Now that the 2021 US OCS incident spreadsheet has been posted and I have commented on the fatalities, I’ll be looking at some incidents by category starting with losses of well control (LWCs). Incident summaries and links to investigation reports follow the bullet points.
- 4 LWCs incidents in 2021
- None posed a significant threat to worker safety or the environment
- All were deepwater wells
- 3 were during exploratory drilling and 1 was during completion operations
- All 3 drilling incidents involved water flows after setting 22″ surface casing.
- Gas/water flows during/after cementing operations continue to be the leading cause of LWCs.
- At least one resulted in the loss of the well; unclear regarding the other 2.
- All 3 were exploration wells
- Per the Lars Herbst review, there were 29 new deepwater exploration well spuds in 2021, so >10% of these experienced losses of well control due to water flows. Much work has been done on preventing top-hole water flows while drilling deepwater wells, but it appears there is more work to do.
- The completion LWC was the result of the inadvertent opening of fluid control devices. The report on this incident provides important information for well completion risk assessments.
Incident summaries
Spreadsheet incident 19: Well completion operation. Inadvertent shearing and opening of the fluid loss control devices were not adequately assessed during the planning and review phases of the completion. While displacing the wellbore from 14.8 ZnBr to 14.8 packer fluid, the downhole equivalent circulating density sheared the upper and lower fluid loss control devices. The rig immediately began to experience fluid losses of 600 bph. A 50 bbl fluid loss pill was spotted and losses slowed to 345 bph. A second fluid loss pill was pumped which significantly decreased the losses eventually resulting in zero losses. After losses stopped, the rig experienced approximately a 14 bbl gain on the trip tank. The well was shut in on the annular and circulated out using the driller’s method. Oil was observed in the returns. While waiting on additional fluids and materials, wellhead pressure was managed by bullheading 14.8 brine when required. The well was killed via bullheading down the annulus followed by bullheading down the workstring with 3 CaCo3 pills. investigation report
BOE comment: While the cause of this incident is classified as “human error,” the failure to properly assess and plan for risks associated with the inadvertent shearing and opening of the fluid loss control devices is an organizational/management issue.
Incident 186: Shallow water flow during exploration drilling. Lost well. A shallow water flow was observed from one of the ports in the 38″ wellhead housing following cementation of the 22″ riserless casing string at Caramel Keg (GB 962 #1). Additional wireline logging (casing bond log and temperature log) runs were performed to gain additional insights into the potential source/location of the flow, as well as the quality and presence of cement behind the 22″ casing string. Approval from BSEE Lafayette district was received on April 1st to proceed with running the riser/BOP and continue with subsequent planned operations. Flow from the wellhead was monitored and a general reduction trend in flow from wellhead port was observed. Approval was received from BSEE on April 19th to install and close ball valves on two wellhead ports to isolate flow from wellbore. On April 20th, the ball valves were closed and flow from the wellbore ceased approximately 23 days after initial observation. Approval to temporarily abandon the well was received from BSEE on April 25, along with a monitoring plan of the wellbore and the surrounding area. TA operations concluded on April 27th. The ongoing monitoring program has since identified no indications of flow/broaching at or near the GB 962 #1 wellbore as of May 7th. No personnel were injured or evacuated as a result of this subsurface shallow water flow. report
Comment: The BSEE incident investigation team determined that salt contamination probably caused the cement to go under-balanced triggering flow and channeling behind the 22-in casing.
Incident 478: Exploration well – 7188′ WD; exploration. The 22″ casing cement job went as planned with positive cement returns to the mudline from dye and pH meter. The rig observed post cementing flow. Flow was predominantly gas. The flow started with a single source from the seabed, about 20 ft away from the wellhead. Within the next 2-3 hours, two other flow sources developed, one immediately adjacent to the jetpipe while another flow source surfaced about 10ft away from the wellhead. The rig continued to monitor the post cementing flow and completed multiple ROV wagon wheel surveys. No new seafloor anomalies or active flow points were identified away from the wellhead. Minor flow of water and gas continued at the wellhead. No investigation report.
Incident 507: Post Cement Flow Summary: The 22″ casing was cemented in place at 2:30 AM on August 18, 2021. At approximately 5:45 AM, a minor post cementing flow was observed by the ROV. The flow was only observed from 1 cement port/ball valve connected to the 28″x22″ annulus. The flow composition was predominately cement and absent hydrocarbons. The ROV continued to monitor the flow. No investigation report.
Bud's Offshore Energy (BOE) 