Different configurations for riser systems have been emerged as suitable technological and economical solutions for offshore petroleum fields in ultra deep water. The study and development of methodologies for riser project considering the uncertainties involved in the manufacture process of offshore risers and effects of meteocean conditions, such as waves, current and platform motions for the fatigue failure is fundamental to increase the reliability of riser structure design. The present work presents a procedure to evaluate the probability of fatigue failure in offshore Steel Catenary Risers (SCR) identifying the influence of the main parameters in the failure process due to fatigue. Meteocean conditions and uncertainties due to accumulated fatigue damage given by Miner-Palmgren’s rule are here considered. The probabilistic methodology is taken into account, and the analytical approach based on the First Order Reliability Method (FORM) is applied considering two practical cases. In the first case, calculations are performed to compare with the results from the literature, and the second one calculation is carried out considering a typical Brazilian offshore field operation. In the calculations, results for the probability of failure, as well as, the riser service life are observed in four different locations along the SCR length. Finally, conclusions are shown to the probability of failure due to fatigue such as influence of each parameter in the process.

The key to finding the highest-value concept in deepwater full-field development is by making high-quality decisions during the Concept Select stage of a project. One of the critical elements to achieve this is by considering a broad range of conceptual alternatives and evaluating them rapidly, providing timely feedback, and facilitating an exploratory learning process. However, concept-select decisions are challenged by competing objectives, significant uncertainties, and many possible concepts. Further, deepwater full-field developments require strong connectivity and interfaces across multiple disciplines, which include reservoir, wells, drilling, flow assurance, subsea, flowlines, risers, topsides, metocean, geotechnical, marine, costing, and project economics. Key challenges to the current methodology include a lack of capacity to consider multiple concepts, slow evaluation turn-around for each concept generated, continuous evaluation and revisions with new data and information, lack of ability to integrate processes across multiple disciplines, and poor risk management driven by technical/commercial uncertainties and unavailable data. This paper addresses these challenges by combining concepts from the Decision Quality (DQ) framework and FLOCO® (Field Layout Concept Optimizer), which is a metaheuristic model-based system-engineering software, to efficiently identify the highest value field development concepts among several possible alternatives. This novel approach applies a new framework to an offshore deepwater full-field development. Specifically, we explore the trade-space, evaluate the trade-offs between risk and reward, perform integrated techno-economic analysis, and identify the best concepts. Key outputs are the identification of development concepts that meet the given constraints and functional requirements for further optimization, while eliminating those that do not meet such requirements. The results demonstrate that the challenges in the current Concept Select phase can be simplified and that the proposed approach offers a quick, logical, and insightful means of selecting the highest-value concept. The case study demonstrates that the proposed improvement to the concept-select stage of deepwater full-field development process can lead to significantly improved project economics, as it fully explores the decision-space, key uncertainties, multiple technically feasible concepts, and key performance indicators such as net present value (NPV) and capital expenditures (CAPEX). This paper addresses the development of economic oil and gas projects through decision making enhanced by rapid digital prototyping and analysis. The integration of Decision Quality methodologies with systems-engineering decision-support tools is novel and is likely to become more important as the industry explores and develops more complicated targets in the future.

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.

The development of pre-salt fields in the Santos Basin has presented a plenty of technological challenges, which include the production of fluids with high values of GOR (Gas Oil Ratio) and high values of WAT (Wax Appearance Temperature). To avoid the wax deposition, it is absolutely imperative handling the temperature by insulation and/or heating. If in one hand the production system thermal insulation minimizes the heat losses to the environment, on the other hand the cooling due the thermodynamic effect of gas expansion is inevitable, mainly in fields with high GOR values. To mitigate the problem of temperature drop, mainly in the risers where the expansion effects are pronounced, various heating systems for subsea pipelines have been studied by PETROBRAS. In parallel to these studies, it was noted that the design philosophy of the offshore production units for the pre-salt fields have indicated the use of turbo–generators to supply electrical power to the production unit, leading to the opportunity of using the generated super heated gases, originally discharged into the atmosphere, in order to feed the riser heating systems based on heated fluids circulation. Studies of heat exchange performed indicated a great potential for the risers heating by the flow of heated water through the annular of a Pipe-in-Pipe riser, by using a WHRU (Waste Heat Recovery Unit) to recover the power discharged into the atmosphere from the turbo–generators. It was identified the possibility of heating Pipe-in-Pipe risers by circulating heated fresh water in a closed loop with water return to the production unit, or by coupling the riser heating system with the water injection system, using all the facilities for treatment and pumping of water injection. This paper aims to describe the methodology considered in the development of a conceptual design of a heating system for a Pipe-in-Pipe riser, by the flow of heated water in the annular, in a Free Standing Hybrid Riser configuration. The paper will also present the characteristics associated with the two possibilities of heated water circuit, as well as advantages and disadvantages of each system, and the aspects related to subsea production layout.

When in shallow waters, not only the risers, but also the structures and equipment are submitted to different conditions from the ones related to deepwater applications. OGX has developed offshore applications in shallow waters in Campos Basin, Brazil, using a FPSO with Lazy S riser configuration, based on the Midwater Arch systems (MWA). MWA systems are feasible due to OGX application scenario, but they present some disadvantages, such as: high compliance of the buoyant section to the FPSO, large static offset (common issue in shallow waters applications), which makes the MWA carry the risers that are clamped at the top; high manufacturing and installation costs, associated to the high weight of the structure, which includes large and heavy buoys; limitation regarding transportation, sometimes requiring heavy duty trucks, and consequently, more expensive ones. These disadvantages could be avoided by using another type of support structure, but it depends on the application conditions. Aiming to optimize the Lazy S configuration for new applications in shallow waters, a viability study of a most simplified concept of support, fixed and less compliant, was carried out considering as a standard scenario the Waimea field (under development), located in Campos Basin, Brazil. As a result of this study, OGX and Wood Group Kenny developed the conceptual project of an innovative design of Riser Support Structure (RSS). Therefore, this paper addresses the technical challenges that were faced during the design of this new concept of Riser Support Structure for shallow waters in offshore applications, including issues regarding the required structural safe response and aspects comprising installation and some decommissioning considerations. Regarding the design, this paper discusses the structural analyses performed to validate the RSS, which include VIV and Finite Element Analyses, presenting its main results, and the critical issues encountered during these analyses. They include issues such as: Overstress due to combined loads; stress concentration in important structural components; and stress concentration due to impact load (issue recognized during dynamic analysis to simulate the pile driving operation).