Dmac: Flowline And Umbilical Connections For Commercial Application
Authors: Hadfield P.E. , Balnaves Charles , Brookes D.A. , Knudsen T.W. 
Published: October 2008

Significant advances have been made in Diverless Maintained Cluster (DMaC) technology since the conclusion of the Esso Exploration and Production (UK) development program in 1991. A Joint Industry Program sponsored by BHP (Americas), BP, EXXON and STATOIL has detailed the designs of the flowline and umbilical jumper connection systems, and has enhanced the capabilities of the tooling that operates them. Several potential applications for DMaC have been identified, and a fast track program has been initiated by BP with some funding from other JIP partners, to demonstrate the JIP designs offshore, in deep water, under severe working conditions.

INTRODUCTION

This paper describes the progress that has been made in commercializing the Diverless Maintained Cluster (DMaC) system, in particular the Retlock connector and the flowline and umbilical jumper connection systems, since the conclusion of the Esso Exploration and Production UK (EEPUK) funded development program in 1991.

Further development of the DMaC system, from January 1992 until mid 1993, was undertaken by Costain Oil, Gas and Process Limited, FUEL Subsea Engineering (COGAP).

Full descriptions of the DMaC subsea production system and the prototype testing of the flowline and umbilical jumper connection systems have been presented in previous OTC papers, References 1 and 2, so only brief overviews are given here.(Available in full paper)

The paper gives details of work undertaken during a Joint Industry Program that was concluded early 1994; it outlines some of the potential applications for DMaC identified by the JIP participants; and describes the first steps that are being taken by them towards commercialisation of the flowline jumper connection systems.

The paper describes the capabilities of the Retlock connector and the DMaC connection systems, and their current technical status.

OVERVIEW OF THE DMaC SYSTEM

The DMaC system concept is illustrated in Figure 1. As configured for the EEPUK development program, the system provides up to 50,000 bbls/day production, round trip pigging and well test by subtraction with no loss of production. It comprises an eight well gathering manifold with an 8 inch production header and pigging loop. Manifolding is accomplished in two circular, block manifolds. Foundations are provided by a single pile, or by skirts, depending upon soil conditions.

Production can be through conventional satellite trees, although for deepwater applications the trees can be fitted with ROV relievable chokes and control pods.

Connection between the tree and the manifold is achieved by twin four inch bore flexible flowline jumpers for production/testing and by umbilical jumpers for control; the end terminations being by two-bolt clamps and stab plates, respectively. The clamps and stab plates utilise the Retlock which was developed, built, and tested under the DMaC program. The design of the Retlock has been developed further by COGAP and applied on two significant deepwater field developments in USA and Norway. Control is accomplished with a conventional multiplexed electro-hydraulic control system. Each tree is controlled by its own control pod.