Programme For Standardization Of Subsea Equipment
Authors: Paulo C.A.S. , Moreira C.C. 
Published: October 2008

Since the first subsea well started producing in Brazil, Campos Basin has turned out into a big laboratory where innovations and different concepts ranging from one-atmosphere chambers to diverless guidelineless wet Christmas trees have been tested.

Supported by the operational experience acquired throughout the years, motivated by the large number of subsea wells to be drilled and completed in the new fields and pressed by the need of some rationalization to deal with rigs, tools, risers, wellheads, trees and spare parts for more than two hundred wells, PETROBAS started its own efforts on standardization of subsea equipment.

To achieve the desired interchangeability with equipments manufactured in different occasions and even by different suppliers, it is necessary to define not only functional and performance requirements, normally found on API Specs, but also some crucial geometry and dimensions, mostly of interfaces.

This paper describes the experience with some standardization made in the past, the programme being carried out in the present, the equipments and interfaces being standardized and how far PETROBAS is going into equipment definition.

INTRODUCTION

After hundreds of wells drilled in Brazilian waters, more than 170 wet x-mas trees installed in water depths from 70 to 781 meters, 10 floating production systems and 14 fixed platforms installed, and a considerable mileage of flowlines and umbilicals laid, the experience obtained with these offshore operations performed in Campos Basin has made it possible to evaluate the pros and cons of standardization of subsea equipment.

The simple conclusion was that standardization really brings considerable benefits. The resulting operational flexibility associated to the use of proven equipment and procedures saves rig time and can reduce production loss during workovers. Savings can also be detected from the reduction of the number of spare parts and tools, but the savings in values related to the operations exceed considerably those ones connected to equipment acquisition and store. So the great benefit is the operational flexibility.

On the other hand, non-standardized equipment serves as an open door to continuous modifications of equipment design, which is welcome when the equipment is not satisfying customer's requirements. But once the equipment is properly tested and proven, unnecessary proliferation of slightly differing designs need to be avoided.

FIRST STEPS ON STANDARDIZATION

The first significant interface adopted as a standard by PETROBAS in the early 1980's, was the subsea wellhead external profile and the sealing area for VX/Ax rings. At that time, the various rigs contracted to drill in Brazilian waters had BOPS provided with H4 connectors of different sizes: 21.1/4", 18.3/4", 16.3/4" and 13.5/8", leading to the use of different wellhead systems and x-mas trees connectors. PETROBR&3 then defined the 18.3/4" H4 profile as the standard external profile for all high pressure housings, and the BOPS were equipped with appropriate connectors. More recently, this definition had to be divided in accordance to the drilling system type: