Restore Flowing Annulus with PWC

Abstract

Well TN-XX was drilled with swamp barge rig Hibiscus. 24" CP has been driven to 124 m. Well was spudded on October 6th, 2003. 17-1/2" hole was drilled to 1644 mMD/ 1238 mTVD with 1.16 SG mud. 13-3/8" casing was then run to 1639 m, cemented and tested to 2500 psi. No losses and back flow was reported during the cementing operation. Some operations performed while Waiting-On-Cement were rig down the cement head, lay down the diverter and installing gate valves on the wellhead. Gas influx was flowing from the 13-3/8" x 24" annulus. ERT was activated, followed by mustering for all non essential personnel. The Rig was demobilized on October 12th.

As prevention, the production flow line was depressurized and well intervention barge was mobilized to secure all adjacent wells. The Well Intervention barge was then performing CBL, temperature log. USIT, noise and RST logs on TN-XX. The logging interpretation identified that possible flowing zones were at 1250, 1150, 675 and 350 m. Perforations and cement plugs were performed over these intervals to regain the integrity of the annulus. Additional shallow interval was chosen to establish circulation to the surface thru annulus at 279-291 m based on USIT log. 13.5 bbls of 1.2 SG mud was pumped into the perforations and the well flow suddenly stopped. Hesitation squeeze was performed at 183380 m interval. The Well was secured.

The drilling was continued on December 14th 2003 by the same rig on and completed on January 30 2004. The well was then put on production till fully shut-in condition later in May 2015. No sustain casing pressure was reported on Annulus C (annulus between 24" CP to 13-3/8" surface casing). The perforation and cement plug were successfully restoring the integrity of the well.

Poor annular cement led to sustain casing pressure. A section milling will be required to regain the integrity on the annulus. The perforation, wash and cement (PWC) technology then was introduced later by Hydrawell in North Sea in 2011 to replace section milling activity. The concept was to punch casing to access to poor cement section and established circulation thru annulus prior to perform cementation to restore the integrity of the annulus - similar to what we've done back in 2003. The technology has been proven with more than 95% success rate over 213 plugs. The solution will be adopted for securing wells with leak on open type CP and/or sustain casing pressure on outermost annulus.