DENBURY GULF COAST PIPELINES, LLC

Incident Narrative

ON 11/9/2018 AT 17:15, TWO DENBURY EMPLOYEES OVERSEEING THE RELOADING OF THE DELTA PIPELINE WITNESSED A RUPTURE OF A CO2 PIPELINE WITHIN THE PERIMETER OF A DENBURY CONTROLLED VALVE LOCATION. THE PIPELINE FOREMAN ONSITE IMMEDIATELY NOTIFIED THE APPROPRIATE PIPELINE PERSONNEL TO INCLUDE THE DENBURY CONTROL CENTER (DCC). THE DCC CLOSED AND ISOLATED THE TWO PIPELINES FEEDING THE DELTA PIPELINE BY REMOTELY SHUTTING TWO ISOLATION VALVES UPSTREAM FROM THE FAILURE LOCATION. THE TWO ISOLATION VALVES WERE CLOSED AT 17:20 AND 17:22, RESPECTIVELY. THE AREA IMMEDIATELY SURROUNDING THE FAILURE LOCATION WAS SECURED. AT 18:10 PERSONNEL WERE DISPERSED DOWNWIND OF THE FAILURE LOCATION AND THROUGHOUT THE AREA TO MONITOR THE CONCENTRATION OF CO2 IN THE ATMOSPHERE. THE RELEASE DID NOT RESULT IN EXPLOSION, FIRE, DEATH, PERSONAL INJURY, SIGNIFICANT PUBLIC PROPERTY DAMAGE, OR POLLUTION OF ANY WATER BODY, AND WAS CONFINED TO COMPANY CONTROLLED PROPERTY APART FROM DISPERSION OF A VAPOR CLOUD. IT WAS DETERMINED TO BE A SIGNIFICANT EVENT AT 21:38 AND AN NRC TELEPHONIC REPORT WAS INITIATED AT 22:28 ON 11/9/2018 (INCIDENT REPORT #1230011). A CONTROLLED BLOWDOWN AT THE FAILURE SITE OCCURRED THROUGHOUT THE NIGHT TO PREPARE FOR INVESTIGATION, EXCAVATION, AND REPAIR. ON 11/10/2018 AT 07:30 DENBURY PERSONNEL ACCESSED THE FAILURE LOCATION TO ASSESS THE SITUATION. AT 07:40 TWO ISOLATION VALVES WERE SHUT AT THE FAILURE LOCATION TO STOP ALL FLOW BETWEEN THE FAILURE LOCATION AND THE SOURCE PIPELINE. AN EXCAVATION CREW WAS CONTACTED, AND EXCAVATION BEGAN AT 14:00. DUE TO WEATHER/RAIN CONDITIONS, EXCAVATION CONTINUED 11/11/2018 AND 11/12/2018. A 48-HOUR NRC TELEPHONIC REPORT UPDATE WAS INITIATED AT 06:52 ON 11/12/2018 (INCIDENT REPORT #1230120). THE FAILURE LOCATION WAS FULLY EXCAVATED ON 11/13/2018. AN ENGINEERING CONTRACTOR PERFORMED A FIELD EVALUATION AT THE FAILURE LOCATION AND THE FAILED PIPE WAS REMOVED FROM THE EXISTING PIPELINE AND SENT TO A LAB FOR FURTHER TESTING TO DETERMINE CAUSE. ON 11/14/2018 FOUR WELDS WEST OF THE FAILURE LOCATION WERE NON-DESTRUCTIVELY TESTED TO ASSURE INTEGRITY. IN ADDITION, THE LOCATION WAS PREPARED FOR THE FITMENT OF NEW, PRE-TESTED REPLACEMENT PIPE. SITE PREPARATION AND PIPE FITMENT CONTINUED 11/15/2018. ON 11/16/2018 THE REPLACEMENT PIPE WAS INSTALLED AND WELDED IN PLACE. ON 11/17/2018 EXCAVATION TOOK PLACE TO EXPOSE TWO ADDITIONAL WELDS EAST OF THE FAILURE LOCATION. THESE TWO EXISTING WELDS AND THE TWO REPAIR WELDS WERE NON-DESTRUCTIVELY TESTED AND ACCEPTED. ON 11/18/2018 AT 08:40 REFILL OF THE DELTA PIPELINE BEGAN AND ON 11/20/2018 AT 21:15 THE DELTA PIPELINE RETURNED TO SERVICE WITHOUT INCIDENT. ON MARCH 19, 2019 DENBURY RECEIVED A FINAL LAB REPORT STATING THE RELEASE WAS THE RESULT OF LARGE THERMAL DIFFERENTIAL STRESSES BEING EXERTED ON THE PIPELINE FROM CO2 LOADING AT TWO DIFFERENT LOCATIONS. THE REPORT INDICATED THERE WAS NO EVIDENCE OF ANOMALIES IN THE MECHANICAL PROPERTIES OR CHEMICAL COMPOSITION OF THE RUPTURED WELD PIPE. DENBURY IS REVIEWING RECOMMENDATIONS TO ENSURE THIS FAILURE WILL NOT HAPPEN IN FUTURE PIPELINE LOADING WHICH MAY INCLUDE: PERFORMING A PRE-LOADING ENGINEERING ASSESSMENT TO EVALUATE THERMAL STRESSES AND RESTRAINED PIPELINE, PERFORM STRESS ANALYSIS TO VERIFY THERMAL STRESS LOADING EFFECTS, PROCEDURE CHANGE TO AVOID LOADING FROM TWO SEPARATE LOCATIONS, PERFORM LOADING BY THROTTLING TO CONTROL TEMPERATURE LEVELS, PRE-HEAT CO2 PRIOR TO LOADING, OR USE OF NITROGEN IN PRE-LOADING.