Screened and unscreened axially-cylindrical surface-waves

Barlow, H.E.M.

doi:10.1088/0022-3727/4/3/305

Cited by 11 publications

(3 citation statements)

References 4 publications

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“…This is well known as reflected guided BHR electromagnetic (EM) wave events which are often ob-served as obliquely striped patterns in BHR profiles when a conventional BHR is attached to a metallic communication cable, or used in a conductive saline water-filled borehole (Wright, Watts and Bramsoe 1984;Sato and Thierbach 1991;Dubois 1995;Ebihara, Sato and Niitsuma 1998;Guy and Radzevicius 2001;Vogt 2004;Ellefsen and Wright 2005;Mason et al 2008). These guided BHR waves are formed by Goubau waveguides (Goubau 1950;Barlow 1971;Laurette et al 2012). They are usually considered as 'unwanted' interference to the normal BHR surveying, and should be suppressed through either BHR hardware design (Cho et al 2013) or data processing (Ebihara, Sasakura and Takemoto 2011;Huo et al 2019a,b).…”

Section: Guided Bhr Wave Imaging and Top Coal Predictionmentioning

confidence: 99%

Coal top detection by conductively guided borehole radar wave imaging for open cut blast‐hole drilling

Zhou

Werken

Huo

2019

Geophysical Prospecting

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Damage to the top of coal seams, caused by incorrect blast stand‐off distances, results in coal losses of up to 10–15% to the Australian open cut coal mining operations. This is a serious issue to be addressed. Here we propose to use a new forward‐looking imaging technique based on the borehole radar technology to predict the coal seam top in real time while drilling blast holes. This is achieved by coupling the conventional borehole radar waves on to a steel drill rod to induce a guided wave along the axial drill rod. The drill rod ahead of the borehole radar behaves as a forward‐looking antenna for the guided waves. Both numerical modelling and field trials simulating a drill rod as an antenna are used to investigate the feasibility of the proposed technique for prediction of the coal top under typical open cut environments. Numerical modelling demonstrated that conductivity of the overburden is the most important factor affecting our ability to see coal seams ahead of the drill bit, the guided borehole radar waves could be used for top coal prediction and a theoretical prediction error less than 10 cm and a forward‐looking capability of 4–6 m can be achieved. Field trials at Australian open cut coal mines also demonstrated that guided borehole radar waves can be observed and used for prediction of coal top ahead of drill bit during blast‐hole drilling in resistive, open cut environments (the average resistivity should be higher than 75 Ωm).

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Section: Guided Bhr Wave Imaging and Top Coal Predictionmentioning

confidence: 99%

Coal top detection by conductively guided borehole radar wave imaging for open cut blast‐hole drilling

Zhou

Werken

Huo

2019

Geophysical Prospecting

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“…The guiding characteristics of a conductor coated with a dielectric sheath, in this case water, are well-known [5], [9], [16]- [18].…”

Section: B Guided Wave Operationmentioning

confidence: 99%

The Effect of Conduction on VHF Radar Images Shot in Water-Filled Boreholes

Mason

Bray

Sindle

et al. 2008

IEEE Geosci. Remote Sensing Lett.

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A downhole digital memory-logging pulsed borehole radar transceiver operating in the 10-125-MHz band was run repeatedly down two 1.25-km-deep, uncased, water-filled 60-mm boreholes in the Northern Limb of the Bushveld Complex, South Africa. Suspended on an insulating cord, it mapped a steep fault in the Main Zone from a range of 75 m down through its intersection with the borehole. Lowered on a wire rope, the transceiver launched guided ∼ 75 m/µs first-order transverse magnetic pulses which shuttled axially between the radar and the bedding planes. Decoupled from the wire by 2 m of insulating cord, it yielded a profile in which radar reflections and guided bedding plane echoes superimposed. As the radar descended through the mineralized, stratified Platreef, traces were found to be imprinted with voltage level shifts that showed, with Laterolog-comparable resolution, the conductivity profile of the Platreef.

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“…Guided BHR EM wave propagation can be then observed along the wire [1], [22]- [26] and the conductive water column [25]- [28]. The EM wave guiding characteristics of a conductor in a dielectric layer or water for the case of BHR are well investigated [ [29]- [31]. The guided BHR EM wave can interfere with normal BHR waves and should be suppressed through BHR design [32] or data filtering [33].…”

Section: Introductionmentioning

confidence: 99%

Conductively Guided Borehole Radar Wave for Imaging Ahead of a Drill Bit

Zhou

Werken

2015

IEEE Geosci. Remote Sensing Lett.

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A guided wave is induced along a conductive logging cable or a conductive water-filled borehole during borehole radar (BHR) surveying. Such a guided wave is normally considered as unwanted interference to normal BHR waves and needs to be suppressed, either through BHR designs or data processing. In this letter, we advocate that the guided wave can be coupled onto a drill string, which can act as a forward-looking antenna for imaging ahead of the drill bit while drilling. Using data collected by a monostatic BHR with different configurations at an abandoned mine site in Brukunga, South Australia, we demonstrate that the forward-looking capability of the BHR is about 2-6 m in the tested borehole section. Index Terms-Borehole radar (BHR), guided electromagnetic (EM) wave, imaging.1545-598X

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Screened and unscreened axially-cylindrical surface-waves

Cited by 11 publications

References 4 publications

Coal top detection by conductively guided borehole radar wave imaging for open cut blast‐hole drilling

Coal top detection by conductively guided borehole radar wave imaging for open cut blast‐hole drilling

The Effect of Conduction on VHF Radar Images Shot in Water-Filled Boreholes

Conductively Guided Borehole Radar Wave for Imaging Ahead of a Drill Bit

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