Protective Deployment of Subsea Equipment
Authors: Lallier E.B. , Ross C.L. , Davis C.I. 
Published: October 2008

The primary objective of protective deployment systems is to safely deploy, position, and land subsea equipment while preserving personnel safety and protecting investments. There are several protective design concepts available to meet today's deepwater operating needs. Future considerations are being examined to meet the demands of new challenges. This paper primarily addresses the deployment and recovery of work class remotely operated vehicle (ROV) systems and designs that can be applied to a wide variety of applications including the installation of subsea equipment.

Introduction

As subsea field development expands to include a wider range of applications in increasingly harsh environments, surface deployment systems continuously evolve to overcome the demanding design requirements. Deployment system configurations range from stationary to overboarding with installations being permanently built-in, modular with semipermanent components, or entirely mobile. Protective deployment systems are used extensively in the launch and recovery of ROV's. Other applications include tools, trees, connectors, pipeline jumpers, wirelines, manifolds, umbilical termination assemblies, workover equipment, and other subsea hardware. By incorporating protective methodology in current designs for deploying subsea equipment, financial liability is reduced by minimizing the risk of equipment damage while increasing the window of environmental limits. The end results are protective deployment systems used for a wider range of applications with improved performance, less down time, and most importantly, fewer accidents.

There are several variables in the offshore environment that present challenges. These variables impose limitations on the system's overall capabilities and performance. Variables with the largest impact are environmental conditions in which the installation will be operating. Mechanical designs and operational procedures provide the best solutions to the challenges of the ocean environment. These methods incorporate ways to safely control deployed loads due to varying sea states, high winds, high currents, and increasing water depths.

Dynamic loads induced by the vessel's motion are another design challenge. Dynamic loads become proportionally more significant on installations using smaller vessels such as multi-service vessels. By using protective deployment systems, smaller vessels can provide more costeffective operations by reducing or eliminating the need for larger, more expensive surface vessels. Protective deployment systems find applications on various types of vessels, including ships, semi-submersibles, barges, spar platforms, and TLPs, each of which has its own set of requirements. Their configurations are limited by a vessel's deck load capacity, the amount of space available for an installation, and the dynamic motions for a particular sea state. Advantages on larger vessels allow deployment operations to move to the less congested perimeter locations and free up prime operations area, which is especially important on drilling units.

Maintaining personnel safety when operating in harsh environments is the most critical factor considered for these systems. Designs must be constructed to protect life and equipment, and procedures for operation must be properly outlined to foresee/prevent any unsafe operating conditions.