Rotating Tension Anchor Improves Cement Bond Quality in Steam Well Applications in a Heavy Oil Field Onshore Germany

Abstract

A rotating tension anchor was developed to improve the cement bond by enabling rotation of the production casing of steam injection wells during cementing. This would be a world-first application of this casing pre-tensioning system in the application of steam well design. A good cement bond is crucial for the integrity of a well; this is especially true in the harsh environment created by a 300°C injection temperature in steam well applications. A common and relatively simple approach to improve the cement bond quality is to rotate the casing during cementing. The rotation creates a helical flow pattern, which has an improved displacement efficiency compared to a uniaxial flow. The design of steam injection wells in this heavy oil field requires a deep-set anchor to pre-tension the casing string with the required pick-up force. The existing anchor system had to be engineered and modified to enable casing rotation during cementing. Although no breach of integrity has been found in previous steam injection wells, the operator identified improvement potential for the long term cement integrity through ultra-sonic cement bond measurements of existing wells. The 7-in production casing of a steam injection well was pre-tensioned with 264.000 lbs [120 metric tons] overpull and rotated with 20 revolutions per minute during cementing. This world-first field trial of a rotating anchor tensioning system demonstrates, that the existing tension anchor system can be modified to enable rotation of the casing. An ultra sonic cement bond run, several weeks after cementing, confirmed that use of this equipment produced an improved cement bond quality compared to offset wells of similar age and status.