Table T4. Measurement performance specifications of the geoVISION tool.
| Measurement | Vertical resolution (inch) | Depth of investigation (inch) | Diameter of investigation (inch) |
Horizontal resolution (inch) |
Midpoints of extremes (inch) | |||
|---|---|---|---|---|---|---|---|---|
| Rt/Rxo = 10 | Rt/Rxo = 0.1 | Rt/Rxo = (10 × π)/56 | Rt/Rxo = (0.1 × π)/56 | |||||
| Resistivity at the bit | 12−24 | 12 | 32 | 32 | ||||
| Ring resistivity | 2−3 | 7 | 22 | 25 | ||||
| Button resistivity | ||||||||
| Shallow focused | 2−3 | 1 | 19 | 24 | 1.07 | 1.35 | 1.2 | |
| Medium focused | 2−3 | 3 | 15 | 21 | 0.84 | 1.18 | 1 | |
| Deep focused | 2−3 | 5 | 11 | 16 | 0.62 | 0.9 | 0.75 | |
| Gamma ray | 12 | 10 | ||||||
Rt = true resistivity of formation. Rxo = resistivity of zone invaded by drilling fluid. Invasion may be minimal due to measurement of resistivity soon after cutting of hole. Then Rt/Rxo = 1. Horizontal resolution for each of tools intermediate between extremes of Rt/Rxo in table above. Imaging tools record 56 times with each revolution of the tool. Accuracy of segment location is ±1°.
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