Logging-While-Drilling arcVISION* Tool
Description
The Logging-While-Drilling-arcVISION (LWD-arcVISION) is a compensated array resistivity tool developed by Schlumberger for medium to large boreholes. The 6.75 in (17 cm) diameter tool makes multiple, borehole-compensated phase shift and attenuation resistivity measurements at two frequencies: 2MHz and 400kHz. The tool’s antenna array consists of five transmitters and two receivers to achieve both a range of depths of investigations as well as borehole compensation. Multiple depths of investigation are useful to differentiate between borehole effects, invasion, shoulder beds, and anisotropy. Borehole compensation is important because it significantly reduces the effects of borehole rugosity. In addition to the resistivity measurements, the arcVISION also provide a non-azimuthal gamma ray measurement performed with a plateau sensor (NaI detector) and annular pressure-while-drilling (APWD), including real-time static pressure.
The arcVISION tool can be operated in memory mode or in real-time mode in combination with the TeleScope MWD tool; also, it is combinable with any other LWD tool.
Applications
Formation anisotropy. The separation between the vertically matched resistivities can be used to discriminate between invasion and formation anisotropy.
Lithology. Identification of impermeable beds – the resistivity curves will match in shales.
Tool Specifications
| Temperature rating : | 300° F (149° C) |
| Pressure rating: | 25 kpsi (173 MPa) |
| Length: | 18 ft (5.49 m) |
| Weight: | 1,800 lbs (817.2 kg) |
| API nominal collar outside diameter: | 6.75 in (17 cm) |
| Maximum outside diameter: | 7.5 in (19.05 cm) |
| Minimum bit size: | 8.5 in (21.59 cm) |
| Maximum bit size: | 10.5 in (26.67 cm) |
| Flow range: | 0-800 gpm |
| Pressure drop coeffecient (C)*: | 121,000 |
| Maximum curvature – sliding: | 16 deg/100 ft (16 deg/31 m) |
| Maximum rotary torque: | 0 rpm |
| Minimum operating RPM: | 30 rpm |
| Uphole connection: | 5-1/2 FH box |
| Downhole connection: | 5-1/2 FH box |
| (*) pressure drop = [mudweight in ppg] x [flow in gpm]²/C |
Measurement Specifications
| Gamma Ray | ||
| Range: | 0-250 GAPI | |
| Accuracy: | 3% | |
| Statistical resolution: | ±2 GAPI at 100 ft/hr (31 m/hr) | |
| Vertical resolution: | 6 in (15.24 cm) | |
| Resistivity | Attenuation | Phase |
| Range: | 0.2-50 ohm-m | 0.2-3,000 ohm-m |
| Accuracy (<25 ohm-m): | ±3% | ±2% |
| Accuracy (>25 ohm-m): | ±1.5 mmho/m | ±0.3 mmho/m |
| Vertical resolution at 0.2 ohm-m: | 12 in (30.48 cm) | 8.4 in (21.33 cm) |
| Pressure While Drilling | ||
| Range: | 20 kpsi (137 MPa) | |
| Accuracy: | ||
| Vertical resolution: | ±1 psi (6.9 kPa) |
Major Outputs
| GR: | Gamma Ray (API units) |
| PnB: | Phase Shift Resistivity Blended, n=16, 22, 28, 34, 40 in (ohm-m) |
| PnH: | Phase Shift Resistivity, 2 MHz, n=16, 22, 28, 34, 40 in (ohm-m) |
| PnL: | Phase Shift Resistivity, 400 KHz, n=16, 22, 28, 34, 40 in (ohm-m) |
| AnB: | Attenuation Resistivity Blended, n=16, 22, 28, 34, 40 in (ohm-m) |
| AnH : | Attenuation Resistivity, 2 MHz, n=16, 22, 28, 34, 40 in (ohm-m) |
| AnL: | Attenuation Resistivity, 400 KHz, n=16, 22, 28, 34, 40 in (ohm-m) |
| APRS: | Annulus Pressure (psi) |
| ATMP: | Annulus Temperature (degC) |
| ECD: | Equivalent Circulating Density (lb/gal) |
| AGTM: | Gamma Ray Time After Bit (s) |
| ARTM: | Resistivity Time After Bit (s) |
| ROP5_RM: | Rate of Penetration, average over last 5 ft (m/hr) |
| RPM: | Tool Rotational Speed (rpm) |
* ®trademark of Schlumberger