Diverless Jumper Connection System For A 12-In. Pipeline
Authors: Beckmann M.M. , Hale J.R. , Davis S.W. , Prescott C.N. 
Published: October 2008

This paper describes the diverless pipeline jumper connection system that will be used to tie-in two 12-inch export pipelines to a subsea template in 2130 feet water depth. The paper discusses selection of the connection method and design of the jumper system. Key features of the system include a ROV deployed and operated measurement tool, diverless mechanical connectors, a load-limiting anchor flange, flexibility to accommodate installation and operating conditions, and a pipeline Iaydown sled capable of being layed through a stinger.

INTRODUCTION

Several diverless pipeline connection systems have been used in the past and several others are being developed. These systems are designed with hydraulically operated mechanical connectors and rely on the ROV (Remote Operated Vehicle) to execute the activities previously performed by divers. To facilitate ROV intervention, connection operations are made simple and reversible to allow recovery of malfunctioning equipment for diagnosis and repair or replacement. This approach has been adopted for design of the jumper connection system for tie-in of two 12-inch export pipelines to Enserch's Garden Banks 388 subsea template in 2130 foot water depth, described in this paper.

Alternative jumper configurations were evaluated prior to selection of the system depicted in Figures 1 and 2. The design of the jumper system involved:Flexibility analysis to determine jumper length, overall geometry and required measurement/fabrication accuracy. In addition, target areas for pipe end placement relative to the subsea template were defined.Evaluation of the mechanism for aligning the mating halves of the mechanical connector. A coarse alignment system was needed to bring the mating halves within the capabilities of the mechanical connector.Installation and operation analysis to determine loadings and verify that all stresses in the piping and structural components of the jumper system were within allowable limits.Failure mode analysis of the jumper piping and load- Iimiting flange to verify that the design loads for the template mounted receiver structure and associated piping were sufficient to prevent damage resulting from a pipelines nag load.

Fabrication and land testing of the jumper system depicted in Figures 1 and 2 is scheduled to be completed in April 1994. The jumper system is currently planned to be used to tie-in the oil and gas export pipelines to the subsea template in August 1994.

BACKGROUND

Two diverless tie-in methods were evaluated prior to selection of jumpers for connection of the 12"diameter oil and gas export pipelines to the subsea template. These included:the lateraldeflection method;andpipejumper or spool piece method.

First end connection methods such as direct pull and stab & hinge-over were considered and eliminated early in the evaluation process, since these methods impact selection of installation equipment. The direct pull method requires two vessels and results in high loads imparted onto the template. The stab & hinge-over method requires a purpose built connection system and requires the pipe end to be lowered in a vertical orientation which is most suitable to the J-lay method of pipeline installation.