Comissioning and Startup of Subsea Marlim Oil and Water Separation System

Abstract

The objective of this paper is to describe the adopted procedures and operations that were used to process commissioning and start-up the Marlim Subsea Oil and Water Separation and Water Re-injection System. This system is much more complex than the conventional subsea manifolds and, similarly to the previous phases of this project, the commissioning and start-up phases also faced many challenges that had to be overcome. Several subsea equipment are part of the system; among them we should mention an unconventional "harp" gas-liquid separator, an oil-water "pipeseparator", cyclonic desanders (both for multiphase inlet stream and for produced water stream), two stages of hydrocyclones to remove oil from produced water and a water injection pump. Besides these equipments, instruments and multi-functional control modules are also part of the system. The problems faced during commissioning and start-up activities and the adopted solutions to solve them are also discussed. This paper will cover the start-up activities describing the following sequence:re-start-up of the production well through the subsea system by-pass line to topside,alignment of well multiphase production stream through the subsea separation system to check separation performance and suitability of produced water quality for re-injection andfinally start up of re-injection of produced water into the injection well. The requirements for logistic support that are very much different from the ones required for topside installations are also discussed. New " paradigms" of operating facilities imposed by subsea environment constraints, are also suggested and discussed. Introduction The Marlim Subsea Oil and Water Separation and Water Re-injection System (SSAO) is an innovative pilot project installed as a Pilot System for the well MRL-141, connected to the host production unit (FPSO), P-37, in Marlim Field, Campos Basin. The objectives of the project are: platform debottlenecking of the water treating facilities; increasing production by reduction of back pressure on the wellhead. Besides these objectives, another important aim of the project is to prove the concept and qualify the adopted technologies for future other applications. As a pilot project, the SSAO was designed to work for a minimum of 5 years, without retrieving of any components, removing, treating and re-injecting free water from the production of MRL-141, as shown in Table 1.