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39 Cards in this Set
- Front
- Back
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(ACOUSTICS) Name 4 short spaced tools. Name a long spaced tool.
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Short: BSAT, BCDT, ASAT, ISAT
Long: WSTT |
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(ACOUSTICS) What are the benefits of long spaced?
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Long spaced can measure compressional and shear/flexural and stonely.
Short spaced measures only compressional. |
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(ACOUSTICS) When does a monopole fail to generate critically refracted shear waves?
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Vshear < Vborehole
This happens in about 30% of formation. |
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(ACOUSTICS) How can we get stoneley waves?
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Stonley waves are generated from monopole. Created
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(ACOUSTICS) What is the main job for acoustic tools?
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To measure the speed of sound.
slowness = usec/ft fastness = feet-per-second |
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(ACOUSTICS) What is a limitation of short-spaced tools?
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Less time separation if P and S waves so can only determine P-wave velocity. S-waves require a long-spaced tool.
In larger borehole diameters (17"), short-spaced might only provide measure of borehole fluid velocity. (fluid is much faster than solid) |
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(ACOUSTICS) Do sonic tools have gains and offsets?
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No. No calibrations.
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(ACOUSTICS) Are there borehole corrections for the sonic tools?
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No.
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(ACOUSTICS) Decribe the skin effect.
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When the acoustic signal only travels deep enough to acquire information from the invaded part of the formation.
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(ACOUSTICS) What are the three minimum applications/data you can acquire with BSAT and WSTT?
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1. Determine effective porosity
2. Lithology estimates 3. Depth correlation for surface seismic data (+ rock properties for WSTT) |
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(ACOUSTICS) If decentralize the WSTT, what cannot be investigated?
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Anistotropy. Just getting data from monopole
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(ACOUSTICS) What can we determine from Stonley waves?
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Indication of Permeability.
Frequency if inversely proportional to permeability |
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(ACOUSTICS) Name 4 slow formations.
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1. Diatomite (foam)
2. Coal 3. Shaly Sand 4. Unconsolidated sands |
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(ACOUSTICS) What condition must be true to have critically refracted P-waves?
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Vfm >= Vbh
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(ACOUSTICS) When are stonely waves NOT created?
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When Vs< Vbh
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(ACOUSTICS) What is the Stoneley wave definition for how it is created?
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Created by flexing of interface between borehole fluid and formation fluid.
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(ACOUSTICS) How can you generate non-refracted shear waves?
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Flexural waevs (travel at the shear velocity)
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(ACOUSTICS) WHat is critical frequency?
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When Vflexural = Vshear
Has no dispersion There is NO real-time correction for Dispersion. |
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(ACOUSTICS) When Isotrpoic formation are shear waves equal of not in all directions?
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Equal.
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(ACOUSTICS) When is dispersion corectd needed?
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Fdipole > Fcritical then Vflexuaral < Vshear
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(ACOUSTICS) Descrobe semblance.
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When try to find coherence between one waveform in one receiver and another waveform in the next receiver.
(Coherence of 1 = Best= 100%) (Your delta-t is mre accurate) |
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(ACOUSTICS) How many total signals is the wavesonic processing?
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96 signals.
Mono Rx-32 ; DipX-32 ; DipY-32 |
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(ACOUSTICS) Which formation is slower, one that has delt-t of 120 usec or 100usec?
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120usec.
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(ACOUSTICS) Why does the Wyllie equation sometimes needs correction?
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Because in unconsoodated rocks, the linear Wyllie equation overestimates porosity
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(ACOUSTICS) How many transmitter and receivers does the BSAT have?
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2 Tx
5 Rx Produces a total number of 10 signals |
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(ACOUSTICS) Does a caliper perform borehole corrections to the BSAT?
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No.
Caliper serves only as a log quality control. (Sonic tools are mechanical measurements) |
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(ACOUSTICS) When might it be necessary to rubber band?
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When there are large washouts.
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(ACOUSTICS) Does BSAT compensate for washouts AND tool tilt?
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Yes.
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(ACOUSTICS) What are typical assumptions for delta-t of FW>, SWM, and OBM
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Fresh: 189 usec/ft
Salt-water: 185 usec/ft Oil: 205 usec/ft |
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(ACOUSTICS) Through what pins is instrument power sent through?
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Pins 7 and 8.
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(ACOUSTICS) WHat is the objective of logging the WSTT?
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Compute compressional and shear slowness (delta-t)
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(ACOUSTICS) On WSTT, does semblance use a threshold?
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No.
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(ACOUSTICS) Do fast formations have low or high delta-t?
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Low delta-t
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(ACOUSTICS) Is the MIT a hardware or software configuration?
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Hardware configuration
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(ACOUSTICS) Where on your wavesonic is the brains (INC Board) located?
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In the lower electronics. (Communication)
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(ACOUSTICS) Decribe the operations of the Upper Electronics.
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Transmitter everything.
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(ACOUSTICS) Explain the need for a 1.4 window.
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Window in which to find the shear wave
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(ACOUSTICS) What is the tolerance for monopole and dipole?
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+/- 1usec and +/-2usec, respectively
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(ACOUSTICS) What is the delta-t compressional for sandstone, limestone, dolomite, anhydrite and halite?
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sandstone: 55.5
limestone: 47.6 dolomite: 43.5 anhydrite: 50 halite: 67 |
