The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
James W. Rector - One of the best experts on this subject based on the ideXlab platform.
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Analysis and removal of multiply scattered tube waves
GEOPHYSICS, 2000Co-Authors: Gérard C. Herman, Paul A. Milligan, Qicheng Dong, James W. RectorAbstract:Because of irregularities in or near the Borehole, vertical seismic profiling (VSP) or crosswell data can be contaminated with scattered tube waves. These can have a large amplitude and can interfere with weaker upcoming reflections, destroying their continuity. This type of organized noise cannot always be removed with filtering methods currently in use. We propose a method based on modeling the scattered tube‐wave field and then subtracting it from the total data set. We assume that the scattering occurs close to the Borehole Axis and therefore use a 1-D impedance function to characterize Borehole irregularities. Estimation of this impedance function is one of the first steps. Our method also accounts for multiply scattered tube waves. We apply the method to an actual VSP data set and conclude that the continuity of reflected, upcoming events improves significantly in a washout zone.
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Drill bit wavefields
54th EAEG Meeting, 1992Co-Authors: James W. RectorAbstract:The seismic body wave radiation pattern of a working rock bit can be characterized by theoretical modeling and field data examples. My model of drill-bit signal generation is a pseudo-random series of bit tooth impacts that create both axial forces and tangential torques about the Borehole Axis. Each drill tooth impact creates an extensional wave that travels up the drillstring and body waves that radiate into the Barth. The model predicts that P waves radiale primarily along the Axis of the Borehole, and shear waves radiate primarily perpendicular to the Borehole Axis. In a vertical hole the largest P waves will be recorded directly above and below the drill bit; whereas, the largest shear waves will be recorded in a horizontal plane containing the drill bit. In a deviated Borehole, the radiation patterns should be rotated by the inclination angle of the bit. The proposed seismic body wave radiation is investigated with field data examples using multichannel arrays of vertical geophones. The modeled radiation pattern is also investigated with a three-component inverse VSP data example shown in Figure 1 . The variation in the signal-to-noise ratio witti drill bit depth and the partitioning of S-wave energy between radial and transverse components is consistent with the proposed radiation pattern. A quantitative measure of the drill bit radiation pattern, taken from calculating the rms ratio between the shear wave direct arrival on the radial component and the P-wave direct arrival on the vertical component, is also consistent with the proposed radiation pattern .
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Radiation pattern and seismic waves generated by a working roller-cone drill bit
GEOPHYSICS, 1992Co-Authors: James W. Rector, Bob A. HardageAbstract:The seismic body wave radiation pattern of a working roller‐cone drill bit can be characterized by theoretical modeling and field data examples. Our model of drill‐bit signal generation is a pseudo‐random series of bit‐tooth impacts that create both axial forces and tangential torques about the Borehole Axis. Each drill tooth impact creates an extensional wave that travels up the drill string and body waves that radiate into the earth. The model predicts that P‐waves radiate primarily along the Axis of the Borehole, and shear waves radiate primarily perpendicular to the Borehole Axis. In a vertical hole, the largest P‐waves will be recorded directly above and below the drill bit; whereas, the largest shear waves will be recorded in a horizontal plane containing the drill bit. In a deviated Borehole, the radiation patterns should be rotated by the inclination angle of the drill bit. This proposed seismic body wave radiation pattern is investigated with field data examples. The presence of the drill string ...
