At-Bit Resistivity – GeoTracker
Near-bit Azimuthal Propagation Resistivity Tool
The GeoTracker* tool delivers, for the first time, compensated propagation resistivity measurement at the bit.
With the patented side-mounted antennas, the tool provides 16 sectors of attenuation and phase-shift measurements from a rotating BHA. The depths of investigation of the measurements range from a few inches to 30 inches. The tool may be run either below a motor, right above a rotary steerable system (RSS), or as part of an RSS. When run below a motor, the measure point is as close as 12 inches from the bit. EM short-hop is available for transmitting the data across the motor to the MWD system. Like traditional propagation resistivity tools, the GeoTracker* tool works in almost all kinds of mud.
The GeoTracker* tool offers several important applications, including oil-water contact detection, overpressure detection, well placement in conventional and unconventional reservoirs, and especially geosteering in thinly bedded payzones. With the unprecedented depths of investigation for a near-bit tool, the GeoTracker* tool allows earlier detection of approaching resistivity boundaries than ever before. When run with an RSS, the tool may enable truly autonomous geosteering downhole, making the RSS intelligent.
The GeoTracker* tool is available in both 4.75” and 6.75” sizes. The nominal temperature and pressure ratings are 150°C and 20,000psi. Higher temperature and pressure ratings of 175°C and 25,000psi are also available.
Advantages
- Compensated propagation resistivity measurement at or near the bit
- Geosteering in thinly bedded payzones
- Works in almost all mud types
Features
- 16-sector dual-frequency attenuation and phase-shift resistivities
- Fully compensated measurements
- Depth of investigation up to 30in.
- Measure point to bit 12in.
- Combinable with motors or RSS’s
- Sub length 35in. (31in. for RSS)
- Rated at 150°C/20000psi (175°C/25000psi option)
Specifications
At-bit Sub
| Tool size | 4.75 in. | 6.75 in. |
|---|---|---|
| Length | 35 in. | 35 in. |
| Nominal OD | 5.0 in. | 6.75 in. |
| Max OD | 5.25 in. | 7.0 in. |
| Max ID | 1.313 in. | 2.375 in. |
| Connection PIN Up | 3-1/2 REG (IF option) | 4-1/2 REG (IF option) |
| Connection BOX Down | 3-1/2 REG | 4-1/2 REG |
| Yield Strength | 15,140 lbf-ft | 29,900 lbf-ft |
| Make-up Torque | 12,000 lbf-ft | 24,000 lbf-ft |
| Max DLS Rotating | 15°/100ft | 8°/100ft |
| Max DLS Sliding | 30°/100ft | 16°/100ft |
| Max Downhole Drilling Torque | 12,000 lbf-ft | 24,000 lbf-ft |
| Max RPM (Downhole) | 250 RPM | 250 RPM |
| Max Flow Rate | 340 gpm | 750 gpm |
| Max Operating Pressure | 20,000 psi | 20,000 psi |
| Max Operating Temperature | 150°C (175°C option) | 150°C (175°C option) |
| Max Operating WOB | 25,000 lbs | 50,000 lbs |
| Max Sand Content | 1% | 1% |
| Max Number of Recuts | 4 | 4 |
Receiver Sub
| Tool size | 4.75 in. | 6.75 in. |
|---|---|---|
| Collar Gap Length | 35 in. | 35 in. |
| Collar Gap Max OD | 4.75 in. | 6.75 in. |
| Collar Gap Connection | 3-1/2 IF | 4-1/2 IF |
| Collar Gap Yield Strength | 18,000 lbf-ft | 34,000 lbf-ft |
| Collar Gap Make Up Torque | 12,000 lbf-ft | 24,000 lbf-ft |
| Receiver Electronics Housing OD | 1.875 in | 1.875 in |
Measurement
| Inclination @ Bit | |
|---|---|
| Range | 0 – 180 degrees |
| Repeatability | ±0.2 degrees while sliding or ±0.5 degrees while rotating |
| Measure Point to Bit | 12 in. |
| Azimuthal Resistivity @ Bit | |
|---|---|
| Range | 0.2 – 2,000 ohmm |
| Accuracy | 5% (<10 ohmm) or 5 mmhos (>10 ohmm) |
| Max Depth of Investigation | 30 in. |
| Number of Sectors | 16 |
| Measure Point to Bit | 16 in. |
Battery Life
| Nominal Operation Time (Azimuthal Gamma only) | Up to 150 Hours |
Recommended Operating Parameters
| RPM | Max 200 for minimum fatigue |
| Formation Resistivity | 2 -200 Ohmm for optimal short-hopping |
| Mud Resistivity | 1 ohmm or higher |
| Vibration | Max 20 Grms, 50-1,000Hz |
| Shock | Max 500 G, 0.5ms (z-axis), 1,000 G, 0.5ms (x- or y-axis) |
Running Below a Mud Motor¹²
| Tool size | 4.75 in. | 6.75 in. |
|---|---|---|
| Max Bend Setting | 1.50º | 1.50º |
| Max DLS Rotating | 15º/100ft | 8º/100ft |
| Max Surface RPM | 60 | 60 |
| Max Mud Motor RPM | 180 | 180 |
¹ Do not run any motor stabilization with Inc @ Bit sub
² WOB capacity of most mud motors is higher than Inc @ Bit sub