A new operability and predictability enhanced riser control system for deepwater marine operation: an integrated riser hybrid tensioning system

This dissertation presents a novel riser hybrid tensioning system by integrating an electrically powered riser tensioning system into existing hydro-pneumatic tensioners. Compared to current passive hydro-pneumatic tensioners, this new riser hybrid tensioning system provides the capability of dynamically controlling the tension in the riser string. This feature opens a wide horizon of different active riser control strategies to achieve the systematic riser control solution. The objective of this study is to increase the predictability and safety of the whole riser system, and to extend the operability of the riser tensioning system into other operations. An overall structure framework of this novel hybrid riser tensioning system is proposed, comprising a direct driven electrical tensioners, hydro-pneumatic tensioners, a super-capacitor based energy storage system, power dissipaters, an overall tension controller and a power management controller. Hardware configurations are suggested. A riser data logging system is introduced, providing more comprehensive riser status data. A power management control strategy and overall coordination architecture to integrate the whole system are proposed. As the main functionality of the riser tensioning system, a new active heave compensation control strategy is analyzed in detail, by using this new riser hybrid tensioning system. A LQG controller and a H [subscript infinity symbol] controller are designed. The position chasing technique produces predictive and accurate tension commands for the electrical tensioners. Both Matlab simulation and hardware implementation confirm the feasibility of this concept, and further verifies that a more accurate control performance could be achieved by the electrical tensioners 180° compensating the tension fluctuation caused by the hydro-pneumatic tensioners. A novel testability and predictability enhanced anti-recoil control algorithm is implemented in the electrical tensioners. A position control strategy is proposed with the objective of moving the riser body to a desired elevation height in a predictive manner. A system model and a Kalman estimator are built, and a LQG controller is designed. The simulation demonstrates that the riser lifting height can adjust to any reasonable value for different test environment. This anti-recoil control concept reduces the risk of catastrophic damage, and allows us to perform maintenance tests much more frequently to bring back operator’s confidence. During harsh sea state, the VIV can be suppressed by using the dynamic control of the hybrid tensioning system, at frequencies and magnitudes made available by the electrical tensioning system. The objective is to achieve the VIV suppression by avoiding the excitation of the oscillation locking into the resonance conditions, and by reducing oscillation energy to be built in riser. A modal analysis of a tensioned Euler-Bernoulli beam is studied. Two control methods are proposed. Simulations results demonstrate that the oscillation is effectively reduced at the dominant lock-in frequency. Finally, this riser hybrid tensioning system opens the possibility to extend the tensioning system operability into other drilling operations. A motion stabilizer supporting the heave compensation of the drill pipes and the DST tools can be eliminated by connecting the drill pipes onto the telescopic joint. Another application would be that the electrical tensioners can run under position control mode after the riser is recoiled and soft hang-off on tensioners. The riser string position with respect to the seabed can still be controlled, during the vessel moving among different well heads.Electrical and Computer Engineerin

Installation of subsea equipment in ultra-deep water using fibre rope deployment system

Master's thesis in Offshore Technology: Marine and subsea technologyAs the demands for installation at deeper waters is increased, technology for such installations must be adapted to the conditions of the deep and ultra-deep water depths. This thesis provides information of such installations methods, including non-conventional installations methods. The main focus of the thesis is using fibre rope deployment system to deploy equipment at water depths up to 4000 m. The use of fibre rope instead of the traditional steel wire is popular due to the similar specific gravity to water, which makes the fibre rope naturally buoyant in water. This cancels the self-weight problem of the steel wire as hoist line. Due to the different properties of the fibre rope, a new and cutting-edge technology was developed by the industry for deployment using fibre rope. To investigate the possibilities of deploying equipment to water depths of 4000m, numerous simulations were conducted using the simulation program the SIMO. The results of the simulations show no significant problems using fibre rope to deploy various common subsea equipment. However, the positioning of the equipment is demonstrated to be a major challenge at thesesubmittedVersio

