Numerical simulations of the distribution of rock stress and pore pressure in division of mining safety range

Rock Stress ◽  
2020 ◽  
pp. 463-468
Author(s):  
P. Sun
Keyword(s):  
Numerical Simulations ◽  
Pore Pressure ◽  
Rock Stress ◽  
Mining Safety ◽  
Safety Range

Calculation and Analysis of Rock Stress State near the Bit

2012 ◽  
Vol 594-597 ◽  
pp. 65-69
Author(s):  
Wei Li ◽  
Tie Yan ◽  
Si Qi Li ◽  
Ling Zhang ◽  
Xing Hua Xu
Keyword(s):  
Stress State ◽  
Pore Pressure ◽  
Penetration Rate ◽  
Oil Field ◽  
Rock Stress ◽  
Concentrated Force ◽  
Underbalanced Drilling ◽  
Permeable Rock ◽  
Mechanics Characteristic ◽  
Column Pressure

Underbalance drilling has been applied to each oil field at home and abroad, due to the advantage of increasing the penetration rate substantially, protecting the reservoir effectively and reducing the drilling costs. But in respect of rock stress state characteristics near the bottom, relatively speaking, the study was rarely.Take the borehole near the bottom in underbalance drilling as the research object, analyze the influence of terrestrial stress, pore pressure and fluid column pressure on mechanics characteristic of rock in the bottom, to study the rock crushing efficiency, well deviation and hole stability of non-permeable wellbore and permeable wellbore in underbalanced drilling. The result shows that the mechanical properties of rocks near the bottom are subject to terrestrial stress, pore pressure and fluid column pressure. In non-permeable rock, the rock crushing efficiency, the penetration rate and the concentrated force of well trend to increase, the well trends to inclination. In permeable wellbore, with the permeability increasing, the rock crushing efficiency, the penetration rate and the concentrated force of well trend to decrease, the tendency of inclination becomes lower.

Rock Bolts Health Monitoring Using Self-Excited Phenomenon

2016 ◽  
Vol 248 ◽  
pp. 186-191 ◽  
Author(s):  
Janusz Kwaśniewski ◽  
Ireneusz Dominik ◽  
Krzysztof Lalik ◽  
Waldemar Korzeniowski ◽  
Krzysztof Zagórski ◽  
...  
Keyword(s):  
Health Monitoring ◽  
The State ◽  
The Self ◽  
Stress Change ◽  
Rock Stress ◽  
Rock Bolts ◽  
Change Measurement ◽  
Mining Safety

Health monitoring of rock bolts can indirectly indicate the state of rock which is crucial for mining safety. This paper presents an innovative application of the Self-excited Acoustical System SAS for stress change measurement in rock bolts which are used to secure roofs and walls in mines and tunnels. The method gives information on the change of rock stress in the immediate area next to the bolt. It can be used also to determine the necessity of the exploited bolt replacement.

scholarly journals Can Heating Induce Borehole Closure?

2020 ◽  
Vol 53 (12) ◽  
pp. 5715-5744
Author(s):  
Xiyang Xie ◽  
Andreas Bauer ◽  
Jørn F. Stenebråten ◽  
Sigurd Bakheim ◽  
Alexandre Lavrov ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Pore Pressure ◽  
Rock Failure ◽  
Field Scale ◽  
Thermally Induced ◽  
Pierre Shale ◽  
Lab Experiments ◽  
Post Test ◽  
Operation Cost ◽  
Cased Borehole

