The effect of divalent ions on the elasticity and pore collapse of chalk evaluated from compressional wave velocity and low-field Nuclear Magnetic Resonance (NMR)

Katika, Konstantina; Addassi, Mouadh; Alam, Mohammad Monzurul; Fabricius, Ida Lykke

doi:10.1016/j.petrol.2015.10.036

Cited by 14 publications

(10 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Several explanations have been attempted, including capillary pressure or chemical dissolution (e.g. Schroeder et al, 1998;Risnes et al, 2005;Katika et al, 2015). Recently Nermoen et al (2018) proposed a simple electrostatic addition to Biot's equation, here as formulated for equal stress in all directions:…”

Section: Theory and Methodologymentioning

confidence: 99%

See 1 more Smart Citation

Porosity in chalk – roles of elastic strain and plastic strain

Fabricius

2020

Sedimentology

View full text Add to dashboard Cite

Chalks originate as Cretaceous to Recent pelagic or hemipelagic calcareous ooze, which indurate via burial diagenesis to chalk and limestone. Because they accumulate in pelagic settings with high environmental continuity, chalks may form thick formations and even groups. For this reason, and because chalks have a simple mineralogy (low magnesium calcite, silica and clays), they are ideal for the study of diagenetic processes including the depth-related decrease of porosity. It is the aim of this study to illustrate how the evaluation of in situ elastic strain can help in understanding these processes including the interplay between stress-controlled diagenetic processes and processes furthered by thermal energy. Petrophysical core and well data can be used for analyses of how porosity reduction via pore collapse and pressure dissolution is related to in situ elastic strain. The data in question are: depth, density of overburden, pore pressure, ultrasonic P-wave velocity and dry density/porosity. The analysis reveals that the transition from ooze to chalk is associated with high elastic strain and consequent pressure dissolution at calcite-particle contacts causing contact cementation. The transition from chalk to limestone is also associated with high elastic strain, especially at clay-calcite interphases causing development of stylolites via pressure dissolution, and consequent pore-filling cementation. Following each transformation the elastic strain drops rapidly. The observation of this diagenesis-related pattern in elastic strain of the sedimentary rock is novel and should not only be helpful in understanding the porosity development in sedimentary basins, but also add basic scientific insight.

show abstract

Section: Theory and Methodologymentioning

confidence: 99%

“…Several explanations have been attempted, including capillary pressure or chemical dissolution (e.g. Schroeder et al ., 1998; Risnes et al ., 2005; Katika et al ., 2015). Recently Nermoen et al .…”

Section: Theory and Methodologymentioning

confidence: 99%

Porosity in chalk – roles of elastic strain and plastic strain

Fabricius

2020

Sedimentology

View full text Add to dashboard Cite

show abstract

“…Pore-like flaw (void) is a typical defect found in natural detrital sedimentary rocks, which are the major host rocks of natural oil and gas resources (Chen et al, 2017;Katika et al, 2015;Yang et al, 2018;Zhang et al, 2017). In general, sedimentary rocks can have a porosity as high as 50% which is mainly attributed to these pore-like flaws (Wong and Baud, 2012).…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of micro-cracking behavior of brittle rock containing a pore-like flaw under uniaxial compression

Wong

Peng

2020

International Journal of Damage Mechanics

View full text Add to dashboard Cite

Pore-like flaws, which are commonly encountered in brittle rock, play an important role in the engineering performance of structures constructed in or on rock. Experimental and numerical investigations of micro-cracking mechanism of rock containing a pore-like flaw can enhance our knowledge of rock damage/failure from a microscopic view. In this study, the influences of a two-dimensional circular pore-like flaw with respect to its diameter and position on the strength and micro-cracking behavior of brittle rock under uniaxial compression are numerically investigated. The results reveal that the strength and elastic modulus are significantly affected by the diameter and position in the pore. The uniaxial compressive strength and elastic modulus of the numerical model with a pore diameter of 15.44 mm located in the center of the model are found to decrease by 58.6% and 56.4% respectively when compared with those of the intact model without a pore. As the pore position varies while the porosity remains unchanged, the simulated uniaxial compressive strength and elastic modulus are also found to be generally smaller than those of the intact model without a pore. When a pore-containing numerical model is loaded, the micro-cracks are found to mostly initiate at the top and bottom of the pore, due to the local tensile stress increase. The simulation results of the early-stage micro-cracking process and stress distribution are in a generally good agreement with the analytical solution obtained from the Kirsch equations. The grain-based model used in this study can not only study the crack initiation on the boundary of the pore but also provide a convenient means to analyze and visualize the temporal and spatial micro-cracking process after the crack initiation, which accounts for the variations in the simulated strength and modulus satisfactorily from a micro-cracking view.

show abstract

“…At high temperatures, sulfate and magnesium ions are particularly important to trigger accelerated creep strain rates during continuous flow-through and compaction, although the way that these two ions dictate overall compaction rates differ (e.g., Nermoen et al, 2014Nermoen et al, , 2015. Experiments indicate that the ion exchange on available surface sites as well as the dissolution of calcite and formation of secondary minerals can play a role in dictating the observed mechanical response (Madland et al, 2011); (5) Within the elastic domain, water softening of chalk at elevated temperatures has been observed, in triaxial cell experiments (e.g., Madland et al, 2011;Megawati et al, 2013Megawati et al, , 2015 and in elastic moduli derived from ultrasonic velocities (Japsen et al, 2004;Katika et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Incorporating electrostatic effects into the effective stress relation — Insights from chalk experiments

et al. 2018

View full text Add to dashboard Cite

Which forces are responsible for holding highly porous chalks together? We use the effective stress to quantify the electrostatic effects around particle contacts originating from the adsorption of ions onto charged mineral surfaces. The induration of chalk indicates that it is held together by contact cement, where planar crystal contacts allow the action of short-ranged adhesive Van der Waals forces. At particle distances exceeding a few nanometers, recent studies have indicated electrostatic repulsion between water-embedded adjacent particles. The magnitude of the repelling force depends, among other parameters, upon temperature and brine composition. Our premise is that by perturbing the electrostatic forces at the particle level, we can control the mechanical behavior of chalk samples tested in triaxial cells. We report the results of an experimental series, investigating how the mechanical strength and stiffness varied among samples saturated with four different brines, tested at two temperatures, and tested directly or after aging for three weeks at high temperature. We associate stiffness with bulk modulus and strength with the stress at yield. Systematic softening and weakening is observed, especially when the pore fluid is sulfate bearing, as well as for some high-temperature experiments and for aged samples. However, softening and weakening are not totally correlated, and neither brine composition, temperature, nor aging can alone dictate the mechanical behavior of the chalk — a combination is required to predict the chalk stiffness and strength. To obtain a coherent description of our experimental results, we estimated the electrostatic stress arising from ion adsorption and found it unnecessary for these experiments to postulate significant dissolution or precipitation-related changes to the rock frame.

show abstract

The effect of divalent ions on the elasticity and pore collapse of chalk evaluated from compressional wave velocity and low-field Nuclear Magnetic Resonance (NMR)

Cited by 14 publications

References 23 publications

Porosity in chalk – roles of elastic strain and plastic strain

Porosity in chalk – roles of elastic strain and plastic strain

Numerical investigation of micro-cracking behavior of brittle rock containing a pore-like flaw under uniaxial compression

Incorporating electrostatic effects into the effective stress relation — Insights from chalk experiments

Contact Info

Product

Resources

About