A chemical induced enhanced weakening of chalk by seawater

Heggheim, T.; Madland, Merete Vadla; Risnes, Rasmus; Austad, Tor

doi:10.1016/j.petrol.2004.12.001

Cited by 146 publications

(82 citation statements)

References 9 publications

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“…It has been shown that the mechanical strength of chalk is significantly affected by both water activity , and the presence of salts such as NaCl, Na 2 SO 4 , or MgCl 2 [Megawati et al, 2012;Madland et al, 2011;Zangiabadi et al, 2011]. Heggheim et al [2005] found that the water weakening effect seen in chalk must be at least partly chemical in nature. This is supported by Gutierrez et al [2000], as well as Baud et al [2009], who demonstrated a water weakening effect in Majella grainstone and Saint-Maximin limestone.…”

Section: Introductionmentioning

confidence: 99%

“…It has also been found that synthetic sea water and water with moderately high concentrations of MgCl 2 (0.1-0.2 M) cause increased strain rates in stressed chalk when comparing with pure water and water with NaCl [Madland et al, 2011]. Several studies have also found that the concentration of Na 2 SO 4 affects the strength of chalk, with reduced strength for higher concentrations [Korsnes et al, 2014;Heggheim et al, 2005].…”

Section: Introductionmentioning

confidence: 99%

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The effect of fluid composition, salinity, and acidity on subcritical crack growth in calcite crystals

et al. 2016

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Chemically activated processes of subcritical cracking in calcite control the time‐dependent strength of this mineral, which is a major constituent of the Earth's brittle upper crust. Here experimental data on subcritical crack growth are acquired with a double torsion apparatus to characterize the influence of fluid pH (range 5–7.5) and ionic strength and species (Na2SO4, NaCl, MgSO4, and MgCl2) on the propagation of microcracks in calcite single crystals. The effect of different ions on crack healing has also been investigated by decreasing the load on the crack for durations up to 30 min and allowing it to relax and close. All solutions were saturated with CaCO3. The crack velocities reached during the experiments are in the range 10−9–10−2 m/s and cover the range of subcritical to close to dynamic rupture propagation velocities. Results show that for calcite saturated solutions, the energy necessary to fracture calcite is independent of pH. As a consequence, the effects of fluid salinity, measured through its ionic strength, or the variation of water activity have stronger effects on subcritical crack propagation in calcite than pH. Consequently, when considering the geological sequestration of CO2 into carbonate reservoirs, the decrease of pH within the range of 5–7.5 due to CO2 dissolution into water should not significantly alter the rate of fracturing of calcite. Increase in salinity caused by drying may lead to further reduction in cracking and consequently a decrease in brittle creep. The healing of cracks is found to vary with the specific ions present.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The effect of fluid composition, salinity, and acidity on subcritical crack growth in calcite crystals

et al. 2016

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“…In terms of chalk mechanical behavior, earlier works (Heggheim et al, 2005;Korsnes et al, 2006a,b;Madland et al, 2011) have shown that not only the aqueous chemistry of the pore fluid, but also the presence of non-carbonate minerals such as silica and clay minerals control the chalk mechanical behavior. In Madland et al (2011) injecting MgCl2 brine leads to supersaturation of new minerals which further shift the chemical equilibrium towards dissolution of calcite.…”

Section: Introductionmentioning

confidence: 99%

“…Simplified brines with seawater ionic strength (0.219 M MgCl2 and 0.657 M NaCl) were used. Since mechanical properties measured under isotropic compression are less scattered and highly repeatable as shown from previous studies (Risnes et al, 2003;Heggheim et al, 2005;Korsnes et al, 2006bKorsnes et al, , 2008Zangiabadi et al, 2009;Madland et al, 2011), this type of test is chosen. Microscopic studies by Scanning Electron Microscopy (SEM) are included.…”

Section: Introductionmentioning

confidence: 99%

Mechanical and physical behavior of high-porosity chalks exposed to chemical perturbation

Megawati

Madland

Hiorth

2015

Journal of Petroleum Science and Engineering

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Extensive study on the effect of dissolution-precipitation on mechanical behavior of various high-porosity outcrop chalks (Liége, Aalborg, Kansas, Stevns Klint, and Mons) flooded with simplified aqueous chemistry at 130 °C under isotropic stress beyond the yield is performed.Chemical effects induced by injection of 0.219 M MgCl2 solutions into impure chalks (Liége, Aalborg, Kansas) lead to an immediate enhancement on the macroscopic creep with more than a factor of 2 larger than that of exposed to 0.657 M NaCl solutions. In pure chalks The chemical effects are also demonstrated by marked reduction in the permeability. The porosity-permeability relationship measured at the end of creep test is shifted down from the initial correlation, indicating a dramatic increase in the chalk specific surface area.

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“…Some scholars studied and analyzed the causes of the softening phenomenon of soft rocks upon encountering water [19][20][21][22]. Heggheim et al [23] studied the mechanism of the saline solution-softening limestone. Yang et al [24] analyzed the causes of changes in mechanical properties of slate by comparing its microstructures before and after encountering water.…”

Section: Introductionmentioning

confidence: 99%

Acoustic Emission Characteristics of Compressive Deformation and Failure of Siltstone under Different Water Contents

Chen

Zhao

Zheng

2017

Advances in Materials Science and Engineering

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The uniaxial compression and acoustic emission (AE) monitoring of siltstone specimens in the Gongchangling open-pit iron mine in Liaoning Province was conducted by evaluating the effects of three water saturation levels: dry, natural, and water-saturated. The siltstone AE characteristics were analyzed according to water content; the relationship between the AE characteristics and the growth and expansion of siltstone cracks was subsequently discussed. Research results indicated the following: siltstone specimens had distinctly different mechanical properties and AE characteristics according to water content; as the water content increased the compressive strength and elasticity modulus of specimens decreased. In the compacting phase of specimens under compression, the AE count rate of the water-saturated specimen was relatively small and the events were relatively stable. In the linear-elastic deformation phase, the AE count rate of the dry specimen increased sharply, reaching approximately 400 times/s. In the plastic yield deformation phase, the peak value of the AE count rate of the dry specimen ranged between 955 and 1,068 times/s, whereas that of the water-saturated specimen only attained a range of 635 to 782 times/s. In the failure phase, the time to reach the peak stress value of the dry specimen was increased as compared to that of the AE count rate.

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A chemical induced enhanced weakening of chalk by seawater

Cited by 146 publications

References 9 publications

The effect of fluid composition, salinity, and acidity on subcritical crack growth in calcite crystals

The effect of fluid composition, salinity, and acidity on subcritical crack growth in calcite crystals

Mechanical and physical behavior of high-porosity chalks exposed to chemical perturbation

Acoustic Emission Characteristics of Compressive Deformation and Failure of Siltstone under Different Water Contents

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