Recent deepwater projects are considering Subsea Gas-Liquid Separation aspotential technology to unlock oil reserves. Eni e&p is currently workingon R&D and development studies to evaluate the benefit of this technologyfor a number of representative assets in its deepwater portfolio. The paper presents several findings of this original analysis. Case studies arerepresentative of a wide range of potential applications: from secondarytiebacks in standard deepwater depth to 1500 m water depth oil developmentapplications and heavy/difficult oil cases to condensate/gas fieldsapplications. The results are presented with the comparisons between standard deepwaterarchitectures and configurations based on Subsea Gas-Liquid separation in termsof flowassurance strategy, field layout, capital costs and benefits for theoperators in terms of potential additional recovery and production. SubseaGas-Liquid separation may become an enabling technology for deepwaterdevelopments if oil industry is able to resolve and mitigate possible risksassociated. INTRODUCTION Subsea processing coupled with innovative field architectures are one of themost attractive tools currently being utilized and considered by the oil andgas industry to open new opportunities and achieve more effective exploitationof offshore fields. Every day new oil and gas reservoirs are being discoveredin unconventional and remote areas in deep and ultra-deep water, typically farfrom existing treating and storage facilities. Subsea processing technologiesare becoming faster and faster applicable options to improve technical andeconomic performance of those challenging subsea field developments, improvingthe reserves recovery and operation strategy, and, in some cases, reducing theassociated development CAPEX. The term " subsea processing" can be defined as any treatment of the producedfluids performed on the seabed prior to reaching the offshore installation andthe conventional surface process facility. Different devices have beenqualified and installed to boost the raw wellstream, like subsea multiphasepumps and wet gas compressors. In the last ten years, technologies to separatethe gas phase from a liquid stream and produced water from hydrocarbons rapidlyevolved thanks to great efforts on qualification program and testing campaign. Moreover, a few installations of separation and boosting devices have beenachieved, presenting really encouraging results but not neglecting operationalissues they have encountered during field life.
The acquisition of representative fluid samples from deep and ultra-deepwater field development is crucial for the correct evaluation of oil reserves and for design optimisation of subsea production and processing facilities. Due to regulatory requirements for fiscal allocations, samples collected from topside facilities do not represent the fluid being measured, occasioned by chemical injection downstream the Subsea Multiphase Flowmeter (SMPFM) and possible liquid separation / hold-up, which further complicates these challenges. However, the issue of subsea intervention and transportation of fluid samples present another significant challenge coupled with the cost impact and risk to the subsea environment. Therefore, the synergy to acquire representative fluid samples to determine the right window to employ subsea processing must be sort to realise value on field development projects in maximising oil recovery. Applications Acquiring representative fluid samples play a key role in the design optimization of field development, to enable efficient reservoir performance management. Inaccurate and unreliable fluid characterization leads to high uncertainties in hydrocarbon volume estimates, thus negatively impacting ultimate recovery predictions and hence the asset value. With the virtual fluid sampling model developed from a 'Transient Multiphase flow' program, every single fluid component was accounted for throughout the calculation, enabling simulation of scenarios such as start-up and blowdown with a high level of detail and accuracy. Remote Opperated Vehicle (ROV) deployed fluid sampling also play a key role in the representative fluid sample capture at the wellhead or subsea tree for laborary analysis of PVT and fluid compositions. Results, Observations, and Conclusions Results from the developed virtual fluid model demonstrates the capability in improving understanding of well flow stream, with a proactive and cost effective fluid sampling operations. Another benefit is the value it adds in deciding when to employ subsea processing to manage water breakthrough as the field matures. This can be achieved through efficient processing of the fluid delivered to the topside facilities or for water re-injection to the reservoir. The acquired results from a deepwater field case study, establish the fact that the virtual model can accurately predict the fluid compositions at the well source and production flowlines. Therefore, this has enabled the development of a predictive tool for advanced subsea intervention operations to test and monitor reservior conditions for the life-of-field. Significance of subject matter The developed virtual fluid model does not only bridge the gaps in subsea fluid sampling, it also maximizes value by adding analytical techniques to check and validate present measurement methods of obtaining fluid properties during production well tests. Thus, the virtual model provides a new application and opportunity to optimize individual well testing for Enhanced Oil Recovery (EOR). The present paper explores the synergy in successful application of subsea fluid sampling to maximize value with subsea processing on deepwater field developments.
The scope of the paper is to further present and discuss, in continuation of OTC-28839-MS paper, the results of our technology development program regarding very long oil tiebacks architectures (50-100km) and enabling technologies. It is arrived the time when long tieback solutions are considered for real development projects. The paper will describe how those technological solutions compare with more conventional development schemes in concept selection phases and how our Operating Company is getting prepared for potential implementation. The paper will review key enabling technologies, together with their readiness level and discuss drivers for integration and operation. Sizing references will be presented as a result of Front End Engineering and Design activities developed for real project development opportunities. Technical performances will be discussed and technical-economic indicators will be provided. Risks during development and production will be analyzed and mitigation will be evaluated. A combination of heated high thermal performance flowlines, subsea multiphase boosting, subsea power management, innovative preservation procedures, newest subsea production components together with a reliable integrated control system and digital technologies are the key enablers of a very long tieback solution that may work as kind of highways to bring back production of a whole area to a production hub. Technically the way to go and the gap to cross appear manageable in mid to short terms opening new opportunities for deepwater asset development. It appears now possible to reduce deepwater development costs by increasing the distance between new assets and existing production hubs, shallow water areas or even connecting those assets to shore.
The scope of the paper is to present and discuss results of an extended technology development program regarding very long oil tiebacks architectures (50-100km) and related enabling technologies. The program is based on Eni most recent development projects (started up in the last 4 years) contemplating long tiebacks, new technologies implementation and experimental production periods conducted on those projects. Important field production data and measured performances on development projects have been a key to define the program. Wide ranges of tieback architectures and technologies have been studied. Technology providers and suppliers have been heavily involved. Technology validation and risk analysis approaches were used. Feed design is now ongoing regarding new asset development initiatives. The objectives are to reduce deepwater development costs increasing the distance between new assets and existing production hubs, shallow water areas or even connecting those assets to shore. A cost effective and flexible extra long oil tie back architecture proves to efficiently work on a wide range of applications and a wide range of design basis parameters. Key enablers are boosting, subsea power distribution, multicontrol communication, thermal management technologies, extensive work on reliability and availability and tailored operations procedures. Maturity levels and way forwards to a potential project execution will be discussed in the paper, including projected economics. Recent technology development, qualification and testing together with the experience matured on the most recent deepwater projects allow to seriously consider a "full subsea development approach" at long distances from existing hubs or from shore.
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