AbstractThe current study shows that heating a cased borehole in low-permeability shale rock can induce plastic deformation, leading to the closure of the casing annulus and decreasing annulus connectivity. The thermally induced borehole closure is interesting for the field operation of plug and abandonment (P&A), as it potentially saves operation cost and time by avoiding cutting casing and cementing. Lab experiments and numerical simulations are implemented to investigate the thermally induced borehole closure. Pierre shale and a field shale are tested. The lab experiments are performed by heating the borehole wall in a 10-cm-OD hollow cylinder specimen. Here, a novel experimental setup is applied, allowing for measuring temperature and pore pressure at different radii inside the specimen. Both the experimental data and the post-test CT images of the rock samples indicate the rock failure by borehole heating, and under certain conditions, heating results in an annulus closure. The decrease of hydraulic conductivity through the casing annulus is observed, but this decrease is not enough to form the hydraulic-sealed annulus barrier, based on the results obtained so far. Lab-scale finite-element simulations aim to match the lab results to obtain poro-elastoplastic parameters. Then the field-scale simulations assess the formation of shale barriers by heating in field scenarios. Overall, (i) the lab experiments show that heating a borehole can increase the pore pressure in shale and hence induce rock failure; (ii) the numerical simulations match the experimental results reasonably well and indicate that the heating-induced borehole closure can sufficiently seal the casing annulus in the field-scale simulation.

Numerical simulation of coupled fluid-solid interaction at the pore scale: A digital rock-physics technology

Geophysics ◽  
2019 ◽  
Vol 84 (4) ◽  
pp. WA71-WA81 ◽  
Author(s):  
Vishal Das ◽  
Tapan Mukerji ◽  
Gary Mavko
Keyword(s):  
Numerical Simulations ◽  
Numerical Method ◽  
Pore Pressure ◽  
Structural Mechanics ◽  
P Wave ◽  
Fluid Viscosity ◽  
Pore Scale ◽  
Digital Rock ◽  
Pore Pressures ◽  
Fluid Solid Interaction

We have used numerical modeling to capture the physics related to coupled fluid-solid interaction (FSI) and the frequency dependence of pore scale fluid flow in response to pore pressure heterogeneities at the pore scale. First, we perform numerical simulations on a simple 2D geometry consisting of a pair of connected cracks to benchmark the numerical method. We then compute and contrast the stresses and pore pressures obtained from our numerical method with the commonly used method that considers only structural mechanics, ignoring FSI. Our results demonstrate that the stresses and pore pressures of these two cases are similar for low frequencies (1 Hz). However, at higher frequencies (1 kHz), we observe pore-pressure heterogeneities from the FSI numerical method that cannot be representatively modeled using the structural mechanics approach. At even higher frequencies (100 MHz), scattering effects in the fluid give rise to higher pressure heterogeneities in the pore space. The dynamic effective P-wave modulus [Formula: see text], attenuation [Formula: see text], and P-wave velocity [Formula: see text] were calculated using the results obtained from the numerical simulations. These results indicate a shift in the dispersion curves toward lower frequencies when the fluid viscosity is increased or when the aspect ratio of the microcrack is decreased. We then applied the numerical method on a 3D digital rock sample of Berea sandstone for a sweep of frequencies ranging from 10 Hz to 100 MHz. The calculated pore pressure at the low frequency (1 kHz) is homogeneous and the fluid is in a relaxed state, whereas at the high frequency (100 kHz), the pore pressure is heterogeneous, and the fluid is in an unrelaxed state. This type of numerical method helps in modeling and understanding the dynamic effects of fluid at different frequencies that result in velocity dispersion and attenuation.

scholarly journals Evolution of the geological structure and mechanical properties due to the collision of multiple basement topographic highs in a forearc accretionary wedge: insights from numerical simulations

2022 ◽  
Vol 9 (1) ◽  
Author(s):  
Ayumu Miyakawa ◽  
Atsushi Noda ◽  
Hiroaki Koge
Keyword(s):  
Numerical Simulations ◽  
Pore Pressure ◽  
Compressive Stress ◽  
Plate Boundary ◽  
Structural Features ◽  
Geological Structure ◽  
Accretionary Wedge ◽  
Rapid Reduction ◽  
Compressive Stresses ◽  
Horizontal Compressive Stress

