ORCID Profile
0000-0002-7837-5457
Current Organisations
Monash University
,
Nanyang Technological University
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Publisher: Elsevier BV
Date: 07-2018
Publisher: Elsevier BV
Date: 07-2018
Publisher: Elsevier BV
Date: 04-2018
Publisher: Elsevier BV
Date: 05-2018
Publisher: The Royal Society
Date: 10-2017
DOI: 10.1098/RSOS.170896
Abstract: The mechanical properties of any substance are essential facts to understand its behaviour and make the maximum use of the particular substance. Rocks are indeed an important substance, as they are of significant use in the energy industry, specifically for fossil fuels and geothermal energy. Attenuation of seismic waves is a non-destructive technique to investigate mechanical properties of reservoir rocks under different conditions. The attenuation characteristics of five different rock types, siltstone, shale, Australian sandstone, Indian sandstone and granite, were investigated in the laboratory using ultrasonic and acoustic emission instruments in a frequency range of 0.1–1 MHz. The pulse transmission technique and spectral ratios were used to calculate the attenuation coefficient ( α ) and quality factor ( Q ) values for the five selected rock types for both primary ( P ) and secondary ( S ) waves, relative to the reference steel s le. For all the rock types, the attenuation coefficient was linearly proportional to the frequency of both the P and S waves. Interestingly, the attenuation coefficient of granite is more than 22% higher than that of siltstone, sandstone and shale for both P and S waves. The P and S wave velocities were calculated based on their recorded travel time, and these velocities were then used to calculate the dynamic mechanical properties including elastic modulus ( E ), bulk modulus ( K ), shear modulus ( µ ) and Poisson's ratio ( ν ). The P and S wave velocities for the selected rock types varied in the ranges of 2.43–4.61 km s −1 and 1.43–2.41 km h −1 , respectively. Furthermore, it was observed that the P wave velocity was always greater than the S wave velocity, and this confirmed the first arrival of P waves to the sensor. According to the experimental results, the dynamic E value is generally higher than the static E value obtained by unconfined compressive strength tests.
Publisher: American Geophysical Union (AGU)
Date: 11-05-2020
DOI: 10.1029/2020GL087375
Abstract: Water adsorption on coal plays a significant role in the process of CO 2 sequestration and enhanced coalbed methane recovery. Direct evidence of how coal adsorbs water and swells, affecting permeability, is still limited. Here, we studied the impact of waterflooding on fracture networks in coal by means of in situ synchrotron X‐ray microtomography combined with permeability measurements. We demonstrated that swelling‐induced fracture closure was responsible for an order of magnitude permeability reduction after waterflooding for over 4 days. Permeability loss was found to be time dependent, following a logistic function, and about 80% permeability reduction happened in the first 24 hr. There were probably three driven forces for water uptake, including hydrodynamic forces in fractures and macropores, capillary forces in micropores, and diffusion from micropores into deeper coal matrix. Swelling of coal matrix narrowed down and even closed the fractures and as a result weakened fracture connectivity. Residual fractures were mainly mineral‐supported fractures, which have strong resistance to swelling‐induced stresses.
Publisher: Elsevier BV
Date: 12-2018
Publisher: Elsevier BV
Date: 09-2021
Publisher: CRC Press
Date: 29-07-2016
Publisher: MDPI AG
Date: 28-06-2017
DOI: 10.3390/APP7070664
Publisher: Elsevier BV
Date: 11-2016
Publisher: MDPI AG
Date: 21-12-2018
DOI: 10.3390/EN12010014
Abstract: Hydro-fracturing is a common production enhancement technique used in unconventional reservoirs. However, an effective fracturing process requires a precise understanding of a formation’s in-situ strength behavior, which is mainly dependent on the formation’s in-situ stresses and fluid saturation. The aim of this study is to identify the effect of brine saturation (concentration and degree of saturation (DOS)) on the mechanical properties of one of the common unconventional reservoir rock types, siltstone. Most common type of non-destructive test: acoustic emission (AE) was used in conjunction with the destructive tests to investigate the rock properties. Unconfined compressive strength (UCS) and splitting tensile strength (STS) experiments were carried out for 78 varyingly saturated specimens utilizing ARAMIS (non-contact and material independent measuring system) and acoustic emission systems to determine the fracture propagation. According to the experimental results, the increase in degree of pore fluid saturation (NaCl ionic solution) causes siltstone’s compressive and tensile strengths to be reduced through weakening and breakage of the existing bonding between clay minerals. However, increasing NaCl concentration in the pore fluid generally enhances the compressive strength of siltstone through associated NaCl crystallization effect and actually reduces the tensile strength of siltstone through the corrosive influence of the NaCl ions. Moreover, results show that AE capture and analysis is one of the most effective methods to understand crack propagation behavior in rocks including the crack initiation, crack propagation, and final failure. The findings of this study are important for the identification of fluid saturation dependent in-situ strength conditions for successful hydro-fracturing in low permeable reservoirs.
Publisher: Elsevier BV
Date: 10-2018
Publisher: Springer Science and Business Media LLC
Date: 09-2016
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 05-2018
No related grants have been discovered for Ayal Wanniarachchi.