Improvisation of deepwater weight distributed steel catenary riser

Master's thesis in Offshore technology : subsea technologyNowadays, oil and gas sources are found in deeper water depths and in more hostile environments. This results in the need for more advance technologies. Riser system is a key element in providing safety. Riser failure results in spillage or pollution and could endanger lives. Hence, it is important to establish a high degree of reliability for riser design. Steel catenary risers (SCRs) have been a preferred riser solution for deep-water field developments due to its simple engineering concept, cost effective, flexibility in using different host platform and flexibility in geographical and environmental conditions. Flexible riser, on the other hand, is limited by technical and economical reasons when it comes to deep water field. Larger diameter is required in deep water to increase collapse resistance due to high hydrostatic pressure. Consequently, increase in cost and limit the option of host platform. Alternatively, Hybrid riser is a robust design for deepwater and harsh environments. It is insensitive to motion induced fatigue. However, hybrid riser is considered to be an expensive solution because it comprises a number of complex components (buoyancy can, riser bundle, flex joint, etc). A number of SCRs have been installed worldwide over the past years and more to come in the future oil and gas explorations. However, there is no SCR that has been installed in deepwater with harsh environments to date. It is mainly because SCRs in harsh environments experience a great challenge due to large motions from host platform such as semi-submersibles and FPSOs. Therefore, significant design effort is required to prove that the SCRs could safely withstand environmental loads in harsh environments and the effects of deep water. The study investigates the feasibility of 10 inch production SCR for Offshore Norway in a 1000m water depth with SCR attached to a semi-submersible vessel. Conventional SCR was analyzed and found difficulty in meeting strength design criteria at the touch down point (TDP) and at the riser hang off location. From previous industry work, the weight variation along the riser length has demonstrated a remarkable improvement to SCR response, particularly at TDP. This study concentrates on fundamental aspects related to improvement from conventional SCR to weight distributed SCR. A number of insightful sensitivity analyses were performed in order to understand the correlation between the peak response and some fundamental parameters such as displacement, velocity and acceleration. Feasibility enhancement of present weight distributed SCR concept was also studied to provide more applicable SCR configuration solution. The study addresses global design considerations including analysis of strength and fatigue. Deepwater SCR Installation scheme was also discussed. The study concludes that there is significant improvement in SCR response from conventional SCR to weight distributed SCR concept. It also proves that even though the design of SCR in harsh environments and deep water is technically challenging, innovative solutions can be developed

Development and assessment of electronic manual for well control and blowout containment

DEA ?? 63, Floating Vessel Blowout Control is a blowout containment study which was completed in 1990, and it did not include discussions about operations in the water depths we currently operate in. As offshore drilling is continuously moving into deeper and deeper waters, a need to further investigate well control and blowout containment in ultradeep water has arisen. This project describes the development and assessment of an electronic cross-reference tool for well control and blowout containment, with added focus on ultradeep water operations. The approach of this manual is fully electronic, thus being able to serve the needs of the engineer/driller with greater ease in both pre-planning and in a stressful onthe- job setting. The cross-reference is a manual for the state of the art in well control and blowout containment methodology. It provides easy-to-use topical organization by categories and subcategories, and aims at providing clear links between symptoms, causes, and solutions. Clear explanations to complicated issues are provided, and confirmation of applicable blowout intervention procedures, be it conventional or unconventional, are discussed. Human error and equipment failure are the causes of blowouts, and they are bound to happen in an ultradeep water environment. Well control events are harder to detect andhandle in ultradeep water, and quick reaction time is essential. After detection and shutin, the Driller??s method is the preferred circulation method in ultradeep water, due to its responsiveness and simplicity. In case kick handling is unsuccessful, contingency plans should be in place to handle a potential blowout. If a blowout does occur, and the blowing well does not self-kill through bridging, a dynamic kill through relief well intervention is likely to be necessary, as underwater intervention is difficult in ultradeep water. With new ultradeep water drilling technologies providing potential for increased performance, alternative well control methods might be necessary. Along with these new technologies follow new unfamiliar procedures, and proper education and training is essential

ESSE 2017. Proceedings of the International Conference on Environmental Science and Sustainable Energy

Environmental science is an interdisciplinary academic field that integrates physical-, biological-, and information sciences to study and solve environmental problems. ESSE - The International Conference on Environmental Science and Sustainable Energy provides a platform for experts, professionals, and researchers to share updated information and stimulate the communication with each other. In 2017 it was held in Suzhou, China June 23-25, 2017

Modelling and Optimization of Wave Energy Converters

Wave energy offers a promising renewable energy source. This guide presents numerical modelling and optimisation methods for the development of wave energy converter technologies, from principles to applications. It covers oscillating water column technologies, theoretical wave power absorption, heaving point absorbers in single and multi-mode degrees of freedom, and the relatively hitherto unexplored topic of wave energy harvesting farms. It can be used as a specialist student textbook as well as a reference book for the design of wave energy harvesting systems, across a broad range of disciplines, including renewable energy, marine engineering, infrastructure engineering, hydrodynamics, ocean science, and mechatronics engineering. The Open Access version of this book, available at https://www.routledge.com/ has been made available under a Creative Commons Attribution-Non Commercial-No Derivatives 4.0 license

Underwater Vehicles

For the latest twenty to thirty years, a significant number of AUVs has been created for the solving of wide spectrum of scientific and applied tasks of ocean development and research. For the short time period the AUVs have shown the efficiency at performance of complex search and inspection works and opened a number of new important applications. Initially the information about AUVs had mainly review-advertising character but now more attention is paid to practical achievements, problems and systems technologies. AUVs are losing their prototype status and have become a fully operational, reliable and effective tool and modern multi-purpose AUVs represent the new class of underwater robotic objects with inherent tasks and practical applications, particular features of technology, systems structure and functional properties