Submitted July 31, 2010
We started the day with the sight of ships on the horizon – a lot of ships. We had finally made it to the Deepwater Horizon MC 252 Incident site: About 1700 miles from Newport Rhode Island to the Mississippi Canyon- almost Boston to Denver.
Our plan for first day was to work from 1500 to 500 meters of the wellhead. That is one to one-third of a mile. This may seem like a lot of space, but given that there are three oil rigs and 10 to 15 ships in the area at any given time, the space feels pretty small. There are also a number of support ships outside of the 1500 meter zone.
Our goal was to perform acoustic surveys to look for gas seeps: either natural or wellhead-related. The acoustic data we collect is transferred to shore where it is processed and compared with acoustic data collected by other NOAA ships at the site during prior weeks. We really need to work within 500 meters of the wellhead, but this first day we wanted to get a feel for the ship traffic and communication protocols.
The morning started with a conference call with British Petroleum’s Simultaneous Operations (SIMOPS) out of Houston, the group that’s providing traffic control for the Deepwater Horizon site. All ships in the area called in.
The SIMOPS director took roll call and ships reported persons on board, time to evacuate, air quality issues, mechanical issues, safety issues, and plan for the day. Our first call was uneventful and after about 40 minutes we were ready to work. We had already submitted a daily plan to SIMOPS the day before, which was approved, but the conference call allowed all the ships to get an idea of what everyone else would be doing.
With our SIMOPS clearance, we started acoustic surveys. Our primary instrument is an EK60 splitbeam echosounder. The EK60 transmits sound at different frequencies and then receives the reflection of the sound as it bounces of things in the water: fish, the bottom, and bubbles. We have our EK60 set to 5 second intervals, which means it “makes” sound every 5 seconds and then receives the reflections, also called” returns”, as they bounce back to the ship. The strength of the return is a function of the size and composition of the material in the water. Water has very little reflectance, while a bubble has a lot of reflectance.
More specifically, our mission is to conduct acoustic surveys using the EK60 to look for reflections of bubbles in the vicinity of the wellhead. We examine the data in real time to identify areas of interest – lot of reflection near the bottom–likely gas bubbles. We use this information to design subsequent surveys. We also send the data to shore via a satellite link. Acoustic experts on shore then process and compare the data to previous surveys of the area. It is these experts who are best able to interpret the data we are collecting.
So …we spent the day surveying the north, east and south part of the 1500 to 500 m zone. We “saw” some remotely operated vehicles working near the bottom and umbilical cords connecting the vehicles to the ships a mile above them. We also detected several areas of interest and reported these to the acoustic experts on shore.
After 10 hours of surveying and maybe 30 miles of track line, it was time for our evening SIMOPS conference call: roll call, ship reports, and plan for the next day. We also submitted our plan for the next day electronically. Our first day working in the vicinity of the Deepwater Horizon site ended.
But just because the day ended doesn’t mean the work ended. We can’t work close to the wellhead at night – the risk of collision with all those ships is too great. So we set up for acoustic surveys a couple of miles away. Natural oil and gas seeps are reported from the area, so the purpose of our nighttime survey was locate these seeps and collect data to determine if there has been any change.
Working all day and all night is par for the course. The Bigelow generally works 24 hours a day; different people and different jobs have different schedules, but through the night things are quieter and fewer people are around. Come dawn, we would break our far-field acoustic surveys and move toward the wellhead, requesting permission to survey over it. But for now things are quiet.