Pipeline Shore Approach Installation by Horizontal Directional Drilling

Abstract

Whenever an export pipeline coming from offshore fields to onshore facilities is designed, a shore approach solution needs to be provided, once it can become a very complex project in terms of offshore pipeline installation. At this phase the pipeline on-bottom stability is analyzed for surf zone, the possibility of using concrete coating is verified as well as the necessary burial depth. In addition, the pipeline installation stress analysis is performed, the potential for local scour is verified, among other things. In this context, horizontal directional drilling (HDD) emerges as an alternative method in which, in addition to overcome the technical aspects mentioned above, the environmental issues can also be minimized. Many factors determine the success of an HDD project. Failure to complete the borehole is often the main concern, as the project would not be attempted if the pipeline could not be installed. However, the successful design and construction of an HDD is measured in more than a successful pullback. The achievements, as in any project, include the completion of the project for a reasonable cost with minimal environmental impact and according to the schedule. And of course, the pipeline integrity shall be ensured. That is the focus here in this work. This paper presents discussions regarding to the proper design of the export pipeline section installed by HDD in the shore approach area. To ensure a proper design and pipeline integrity are important parts in the success of a shore approach HDD crossing. It must be noted that there are no methods for in situ repair of damaged pipelines installed by HDD. The point is a proper design, construction and installation, which includes, for instance, do not overstress the pipeline during installation, mainly pullback operation, as well as the proper selection of the drill path in order to place the pipeline within stable ground and isolated from obstacle’s active conditions, to properly consider the corrosion protection, etc., for the design life of the product pipe.