Offshore Units Research Articles

Cybersecurity risks of automated (and autonomous) offshore oil and gas units—the IMO cybersecurity rules framework

Abstract Automated and/or autonomous offshore platforms or units are becoming more important in the energy sector, whether they are being used for oil and gas extraction or for carbon storage purposes. Automation means that harsh working conditions and risks of personal injury to crew could be cut to virtually zero. Automation also provides significant cost savings and helps make less attractive oil and gas fields more economically viable to exploit. However, automation does come with its own set of challenges—the notable one being the cybersecurity threat. Any regulation or international standard dealing with the cybersecurity risk which is relevant to automated offshore units is usually framed within those rules that apply to ships. This article examines to what extent that regulatory approach, especially that of the International Maritime Organisation’s (IMO) regime, could and should apply to automated or autonomous offshore platforms. It argues that whilst, for now, the IMO cybersecurity guidelines are relevant, a more targeted regulatory approach is needed.

Probabilistic evaluation of dynamic positioning operability with a Quasi-Monte Carlo approach

During the design phase of an offshore unit, estimating the station-keeping capabilities of the dynamic positioning (DP) system is mandatory. This means, in conventional offshore applications, to determine the maximum sustainable wind speed as a function of the encounter heading, which the unit may counteract by employing the onboard actuators or mooring lines only. Besides the deterministic estimation of DP capability, it is possible to assess the operability of the DP system following a non-deterministic probabilistic process by employing the site-specific joint wind-wave distributions to model the environment. In such a case, the operability results from a Monte Carlo integration process. Here it is proposed to enhance the applicability of the probabilistic analysis of DP operability, investigating the application of a Quasi-Monte Carlo method. In this sense, the procedure uses quasi-random samplings following a Sobol sequence instead of employing random samples of the joint distributions. In this paper, the Quasi-Monte Carlo process is tested and compared on a reference ship, highlighting the improvements to the established probabilistic DP prediction concerning the number of calculations needed to estimate operability. The significant reduction of computational time makes the newly implemented method suitable for the early design stage applications.

Onshore–offshore correlation of central Lake Erie glacial deposits

Dive observations, echogram transects, core sampling, and a seismic profile revealed that the lake bed of north-central Lake Erie is an extensive terrace cut by storm waves and currents. The terrace is an erosional unconformity on which Late Wisconsinan (Port Bruce and Mackinaw) glacial units crop out. Beds of massive diamictons, and glaciolacustrine sediments containing parallel reflections, crop out alternately from west to east, resulting from an oscillatory ice retreat. These beds correlate with the Port Stanley Drift (Port Bruce phase) and Wentworth Drift (Mackinaw phase) exposed in nearby shore bluffs and onshore moraines. The Port Bruce glacier and earlier readvances formed ice tongues and ice shelves in the central basin. Diamicton layers, some with debris flows, constitute the Port Stanley Till (offshore units M and O). A glaciolacustrine unit N was deposited during Port Bruce glacier recessions. Glaciolacustrine unit P lies between Port Bruce unit O and the Mackinaw Wentworth Till, unit Q. A subsequent glaciolacustrine unit R overlaps unit Q. The onshore Galt and Moffat moraines, composed of Wentworth Till, correlate with ridges of the Norfolk moraine unit Q which extend across Lake Erie between the base of Long Point, Ontario, and Erie, Pennsylvania. The onshore Paris moraine appears to have been eroded on the wave-cut terrace and is evident offshore only near the south shore of Lake Erie. Laminated unit S, younger than unit R, occurs in the western part of central Erie basin, and correlates with overflow of Lake Algonquin from the Huron basin.

Offloading operation bivariate extreme response statistics for FPSO vessel

The Floating Production Storage and Offloading unit (FPSO) is an offshore unit producing and storing crude oil prior to tanker transport. An important design concern is an accurate prediction of risky dynamic hawser tensions during FPSO offloading operations. Bivariate extreme hawser tension contours are important for selecting proper design values. This paper employed the AQWA hydrodynamic software to analyze vessel hydrodynamic wave loads dynamic response, acting on FPSO vessels under realistic sea state conditions. This paper presents an efficient method for estimating FPSO bivariate response statistics based on numerical simulations validated by various experiments. The bivariate Average Conditional Exceedance Rate (ACER2D) method offers an accurate bivariate extreme value probability distribution and return period contours estimation, utilizing available data efficiently. The two-dimensional probability contours, corresponding to low probability return periods, are easily obtained by the ACER2D method. The performance of the presented method has shown that the ACER2D method provides an efficient and accurate prediction of extreme return period contours. The suggested approach may be used for FPSO vessel design, minimizing potential FPSO hawser damage. Bivariate contours yield bivariate design points, as opposed to a pair of uncoupled univariate design points with the same return period as currently adopted in the industry.

