Physical model for downhole orbital vibrator (DOV) — (2) borehole seismic radiation

Walter, L.; Leary, Peter; Crampin, Stuart

doi:10.1190/1.1817795

Cited by 4 publications

(4 citation statements)

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“…Reliable routine stress‐forecasting earthquakes requires cross‐hole seismology at a three (1‐km‐ to 1.5‐km‐deep) borehole Stress‐Monitoring Site (SMS) (Crampin, ) using the Downhole Orbital Vibrator (DOV) (Walter et al ., ) to transmit shear‐waves along specific stress‐oriented directions and angles of incidence. The prototype SMS, the SMSITES Project between existing boreholes (adjacent to the Húsavík‐Flatey transform fault of the Mid‐Atlantic Ridge where it runs onshore in northern Iceland) did not have optimum source‐to‐receiver borehole geometry, yet demonstrated the anticipated butterfly‐effect sensitivity (Section S4; Crampin et al ., ).…”

Section: Potential For Routine Stress‐forecasting At Three‐borehole Smentioning

confidence: 99%

The New Geophysics

Crampin

Gao

2013

Terra Nova

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New Geophysics of critically microcracked rock is a new understanding of fluid-rock deformation that matches much of the behaviour of in situ rock observed throughout the Earth's crust and uppermost mantle. The behaviour of rock in New Geophysics: is self-similar; can be monitored, calculated, predicted, even in principle controlled; prevails in almost all rocks; and has 'butterfly-effect' sensitivity. All of these remarkable features (except controllability) have been observed, in some cases many times. However, New Geophysics is innovative, controversial, and currently "ridiculed" and "violently opposed" (Schopenhauer Stages 1 and 2), and is difficult to get published via consensus-driven peer-review.

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Section: Potential For Routine Stress‐forecasting At Three‐borehole Smentioning

confidence: 99%

The New Geophysics

Crampin

Gao

2013

Terra Nova

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“…A shear-wave source in a cross-hole seismic experiment excited SV-and SH-waves at 500 m-depth between two boreholes 315 m-apart, adjacent (at ~100 m-distant) and parallel to the Húsavík-Flatey Transform Fault (HFTF) of the Mid-Atlantic Ridge (MAR) as it runs onshore in Northern Iceland. The downhole-orbital-vibrator source (DOV) (Walter et al, 2003) was pulsed in sweeps to 250 Hz over 12-20 s, two or three times each minute, and stacked every 100 sweeps for 24 hours each day. 2) There is a minimum SWVA of ~1.5% in almost all in situ rocks.…”

Section: Using Ape To Model the Waveforms Before And Aftermentioning

confidence: 99%

Evidence supporting New Geophysics

Crampin

Gao

2018

Earth and Planetary Physics

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In the last decade a New Geophysics has been proposed, whereby the crust and uppermost ~400 km of the mantle of the Earth are so pervaded by closely‐spaced stress‐aligned microcracks (intergranular films of hydrated melt in the mantle) that in situ rocks verge on failure by fracturing, and hence are critical‐systems that impose a range of fundamentally‐new properties on conventional sub‐critical geophysics. Enough of these new properties have been observed to confirm that New Geophysics is a new understanding of fluid/rock deformation with important implications and applications. Evidence supporting New Geophysics has been published in a wide variety of publications. Here, for clarification, we summarise in one document the evidence supporting New Geophysics.

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“…In response to the surface seismic‐imaging deficiency at the Liaohe oil field, Geospace Engineering Resources International (GERI) was contracted to conduct a series of exploratory crosswell surveys in existing production wells at offsets between 600 and 850 m. Higher‐frequency and lower‐power (300 versus 30 Hz, 500 W versus 500 KW) seismic‐wave generation made possible by downhole reservoir‐proximate sourcing and sensing (Leary et al 2003; Walter et al 2003; Leary & Walter 2005a,b) offer an option to surface seismic imaging if far‐offset crosswell seismic signals can be detected and accurately interpreted in terms of reservoir‐scale heterogeneity structures lying below the resolution of surface seismic imaging.…”

