Treating and Releasing Produced Water at the Ultra Deepwater Seabed
Authors: Daigle Timothy P. , Hantz Savanna Nicole , Phillips Brian , Janjua Rafique 
Published: April 2012

Tomorrow's energy needs are driving the Oil and Gas Industry to achieve ‘No oilleft behind’. This comes at a cost as the pressures in remote deepwaterreservoir pockets are depleted and the water cuts increases. Existingtechnology is evolving to meet the challenges to automate water separation andpurification in deepwater for environmentally safe discharge at theseabed.

To solve the problems the objectives must be defined; the best availablesolutions must be selected and the technology gaps must be identified andclosed. Environmental protection is a priority and the translation of theexisting Statutory Regulations to include the requirements to be met bydischarged water quality is the starting point. Safety and Reliability willfollow along with the flexibility to tailor the system to match the reservoir'schanging needs and incorporate the best, new and fast developing technology. Equipment relocation may also prove commercially attractive.

Major challenges will be remote process train control and monitoring and theability to perform routine maintenance while the wells still flow. Some of thistechnology could have immediate benefits to surface processes that would inturn provide ideal proving grounds before the technology ventures intodeepwater.

Introduction

This paper explains the challenges facing the subsea processing technologies tobe able to handle and treat produced water at the seabed between 5,000 and8,000 feet of water depth. It will discuss the regulatory standards usedthroughout the industry today to oversee produced water treatment. The paperwill look at the marine life in this ultra deepwater environment at the seabedconditions. It will review the latest produced water treatment technologiesused throughout the topside offshore production industry. The paper willillustrate various concepts to perform subsea produced water treatment and lookat the many challenges and gaps to be addressed, to make this technology viableand effective.

The paper will identify the gaps and challenges to applying produced watertreatment and discharge at the seabed in ultra deepwater environments. Researchand compiled information will be presented to support the concepts proposed tomeet the challenges of produced water treatment and discharge at the seabed inan ultra deepwater production system.

Technology Benefits

Seabed discharge of produced water and/or solids can provide many benefits, but this paper has been created with the focus on the three mainbenefits:Eliminate the need to transport huge volumes of water from deep waterproduction sites to the tieback hosts which may be many miles away. Therefore, significantly reducing the production system costs.Decreasing the hydrostatic pressure on the subsea production flow lineswill help reduce the back pressure on the subsea wellhead and ultimately allowfor more subsea production from the reservoirs.Installations of Subsea Produced Water Handling systems will minimize thetopside equipment footprint and protect the equipment for being vulnerable todamaging tropical hurricanes and harsh weather systems.