Offshore Gas Research Articles

VFD-based Coordinated Centralized/decentralized Control to Support Offshore Electrical Power Systems with Wind Power Penetration

This paper proposes a coordinated centralized/decentralized control designed to concomitantly manage the power factor and mitigate voltage variations at the main feeder of an oil and gas offshore platform. The centralized action (i.e., power factor control) is decoupled from the decentralized one (i.e., voltage support) due to the significant disparity in dynamics of the commands sent to the active front-end variable frequency drives (AFE-VFDs). The AFE-VFDs are embedded with a proposed V-Q inverse droop curve, while being remotely coordinated by a central controller using a low-bandwidth communication link. Unlike other strategies, the proposed control is effective in handling unplanned events and unpredictable disturbances. Simulations are conducted to compare the proposed strategy with a literature solution considering a typical Brazilian floating production storage and offloading platform, from Mero Oil Field.

Technology Focus: Offshore Facilities (September 2024)

Offshore wind power involves generating electricity from wind farms located at sea. Because wind speeds are generally higher offshore than on land, these farms produce more electricity for the same amount of installed capacity. Both wind and solar energy are renewable and do not emit carbon, which helps reduce dependence on fossil fuels such as oil and gas. The papers synopsized in this year’s Offshore Facilities feature cover a breadth of related subjects that will be critical to the future of the industry. Automation in the offshore oil and gas industry makes production safer, faster, and more efficient. It reduces human error, improves quality control, and allows real-time monitoring of operations. Machine learning improves offshore industries by enhancing safety, efficiency, and sustainability It tracks and predicts environmental changes, such as oil spills or marine life patterns, aiding in better environmental management and response. Remotely operated vehicles are used in offshore operations to inspect, maintain, and repair underwater infrastructure; the offshore industry uses 3D video imaging technology to provide detailed real-time images of the underwater environment. Corrosion in offshore environments occurs because of factors such as seawater, sea salts, temperature, salinity, and moisture. It is crucial to monitor corrosion because it can lead to major structural failures. Hydrogen can be produced offshore using renewable energy sources such as wind and solar, which do not emit greenhouse gases and help combat climate change. Supply-chain logistics boost efficiency by cutting costs, removing unnecessary steps, and speeding up product delivery. An efficient supply chain can lead to higher revenue, lower operational costs, and better overall performance. Decommissioning is the final stage of an oil or gas project and involves significant technical, economic, social, and environmental challenges. It is a lengthy, costly, and complex process that must be carefully planned and managed to avoid serious problems. Several ideas have come to the surface that show innovative ways to repurpose a decommissioned platform or ways to cut the cost of decommissioning. Recommended additional reading at OnePetro: www.onepetro.org. SPE 217706 Dynamic Simulation of Riser-Gas Handling With a Fixed-Choke Constant Outflow by Zhaoguang Yuan, SLB, et al. OTC 35092 Reducing Carbon Footprint by Using Fiber-Reinforced Polymers in FPSOs by S. Eves, NOV, et al. OTC 35393 Challenges and Approaches to Solutions for Green Decommissioning and Recycling of Offshore Facilities by Carlos Alberto Machado, American Bureau of Shipping, et al.

Risk assessment of general FPSO supply system based on hybrid fuzzy fault tree and Bayesian network

One of the major risks to the operation of a FPSO (Floating, Production, Storage and Offloading) is collision of supply vessels. Experiences have shown that collisons of supply vessel take place frequently, although the consequences are limited. The offshore oil&gas industry has established relevant design standards and operational procedures, which are proven to be effective in reducing this risk. As the risk assessment becomes increasingly applied, there is a need to quantify the likelihood of supply vessel collisions especially duing the early design/project stage when historical incident data does not exist. This paper proposees a method for estimating the likelihood of supply vessel collision based on fault tree analysis (FTA), Bayesian network (BN), hybrid theory and fuzzy theory. In liew of using historicval data, this method combines the fuzzy logic with expert heuristics to determine the basic events(BEs). The triangular fuzzy membership functions and a hybrid theory were adopted to define factors that lack data or had no data in the events. To account for the imprecise information of human error, a scheme is devised to use the fuzzy fault probability(FFP) based on the hybrid theory, or a hybrid fuzzy fault tree analysis (HFFT). The algorithm transforms the FT into a BN with a conditional probability table (CPT). This new method was demonstrated in an example of a FPSO, and the results were has been validated through case studies and accident reports. A sensitivity analysis was also conducted to illustrate key parameters.

