mineral replacement in long-term flooded porous carbonate rocks

Minde, Mona Wetrhus; Zimmermann, Udo; Madland, Merete Vadla; Korsnes, Reidar Inge; Schulz, Bernhard; Gilbricht, Sabine

doi:10.1016/j.gca.2019.09.017

Cited by 17 publications

(32 citation statements)

References 46 publications

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“…Only magnesite and clay are observed, and no calcite is left. For cores flooded for an even longer period, the transition between the two regimes has moved further into the core, indicating that this transformation of mineralogy moves like a front through the cores [30,31].…”

Section: Core Deformation Related To Mineral Alterationmentioning

confidence: 99%

“…Solid black line in b) is the specific surface area development estimated from the experimental permeability and porosity using the Kozeny-Carman equation. a) Newly precipitated magnesite crystals in a large pore (edited from[30]). b) Magnesiumbearing clay minerals crystallized in Aalborg chalk, which contains large amounts of primary opal-CT, after being flooded with MgCl2.…”

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confidence: 99%

“…(a) Newly precipitated magnesite crystals in a large pore (edited from[30]). (b) Magnesium-bearing clay minerals crystallized in Aalborg chalk, which contains large amounts of primary opal-CT, after being flooded with MgCl 2 .…”

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confidence: 99%

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Compaction and Fluid—Rock Interaction in Chalk Insight from Modelling and Data at Pore-, Core-, and Field-Scale

Minde

Hiorth

2019

Geosciences

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Water weakening is a phenomenon that is observed in high porosity chalk formations. The rock interacts with ions in injected water and additional deformation occurs. This important effect needs to be taken into account when modelling the water flooding of these reservoirs. The models used on field scale are simple and only model the effect as a change in water saturation. In this paper, we argue that the water weakening effect can to a large extend be understood as a combination of changes in water activity, surface charge and chemical dissolution. We apply the de Waal model to analyse compaction experiments, and to extract the additional deformation induced by the chemical interaction between the injected water and the rock. The chemical changes are studied on a field scale using potential flow models. On a field scale, we show that the dissolution/precipitation mechanisms studied in the lab will propagate at a much lower speed and mainly affect compaction near the well region and close to the temperature front. Changes in surface charge travel much faster in the reservoir and might be an important contributor to the observed water weakening effect. We also discuss how mineralogical variations impacts compaction.

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Section: Core Deformation Related To Mineral Alterationmentioning

confidence: 99%

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confidence: 99%

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Compaction and Fluid—Rock Interaction in Chalk Insight from Modelling and Data at Pore-, Core-, and Field-Scale

Minde

Hiorth

2019

Geosciences

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“…Different classification algorithms and four principal SEM-AM measurement routines for point counting modal analysis, particle analysis, sparse phase search and EDS spectral mapping are offered by the relevant software providers [1,[10][11][12]. These measurement routines provide the potential for the SEM-AM applications to scientific topics outside of the raw materials processing chain [13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Editorial for Special Issue “Applications of SEM Automated Mineralogy: From Ore Deposits over Processing to Secondary Resource Characterization”

Schulz

2020

Minerals

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“…When magnesium chloride (MgCl 2 ) brine is injected through chalk, dissolution of calcite CaCO 3 and precipitation of magnesite MgCO 3 occur (Madland et al 2011;Nermoen et al 2015;Zimmermann et al 2015;Minde et al 2017Minde et al , 2018aAndersen et al 2018). These dissolution/precipitation processes lead to enhanced bulk volume creep rates in chalk compared to when flooded with weakly reactive sodium chloride (NaCl) brine (Madland et al 2009(Madland et al , 2011.…”

Section: Introductionmentioning

confidence: 99%

Effect of Initial Wettability on Rock Mechanics and Oil Recovery: Comparative Study on Outcrop Chalks

et al. 2020

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Brines containing surface-active divalent ions such as Ca 2+ , Mg 2+ and SO 4 2− impact the stiffness, strength and time-dependent deformation of water wet Mons outcrop chalk. This study documents how stiffness and strength of wettability-altered oil and water-saturated (mixed wet) Mons chalk compare to water-saturated and water wet samples during hydrostatic loading and creep. During hydrostatic creep, the strain rate response to magnesium chloride (MgCl 2 ) brine injection is compared for water wet and mixed wet samples. For the mixed wet samples, the oil production was estimated during compaction and non-equilibrium MgCl 2 flow. The results presented here were then compared to a similar test series on Kansas outcrop chalk. The differences were interpreted in terms of difference in physical parameters such as porosity and pore size. Two Mons samples were wettability-altered and tested in parallel to two completely water wet samples from the same chalk block at hydrostatic conditions and 130 °C. It was found that beyond the experimental uncertainty, the stiffness and yield strength measurements showed insignificant differences for water wet and mixed wet Mons samples. This is contrary to Kansas chalk where mixed wet samples were systematically stronger and stiffer than water wet samples. In the following creep phase, both water wet and wettability-altered Mons chalk samples gave trends comparable to each other during a stagnant phase and a following MgCl 2 injection phase at varying flow rates. Similar observations were reported for water wet and wettability-altered Kansas chalks as well. Further, the same chemical reactions were observed for Kansas and Mons chalks and were found to be insensitive to the initial wettability and oil/water saturations. The oil production observations from Mons chalk showed that 43% of the total oil was recovered during early-stage compaction with no flow, whereas Kansas chalk did not produce any oil at no-flow conditions. After the oil recovery from the first 2-3 pore volumes of brine flow, no further oil production was observed due to compaction or non-equilibrium brine flow in any of the two chalk types.

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Mineral replacement in long-term flooded porous carbonate rocks

Cited by 17 publications

References 46 publications

Compaction and Fluid—Rock Interaction in Chalk Insight from Modelling and Data at Pore-, Core-, and Field-Scale

Compaction and Fluid—Rock Interaction in Chalk Insight from Modelling and Data at Pore-, Core-, and Field-Scale

Editorial for Special Issue “Applications of SEM Automated Mineralogy: From Ore Deposits over Processing to Secondary Resource Characterization”

Effect of Initial Wettability on Rock Mechanics and Oil Recovery: Comparative Study on Outcrop Chalks

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