Underwater Survey for Oil and Gas Industry: A Review of Close Range Optical Methods

Abstract

In both the industrial and scientific fields, the need for very high-resolution cartographic data is constantly increasing. With the aging of offshore subsea assets, it is very important to plan and maintain the longevity of structures, equipment, and systems. Inspection, maintenance, and repair (IMR) of subsea structures are key components of an overall integrity management system that aims to reduce the risk of failure and extend the life of installations. The acquisition of very detailed data during the inspection phase is a technological challenge, especially since offshore installations are sometimes deployed in extreme conditions (e.g., depth, hydrodynamics, visibility). After a review of high resolution mapping techniques for underwater environment, this article will focus on optical sensors that can satisfy the requirements of the offshore industry by assessing their relevance and degree of maturity. These requirements concern the resolution and accuracy but also cost, ease of implementation, and qualification. With the evolution of embedded computing resources, in-vehicle optical survey solutions are becoming increasingly important in the landscape of large-scale mapping solutions and more and more off-the-shelf systems are now available. The issues raised in this review are mainly related to the qualification of the results produced by optical systems and their limitations to cover all the needs expressed by the oil and gas industry field. Interesting qualification works of these solutions are presented in this paper as well as the use of online processing tools such as visual odometry or VSLAM to guide the data acquisition and pre-qualified survey. Finally, it seems interesting to combine acoustic and optical technologies in order to extend the field of application of these methods to low visibility conditions, which remains one of the main limiting factors in the generalization of the use of optical sensors in high resolution underwater cartography applications.

On the Autonomous Inspection and Classification of Marine Growth on Subsea Structures

“…With additions, the following description is based on the comprehensive reviews of optical methods for underwater applications conducted by Chemisky et al [14], Menna et al [15], Massot-Campos and Oliver-Codina [16], and Xi et al [17].…”

“…Several underwater experimental results (with calibrated targets) showed an accuracy of 10mm using the Scale Invariant Feature Transform (SIFT) [22], [23] and the highest accuracy of 0.7mm was obtained using the Speed Up Robust Features (SURF) [24]. While this accuracy is sufficient for MG thickness estimation, the range limitation below 3m and drift issues are the main challenges for using this method on larger diameter structures [14].…”

“…Specifically, soft MG is non-rigid which imposes an issue when triangulation is performed. The method is also affected by poor visibility and flickering from sunlight when operating close to the surface, which is where structures are known to be most affected by MG [14], [16]. Further investigation is also needed to assess if the textures of MG are sufficient for SfM in a setting close to an offshore structure.…”

“…Apart from providing fixed scaling, and some redundancy in the images, SV is generally affected by the same problems known for SfM. A stereo vision technique has increased cost over SfM since a minimum of one extra camera is needed [14].…”

Computational fluid dynamic study on design and modification of underwater remotely operated vehicle

“…In order to guarantee a stable seabed that can support the focused strain needed for subsea structure foundation, all prospective fixed platform locations must be examined with adequate accuracy. Due to incomplete information from early surveys, operators have been forced to relocate the location of a project at the last minute or remove rocks from a site quickly in the North Sea [2]. The necessity for more accurate underwater surveys and better underwater positioning and navigation technologies is highlighted by these situations.…”