Resistivity Module
Wave Propagation Resistivity Sub (WPR™)
EDS WPR sub is a spatially compensated, dual frequency (400 kHz & 2 MHz), dual spacing device designed for wireline-equivalent Logging-While-Drilling (LWD) and Measurements-After-Drilling (MAD) services in all well types. Applications include geosteering, correlation, pore pressure trend analysis, casing point selection, wireline replacement, logging while tripping and logging with and without the flow switch enabled (for air- and foam-drilled wells).
WPR’s symmetrical design, with centrally located receive antennas, provides real-time compensation, eliminates invasion effects due to measurement delays, and improves accuracy by canceling variations in receiver channels.
WPR operates in all mud types including oil-based and salt-saturated and provides real-time resistivity with flexible transmission formats. High-resolution data is stored in downhole memory which can be retrieved and processed during trips.
EDS provides a complete set of software-enabled borehole corrections and applications with WPR, including a dipping bed model for geosteering. EDS offers a Pressure-While-Drilling (PWD) option for 4.75 in., 6.75 in. and 8.0 in. WPR.
WPR General Specifications
Tool Sizes & Maximum Dogleg Severity
Mechanical and electrical connections and interface to EDS SureShot™ MWD
» Resistivity sub is a node on the SureShot RS-485 busPower requirements
» Low operating power for maximum battery life » Designed to run on 2x/3x batteries (10 cell DD) or 0x/1x/2x battery and turbine alternatorTool Programming and Data Dump port
» Hatch cover for easy access via an intrinsically safe connection to allow tool programming and memory dump. Memory data dumps and tool programming can also be performed when the tool string is disconnected from the resistivity via the tool string lower end.
32 MB integrated FLASH memory
| "Tool Size" | Maximum Dogleg Severity | Connection | ||
| Borehole Size | ||||
| Sliding | Rotating | |||
| 3.5 in. | 4.625 - 4.75 in. | 40˚/100 ft | 16˚/100 ft | |
| (89 mm) | (117-121 mm) | (70˚/100 ft with flex-joints | (25˚/100 ft with flex-joints | 2 7/8 AOH |
| for short radius wells) | for short radius wells) | |||
| 4.75 in. | 5.625 - 6.125 in. | 25˚/100 ft | 13˚/100 ft | NC38 |
| (121 mm) | (142 - 165 mm) | |||
| 6.75 in. | 8.375 - 9.875 in. | 24˚/100 ft | 10˚/100 ft | NC50 |
| (172 mm) | (213 - 251 mm) | |||
| 8.0 in. | 12.125 - 14.75 in. | 15˚/100 ft* | 8˚/100 ft* | 6 5/8 Reg. |
| (204 mm) | (308 - 375 mm) | |||
Environmental
| Operating Temperature | 0˚ to 347˚F (0˚ to 175˚C) |
| Pressure | 20,000 psi (138 MPa) |
Compensated Resistivity Measurements
| Frequency | Measurement | Range | Accuracy |
| 2 MHz | Phase Difference | 0.1 - 3,000 ohm-m | ± 1% [0.1 - 50 ohm-m] ± 0.5 mmho/m [above 50 ohm-m] |
| Amplitude Ratio | 0.1 - 500 ohm-m | ± 2% [0.1 - 25 ohm-m] ± 1.0 mmho/m [above 25 ohm-m] | |
| 400 kHz | Phase Difference | 0.1 - 1,000 ohm-m | ± 1% [0.1 - 25 ohm-m] ± 1.0 mmho/m [above 25 ohm-m] |
| Amplitude Ratio | 0.1 - 200 ohm-m | ± 5% [0.1 - 10 ohm-m] ± 5.0 mmho/m [above 10 ohm-m] |
Transmitter / Receiver Spacing's
| Measure Point | ||||||
| UH | DH | |||||
| T1 | T2* | R1 | R2 | T3* | T4 | |
| in. | -36.00 | -22.50 | -4.25 | +4.25 | +22.50 | +36.00 |
| mm | -914.4 | -571.5 | -107.9 | +107.9 | +571.5 | +914.4 |
| * Not included in 3.5 in. size. | ||||||
Depth of Investigation, Vertical Resolution
| Depth of Investigation | |||
| Rf = 1 ohm-m Rxo = 0.5 ohm-m | Short Spacing Radius | Long Spacing Radius | Vertical Resolution** |
| 2 MHz Phase | 21 in. (533 mm) | 28 in. (711 mm) | 8 in. (203 mm) |
| 400 kHz Phase | 30 in. (762 mm) | 39 in. (991 mm) | 12 in. (305 mm) |
| 2 MHz Amplitude | 34 in. (866 mm) | 44 in. (1,118 mm) | 8 in. (203 mm) |
| 400 kHz Amplitude | 52 in. (1,321 mm) | 66 in. (1,676 mm) | 12 in. (305 mm) |
| Depth of Investigation | |||
| Rf = 10 ohm-m Rxo = 0.5 ohm-m | Short Spacing Radius | Long Spacing Radius | Vertical Resolution** |
| 2 MHz Phase | 26 in. (660 mm) | 37 in. (940 mm) | 8 in. (203 mm) |
| 400 kHz Phase | 36 in. (914 mm) | 49 in. (1,245 mm) | 12 in. (305 mm) |
| 2 MHz Amplitude | 40 in. (1,016 mm) | 53 in. (1,346 mm) | 8 in. (203 mm) |
| 400 kHz Amplitude | 60 in. (1,524 mm) | 76 in. (1,930 mm) | 12 in. (305 mm) |