Description
 The
Logging-While-Coring (LWC) system, developed jointly by USIO/LDEO, Schlumberger Drilling and Measurements, and USIO/TAMU, takes advantage of existing logging, drilling
and coring technologies and synthesizes them into a powerful
new exploration system. Recent improvements in battery technology
have enabled the reformatting of the electronics in an 8-inch
Schlumberger Resistivity-at-Bit (RAB) tool. By placing smaller
batteries in the drill collar wall, an existing ODP core barrel can pass through the
RAB to carry out coring operations while making simultaneous azimuthal geophysical
measurements. The coring tool technology consists of the Motor
Driven Core Barrel (MDCB) system developed by USIO/TAMU,
which needed only minor modifications and the fabrication of
crossovers and drilling subs. The assembled system was
tested at the Genesis test facility in Sugarland, Texas, and
successfully deployed for the first time during ODP Leg 204.
Applications
• Core-log data integration capability
• Assessment of borehole breakout for local and regional
stress analyses
• Detection of formation heterogeneity using azimuthal
resistivity images
• Lithology characterization
Tool Specifications
| Tool make-up length: |
13 ft (4 m) |
| Tool weight: |
2,400 lbs (1,090 kg) |
| API nominal collar outside diameter: |
8.25 in (21 cm) |
| Maximum outside diameter: |
9 to 12.25 in (23 to 31 cm) |
| Minimum bit size: |
9.75 in (25 cm) |
| Maximum bit size: |
12.25 in (31 cm) |
| Maximum Temperature: |
300° F (149° C) |
| Maximum pressure: |
18 kpsi (12.4 kPa) |
| Flow range: |
0-1,200 gpm |
| Pressure drop coeffecient (C)*: |
n/a |
| Maximum curvature - sliding: |
13 deg/100 ft (13 deg/31 m) |
| Maximum rotary torque: |
23,000 ft-lbf (7,010 m-lbf) |
| Minimum operating RPM: |
30 rpm |
| Uphole connection: |
6-5/8 FH box |
| Downhole connection: |
6-5/8 Reg box |
| (*) pressure drop = [mudweight in ppg] x [flow in gpm]²/C |
Measurement Specifications
| Gamma Ray |
| |
Measurement range: |
0-250 GAPI |
| |
Accuracy: |
7% |
| |
Vertical resolution: |
6 in (15.24 cm) |
| Azimuthal resistivity |
| |
Measurement range: |
0.2-20,000 ohm-m |
| |
Accuracy: |
5% (0.2-200 ohm-m); 20% (200-2,000 ohm-m) n/a (>2,000 ohm-m) |
| |
Vertical resolution: |
2-3 in (5.08-7.62 cm) |
| Ring resistivity |
| |
Measurement range: |
0.2-20,000 ohm-m |
| |
Accuracy: |
5% (0.2-2,000 ohm-m); 20% (>2,000 ohm-m) |
| |
Vertical resolution: |
2-3 in (5.08-7.62 cm) |
| Bit resistivity |
| |
Measurement range: |
0.2-20,000 ohm-m |
| |
Accuracy: |
5% (0.2-2,000 ohm-m); 20% (>2,000 ohm-m) |
| |
Vertical resolution: |
12-24 in (30.5-61 cm) |
Additional information
|
|
| Assembly of the LWC-RAB8 Tools during an early test in
Texas. |
Registivity image and average resistivity data from the
LWC-RAB8 plotted with physical properties data from
cores. |
* ®trademark of Schlumberger
|
