SPRINGS® (Subsea PRocessing and INjection Gear for Seawater) is a qualified process for subsea water treatment and injection. It uses membrane technology for water desulfation upstream of water injection wells to prevent sulfate scaling on the production side (nearwell bore, well and production equipment). It moves the water treatment from topside to subsea locations close to the injection wells with only power and communication tie-backs to existing topside facilities. Qualification of the process was achieved through both onshore and offshore trials. In advance of deploying the first industrial application, an industrialisation programme was undertaken in order to ensure that every component necessary for the subsea process implementation was available and had a sufficient technology readiness level to be safely installed and operated within the subsea plant. The existing and available technologies were reviewed vis-À-vis the requirements arising from both the process and the business strategy. Several industrial partners were engaged to determine the elements of novelty that needed to be brought to each technology or component to satisfy such requirements. The new technologies included: Subsea barrier-fluidless pumps Open framework all-electric control systems High-cycling electric actuators and valves Subsea water analyser Subsea storage and injection units for chemicals The design basis for the development of each technology, which in most cases included the realisation of a prototype and relevant qualification testing, was set up to consider a range of possible applications with differing environmental conditions, process data and/or IMR scenarios. The most challenging conditions were selected for each development to determine the relevant required performance. Where available, specific standards, such as API 17F (ref. [8]) for subsea electronics, were followed to determine the qualification plans. In those cases where no dedicated specific standard was available, the evaluation of the proposed solution was performed in conjunction with the technology provider through the risk based approach stated in API 17N (ref. [9]) and DNV A203 (ref. [10]). Failure Modes, Effects and Criticality Analyses (FMECAs) as well as technology readiness assessments were performed in order to develop the technology qualification plans. Most of the key equipment qualification plans will be completed by mid-2019, establishing an industrial platform for the deployment of the subsea water treatment and injection technology in a completely all-electric configuration, i.e. connected to the surface only through a communication and power cable. Such an industrial platform will also contain the building blocks for other subsea processes. The presentation and paper will introduce the elements of technological novelty and will describe the process, the challenges and the results of the relevant qualifications.

This paper is based on work performed for Deepstar CTR11901 (for more information on the program see www.deepstar.org). On average, only a third of in-place oil is recovered in Miocene reservoirs in the Gulf of Mexico. Water injection has been used to enhance the oil recoveries with limited success. Low salinity water injection could potentially further increase the oil recoveries achievable through seawater injection. For deepwater oil fields and those requiring long tie-backs to the existing host processing platforms, local subsea processing systems providing low salinity water injection could be useful in improving development economics. A Deepstar study has been carried out to evaluate the existing technologies for such subsea processing system to generate the low salinity from the seawater at 10,000 feet of water depth. Several conceptual process schemes have been defined and evaluated, employing various combinations of technologies, and compared from the point of view of operability, maintainability and technology maturity level. Technology gaps have been identified in the selected technologies and roadmaps have been defined to fill those gaps. The paper describes the methodology that has been used to review the existing technologies for water treatment and evaluate their potential for subsea application, presents the main results of the state of the art review and gives an overview of four process schemes defined for subsea implementation of a low salinity water injection station. Whole range of technologies for water desalination have been studied including membranes, electro-dialysis and the use of hydrate formation. The defined schemes combine desalination with other function technologies in order to optimize the make-up of the low salinity water to meet the particular reservoir needs.

New local subsea processing systems will need to be developed to allow remotely located satellite oil fields to be produced economically. One such system treats seawater for injection into the reservoir.As reservoir waters often contain elevated concentrations of barium or calcium, treatment systems need membranes to remove any sulfates that may form in the seawater before it is injected into the reservoir, in order to avoid severe scaling. SPRINGS (Subsea PRocess and INjection Gear for Seawater)is a collaboration project between Total, Saipem, Veolia Water and VWS Westgarth. It was initiated in 2007 and aims to provide robust solutions featuring the use of membranes for treating seawater on the sea bed in deepwater areas.SPRINGS has now reached qualification stage and a first industrial application is planned for 2015.This paper describes the SPRINGS development project, including an update on the latest progress to date. It presents a specific case study conducted in the Gulf of Guinea which illustrates the commercial and technological advantages, along with the limitations, of deploying this technology for future remote applications. It compares the conventional field architecture utilized in conjunction with water injection from FPSO topsides with the architecture required for a SPRINGS solution on the ocean floor.The information provided allows operators to consider an alternative development strategy for the application of membranes to water injection in remote satellite fields.

A new seawater laboratory pilot has been installed in order to evaluate the impact of the seawater quality on the performance of nanofiltration membranes and filters. The test program implemented was designed to produce the data required to optimize the design and operating parameters of a subsea sulfate removal plant, particularly with respect to the technology developed by Total, Saipem and Veolia, co-owners of the development. The equipment qualification plan is approaching completion with the development of subsea barrier-fluidless pumps, all-electric control systems, high-cycling valves operated by electric actuators and subsea water analyzers. This presented pilot laboratory study completes this plan. Nanofiltration membranes are commonly used to remove the sulfates found in seawater before the water is injected into wells. The principal advantages of relocating this equipment from topside to subsea are better reservoir sweep control, a substantial subsea water injection network reduction and savings on space and weight on the topsides deck. The move to subsea offers the opportunity to simplify the process due to improved deep water quality. This was previously demonstrated through a subsea test campaign. This new pilot study provides data both on the performance of a plant operating with different feed water quality and on the success of operating changes to further optimize the plant performance. The pilot has been installed at the Palavas-les-Flots site in France. Raw water collected from the basin was mixed with ultra-filtered water in order to calibrate the feed water quality. The pilot includes a two stage nanofiltration configuration and single stage nanofiltration unit. The two stage configuration was used to produce data for operation across an array of feed water quality and plant operating conditions. The single stage unit was used to produce data on membrane fouling over a long operating duration. Results from these tests and discussion on how this data relates to subsea plant performance shall be presented. This innovative approach enables a wide range of subsea water quality to be simulated and tested against different process configurations of the subsea unit. Indeed, for each industrial subsea application, the raw seawater quality is dependent on both the region and the depth of the seawater inlet. With this experimental data acquisition campaign and understanding of the seawater quality at inlet, the system design can be tailor-made for each future application case.

A new subsea-to-shore oil field architecture is presented where produced water is separated, treated and re-injected locally. This solution reduces the overall power consumption and the global CO2e footprint of the development compared to an architecture where the whole production is sent to shore. The paper will present the results of a study for the development of a 200 000 bpd oil field requiring 300 000 bpd water injection located 150 km from shore in 1500 m water depth and with a field life of 15 years. Preliminary design work performed covers flow assurance, subsea process, subsea equipment, subsea layout as well as CO2e footprint comparison with a scenario where all the production is sent to shore. The system incorporates a gravity-based liquid-liquid separator for bulk oil-water separation, produced water is then treated, mixed with desulfated seawater and re-injected. Oil, gas and residual produced water are sent to shore via a single wet insulated line with continuous injection of low-dosage hydrate inhibitors. This scenario has two main advantages compared to a subsea-to-shore without subsea processing. The first is that the power required to boost production is significantly reduced. The second is that the volume of produced water to be treated onshore is also significantly reduced, which is advantageous, not only in terms of cost, but also in terms of reducing the shore operations’ footprint. Particular focus will be made on the produced water treatment design which is a two-stage design using two different technologies for increased robustness in order to reach a specification of 30 ppm oil-in-water for injection water.