Schlumberger

LWF Logging While Fishing

Overview Library

Reduce Fishing Time and Complete the Logging Run

LWF logging-while-fishing technology saves time and reduces cost by enabling the resumption of logging operations during fishing. In most cases, the LWF technique eliminates the conditioning trip required before relogging because the fishing job is converted to a drillpipe-assisted log that completes the original descent in the wellbore.

LWF technology can be used with most stuck wireline tools. LWF operations begin by preparing the wireline for cut-and-thread fishing. The connected rope sockets on the cable ends are housed in a load-bearing protective torpedo to reestablish both the mechanical connection and electrical communication with the stuck tool string. The tool overshot and drillpipe are threaded over the cable until the placement depth is reached for the cable side-entry sub (CSES).

The CSES is placed to provide an overlapping, continuous log, with the maximum continuous log interval equal to the distance between the casing shoe and rig floor. The wireline passes through the CSES to the outside of the drillpipe to prevent wireline damage during logging. A downhole cable-severing device (DSCD) is also installed to allow retrieval of the wireline if the drillpipe becomes stuck while logging.

The fishing tools on the rig floor are then removed from the wireline, and the tool is repowered to prepare for engagement of the overshot and tool. The speed of the operation now increases because tripping drillpipe is quicker than threading cable through drillpipe. When the stuck tool is reached, engagement is less likely to damage the tool because the reestablished electrical communication allows monitoring tension at the tool in addition to the usual driller's method.

Once the tool is freed, TLC-style logging is conducted to continue the recording of continuous or stationary logs.

Gulf of Mexico case studies

Three case studies from the Gulf of Mexico illustrate the rig time and cost saved by employing LWF technology in various fishing situations.

In the first two case studies, LWF service was used to recover MDT modular formation dynamics tester tools that became stuck following successful wireline gravity descents. The first well was drilled to 11,000 ft, with the lower part deviated up to 35°. Pressure testing revealed that the well was considerably overbalanced, and the 80-ft-long tool subsequently became stuck at 10,200 ft. Using the LWF method to capture the MDT tool allowed continuing pressure and fluid sampling to 100 ft below where the tool had been stuck.

The second case study is an exploration well drilled to a depth of 16,350 ft. Although the stability of the relatively straight hole was borderline, there had been no overpull or other evidence of sticking. However, the 113-ft-long MDT tool became stuck at 14,620 ft while performing the tie-in log. The LWF operation reestablished logging operations within 17 h, and the drillpipe-conveyed tool recovered additional pressure measurements and fluid samples for 13 h.

The third case study is a 9,200-ft well deviated 27°, with 10 3/4-in casing set to 2,000 ft. The 82-ft-long triple-combo tool became stuck at 8,900 ft. Once the tool was reengaged using the LWF method, it was lowered by one stand of pipe to obtain the data required for a continuous log from total depth to 2,000 ft above the point where the tool became stuck.

Benefits

  • Zone of interest logged during fishing operations
  • Compatible with standard wireline fishing operations and equipment
  • Less rig time spent on cut-and-thread fishing
  • Increased safety from fewer threading procedures
  • Fish engagement ensured by reestablished tool communication
  • Reduced need for conditioning trips

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