Case Study: Total E&P Reduces Risk and Cost During Seismic Operations in Complex Currents with USV-Acquired Real-Time Data, Uruguay

Challenge: Efficiently obtain metocean data near the confluence of two ocean currents to improve operational safety during seismic survey acquisition.

Solution: Deploy an unmanned surface vehicle (USV) to measure current strength while holding station during the seismic survey and transmit the data in real time via satellite as the survey is under way.

Result: Optimized seismic survey acquisition while reducing risk and cost by using the USV measured real-time data to account for the prevailing currents.

Real-time current data to improve operational efficiency and safety

Total E&P was conducting a hydrocarbon exploration project offshore Uruguay in an area with highly complex circulation. During such exploration, surface currents can affect seismic vessels’ receiver cables. Waves and deep currents must also be accounted for in exploratory drilling operations, including selection of an appropriate drillship. To perform the exploration program efficiently and promote safety, precise knowledge of meteorological and oceanographic (METOC) conditions in the area was necessary.

Autonomous USV METOC data collection in turbulent water and around structures

Schlumberger Robotics Services recommended deploying METOC services via a USV to collect metocean measurements of surface currents, wave height, and wind speed and direction, which would provide valuable insight into the survey area during the seismic operation. The measurements collected would be transferred in real time for immediate use.

The autonomously maneuverable USV was the ideal approach for measuring the conditions around the Uruguayan offshore platform, which is located in the highly complex current circulation area at the turbulent crossing of two major streams: a cold Malvinas current to the north and the warm Brazil current to the south.

The two main objectives of the mission would be to

  • provide support to avoid acquisition in areas with strong currents
  • validate data obtained from the USV by comparison to that of a fixed buoy.

Optimized survey design for successful data delivery

The pilot navigated and held the USV at a predetermined position while the vehicle relayed the requisite intelligence to the party chief on the survey vessel. This allowed the onboard navigation team to make the necessary survey design to run an optimal survey. A key element in the survey design was to identify uncertainties that drive commercial aspects such as costing and timeline estimates, as well as HSE aspects.

The measurements taken by the USV compared extremely well with measurements conventionally obtained with a moored buoy. The USV provided current data to a depth down to 40 m, which was an important aspect because streamers are not placed at the surface. Measuring the wave height was also crucial for the operation although the difference seems small (0.2–0.4 m). This may be attributed to the position of the two sensors, which although very close were measuring slightly different positions in the water column.

Total E&P successfully ran this project for 100 days. The data collected by the USV was integrated in real time in the planning of the survey. This enabled the party chief to prioritize areas of acquisition, avoid entangling the streamers, and reduce the amount of feathering.

METOC services’ ability to provide persistent operations and to hold station within a tightly defined area proved to be a great benefit to the operator. The USV was able to replicate the measurements and functions of a moored ocean monitoring buoy at reduced cost, time, and risk compared with that incurred with a traditional network of buoys, which must be deployed, recovered, and maintained with a ship and a crew. The small size of the USV facilitates rapid deployment and greater flexibility to detect, observe, and monitor unforeseen or rapidly changing events below, above, or on the ocean surface.

Obtained independently from vessels using satellite communications and with zero additional operational risks, the acquired data added significant confidence in the seismic survey area of operations.

Download: Total E&P Reduces Risk and Cost During Seismic Operations in Complex Currents with USV-Acquired Real-Time Data, Uruguay (0.19 MB PDF)

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Data Collected by USV and Moored Buoy

Amplitude and current direction chart based on measurements collected from the USV and a moored buoy.
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