3D At DepthBringing Laser Scanning to New Depths in the Subsea Oil and Gas Market

A 2.311Mb PDF of this article as it appeared in the magazine complete with images is available by clicking HERE

It was a warm clear day on the deck of the Global Orion. We had sailed out of Carlyss, Louisiana two days ago and I was excited and a bit nervous for the upcoming project. It was not my first time working offshore but the stakes were high as we attempted to do something that had never been done before. Over the past four years, our team had developed an underwater laser scanner and although we had tested the system a number of times and completed a couple of small trials, it was finally time to see what it could do in a real project situation; performing spool piece metrology.

The Research Partnership to Secure Energy for America (RPSEA) had helped put these wheels in motion in 2010 with a grant to develop subsea laser scanning in support of the ultra-deep water oil and gas industry. They not only provided funding but helped us build relationships and a project steering committee of subsea experts within our specific field of survey. It was this committee that suggested that our first application should be spool piece metrology and so we geared up to tackle that problem.

After months of trials, accuracy validation in test tanks and a couple of small projects, Technip, a project steering committee member and the biggest offshore construction contractor in the world, were giving us a chance to prove that laser scanning could work on a subsea metrology project. We had been working closely with Technip over the past couple of years to bring subsea laser scanning to market and they guided us through their new technology validation process when we proved the accuracy of the system in a 600 ft. test tank. But now we were on a "real" subsea construction project where the measurements that we collect must be correct as hundreds of thousands of dollars were at stake and the overall project depended on the results.

Spool pieces (called jumpers in deep water fields), are the final components of a production hydrocarbon network and one of the final steps to reach "first oil" for producers. The spool pieces connect subsea assets such as manifolds to wells and can range from 10-100 meters in length. In the Gulf of Mexico, spool pieces are typically less than 30 meters. Spool piece metrology is a survey process that measures the relative distances and pitch and roll angles between two "hubs" on subsea structures. Basically the hubs are the connecting points for the pipe work on the structures. The structures are placed on the seabed and then the spool piece metrology is performed. Once the measurements are collected, they are sent to a fabrication yard where the jumpers are built and then shipped to the field for installation.

There are two factors that drive producers to speed up this process; vessel time and first oil. Typical vessel time could run upwards of $200k per day so saving hours means saving significant money. But more important to the operators is the ability to reach first oil. Once in production, each day yields millions of dollars in oil, so shaving days from the construction schedule equates to more revenue for the operators.

Traditional jumper metrology processes are based on acoustics and the use of long baseline transponders (LBL). The error budget for metrology depends on the spool stress analysis but is nominally 50-150 mm in distance and between 0.5 and 1.0 degrees in pitch and roll. LBL provides the accuracy required but takes a minimum of 12 hours to acquire the data and possibly longer depending on various environmental factors. LBL methods also require the deployment of specialized tooling which requires additional time and expense to the process. It was our goal to meet the specified accuracies without tooling and in less time.

The field was 300 miles south of the coast of Louisiana at a depth of 2200 meters (7000 ft.) The first four metrologies were to be performed with both LBL and LiDAR for head to head comparison. If the comparison was within tolerance, then the rest of the metrologies would be completed with LiDAR.

It was just after lunch, the weather was warm and the seas very calm on this 22nd of January. We were due to perform the first jumper metrology between a well and a manifold and since it was the first one, I decided to sit in the shack with the ROV crew rather than try and manage the process from the ship’s bridge. The shack is a 10′ x 20′ shipping container outfitted with state of the art equipment for controlling an ROV. A wall of monitors displays real time video, SONAR and a real time vehicle positioning tool called WinFrog which shows the location of the vessel and ROV in relation to the subsea structures.

Maneuvering a tethered ROV the size of a small car through a dense subsea field takes lots of skill. But we would not be putting these skills to much use on this task as the ROV would be used as a big tripod. Typically asked to deftly move from one location to another and manipulate one of their robotic arms to perform a variety of highly technical tasks, we asked the ROV pilots to do the opposite–just sit on the seabed and be as still as possible.

We landed at a location that allowed us to scan both structures from the same setup. The SL1 laser scanner has the capability to pan 180 degrees in 30 degree increments so this location allowed us to scan both structures and the seabed in one instance.

Using the ROV cameras as a guide, I panned the unit to the left towards the tree which sits atop the well and pressed SCAN. On the video screen a burst of green light illuminated the dark water and lit up the tree one horizontal line at a time. The four of us sat back and watched as the scanner painted the structure with light. The image was presented on my laptop and looked like a black and white picture–it worked. Two hours later and after years of development we successfully performed the first subsea LiDAR metrology.

Over the next few days, the team performed three additional LiDAR metrologies. When the results were compared to the LBL measurements it was determined that the LiDAR system would now be the primary metrology tool for the rest of the campaign. In March, six weeks after the first metrology was completed, all 13 jumpers were successfully installed in the field–the ultimate proof for this new capability.

As of this writing, over 40 LiDAR metrologies have been successfully completed by our partners and the industry has found several new applications for subsea LiDAR. We have enhanced the SL1 sensor and have launched our second subsea LiDAR sensor the SL2, a two canister design that includes an integrated pan and tilt. Based on the feedback from our partners and the community, we have developed new software tools, developed optimized workflows for data collection and continue to develop new applications including a mobile scanning solution.

Meanwhile the industry has begun to apply subsea LiDAR to other areas of their business which coincides with their topside counterparts. The first large area subsea laser scanning project was completed in 2014 which provided the operator with an accurate 3D model of their assets and forms the baseline for their life of field activities. Subsea LiDAR datasets are now being integrated into GIS and subsea plant management applications and are becoming part of an overall data management strategy–following the lead of the terrestrial laser scanning market.

If it were not for the support of Technip and RPSEA, we would not have had the opportunity to bring subsea LiDAR to market within this timeframe. Technip’s culture of innovation and willingness to push the boundaries were critical to the success of this new capability. RPSEA not only provided us with funding but helped us put together a team of subsea survey experts that worked with us to set direction as well as provide resources, time and much needed support.

We would like to extend our thanks to Technip and RPSEA and the countless others along the way that helped us bring subsea LiDAR to market, which brings me to the moral of the story. New technologies are only successful when coupled with industry experts and focused applications. We have been fortunate to have had the opportunity to work with great organizations that have helped us bring laser scanning to new depths.

Mark Hardy is a co-founder and Director of Client Services for 3D at Depth. Mark works with clients and partners to develop new processes and applications for subsea LiDAR. For more information on subsea LiDAR please visit www.3datdepth.com.

A 2.311Mb PDF of this article as it appeared in the magazine complete with images is available by clicking HERE