Large volumes of produced water are being discharged globally as byproducts of oil production. Commercial production chemicals are conventionally needed to avoid problems such as bacterial growth, pipe corrosion, and oil/water separation issues. These chemicals will partition between oil and water phases and may affect both treatment processes and the environmental impact when water is discharged to the ocean after treatment. Capillary zone electrophoresis is used to measure partitioning coefficients of oilfield chemicals when these are dissolved in the water phase and in contact with either octanol or crude oil. The technique is fast and, due to simplicity, could have merits as on-site assessment of the partition coefficient for direct assessment of the fate of chemicals. The method was first qualified by estimating partitioning coefficients of aliphatic carboxylic acids and chemicals with a molecular structure similar to those of some production chemicals. Subsequently, the coefficients were determined for two different commercial corrosion inhibitors and a biocide that are used in the oilfield as production chemicals. The results showed that the chemicals predominantly preferred to remain in the water phase after contact with either octanol or crude oil. The partitioning coefficients log(p) spanned between −0.36 and −1.68 in the case of water/octanol contact and between 2.68 and −1.41 in the case of water/crude oil contact. One of the corrosion inhibitors exhibited a significant difference in the partitioning depending on whether the organic phase was octanol or crude oil. The chemical had a preference for the water phase in the case of the former but a preference for the crude oil phase in the case of the latter. The result demonstrates that it makes it challenging to evaluate the use of partitioning coefficients for oilfield applications.
Objective: To promote the physical and mental health of employees in a maritime setting and provide knowledge and tools to assist seafarers in managing daily challenges.
Materials and methods: The intervention drew on a goal-based approach, including workshops, coaching,health checks, interviews, and questionnaires.
Results: A process evaluation was used to explore intervention challenges and barriers. Results show that an intervention at sea is complex and needs flexibility. Findings varied, and the main challenges were low participation in one group and lack of continuity due to Covid-19. Data showed a significant positive shift in how the crew rated perceived stress and a statistically significant increase in intake of salad, fish, and vegetarian food.
Conclusions: Workplace interventions in poor health status settings are complex, necessary, and possible, and management’s participation is crucial. Increased awareness was achieved. Learning outcomes: The results showed some positive changes, such as lower stress levels and more intake of salad, fish, and vegetarian food. Flexibility is important for workplace interventions. Work place interventions contribute to health and wellbeing with appropriate management support.
Floating breakwaters (FBs) are frequently used to protect marinas, fisheries, or other bodies of water subject to wave attacks of moderate intensity. New forms of FBs are frequently introduced and investigated in the literature as a consequence of technological advancements. In particular, a new possibility is offered by High-Density Polyethylene (HDPE) by extruding pipes of large diameters (e.g., 2.5 m in diameter) and with virtually no limit in length (hundreds of meters). By connecting two or three such pipes in a vertical layout, a novel low-cost floating breakwater with deep draft is devised. This note investigates numerically and experimentally the efficiency of this type of multi-cylindrical FBs in evaluating different geometries and aims at finding design guidelines. Due to the extraordinary length of the breakwater, the investigation is carried out in two dimensions. The 2D numerical model is based on the solution of the rigid body motion in the frequency domain, where the hydrodynamic forces are evaluated (thanks to a linear potential flow model), and the mooring forces do not include dynamic effects nor drag on the lines. The numerical predictions are compared to the results of a 1:10 scale experimental investigation. An atypical shape of the wave transmission (𝑘𝑡) curve is found, with a very low minimum in correspondence with the heave resonance frequency. The results essentially point out the influence of the position of the gravity center, the stiffness, and the mutual distance among cylinders on 𝑘𝑡.
Various sources of harmonic problems in large wind power plants (WPPs) and optimized harmonic mitigation methods are presented in this paper. The harmonic problems such as sources of harmonic emission and amplification as well as harmonic stability are identified. Also modern preventive and remedial harmonic mitigation methods in terms of passive and active filtering are described. It is shown that WPP components such as long HVAC cables and park transformers can introduce significant low-frequency resonances which can affect wind turbine control system operation and overall WPP stability as well as amplification of harmonic distortion. It is underlined that there is a potential in terms of active filtering in modern grid-side converters in e.g. wind turbines, STATCOMs or HVDC stations utilized in modern large WPPs. It is also emphasized that the grid-side converter controller should be characterized by sufficient harmonic/noise rejection and adjusted depending on WPPs to which it is connected.
Chalk reservoirs, due to their high porosity and very low permeability, represent one of the most interesting cases for engineering studies of carbonates. They exhibit complex fluid-rock interactions because of their reactive surfaces and dense porous medium. The reinjection of produced water is an attractive strategy for managing wastewater flow from oil wells. However, the complex composition of produced water, the reactive nature of carbonate rocks, and their low permeability create challenges related to permeability loss.