Section: Introductionmentioning

confidence: 99%

“…This cutoff rules out the majority of crosswell ray paths for data acquired at Liaohe on strictly geometric grounds. Further, the downhole orbital vibrator source used at Liaohe (Leary et al 2003; Walter et al 2003; Leary & Walter 2005a,b) has a radiation pattern that highly favours horizontal over vertical radiation, and does not generate source energy within the processing angular passband considered acceptable by Rowbotham & Goulty (1994) Finally, at far offsets the ray theoretic basis for reflector inversion is increasingly suspect as the source wavefield is spherical rather than pseudo‐planar, and high‐angle (far‐offset) reflection of spherical waves is physically far more complex than low‐angle (near‐offset) reflection of plane waves. illustrates that even when prominent reflectors can be clearly distinguished from the first arrival energy, the far‐offset geometry does not yield a reliable image.…”

Section: Introductionmentioning

confidence: 99%

Crosswell seismic waveguide phenomenology of reservoir sands & shales at offsets >600 m, Liaohe Oil Field, NE China

Leary¹,

Ayres²,

Yang

et al. 2005

Geophysical Journal International

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S U M M A R YCrosswell seismic data recorded at 620-650 m offsets in an oil-bearing sand/shale reservoir formation at the Liaohe Oil Field, northeast China, provide robust evidence for waveguide action by low-velocity reservoir layers. Crosswell-section velocity models derived from survey-well sonic logs and further constrained by observed waveguide seismic wavegroup amplitudes and phases yield plausible evidence for interwell reservoir-sand continuity and discontinuity. A pair of back-to-back Liaohe crosswell vector-seismic surveys were conducted using a source well between two sensor wells at 650 and 620 m offsets along a 200-m-thick reservoir formation dipping 7 • down-to-east between depths of 2.5 and 3 km. A downhole orbital vibrator generated seismic correlation wavelets with frequency range 50-350 Hz and signal/noise ratio up to 5:1 over local downhole ambient noise. The sensor wells were instrumented with a mobile 12-to 16-level string of clamped vector-motion sensor modules at 5 m intervals. Using 5 m source depth increments, crosswell Surveys 1 and 2 cover source/sensor well intervals above and through the reservoir of, respectively, 600 m/600 m (13 000 vector traces in 9 common sensor fans) and 300 m/560 m (7000 vector traces in 7 common sensor fans). Survey 1 common sensor gathers show clear, consistent high-amplitude 20 ms waveletgroup lags behind the first-arrival traveltime envelope. Such arrivals are diagnostic of seismic lowvelocity waveguides connecting the source and sensor wells. Observed Survey 1 retarded wavegroup depths tally with source and sensor depths in low-velocity layers identified in sonic well logs. Finite-difference acoustic model wavefields computed for waveguide acoustic layers constrained by well-log sonic velocity data match the observed waveguide traveltime and amplitude systematics. Model waveforms duplicate the observed m-scale and ms-scale sensitivity of waveguide spatio-temporal energy localization. Survey 2 crosswell data, in contrast, provide no comparable evidence for waveguide action despite a sensor-well sonic well log similar to that of Survey 1. Instead, acoustic wavefield modelling of Survey 2 data clearly favours an interpreted waveguide model with 10 • downdip interrupted by a 75-100 m throw downfault near the sensor well. The absence of clear waveguide arrivals is adequately explained by dispersal of waveguide energy at the fault discontinuity. Auxiliary well sonic velocity and lithologic logs confirm the model-implied 75-100 m of down-throw faulting near the sensor well.

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Physical model for downhole orbital vibrator (DOV) — (2) borehole seismic radiation

Cited by 4 publications

References 0 publications

The New Geophysics

The New Geophysics

Evidence supporting New Geophysics

Crosswell seismic waveguide phenomenology of reservoir sands & shales at offsets >600 m, Liaohe Oil Field, NE China

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