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Line 81: + + + + + + + + − Acoustic borehole televiewers all contain a rotating ultrasonic transducer that emits a pulse and receives the signal reflected by the borehole wall (Figure 1). The transducers are either focused or unfocused and have frequencies in the range of 200 kHz to 1 MHz; they typically perform 3 to 16 rotations per second. Orientation of the transducer is normally provided through a magnetometer. Two types of images can be obtained: one based on the reflected amplitude and one on the two-way traveltime. By convention, darker gray tones are used for lower reflected amplitudes and higher two-way traveltimes. − [[file:borehole-imaging-devices_fig1.png|thumb|{{figure number|1}}Borehole televiewer technique. (From <ref name=pt04r23>Zemanek, J., Caldwell, R. L., Glenn, E. E., Holcomb, S. V., Norton, L. J., Straus, A. J. D., 1969, The Borehole Televiewer—a new logging concept for fracture location and other types of borehole inspection: Journal of Petroleum Technology, v. 21, p. 762–774., 10., 2118/2402-PA</ref>.)]] − − [[file:borehole-imaging-devices_fig2.png|thumb|{{figure number|2}}Drill marks (arrow) on borehole televiewer images.]] − − [[file:borehole-imaging-devices_fig3.png|thumb|{{figure number|3}}Borehole televiewer Image showing fracture (arrow) crossing the wellbore.]] − − [[file:borehole-imaging-devices_fig4.png|thumb|{{figure number|4}}Borehole televiewer images showing shale layers (dark) intercalated with limestone layers (bright).]] − − [[file:borehole-imaging-devices_fig5.png|thumb|{{figure number|5}}Borehole televiewer image showing breakouts (dark patches) at NNW and SSE.]]
Borehole imaging devices (view source)
Revision as of 19:08, 13 January 2014
, 19:08, 13 January 2014→Ultrasonic reflection technique: the borehole televiewer
==Ultrasonic reflection technique: the borehole televiewer==
==Ultrasonic reflection technique: the borehole televiewer==
<gallery>
file:borehole-imaging-devices_fig1.png|'''Figure 1.''' Borehole televiewer technique.<ref name=pt04r23>Zemanek, J., Caldwell, R. L., Glenn, E. E., Holcomb, S. V., Norton, L. J., Straus, A. J. D., 1969, The Borehole Televiewer—a new logging concept for fracture location and other types of borehole inspection: Journal of Petroleum Technology, v. 21, p. 762–774., 10., 2118/2402-PA</ref>]]
file:borehole-imaging-devices_fig2.png|'''Figure 2.''' Drill marks (arrow) on borehole televiewer images.
file:borehole-imaging-devices_fig3.png|'''Figure 3.''' Borehole televiewer Image showing fracture (arrow) crossing the wellbore.
file:borehole-imaging-devices_fig4.png|'''Figure 4.''' Borehole televiewer images showing shale layers (dark) intercalated with limestone layers (bright).
file:borehole-imaging-devices_fig5.png|'''Figure 5.''' Borehole televiewer image showing breakouts (dark patches) at NNW and SSE.
</gallery>
Acoustic borehole televiewers all contain a rotating ultrasonic transducer that emits a pulse and receives the signal reflected by the borehole wall (Figure 1). The transducers are either focused or unfocused and have frequencies in the range of 200 kHz to 1 MHz; they typically perform 3 to 16 rotations per second. Orientation of the transducer is normally provided through a magnetometer. Two types of images can be obtained: one based on the reflected amplitude and one on the two-way traveltime. By convention, darker gray tones are used for lower reflected amplitudes and higher two-way traveltimes.
The borehole televiewer provides strictly a borehole wall surface measurement and as such is affected by rugosity, drill marks (Figure 2), borehole ellipticity, and tool eccentering. It is an effective tool when good hole conditions with relatively smooth borehole walls prevail. Reflected amplitude images are successfully used in the characterization of fractured reservoirs (Figure 3) and to a lesser degree for layered reservoir analysis (Figure 4). The transit time images provide an acoustic, full-circumference caliper of the borehole which is used for wellbore volume calculations, breakout analysis (Figure 5), and wellbore rugosity estimates.
The borehole televiewer provides strictly a borehole wall surface measurement and as such is affected by rugosity, drill marks (Figure 2), borehole ellipticity, and tool eccentering. It is an effective tool when good hole conditions with relatively smooth borehole walls prevail. Reflected amplitude images are successfully used in the characterization of fractured reservoirs (Figure 3) and to a lesser degree for layered reservoir analysis (Figure 4). The transit time images provide an acoustic, full-circumference caliper of the borehole which is used for wellbore volume calculations, breakout analysis (Figure 5), and wellbore rugosity estimates.
==Electrical borehole scanning: the formation microscanner==
==Electrical borehole scanning: the formation microscanner==