Strategic location model for oil spill response vessels (OSRVs) considering oil transportation and weather uncertainties

In the event of oil spills in offshore oil and gas projects, containment and dispersion equipment must be sent to the affected areas within a critical time by vessels known as oil spill response vessels (OSRVs). Here, we developed an optimization tool, integrated with an oil spill trajectory simulation model, both in deterministic and stochastic alternatives, to support decision-making during the strategic planning of OSRV operations. The tool was constructed in Python using GNOME for oil spill simulations and the GUROBI to solve the optimization model. The tool was applied to a case study in Brazil and afforded relevant recommendations. In terms of research contributions, we proved the viability of the integration between oil spill simulation and mathematical modeling for OSRV strategic operation planning, we explored the stochasticity of the problem with an innovative strategy and we demonstrated flexibility and easy applicability of the framework on real operations.

Design and hydrodynamic analysis of an automated polymer composite mattress deployment system for offshore oil and gas pipeline protection

The protection of offshore oil and gas pipelines has become increasingly important due to its application in maritime transportation. Currently there are few deployment devices for pipelines and their operation was complicated. Therefore, a novel automatic polymer composite mattress deployment system is designed in this study, and its hydrodynamic performance is analyzed based on computational fluid dynamics (CFD). Firstly, the conceptual design of the system is introduced. Then, modeling and simulation are carried out on the system, including its forward movement, lateral movement, and heave movement at various speeds. Significant surface pressure was brought to the system during forward and lateral movement by the open frame design, with the maximum pressure during lateral movement reaching 719.46 Pa. During the heave movement, the mattress blocks the water flow, causing negative pressure on the surface of the system. The huge flow separation generated significant drag, with a maximum value of 12620.3 N. However, the mattress avoids the impact of water flow on the system. The longitudinal length of the mattress means the Reynolds number is greater than the other movements. The proportion of pressure drag further increases, reaching a maximum of 98.7%. This research provides new perspectives and solutions for the protection technology of pipelines.

Effect of soil spatial variability on the stability of pipelines under horizontal loading

Submarine pipeline has been utilized more and more widely in offshore oil and gas transportation engineering. Given that these pipelines frequently subject horizontal loading during operation, thus precise predicting their horizontal bearing capacity is essential. However, most previous studies employ deterministic analysis without considering soil spatialvariability. This article introduces a two-dimensional (2D) random finite element analysis to study the horizontal pullout behaviour and failure mechanisms of a pipeline in a spatial variability soil. It is observed that the effect of soil spatial variability on the horizontal bearing capacity factor and failure mechanisms is remarkably substantial, with the distribution of the former showing a close approximation to a log-normal distribution. Furthermore, the average horizontal bearing capacity typically falls below the corresponding deterministic value. Consequently, the deterministic estimation of the horizontal bearing capacity tends to be inflated. Eventually, a reliability-based approach is formulated, where a factor of safety is incorporated to account for the uncertainties arising from spatial variability and ensure a sufficient safety margin. This methodology enables engineers to determine appropriate factor of safety tailored to the specific requirements of each project.

A novel casing-pipe type TMD for seismic control of free-spanning submarine pipelines: Shaking table tests and numerical simulations

Submarine pipelines are vital lifeline engineering structures for transporting offshore oil and gas resources, which may experience adverse vibrations against structural safe operation when encountering strong offshore earthquakes. This paper proposes an innovative casing-pipe type tuned mass damper (CPTMD) for the seismic control of free-spanning submarine pipelines (FSSPs). The design concept and control mechanism of the CPTMD are firstly presented. Both shaking table tests and numerical simulations are performed to examine the effectiveness of using the CPTMD to reduce seismic-induced vibration of FSSPs, through comparing structural seismic responses with and without damper device. In the experimental and numerical studies, the effect of seawater around submarine pipelines is simplified using the added hydrodynamic mass method. The experimental and numerical results consistently demonstrate that the proposed CPTMD has a good capacity for suppressing seismic-induced vibration of FSSPs. Moreover, the impacts of stiffness, damping coefficient, mass ratio and casing-pipe length on the seismic control effectiveness of the CPTMD device are investigated and discussed comprehensively, and the optimal values of these design parameters are determined. As a result, the proposed CPTMD could be an effective and simple solution for the vibration control of FSSPs induced by offshore seismic motions.

Analysis of Safety of Offshore Oil and Gas Facilities

Analysis of Safety of Offshore Oil and Gas Facilities

Evaluating the Impact of Environmental Factors on Corrosion Rates in Offshore Oil and Gas Pipelines: Insights from the Levantine Basin

The Levantine Basin is an important area for oil and gas exploration. However, the region's high salinity and corrosive conditions significantly threaten the durability of pipelines and equipment, resulting in substantial maintenance and repair expenses. This study seeks to evaluate the environmental and industrial influences on the corrosion rates of different oil and gas streams within the Levantine Basin. This study collected and analyzed data from the Levantine Basin, including physical and chemical properties of the streams, environmental factors such as temperature, pressure, and humidity. The Larkton corrosion software was utilized to simulate and predict corrosion rates under various conditions. Findings of this experiment demonstrate the significance of temperature on corrosion rates, showing a marked increase as temperatures rise. At lower temperatures, H₂S corrosion is more prominent, whereas CO₂ corrosion becomes the dominant factor at medium to high temperatures, especially when coupled with high CO₂ concentrations.

Haunted Sicilian Landscapes: Orazio Labbate Petrovisions and the Italian Energy Hubris

This paper explores the socio-environmental implications of energy extraction and production in Gela, Sicily. It examines narratives surrounding oil encounters and the manipulation of social and environmental consciousness by national energy companies. Two toxic narratives are examined: the formation of petrofictions and the use of myths and eco-efficiency rhetoric for greenwashing, drawing on environmental and energy humanities perspectives. Through a critical analysis of Orazio Labbate’s novel Suttaterra, the paper explores the trauma induced by encounters with oil and environmental conflicts documented in Sicilian landscapes. It also examines the manipulation of public perception by national energy companies through mythological storytelling, using the example of Eni’s offshore gas exploration project in Sicily. The paper points to the urgent need for a transition to sustainable energy practices and calls for greater environmental and energy justice in the region.

The development of bend clamp of carbon-based fiber offshore gas lift pipelines: A primary experimental approach

The work reports the proposed development of the laminated carbon fiber-reinforced polymer composites (CFRP), at a uniaxial angle as a primary bend clamp material assembly of the offshore gas lift pipelines. Generally, the clamps are utilized to repair the defect of the metallic pipelines due to their practical and mechanical strength. The existing bend clamp model poses challenges especially when applied to the J-tube bending side due to mechanical buckling and corrosion. This study evaluates the effect of laminated CFRP subjected to uniform uniaxial and in-plane compression on API 5 L X52. Several tests, including tensile, bend, and impact tests, are chosen to assess the effect of multiple and thick carbon layers to improve the clamp's mechanical properties. Scanning electronic microscope (SEM) intends to reveal the surface characterization of carbon fiber clamp. The result shows that laminated carbon fiber increases the durability and mechanical properties of the bend clamp for two weeks. The tensile test result shows that the uniaxial orientation has the highest tensile strength of about 2000N and is affected by the strong interfacial bond between the fiber and metal layers. The high impact energy of 2242 ± 0.001 J of the same orientation shows the stability of the clamp under unprecedented dynamic load and enhances the safety. The SEM result at uniaxial shows the resistance towards fracture has increased and was initiated from the air pocket in the composite.

Assessment of Initial Seismicity for Offshore Platforms on the Example of the Pechora Sea

Seismotectonic and seismoacoustic studies carried out during the expedition onboard the R/V ʺAkademik Boris Petrovʺ in the Pechora Sea revealed a paleoseismodislocation confined to a fault zone tracing the Severoural seismic lineament. The amplitude of this dislocation (the relative displacement of its sides) makes it possible to estimate the magnitude of the ancient earthquake that occurred within the Severoural lineament. Using the value of this magnitude, estimates were made of the maximum seismic impacts on offshore oil and gas facilities that are already in operation and are being designed for construction in the northeastern part of the Pechora Sea. These assessments of essential images differ in a big way from similar assessments made earlier. The method of searching for paleoseismic dislocations using seismoacoustic methods, as well as lineament analysis, can be used to assess the initial seismic impacts in water areas.

A Decoupled Buckling Failure Analysis of Buried Steel Pipeline Subjected to the Strike-Slip Fault

Over the past few years, there has been an increased focus on offshore pipeline safety due to the development of offshore oil and gas resources. Both onshore and offshore pipelines may face significant geological hazards resulting from active faults. Pre-excavated soil can be used as backfill for trenches to prevent major pipeline deformations. Since these backfill materials have been heavily remolded, they are softer than the native soil. Therefore, the difference in shear strength between the backfill and native ground may have an effect on the interaction between the pipeline and the backfill. In this paper, the pipeline–backfill–trench interaction is investigated using a hybrid beam–spring model. The P-Y curves obtained from CEL analysis are incorporated into a 3D beam–spring model to analyze the pipeline’s response to lateral strike-slip faults. Additionally, the nonlinearity of pipeline materials is considered to study pipeline failure modes under strike-slip fault movements. A series of parametric studies were conducted to explore the effects of fault intersection angle, pipe diameter, buried depth of the pipe, and soil conditions on the failure modes of buckling pipelines. The developed method can be used to analyze and assess pipeline–backfill–trench interaction when subjected to strike-slip fault displacements.

Temperature and pressure prediction of offshore high CO2-content associated gas lift and analysis of influencing factors

With the continuous injection of CO2 into the reservoir, a portion of the sequestered CO2 is co-produced with crude oil, resulting in a significant concentration of CO2 in the associated gas. Utilizing high CO2-content associated gas for offshore gas lift operations improves the reutilization of such gas and reduces costs related to sourcing and transporting it. To ensure smooth activation of the gas lift valve, conducting a thorough study on temperature and pressure within the wellbore during the gas lift process is essential. This study developed a dynamic model for calculating the transient temperature and pressure within offshore gas lift wellbores and fitted equations to calculate the physical properties of high CO2-content associated gas for specific compositions. This refinement minimized computational discrepancies arising from fluctuations in physical property parameters. When applying this model to oilfield scenarios, the maximum error observed was 3.83%, which aligned well with the accuracy standards required for oilfield computations. By integrating oilfield production data, this research explored the influence of injection parameters on temperature and pressure dynamics within the gas lift wellbore. The results revealed that variations in injection temperature and pressure had minimal impact on the temperature at the gas lift valve. Yet, they induced significant changes in the pressure at that point. An increase in CO2 concentration within the gas source composition was associated with considerable shifts in temperature and pressure gradients throughout the wellbore. At high mass flow rates, the temperature gradient of the wellbore was notably reduced, while the pressure gradient was significantly enhanced. These research findings provided a theoretical basis for optimizing gas lift operations using high CO2-content associated gas in offshore settings.

Buckle propagation failure of subsea pipelines; experimental, analytical, and numerical simulations

This research program investigates buckle propagation in subsea pipeline systems, The study aims to understand and predict propagation pressure (PP ), essential for ensuring the structural integrity and safe operation of these pipelines, hypothesizing that incorporating strain hardening effects into the strain energy approach can significantly enhance the prediction of propagation pressure (PP ) and that geometric parameters, particularly the diameter-to-thickness (D/t) ratio, play a major role in PP prediction. Accurate PP prediction is essential for ensuring the structural integrity and safe operation of these pipelines. The investigation is conducted through analytical, experimental, numerical, and machine learning approaches. A new analytical solution for PP is proposed, incorporating strain hardening effects using a strain energy approach. Experimental tests conducted using a hyperbaric chamber cover a wide range of pipeline configurations and materials, including steel, aluminum, and stainless steel. Complementing experimental data, numerical simulations using finite element methods facilitate parametric dependence analysis and the visualization of results through 3D charts. More than 600 FE models were simulated to investigate the influence of geometric and material parameters on PP . The findings from both experimental and numerical analyses indicated that the geometric and material properties have a significant impact on PP , specifically, the diameter-to-thickness (D/t) ratio, yield stress (σy ), and tangent modulus (E′). Furthermore, Machine Learning (ML) techniques have been used to predict the PP value and have concluded that the Random Forest (RF) technique outperformed the K-Nearest Neighbors (KNN), and Multi-layer Perceptron (MLP) neural network techniques. Overall, this study concludes that analytical, numerical, and machine learning approaches offer valuable insights into buckle propagation in subsea pipelines, contributing to improved safety and reliability in offshore oil and gas operations.

Effect of seawater salinity, pH, and temperature on external corrosion behavior and microhardness of offshore oil and gas pipeline: RSM modelling and optimization

This research aims to investigate the effects of seawater parameters like salinity, pH, and temperature on the external corrosion behaviour and microhardness of offshore oil and gas carbon steel pipes. The immersion tests were performed for 28 days following ASTM G-1 standards, simulating controlled artificial marine environments with varying pH levels, salinities, and temperatures. Besides, Field emission scanning electron microscopy (FESEM) analysis is performed to study the corrosion morphology. Additionally, a Vickers microhardness tester was used for microhardness analysis. The results revealed that an increase in salinity from 33.18 to 61.10 ppt can reduce the corrosion rate by 28%. In contrast, variations in seawater pH have a significant effect on corrosion rate, with a pH decrease from 8.50 to 7 causing a 42.54% increase in corrosion rate. However, the temperature of seawater was found to be the most prominent parameter, resulting in a 76.13% increase in corrosion rate and a 10.99% reduction in the microhardness of offshore pipelines. Moreover, the response surface methodology (RSM) modelling is used to determine the optimal seawater parameters for carbon steel pipes. Furthermore, the desirability factor for these parameters was 0.999, and the experimental validation displays a good agreement with predicted model values, with around 4.65% error for corrosion rate and 1.36% error for microhardness.

Advanced materials and deepwater asset life cycle management: A strategic approach for enhancing offshore oil and gas operations

Offshore oil and gas operations are inherently complex, requiring a strategic approach to asset life cycle management to ensure efficiency, safety, and environmental sustainability. This review explores the use of advanced materials in deepwater asset management, highlighting their role in enhancing operational performance and longevity. The review begins by discussing the challenges associated with deepwater operations, including harsh environmental conditions, high pressures, and corrosive fluids. These challenges necessitate the use of advanced materials that can withstand such conditions while maintaining structural integrity and operational efficiency. The review then outlines the strategic approach to asset life cycle management, emphasizing the importance of integrating advanced materials into design, construction, and maintenance processes. This approach includes the selection of materials based on their performance characteristics, compatibility with existing infrastructure, and cost-effectiveness. Furthermore, the review discusses the benefits of using advanced materials in deepwater asset management, including improved corrosion resistance, enhanced structural strength, and reduced maintenance requirements. These benefits translate into increased operational uptime, reduced downtime for repairs, and overall cost savings. Finally, the review concludes by highlighting the importance of collaboration between industry stakeholders, including operators, manufacturers, and research institutions, to drive innovation in advanced materials and deepwater asset management. By embracing a strategic approach and leveraging advanced materials, offshore oil and gas operations can achieve higher levels of efficiency, safety, and sustainability. Keywords: Advanced Materials, Deepwater Asset, Strategic Approach, Life Cycle Management, Oil and Gas Operations.

Unveiling Turbulent Flow Dynamics in Blind-Tee Pipelines: Enhancing Fluid Mixing in Subsea Pipeline Systems

Blind tees, as important junctions, are widely used in offshore oil and gas transportation systems to improve mixing flow conditions and measurement accuracies in curved pipes. Despite the significance of blind tees, their unsteady flow characteristics and mixing mechanisms in turbulent flow regimes are not clearly established. Therefore, in this study, Unsteady Reynolds-Averaged Navier–Stokes (URANS) simulations, coupled with Explicit Algebraic Reynolds Stress Model (EARSM), are employed to explore the complex turbulent flow characteristics within blind-tee pipes. Firstly, the statistical flow features are investigated based on the time-averaged results, and the swirl dissipation analysis reveals an intense dissipative process occurring within blind tees, surpassing conventional elbows in swirling intensity. Then, the instantaneous flow characteristics are investigated through time and frequency domain analysis, uncovering the oscillatory patterns and elucidating the mechanisms behind unsteady secondary flow motions. In a 2D-length blind tee, a nondimensional dominant frequency of oscillation (Stbt = 0.0361) is identified, highlighting the significant correlation between dominant frequencies inside and downstream of the plugged section, which emphasizes the critical role of the plugged structure in these unsteady motions. Finally, a power spectra analysis is conducted to explore the influence of blind-tee structures, indicating that the blind-tee length of lbt = 2D enhances the flow-mixing conditions by amplifying the oscillation intensities of secondary flow motions.

Gas Hydrate Plugging Mechanisms during Transient Shut–In/Restart Operation in Fully Dispersed Systems

Gas hydrate formation poses a significant challenge in offshore oil and gas production, particularly during cold restarts after extended shut–ins, which can lead to pipeline blockages. Although steady–state models have traditionally been used to predict hydrate formation under continuous production conditions, these models are often inadequate for transient operations due to issues like near–zero fluid flow shear affecting the viscosity calculations of hydrate slurries. This study introduces novel conceptual models for dispersed water–in–crude oil systems specifically designed for cold restart scenarios. The models are supported by direct observations and various experimental approaches, including bottle tests, rheometer measurements, micromechanical force apparatus, and rocking cell studies, which elucidate the underlying mechanisms of hydrate formation. Additionally, this work introduces a modeling approach to represent conceptual pictures, incorporating particle settling and yield stress, to determine whether the system will plug or not upon restart. Validation is provided through transient large–scale flowloop tests, confirming the plugging mechanisms outlined. This comprehensive approach offers insights into conditions that may safely prevent or potentially lead to blockages in the fully dispersed system during field restarts, thereby enhancing the understanding and management of gas hydrate risks in offshore oil and gas operations.

Short-term extreme response estimation methodology for marine umbilical cables with two configuration types

This study investigates the critical engineering problem of the short-term extreme responses of marine umbilical cables, which are essential components in offshore oil and gas operations. Umbilical cables play a pivotal role in connecting subsea systems to surface platforms, necessitating a safe design to withstand external loads. This study focused on two primary umbilical cable configuration types: deep-water catenary and shallow-water lazy wave. For each configuration type, 100 3-h dynamic numerical simulations were performed, with maximum values fitted by using the Gumbel distribution, and the most probable maximum (MPM) values were set as benchmark values. The average conditional exceedance rate (ACER) method and uncertainty-incorporated ACER method were applied to study the short-term extreme values of umbilical cable responses based on limited sample data. The predicted results have been compared with the MPM values, and the accuracy and uncertainty of different efficient extreme-value analysis methods are discussed. This study provides a comprehensive methodological framework for the reliability analysis and safety design of umbilical cables in marine engineering.