Acoustic waveforms are acquired while drilling with the Anadrill Isonic tool. One transmitter and four receivers are positioned within a drill collar just above the bit to collect compressional transit times just seconds after the rock has been cut. As with all Logging-While-Drilling tools, formation data are collected before the borehole alteration or invasion occurs. The data are stored in memory and dumped upon collar retrieval, or they are pulsed in real time if an MWD sub is in use. Isonic data are then utilized in the tradional manner for sonic porosity, synthetic seismogram and correlation with wireline logs.
Porosity and "pseudodensity" log
The sonic transit time can be used to compute porosity by using the appropriate transform and to estimate fracture porosity in carbonate rocks. In addition, it can be used to compute a "pseudodensity" log over sections where this log has not been recorded or the response was not satisfactory.
Seismic impedance
The product of compressional velocity and density is useful in computing synthetic seismograms for time-depth ties of seismic reflectors.
Sonic waveforms analysis
If a refracted shear arrival is present, its velocity can be computed from the full waveforms, and the frequency content and energy of both compressional and shear arrivals can also be determined.
Fracture porosity
Variations in energy and frequency content are indicative of changes in fracture density, porosity, and in the material filling the pores. In some cases compressional-wave attenuation can also be computed from the full waveforms.
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Drill collar nominal OD:
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6.75 in. |
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Drill collar IDs:
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4.75 in.
2.38 in. |
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Drill collar joints:
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5.5-in. FH |
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Pony collar and saver sub joints:
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5.5-in. FH |
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Makeup length:
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22.08 ft without saver sub |
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Measure point to tool bottom:
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13.5 ft |
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Total tool weight in air:
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2100 lbm |
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Maximum temperature:
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300° F |
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Operating pressure:
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20,000 psi |
| Maximum flow rate: |
800 gpm |
| Pressure drop at maximum flow rate: |
30 psi at 11 ppg |
| Maximum tool curvature: |
|
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Rotating mode: |
4°/100 ft |
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Sliding mode: |
16°/100 ft |
| Bending strength ratio (BSR): |
2.0 |
| Equivalent bending stiffness: |
23 ft of 6.5 in. x 2.81 in. |
| Average inertia: |
85 in.4 |
| Maximum bit size: |
9.875 in. |
| Maximum jarring load: |
330,000 lbm |
| Maximum weight on bit: |
74 million / L2 lbm, where L = distance betweeen stabilizers in feet |
| Joint makeup (6.625-in. FH): |
21,000 ft-lbf |
| Maximum rotary: |
16,000 ft-lbf |
| Maximum torque (pin yield): |
43,000 ft-lbf |
* ®trademark of Schlumberger |