This study examines the stages of permeability change during core flooding experiments up to the point of complete clogging. A distinctive feature of this study is the presence of residual oil in the core samples, which simulates real reservoir conditions during produced water reinjection. The presence of residual oil is an additional factor influencing the change in core permeability, but there is no clear consensus in the research community on its impact on permeability during produced water injection.
All experiments were conducted in a core flooding system simulating well conditions in terms of pressure (170 bar) and temperature (70 ◦C). Produced water samples from the Dan field were used to replicate the chemical and thermodynamic processes occurring in a real well. The experiments identified three stages of permeability change: an initial increase in permeability (+12%), a period of pressure stabilization, and a subsequent decrease in permeability (− 8%) due to the formation of inorganic precipitates within the core channels.
The primary objective of the experiments is to investigate the relationship between permeability changes and the stages of reinjection, with a focus on the effects of residual oil. The study focuses on identifying the processes occurring up to the point of complete clogging, considering the impact of residual oil saturation in the chalk core samples. Image analysis using scanning electron microscopy, particle size measurement with a zeta-potential meter, and thermodynamic scale formation modeling with ScaleCERE software were employed to explain these processes.
Three stages of permeability change were identified during the injection of 200 pore volumes of produced water: increased permeability (+12%), pressure stabilization, and decreased permeability (− 8%). The positive influence of residual oil saturation on the filtration and storage properties of the reservoir was established, due to the mobilization of chalk core particles. Additionally, the theory of core channel clogging during the reinjection of formation water by the formation of inorganic precipitates within the channels was confirmed.
Understanding the causes of permeability reduction that occurred during the stage of permeability decrease enables the development of water purification methods specifically targeted at the causes of rock clogging. Predicting the process of injecting a mixture of produced and seawater will help in interpreting the data during disposal operations by injecting formation water into an injection well, and it will allow for the selection of effective measures to mitigate the impact on the reservoir.
A crucial component for unmanned underwater vehicles (UUVs), including remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs), are the thrusters, which, in addition, are sensitive to damage during operations in harsh environments. This paper presents a study on the impact of incipient faults on the performance of thruster propellers used in offshore operations. The study evaluates the reduction in propeller performance due to wear and tear under realistic working conditions. The study employs a combination of experimental data analysis and signal processing techniques, including fast Fourier transforms and harmonics analysis, to identify faults and assess their severity. The results show that worn propellers can be identified through 5th-order harmonics and rotational velocity changes. The paper concludes with a proposal for future research using a model-based approach to enhance fault detection capabilities further.
This study investigates the critical parameters necessary for evaluating large-scale renewable offshore energy hubs, based on insights from industry experts. Using a Multi-Criteria Decision Analysis methodology, the experts emphasized that, in their view, technical and economic parameters rank higher than environmental and societal considerations when evaluating large-scale renewable offshore projects, including green hydrogen production. Environmental and societal parameters should not be neglected, but they ought to be evaluated outside this assessment framework. This could refer to the environmental impact assessment already in use. These findings provide a foundation for evolving the traditional Triple Bottom Line theory into a Quadruple Bottom Line approach by incorporating technical parameters alongside economic, social, and environmental factors, while addressing the specific challenges of offshore energy hubs. Among all the parameters ranked across the four domains, the top 15 were exclusively techno-economic, with technical and economic scores averaging 4.5 and 4.3 out of 5, respectively. In contrast, societal and environmental scores averaged below 3.0. To ensure the successful deployment of offshore energy hubs, a stepwise approach is recommended to manage complexity, reduce risks, and support scalable solutions. This approach aims to align the needed industrial parameters with the demands of the energy transition.
Floating Power Plant (FPP) develops a hybrid floating wind and wave energy device. Pitching Wave Energy Converters (WECs) interact with the supporting structure, amplifying the motion of the WECs within the design wave frequency range. In this work we focus on the effect of the chamber geometry – without the WEC – in amplifying the waves inside the chamber. The simulations are carried out using two-phase Navier-Stokes simulations. We investigate the wave propagation and the interaction between waves and the fixed support structure. The simulations are compared to experimental tests performed in the wave basin at Aalborg University.
Physical wave basin tests with a focus on uncertainty estimation have been conducted on a sphere subjected to wave loads at Aalborg University as part of the effort of the OES Wave Energy Converters Modeling Verification and Validation (formerly, OES Task 10) working group to increase credibility of numerical modeling of WECs. The tests are referred to as the Kramer Sphere Cases, and the present note is dealing with wave excitation force tests on a fixed model. The present note is including details to facilitate CFD models which replicate the physical setup in detail.
Physical wave basin tests with a focus on uncertainty estimation have been conducted on a fixed sphere subjected to wave loads at Aalborg University as part of the effort of the OES Wave Energy Converters Modeling Verification and Validation (formerly, OES Task 10) working group to increase credibility of numerical modeling of WECs.
The present note defines an idealized test case formulated to accurately represent the physical tests in a simple way. The test case consists of a fixed, rigid sphere half submerged in water subjected to regular waves of three different levels of linearity. The objective of the present note is to allow for numerical tests of the idealized test case.