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I-Tube inspection in Angola

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Oilfield Technology,

In February 2015, Ocean Atlantic Petroleum inspected an FPSO 44” I-tube for a major oil and gas operating company in Angola using 2G Robotics’ ULS-200 underwater laser scanner. The company’s objective was to obtain as-built geometry of the I-tube to ensure unobstructed installation of a 6” power umbilical through the I-tube.

The I-tube was cleaned to remove any solid mineral growth that would affect the subsequent cutting and gauging operations. Once the cleaning was completed, 36 holes were cut in the I-tube walls to allow for the proper dispersion of heat generated by the high voltage cables to be installed.

The ULS-200 was deployed inside the I-tube using a spring actuated pipe centraliser. A 2G Robotics laser technician operated the ULS-200 while Ocean Atlantic Petroleum personnel managed the winch, cable payout, and overall operation. The result of the inspection was 66 point clouds each capturing an approximate 1-meter section of the inner surface of the I-tube. The point clouds were cleaned and then registered using overlapping regions of adjacent point clouds and using recorded cable payout.

This inspection would typically be performed using calliper pigging. However, calliper pigs for such large diameter pipes (44” ID) are extremely heavy and expensive, making the technical and economic viability of the overall project questionable. Also, gaps between calliper pigs’ sensors give room to interpretation when trying to understand the geometry of the I-tube, which reduces the accuracy of design plans and increases the risk of error during installation. The 3D models generated by laser scanning reduce this risk because, unlike calliper pigging, the submillimeter resolution of these models provides the necessary accuracy for capturing precision measurements and making informed design decisions.

From the high resolution 3D point clouds generated by the ULS-200, the customer gained a detailed understanding of:

  • hole distances from top of the I-Tube,
  • hole orientation with respect to the pipe centreline and I-tube hull,
  • expected versus as-surveyed hole locations and orientations, and
  • inner diameter cross-sections for every 1m of tube.

João Manuel Barradas, President of Ocean Atlantic Petroleum, stated that the “accurate measurements captured from the 3D visualisations of the FPSO I-tube provided comprehensive knowledge of the as-built geometry and notably facilitated the installation of the power umbilical.”

Adapted from press release by Joseph Green

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