AbstractWe propose a conceptual geological model for the collision of multiple basement topographic highs (BTHs; e.g., seamounts, ridges, and horsts) with a forearc accretionary wedge. Even though there are many BTHs on an oceanic plate, there are few examples of modeling the collision of multiple BTHs. We conducted numerical simulations using the discrete element method to examine the effects of three BTH collisions with forearcs. The typical geological structure associated with a BTH collision was reproduced during the collision of the first BTH, and multiple BTH collisions create a cycle of formation of BTH collisional structures. Each BTH forces the basal décollement to move up to the roof décollement, and the roof décollement becomes inactive after the passage of the BTH, and then the décollement moves down to the base. As the active décollement position changes, the sequences of underthrust sediments and uplifted imbricate thrusts are sandwiched between the décollements and incorporated into the wedge. At a low horizontal compressive stress, a “shadow zone” is formed behind (i.e., seaward of) the BTH. When the next BTH collides, the horizontal compressive stress increases and tectonic compaction progresses, which reduce the porosity in the underthrust sediments. Heterogeneous evolution of the geological and porosity structure can generate a distinctive pore pressure pattern. The underthrust sediments retain fluid in the “shadow” of the BTH. Under the strong horizontal compressive stresses associated with the next BTH collision, pore pressure increases along with a rapid reduction of porosity in the underthrust sediments. The distinctive structural features observed in our model are comparable to the large faults in the Kumano transect of the Nankai Trough, Japan, where a splay fault branches from the plate boundary and there are old and active décollements. A low-velocity and high-pore-pressure zone is located at the bottom of the accretionary wedge and in front (i.e., landward) of the subducting ridge in the Kumano transect. This suggests that strong horizontal compressive stresses associated with the current BTH collision has increased the pore pressure within the underthrust sediments associated with previous BTHs.

scholarly journals Evolution of the geological structure and mechanical properties due to the collision of multiple basement topographic highs in a forearc accretionary wedge: Insights from numerical simulations

2021 ◽  
Author(s):  
Ayumu Miyakawa ◽  
Atsushi Noda ◽  
Hiroaki Koge
Keyword(s):  
Numerical Simulations ◽  
Pore Pressure ◽  
Compressive Stress ◽  
Plate Boundary ◽  
Structural Features ◽  
Geological Structure ◽  
Accretionary Wedge ◽  
Rapid Reduction ◽  
Compressive Stresses ◽  
Horizontal Compressive Stress

Abstract We propose a conceptual geological model for the collision of multiple basement topographic highs (BTHs; e.g., seamounts, ridges, and horsts) with a forearc accretionary wedge. Even though there are many BTHs on an oceanic plate, there are few examples of modeling the collision of multiple BTHs. We conducted numerical simulations using the discrete element method to examine the effects of three BTH collisions with forearcs. The typical geological structure associated with a BTH collision was reproduced during the collision of the first BTH, and multiple BTH collisions create a cycle of formation of BTH collisional structures. Each BTH forces the basal décollement to move up to the roof décollement, and the roof décollement becomes inactive after the passage of the BTH, and then the décollement moves down to the base. As the active décollement position changes, the sequences of underthrust sediments and uplifted imbricate thrusts are sandwiched between the décollements and incorporated into the wedge. At a low horizontal compressive stress, a “shadow zone” is formed behind (i.e., seaward of) the BTH. When the next BTH collides, the horizontal compressive stress increases and tectonic compaction progresses, which reduce the porosity in the underthrust sediments. Heterogeneous evolution of the geological and porosity structure can generate a distinctive pore pressure pattern. The underthrust sediments retain fluid in the “shadow” of the BTH. Under the strong horizontal compressive stresses associated with the next BTH collision, pore pressure increases along with a rapid reduction of porosity in the underthrust sediments. The distinctive structural features observed in our model are comparable to the large faults in the Kumano transect of the Nankai Trough, Japan, where a splay fault branches from the plate boundary and there are old and active décollements. A low-velocity and high-pore-pressure zone are located at the bottom of the accretionary wedge and in front (i.e., landward) of the subducting ridge in the Kumano transect. This suggests that strong horizontal compressive stresses associated with the current BTH collision has increased the pore pressure within the underthrust sediments associated with previous BTHs.

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