Schedule robustness in the periodic supply vessels planning problem with stochastic demand and travel time

AbstractThe periodic supply vessel planning problem (PSVPP) consists in determining a periodic schedule and the respective fleet composition for servicing offshore units on a regular basis. One of the challenges for the PSVPP is determining reliable schedules with a good compromise between reliability and cost. This work extends the PSVPP by including stochastic demand and travel time. We also introduce a novel methodology based on a voyage‐based model to deal with the schedule robustness. Basically, key statistical parameters related to the routes' demand and execution time are generated. They are used together with a set of probability combinations to incorporate the schedule reliability into the optimization model. Therefore, schedule reliability is an input parameter in the optimization model. The instances used in the study are based on real data from Brazil. A comparison of the new methodology to conventional approaches is presented, and a Monte Carlo simulation is used to evaluate the quality of the solutions. The proposed methodology is able to generate robust schedules at a lower cost compared to the conventional approaches. The proposed methodology might be applied to other stochastic problems, where schedule reliability is a key parameter for the problem.

OPTIMAL ALLOCATION OF FLEET OF HELICOPTERS AND AIRPORTS TO TRANSPORT PASSENGERS IN OFFSHORE MARITIME UNITS

The choice and distribution of the optimal fleet mix of helicopters to service the offshore air operation is an important logistical problem that has a potential to reduce costs considered in the oil and gas industry. The variability of helicopter models and sizes, as well as the possible operational restrictions of airport bases and airspace, requires that adequate numerical techniques of Operational Research are applied. In this context, this work develops a model to determine the trajectories and distances traveled between airport bases and offshore maritime units and vice-versa, through an airspace modeled by a directed graph. Also develop a helicopter performance model to obtain the estimated payload and flight times for each specified mission and last but not least an integer linear programming model to allocate an optimal fleet and airport mix for passenger transport through the use of different helicopter sizes. The model was applied to offshore units operating in the Santos basin due to their strategic importance in the oil and gas industry. The results obtained included a map of preferred regions for two different helicopter sizes (large and medium), the weekly flight tables showing the allocation of helicopters and airport for different demand scenarios, additionally the impact of fuel prices on different airport bases and the concentration of movements on air routes are also evaluated in order to complement the analysis.

Evaluation of residual strength of polymeric yarns subjected to previous impact loads

The discovery of oil fields in deep and ultra-deep waters provided an opportunity to evaluate the use of synthetic ropes, complementarily or alternatively to traditional steel-based mooring lines in offshore units, mainly because of the former’s lower specific weight. Considering the series of complex dynamic-mechanical mainly axial loads to which these structures may be subjected, originated from different sources, such as wind, water current, tide, etc., there may be cases when at least one of these lines may possibly face an abrupt, shock-like axial load of considerably larger magnitude. The goal of the present study is to evaluate the residual tensile strength of three different synthetic yarns (polyester, and two grades of high modulus polyethylene) after exposure to such axial impact loads. It was observed that, for the tested materials, polyester is the one with the largest impact resistance to the conditions evaluated herein, mainly because of its comparatively greater energy absorption properties.

Abatement of GHG emissions onboard mobile offshore units

The International Maritime Organisation (IMO) is setting clear and ambitious goals for the decarbonisation of the shipping industry through the introduction of new regulations like the Energy Efficiency Design Index (EEDI), Energy Efficiency Existing Ship Index (EEXI) and Carbon Intensity Indicator (CII). However, these new regulations do not cover mobile offshore units like the Floating Production Storage and Offloading (FPSO) units that fall under the same maritime regime. To embrace sustainability in their corporate strategies and improve their public image, it is in the interest of existing oil and gas companies and operators to embark on a program of abating Greenhouse Gas (GHG) emissions through careful measurement and analysis. This paper is aimed at providing an overview of the typical FPSO’s GHG emissions that originates from sources such as power generation, flaring, leakages and tank venting. The paper goes in-depth concerning some potential abatement measures that can be taken to reduce such emissions. This is followed by a case study of an FPSO assessed for the voluntary DNV class notation, Abate, to discuss how a competent third-party like DNV can play a significant role in helping offshore oil and gas companies demonstrate and achieve abatement in GHG emissions from their assets.

Applicability of Machine Learning for Vessel Dimension Survey with a Minimum Number of Common Points

This paper presents the challenges encountered in the dimensional control of ships, platforms, and offshore units. This novel approach utilizes machine learning (MLP—Multilayer Perceptron Neural Network) for three-dimensional (3D) spatial coordinate transformations when only three common points are known. The proposed method was verified based on laboratory and field data. The main issue was to provide a sufficient number of valid training points. The oversampling method was used to meet this criterion. The achieved results indicate equal or better accuracy when the points were located inside the adjustment points array. In the case where the points lay outside this array, no improvement in the accuracy of the transformation was observed. The neural approach restores the transformation symmetry, and in some cases, such as the study of deformation of engineering objects, breaks the symmetry rather than restoring it.

