Remotely Operated, Diverless Subsea Pig Launcher
Authors: Hale James R. , Clegg William R. 
Published: October 2008

This paper describes a remotely operated Subsea Pig Launcher (SPL) designed and built for installation on Shell's Serrano subsea development. This technology provides pigging ability to single-flowline subsea developments and can dramatically reduce costs by enabling single (as opposed to dual) flowline systems. A simple, effective SPL has, to date, not been commonly available in the industry. This SPL should prove easy to use and operate with minimal intervention. Unique features include: remote operation from the host; independent launching of up to nine pigs; diverless pig re-supply; and, diverless installation/removal.

Introduction

The Serrano and Oregano fields are each two or three well developments located six and seven miles, respectively, from Shell's Auger TLP. The developments are located in the Garden Banks area of the Gulf of Mexico in approximately 3,400 feet of water. First production is scheduled for September 2001. An overall field layout is shown in Fig. 1. The developments employ the novel technologies of electric heated flowlines and subsea pigging to enable single flowline systems. Pigging may be required periodically for both developments. A contract was awarded to Oceaneering for the supply of an SPL in June of 2000.

The SPL is run and operates in a vertical orientation. Using a hydraulic connector, the SPL locks onto an upward-facing hub on the pipeline sled. It is designed for a nominal 51/8-inch ID, 10,000-psi flowline system and is portable so that it can be moved between the Oregano and Serrano fields. The SPL has the capacity to carry nine pigs and is designed for reloading with a new nine-pig magazine by an ROV and support vessel. The SPL features a pressure-containing separation gate valve and a sacrificial pig connector as the mechanism by which individual pigs are selected, separated and launched. The SPL receives remotely operated control system commands initiated by host platform personnel whenever a pig is launched. The SPL hydraulic valves control fluid and pig launching fluids are received from the adjacent tree electro-hydraulic control pod.

Background

Many very simple SPLs for commissioning subsea flowlines have been built and used successfully. These have limited use for operational pigging, but demonstrate the general feasibility of successful subsea pigging.

The ability to perform operational pigging from a subsea facility to its host provides advantages over round-trip pigging from the host. These advantages include:single-flowline systems tiebacks may be usedflowline/production debris is not pushed towards the wells and through subsea equipmentproduction interruptions are shortened

Because of these advantages approximately eight previous developments have used SPLs. Each of these has met with different levels of success, but none has been completely successful or remotely operated. Most have been modified versions of surface launchers/receivers and have not worked as intended. A few have been engineered for subsea use and have worked as intended, but these have only handled a few pigs and require vessel intervention to load and launch pigs.