No abstract

The proper development of an offshore oil and gas field relies on a project's ability to deliver the maximum economic benefits while maintaining safety and environmental targets. In this sense, offshore oil and gas companies have continually evaluated ways to optimize system designs and streamline operations to ensure the achievement of these objectives. A set of technological alternatives that have been highlighted is subsea processing, which requires moving a processing system from the topsides to the seabed. The assessment of subsea processing systems has become an important step during the field development strategy definition, especially in terms of flow assurance by mitigating hydrate and wax formation. When combined with mature subsea production technologies, the potential benefits of deploying subsea processing include enhanced reservoir recovery improved facilities availability, reduced topsides processing requirements, and reduced overall field development cost resulting in improvement of project economics. In addition, depending on the subsea architecture chosen, subsea processing can contribute to reducing the carbon footprint, which is in line with the industry's decarbonization goals. Due to the potential benefits of the subsea processing architectures, new technologies are emerging to overcome the technical challenges to enable this transfer of strategic processes from the topsides to the subsea. The objective of this paper is to present and discuss the mapped subsea processing system archetypes that may significantly increase hydrocarbon production in a cost-optimized way for new fields, tiebacks, and operating facilities. The mapped archetypes are implemented in an Expert System that integrates all technical areas for offshore field development, providing hundreds of conceptual alternatives to understand the impact of using subsea processing systems. This paper provides an overview of promising technologies that have the potential to increase the scope of subsea processing, leading to the identification of the most favorable architectures for each project. This study incorporates a detailed analysis of 27 different subsea archetypes, combining processes such as liquid boosting to host, gas compression to host, two-phase and three-phase separation, produced water reinjection or disposal, seawater injection with sulphate removal, dense phase (natural gas or CO2) boosting to reinjection, gas dehydration, and gas compression. Such analysis indicated that equipment with different technological maturity levels can be combined to create a subsea processing arrangement that meets the project requirements.

No abstract

The use of seawater treatment and injection to increase oil recovery is extensively practiced worldwide. Seawater can be treated at different levels to provide the required water quality compatible with the reservoir for pressure maintenance. In this respect, membrane technologies including ultrafiltration, nanofiltration and reverse osmosis can be used for fines, sulphates and salt removal respectively. The use of subsea treatment systems built on these filtration technologies is proposed as an alternative to bulky and heavy conventional topside systems. Subsea systems can eliminate the need for expensive floating facilities that often have space and weight restrictions. For a reliable operation of a subsea system it is required to verify the filtration membranes performance at water depths that can reach 3000 m (300 bar and 4°C). Laboratory tests of hollow fiber ultrafiltration (UF), spiral-wound nanofiltration (NF) and spiral-wound reverse osmosis (RO) membrane modules were performed at simulated deep-water conditions to assess their integrity and performance. A high-pressure dynamic testing system, with precision temperature and pressure control was built to enable accurate measurements. Short and long-term dynamic tests, including pressure cycling fatigue tests, were performed by operating membrane modules at the simulated subsea environment (300 bar and 4°C). Static tests were also performed to assess the impact of deep subsea conditions on membrane module structural integrity and membrane physical properties. The results indicate that the tested UF, NF, and RO membrane modules are promising for deep subsea applications. The mechanical integrity and membrane module performance were maintained within the predefined acceptable limits at both static and dynamic test conditions. These promising results are a big step towards the technical feasibility of using membrane technology for subsea seawater injection systems.