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Radiation pattern and seismic waves generated by a working roller-cone drill bit
GEOPHYSICS, 1992Co-Authors: James W. Rector, Bob A. HardageAbstract:The seismic body wave radiation pattern of a working roller‐cone drill bit can be characterized by theoretical modeling and field data examples. Our model of drill‐bit signal generation is a pseudo‐random series of bit‐tooth impacts that create both axial forces and tangential torques about the Borehole Axis. Each drill tooth impact creates an extensional wave that travels up the drill string and body waves that radiate into the earth. The model predicts that P‐waves radiate primarily along the Axis of the Borehole, and shear waves radiate primarily perpendicular to the Borehole Axis. In a vertical hole, the largest P‐waves will be recorded directly above and below the drill bit; whereas, the largest shear waves will be recorded in a horizontal plane containing the drill bit. In a deviated Borehole, the radiation patterns should be rotated by the inclination angle of the drill bit. This proposed seismic body wave radiation pattern is investigated with field data examples. The presence of the drill string in the Borehole creates other wave modes that are not typically observed when conventional vertical seismic profiles (VSPs) are conducted in fluid‐filled wells. For example, the extensional wave traveling up the drill string creates a head wave traveling away from the drill string, provided the formation velocities adjacent to the Borehole are less than the drill‐string velocity. Likewise, when the extensional wave traveling up the drill string reaches the drill rig, some of the energy continues through the drill rig structure, re‐enters the earth, and travels away from the rig as ground roll or shallow refractions. Secondary events are radiated at the drill bit after they travel up the drill string, reflect off drill‐string discontinuities, and travel back down the drill string to the bit. Each of these drill‐bit arrivals has a characteristic moveout as a function of wellhead offset and drill‐bit depth. A knowledge of the radiation patterns and the wave modes generated by the drill bit is essential to interpreting drill‐bit wavefields.
Bob A. Hardage - One of the best experts on this subject based on the ideXlab platform.
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Radiation pattern and seismic waves generated by a working roller-cone drill bit
GEOPHYSICS, 1992Co-Authors: James W. Rector, Bob A. HardageAbstract:The seismic body wave radiation pattern of a working roller‐cone drill bit can be characterized by theoretical modeling and field data examples. Our model of drill‐bit signal generation is a pseudo‐random series of bit‐tooth impacts that create both axial forces and tangential torques about the Borehole Axis. Each drill tooth impact creates an extensional wave that travels up the drill string and body waves that radiate into the earth. The model predicts that P‐waves radiate primarily along the Axis of the Borehole, and shear waves radiate primarily perpendicular to the Borehole Axis. In a vertical hole, the largest P‐waves will be recorded directly above and below the drill bit; whereas, the largest shear waves will be recorded in a horizontal plane containing the drill bit. In a deviated Borehole, the radiation patterns should be rotated by the inclination angle of the drill bit. This proposed seismic body wave radiation pattern is investigated with field data examples. The presence of the drill string ...
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Radiation pattern and seismic waves generated by a working roller-cone drill bit
GEOPHYSICS, 1992Co-Authors: James W. Rector, Bob A. HardageAbstract:The seismic body wave radiation pattern of a working roller‐cone drill bit can be characterized by theoretical modeling and field data examples. Our model of drill‐bit signal generation is a pseudo‐random series of bit‐tooth impacts that create both axial forces and tangential torques about the Borehole Axis. Each drill tooth impact creates an extensional wave that travels up the drill string and body waves that radiate into the earth. The model predicts that P‐waves radiate primarily along the Axis of the Borehole, and shear waves radiate primarily perpendicular to the Borehole Axis. In a vertical hole, the largest P‐waves will be recorded directly above and below the drill bit; whereas, the largest shear waves will be recorded in a horizontal plane containing the drill bit. In a deviated Borehole, the radiation patterns should be rotated by the inclination angle of the drill bit. This proposed seismic body wave radiation pattern is investigated with field data examples. The presence of the drill string in the Borehole creates other wave modes that are not typically observed when conventional vertical seismic profiles (VSPs) are conducted in fluid‐filled wells. For example, the extensional wave traveling up the drill string creates a head wave traveling away from the drill string, provided the formation velocities adjacent to the Borehole are less than the drill‐string velocity. Likewise, when the extensional wave traveling up the drill string reaches the drill rig, some of the energy continues through the drill rig structure, re‐enters the earth, and travels away from the rig as ground roll or shallow refractions. Secondary events are radiated at the drill bit after they travel up the drill string, reflect off drill‐string discontinuities, and travel back down the drill string to the bit. Each of these drill‐bit arrivals has a characteristic moveout as a function of wellhead offset and drill‐bit depth. A knowledge of the radiation patterns and the wave modes generated by the drill bit is essential to interpreting drill‐bit wavefields.
