Deep Water X-mas Tree Standardization -- Interchangeability Approach
Authors: Paula M.T.R. , Paulo C.A.S. , Moreira C.C. 
Published: October 2008

Aiming the rationalization of subsea operations to turn the production of oil and gas more economical and reliable, standardization of subsea equipment interfaces is a tool that can play a very important role. Continuing the program initiated some years ago, Petrobras is now harvesting the results from the first efforts. Diverless guide lineless subsea christmas trees from four different suppliers have already been manufactured in accordance to the standardized specification.

Tests performed this year in Macae (Campos Basin onshore base), in Brazil, confirmed the interchangeability among subsea Christmas trees, tubing hangers, adapter bases and flowline hubs of different manufacturers. This interchangeability, associated with the use of proven techniques, results in operational flexibility, savings in rig time and reduction in production losses during workovers.

By now, 33 complete sets of subsea Christmas trees have already been delivered and successfully tested. Other 28 sets are still being manufactured by the four local suppliers. For the next five years, more than a hundred of these trees will be required for the exploitation of the new discoveries.

This paper describes the standardized equipment, the role of the operator in an integrated way of working with the manufacturers on the standardization activities, the importance of a frank information flow through the involved companies and how a simple manufacturing philosophy, with the use of construction jigs, has proved to work satisfactorily.

INTRODUCTION

Most segments in the oil industry consider that interface standardization is an important tool that can be used to achieve rationalization of methods and equipment, bringing considerable advantages, mainly economical. Particularly in the subsea equipment area, these advantages can also be obtained. In fact, Petrobras has already gained benefits resulting from standardization made in the past.

The main significant interfaces already standardized by Petrobras are:the H4 profile for subsea wellheads;the internal profiles for wireline set plugs in the tubing hanger and subsea christmas tree reentry mandrel for both production and annulus bores;the tops of tubing hanger running tools and subsea tree/tree cap running tools terminating as a standard completion riser pin;the top of guide posts;the ROV interfaces used on subsea chrisfmas free.

The following facts have been considered when Petrobras decided to implement a standardization program:the operational offshore experience acquired during the last decade;the large number of subsea wells to be drilled and completed to develop Marlim, Albacora and Barracuda fields whose development is being carried out using large number of guide lineless subsea christmas trees;the potential economical advantages in dealing with common rigs, tools, risers, wellheads, subsea trees and spare parts for more than 200 wells

The main concern about the standardization program devised by Petrobras was to achieve the interchangeability with equipment manufactured in different occasions and even by different suppliers. So, it was necessary to define not only functional and performance requirements, but also some crucial geometry and dimensions, mostly of interfaces.