Marine EM Studies of the Scarborough Gas Field

In May/June 2009 we carried out a 32 day cruise on the Scripps research vessel Roger Revelle to conduct experiments over the Scarborough gas field on the northwest shelf of Australia, for a project funded by BHP Billiton Petroleum. The goals of this work are to extend our understanding of marine EM methods and to test new instrument systems, such as towed 3-axis receivers and sensitive instruments to measure gradients of sea floor EM fields. We conducted a dedicated survey for shallow gas and gas hydrate, as well as a combination of 2D and 3D data collection strategies. A total of 144 receiver deployments and recoveries were made and we towed our EM transmitter a total of 320 km (not including turns) over 12 days.

PDF of fall 2009 AGU slides (1.8 Mb)

Preliminary cruise report for this project (10 Mb)

Steve's daily Log from the R.V. Roger Revelle

July 26, 2009. High definition movies are here! This link takes you to the directory with the HD versions of all the movies we posted during the cruise. ( 720p and 75-300 MB). The links below still point to the low def versions.

June 21, 2009. The two SUESIs going home after a job well done. Both instruments contributed to the experiment, which was a huge success, so they deserve their smiles.

June 17, 2009. We haven't seen much marine life this cruise, but tonight we had an amazing spectacle––a pair of Mahi Mahi's in a feeding frenzy during an instrument recovery. Here's video clip showing them attacking some flying fish. If I only had grabbed the video camera two minutes earlier, I would have captured the Mahi swimming around one of our receivers. (Quicktime, 17 MB.)

June 15, 2009. Houston (err, I mean Perth), we've got an anomaly! Here's a sample of the data from the Phase 1 mainline tow. Site s01 is the easternmost site and located off the known gas field. Site s36 is located over the western edge of the gas field, and as expected, exhibits much larger electric and magnetic field amplitudes than the off-target site. These responses were obtained by simple 60 s stacks of 4 s binned data. With a combination of longer stack lengths and robust processing techniques, we expect our ultimate noise floors to be around 10^-15 V/Am² and 10^-18 T/Am.

June 9, 2009. We've been uploading lots of videos of our EM receivers and SUESI's starting to feel neglected. So here you go, this one is for SUESI. (Quicktime, 6.0 MB).

June 8, 2009. Our young apprentice Brent Wheelock just knocked out his first iMovie, showing another spectacular sunrise aboard the Revelle. Brent recommends headphones for the optimal viewing experience. (Quicktime, 9.8 MB).

June 5, 2009. Here's a music video montage of the night crew recovering the seafloor EM receivers. (Quicktime, 4.2 MB).

June 5, 2009. Here's a remix of the fast deployment movie, now with a better soundtrack. (Quicktime, 4.8 MB).

June 2, 2009. We've been a bit busy the past week deploying/towing/recovering/redeploying and there hasn't been much free time for crafting up a new movie clip, until now that is. (3MB Quicktime Movie).

June 2, 2009. In search of the Exmouth Plateau conductivity anomaly. Here's a screen shot of 60 minutes of nice looking magnetotelluric data recorded by four of our receivers. With the longer period MT data, we hope to image a large conductivity anomaly at about 10 km depth that our colleague Graham Heinson discovered a few years ago. This conductor might be related to a deep detachment fault that has been postulated to explain the thinner crust of the Exmouth Plateau as compared to the nearby Pilbara Craton onshore.

June 1, 2009. Does anybody recognize this fish? From 950 meters deep, 20 deg S, 113 deg E.

May 31, 2009. The logo for the cruise T-shirt, cleverly done in the style of Weiss

May 29, 2009. Where's the transmitter? Our newly developed "Barracuda" long baseline navigation system is working really well this cruise. We tow two para-vanes that we've named Barracudas about 300 m diagonally behind the ship. Each Barracuda is outfitted with a gps and radio modem that transmits its position back to the ship, and most importantly each Barracuda has an acoustic transponder on it. We ping on the Barracudas from the Benthos acoustic system mounted on SUESI and then use the known Barracuda positions and acoustic ranges along with depth measured by SUESI's pressure gauge to triangulate SUESI's position. I (Kerry) just finished writing a Matlab interface that reads these data streams in real-time and computes SUESI's position. Below is a screen shot of this tool in action. The red dot is the Revelle and the cyan and magenta triangles are the positions of the Barracudas. The black dots are the navigated positions of SUESI during the tow. With the exception of a few obvious outliers, overall the navigation looks good to 10-30 m scatter or so. We expect to do much better than this in post-processing of this data.

May 27, 2009. SUESI being deployed.

May 27, 2009. A-frame up. The deck team performs final checks on SUESI before she's deployed to the briny deep.

May 27, 2009. Steven Constable leads the deck team in preparing one of SUESI's two antenna electrodes.

May 27, 2009. Arnold Orange standing next to SUESI's antenna spooling winch. SUESI's antenna is made to be neutrally buoyant by a thick casing of foam rubber. The copper pipe near the center of the winch is one of the antenna's electrodes.

May 27, 2009. Chris Armerding prepares the antenna mounts on SUESI's tow frame. This is actually SUESI #2, easily identified by her snaggle tooth.

May 27, 2009. Cambria Colt (right) instructs the deck team on the deployment procedure for our transmitter SUESI. From left to right: Brent Wheelock, David Myer, Arnold Orange, Jeff Markel, Jennifer Shelstead and Cambria Colt.

May 26, 2009. Thanks to Jeremy Prince for sending Steve this nice photo of the Revelle leaving Fremantle last week.

May 25, 2009. Preparing to deploy long-wire electromagnetic sensors (LEMS) from the aft deck of the Revelle. The LEMs have 200 m long antennas capable of recording much smaller electric fields than our conventional EM receivers, but require much more effort to deploy. We use a deep tow frame to hold the LEM receiver while it is lowered by cable to the sea floor. Once it's within a few meters of the sea floor, the deep tow package releases the LEM to the sea floor. The upper photo below shows Chris Amerding, Steve Constable and Brent Wheelock preparing the LEM deeptow vehicle, while Cambria Colt handles the A-Frame controls. In the lower photo, Steve Constable stands next to the LEM instrument, which is tucked inside the stainless steel deeptow vehicle.

May 25, 2009. This image shows the survey area relief, the deployment sites (squares) and CSEM tow paths (white lines). This is actually a screen shot from a 3D rendering program called Fledermaus, which we use to display the realtime position of the Revelle and our transmitter SUESI. The vertical exaggeration is x20.

May 25, 2009. Here's a movie clip of the night crew assembling a marine EM receiver and then deploying it. The clip has been sped up by a factor of 20 (3MB Quicktime file).

May 24, 2009. Here's a short movie clip of a marine EM receiver being deployed this morning (3 MB Quicktime file).

May 24, 2009. The EM receiver deployments are well underway---as of noon 29 are on the sea floor and only 23 more to go. Here's an image taken during a sunrise deployment

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May 24, 2009. I (Kerry) like working the midnight to noon shift since you often get to see sunrises like the one below. This photo also shows the gear on the back deck of the Revelle.

May 22, 2009. Going to Scarborough, short quicktime movie (7 MB)

May 21, 2009. Rainbow in sea spray off the port side during the transit out to the research area (in less than ideal weather).

May 20, 2009. Revelle tied up at Victoria Quay, Fremantle, just prior to pushing off.

Location of the research area:

Layout of the project: