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Case study
Lost-circulation zones identified from inside drill pipe, enabling quick remediation
Drilling Losses Resource ID: CS001

Challenge

Drilling fluid losses can pose a significant risk to personnel safety and the environment, complicate drilling and cementing operations, and cause costly delays.

 

A customer was experiencing mud losses and gas kicks whilst drilling a well with high hydrogen sulphide concentration. All remediation attempts, including mud weight adjustment, had been unsuccessful and mud losses had persisted for several weeks. Chemical, drilling fluid and rig time costs were spiralling upwards so the customer needed to locate the lost-circulation zones quickly and reliably.

Drilling Losses well sketch
Drilling Losses is used in a targeted fashion to quickly locate the lost circulation zone or zones, so normal drilling operations can resume without further delay

Solution

TGT recommended its ‘Drilling Losses’ product and ‘True Integrity’ diagnostic system as a reliable means to pinpoint and explain the source of lost circulation.

 

The True Integrity system utilises methods, measurements and analysis that reveal seal failures throughout the well system, including ‘formation seal’ failures that tend to be the underlying cause of lost circulation. Key to the operation of the diagnostic system is the Chorus platform. Chorus technology records and displays the acoustic energy created by fluid movement throughout the well system. An appropriate diagnostic programme was developed to reveal lost circulation dynamics and Chorus sensors were deployed through the drillstring to survey the well.

CS001 Drilling Losses Logplot
Drilling Losses use the True Integrity system incorporating Chorus technology to detect and locate lost circulation zones from inside the drillpipe. In this example, the acoustic signature recorded by Chorus clearly indicates four lost circulation zones. Subsequent post-treatment surveys show progressively less flow into each zone as the LCM seals the formation.

Result

The diagnostic system with Chorus revealed four active lost circulation zones, labeled A1 to A4 in Logplot. This explains why the operator was having so much trouble solving the issue.

 

The operator deployed lost circulation material (LCM) to all four zones and the diagnostic programme was repeated.

 

The second survey showed that fluid loss had been eliminated in A1 and A2, and considerably reduced but not stopped in A3 and A4.
A second treatment was applied using a different LCM to A3 and A4, and a third survey with Chorus showed that A4 had been sealed, and only minor losses were escaping to A3.