Using conventional methods for landing and cementing casing strings in a surface wellhead for a major operator in the Caspian Sea resulted in zonal communication, mud and cement losses, and poor cement bonding.

Historically, rig up and rig down of conventional casing-running and cementing equipment required extensive manual handling and man-riding operations to be carried out on the critical path, with times of one hour being common. During this time circulation was not possible, leaving thixotropic well fluids static and turning them to a gelled state before cementing operations had begun. This gelling lead to channeling of fluids, mud/cement losses and poor cement placement.

To address these problems, a remotely operated top-drive casing-running tool in combination with a new, remotely operated cement head were deployed. Configured with upper and lower casing-handling joints, the new cement head enabled the top-drive casing-running system to quickly pick up the cement head and make it up into the landing string as a casing joint without manual handling. The cement head was preloaded with remotely launched top and bottom cement plugs and preinstalled plug valve with a cement hose, eliminating the need for man-riding operations.

Circulation through the top drive began immediately after makeup, keeping the casing and well fluids in motion to eliminate gelling. Cement was then pumped through the side port of the cement head, and the casing string was reciprocated throughout the entire operation with increased flow area past the casing hanger, allowing higher displacement flow rates, reducing formation pressures and improving cement placement. The casing string was held in tension during cement displacement.

This combination of new technologies has been successfully implemented to run several 9.625-in. and 13.375-in. casing strings in the previously problematic pseudo-ERD and conventional wells, resulting in:

  • Decreased transition time (static pipe) between casing-running and cementing operations

  • Reduced manual handling of equipment and elimination of man-riding operations

  • Excellent zonal isolation based on cement bond logs

  • Minimized (in some cases eliminated) mud/cement losses during entire cement job

  • Excellent cement seals

  • Successful pressure tests

Keywords:
casing design, circulation, cement placement, cement head, setting casing, Upstream Oil & Gas, top-drive casing-running system, manual handling, man-riding operation, casing-running system
Subjects:
Drilling Operations, Casing and Cementing, Running and setting casing, Casing design
Copyright 2011, SPE/IADC Drilling Conference and Exhibition
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