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Abstract

The Norwegian Continental Shelf (NCS) is subject to stringent requirements regarding offshore discharges. Focus has previously been on dispersed oil concentration (OIW) in produced water (PW) discharge, but management tools like the calculation of the Environmental Impact Factor (EIF) have also shown the important contributions of naturally occurring dissolved components and production chemicals. Even if the legislation seeks a balance between technical feasibility and economic cost, it is believed that regulators may wish to move to requirements where dispersed oil concentration is not the only parameter to be considered.

Furthermore, recently developed water treatment technologies are currently being installed on the NCS. In relation with the various water management actors (operators, manufacturers, researchers, authorities), Total E&P Norge’s R&D department is strongly involved in the issues related to installation and operation of these technologies. The work described in this study was performed in order to set guidelines to define strategy regarding R&D future directions within water management, foreseeing worldwide more restrictive legislation.

The paper presents a methodology, based upon experience from the NCS, to help to meet upcoming issues in produced water management. Efficiency and operating window of various produced water treatment technologies have been defined according to water inlet quality and field characteristics. The results are presented through a database to compare and rank performances and to set up a global vision of water treatment capabilities. The requirements of offshore facilities, operating criteria, etc. are also taken into consideration and are recorded in the database. By use of the database, combined with the EIF approach identifying, the most harmful compounds of a produced water discharge and quantifying the potential environmental benefits of PW management actions, the most appropriate technologies can be selected on a given field. Fewer field trials will have to be performed and new technologies will be installed more efficiently in the produced water treatment line. This methodology has been validated by Total E&P Norge on several cases on the NCS where new technologies have been implemented.

Introduction

Produced Water Management is a worldwide concern with the growing number of mature fields and stringent discharge’s regulations set in many countries. The discharge in the North Sea is regulated by the Convention for Protection of the Marine Environment of the North-East Atlantic (OSPAR) [1]. The purposes of the recommendations issued within OSPAR are, amongst others, to prevent and eliminate pollution by oil and other substances caused by discharge of produced water into the sea. The current legislation concerns only dispersed oil concentration where present limit is 30mg/l (was 40 mg/l until 1^st of January 2007), but the long term objective is that by 2020 discharges shall present no harm to the marine environment.