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 size4.75 in.6.75 in.
Length35 in.35 in.
Nominal OD5.0 in.6.75 in.
Max OD5.25 in.7.0 in.
Max ID1.313 in.2.375 in.
Connection PIN Up3-1/2 REG (IF option)4-1/2 REG (IF option)
Connection BOX Down3-1/2 REG4-1/2 REG
Yield Strength15,140 lbf-ft29,900 lbf-ft
Make-up Torque12,000 lbf-ft24,000 lbf-ft
Max DLS Rotating15°/100ft8°/100ft
Max DLS Sliding30°/100ft16°/100ft
Max Downhole Drilling Torque12,000 lbf-ft24,000 lbf-ft
Max RPM (Downhole)250 RPM250 RPM
Max Flow Rate340 gpm750 gpm
Max Operating Pressure20,000 psi20,000 psi
Max Operating Temperature150°C (175°C option)150°C (175°C option)
Max Operating WOB25,000 lbs50,000 lbs
Max Sand Content1%1%
Max Number of Recuts44

Receiver Sub

Tool size4.75 in.6.75 in.
Collar Gap Length35 in.35 in.
Collar Gap Max OD4.75 in.6.75 in.
Collar Gap Connection3-1/2 IF4-1/2 IF
Collar Gap Yield Strength18,000 lbf-ft34,000 lbf-ft
Collar Gap Make Up Torque12,000 lbf-ft24,000 lbf-ft
Receiver Electronics Housing OD1.875 in1.875 in

Measurement

Inclination @ Bit
Range0 – 180 degrees
Repeatability±0.2 degrees while sliding or ±0.5 degrees while rotating
Measure Point to Bit12 in.
Azimuthal Resistivity @ Bit
Range0.2 – 2,000 ohmm
Accuracy5% (<10 ohmm) or 5 mmhos (>10 ohmm)
Max Depth of Investigation30 in.
Number of Sectors16
Measure Point to Bit16 in.

Battery Life

Nominal Operation Time (Azimuthal Gamma only)Up to 150 Hours

Recommended Operating Parameters

RPMMax 200 for minimum fatigue
Formation Resistivity2 -200 Ohmm for optimal short-hopping
Mud Resistivity1 ohmm or higher
VibrationMax 20 Grms, 50-1,000Hz
ShockMax 500 G, 0.5ms (z-axis), 1,000 G, 0.5ms (x- or y-axis)

Running Below a Mud Motor¹²

Tool size4.75 in.6.75 in.
Max Bend Setting1.50º1.50º
Max DLS Rotating15º/100ft8º/100ft
Max Surface RPM6060
Max Mud Motor RPM180180

¹ Do not run any motor stabilization with Inc @ Bit sub
² WOB capacity of most mud motors is higher than Inc @ Bit sub