P. Amado Mendes - One of the best experts on this subject based on the ideXlab platform.
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Simulation of Wave Propagation in a Fluid-Filled Borehole Embedded in a Cracked Medium Using a Coupled BEM/TBEM Formulation
Bulletin of the Seismological Society of America, 2009Co-Authors: Julieta António, António Tadeu, P. Amado MendesAbstract:Abstract This article simulates the 3D wave propagation in a fluid-filled Borehole, embedded in an elastic medium containing an empty crack, when excited by a sonic tool placed inside the Borehole. The crack is assumed to be empty with thickness tending toward zero. The geometry of the cross section of the Borehole and the crack are assumed to be constant along the Borehole Axis, allowing the 3D problem to be solved as a summation of 2D responses for different wavenumbers along the z direction (2.5D formulation). The problem is formulated in the frequency domain using a coupled formulation incorporating the traction boundary element method, capable of modeling thin-body geometries, and the conventional direct boundary element method. In this formulation all singular and hypersingular integrals are computed analytically. This article assesses the influence of the length of the crack, its orientation, and its position in relation to the acoustic well in the wave field recorded inside the Borehole.
Heng Gao - One of the best experts on this subject based on the ideXlab platform.
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Mechanical properties and failure mode of sandstone specimen with a prefabricated Borehole under true triaxial stress condition
Geomechanics for Energy and the Environment, 2021Co-Authors: Guangzhi Yin, Dongming Zhang, Gun Huang, Heng GaoAbstract:Abstract With the continuous demand for mineral resources, the construction design and stability of underground rock engineering have been a frontier research topic worldwide. Stability analysis of underground caverns, tunnels, Boreholes, and cavities is of critical significance for underground engineering. To investigate the mechanical properties and failure mode of sandstone specimens with prefabricated cavities, experiments were conducted on sandstone samples with the Borehole Axis parallel to different principal stresses and for varying Borehole depths and diameters using a novel true triaxial geophysical apparatus. Computed tomography (CT) was used to analyze the crack development around the Borehole wall. The experimental results indicated that the direction of the Borehole and the principal stress Axis, as well as the Borehole depth and size, significantly affected the strength and damage mode of the rock samples. For a given σ 3 , with increasing principal stress coefficient β , the strength of the samples with the Borehole Axis parallel to the different principal stresses first increased and then decreased, and the maximum strength appeared at β = 0 . 5 . The highest stability of the rock samples appeared when the Borehole was parallel to σ 1 , and the lowest stability occurred when the Borehole was parallel to σ 2 or σ 3 . The strength of the sandstone sample decreased as the Borehole diameter increased. Four types of typical damaged modes were observed in the CT scan results. Moreover, the intermediate principal stress had a significant effect on the damage-zone distribution around the Borehole. This work can help to understand the damage area and failure characteristics of the Borehole surrounding rock, also make a significant contribution to support the design of deep rock engineering.
G. Dresen - One of the best experts on this subject based on the ideXlab platform.
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Influence of Bedding Angle on Borehole Stability: A Laboratory Investigation of Transverse Isotropic Oil Shale
Rock Mechanics and Rock Engineering, 2015Co-Authors: T. Meier, E. Rybacki, T. Backers, G. DresenAbstract:The stability of wells drilled into bedded formations, e.g., shales, depends on the orientation between the bedding and the Borehole Axis. If the Borehole is drilled sub-parallel to bedding, the risk of Borehole instabilities increases significantly. In this study, we examined the formation of stress-induced Borehole breakouts in Posidonia shale by performing a series of thick-walled hollow cylinder experiments with varying orientations of the bedding plane with respect to the Borehole Axis. The thick-walled hollow cylinders (40 mm in diameter and 80 mm in length containing an 8 mm diameter Borehole) were loaded isostatically until formation of breakouts. The onset of Borehole breakout development was determined by means of acoustic emission activity, strain measurements, ultrasonic velocities and amplitudes. The critical pressure for breakout initiation decreased from 151 MPa by approximately 65 % as the bedding plane inclination changed from normal to parallel to the Borehole Axis. The finely bedded structure in the shale resulted in an anisotropy in elasticity and strength from which the variation in strength dominated the integrity of the thick-walled hollow cylinders.