Analysing the interactions and complexities of the operations in the production area of an FPSO platform using the functional resonance analysis method (FRAM)

The technological evolution of several productive sectors of society has demanded the same level of evolution for the oil and gas industry, both for energy production and their own systems’ functioning. The production of crude oil and natural gas in offshore units is one of the answers to this demand. However, these offshore units have critical onboard activities and risks, notably FPSO units; it is necessary to have adequate recognition of the elements that can support these activities and manage these risks, enabling productive and safe operations. In this sense, this article aims to increase the understanding of the complex interactions and inherent safety issues that arise in the operations of FPSOs, observing and analysing the work done onboard such platforms. The FRAM methodology has been chosen because it allows for the recognition and analysis of the complex interactions involving workers, equipment, system and offshore environment, focusing on the oil treatment area of the process plant. The results demonstrated some interesting findings regarding onboard safety and the relationship between human competences, work demands and process safety.

THE CLASSIFICATION OF PIPE-LAY VESSELS AND HEAVY-LIFT CRANE VESSELS

Pipe-lay vessels, heavy-lift crane vessels and dual purpose heavy-lift and pipe-lay vessels are distinct in many ways from other types of ships or offshore units. The unique functions that these vessels carry out can impact directly on the overall safety of the vessel, the personnel on-board and the potential to pollute the environment. This paper outlines some of the hull and machinery safety assurance considerations for classification and design pertinent to pipe-lay and heavy-lift operations. The considerations that are discussed in this paper include the implications of classing the vessel as a ship or an offshore unit; the interaction between classification and marine warranty; general arrangement; station-keeping; structural assessment and the interaction between safety critical systems. Specific hazards for pipe-lay vessels and their use of chemicals on-board are also discussed.

Modeling of spiral wound membranes for gas separations. Part III: A nonisothermal 2D permeation model

In the present study, a previously proposed mathematical model is improved with inclusion of the energy balance, considering the Joule–Thomson effect and the heat exchange between the retentate and permeate streams, in order to explain the temperature effects observed in actual industrial sites, which requires attention to potential problems and failures, such as gas condensation that damages the dense polymeric membrane, reducing separation efficiency. The proposed model was validated with real industrial data and was able to represent the phenomena at different operation conditions, as characterized through extensive sensitivity analyses. In order to do this, a methodology for data acquisition, pre-treatment, characterization, and data reconciliation was employed. Also, an algorithm based on Oriented-Object Programming (OOP) was proposed and implemented to simulate the real membrane separation offshore unit, considering the different configuration levels of the membrane separation setup for the first time: trains, banks, tubes, elements, and leaves. It is shown that the proposed model constitutes a promising tool for design of membrane separation equipment at industrial scale, thanks to its flexibility, model robustness, and the efficiency of the numerical method, which allows the full mapping of dew points on the membrane leaf, which can be used to prevent undesired swelling and ageing of the membrane material.

How does subsea processing safety policy impact safety? Lessons learned from the Brazilian experience

This paper is about the influence of safety regulations on the way major accidents are identified and managed. A case study is presented based on the Brazilian experience in subsea processing units. The oil and gas industry is devoting increased interest to subsea processing due to the limitation of easily accessible oil and gas reservoirs. There are more than 48 units already installed in Brazil. Most of the safety requirements in Brazil's E&P policy are based on offshore units. However, for subsea structures, there are different risks, environments, and operational conditions. In 2015, Brazil presented a safety regulation named SGSS (Technical Regulation of Operational Safety Management System of Subsea System). This regulation explicitly addresses risers and introduces only general safety requirements to other subsea installations and equipment. Thus, this paper assesses the Brazilian subsea safety regulation and the results of this policy implementation through the Brazilian Petroleum Regulator (ANP) inspections and incident communications. The example demonstrates the inefficiency of the policy to promote safety. This paper then proposes simplifying regulations, introducing new technology requirements, and a technical committee to improve safety to subsea equipment.

Novel propane-free mixed refrigerant integrated with nitrogen expansion natural gas liquefaction process for offshore units

The presence of propane inventory in offshore liquefaction processes increases the concerns for platform safety. To address this, we propose a novel liquefaction process that integrates propane-free mixed refrigerant and nitrogen expander cycles (MR-N2). The proposed design adopts the advantages of both nitrogen expander and single mixed refrigerant (SMR) processes. The process was rigorously simulated using Aspen HYSYS, and the specific energy consumption was optimized as an objective function using the genetic algorithm technique. Additionally, the MR-N2 process was investigated using exergy and sensitivity analyses to compare the obtained results with those of the previous studies. The results verify that both liquefaction and exergy efficiencies are improved by 27.15% and 14.92%, respectively, in comparison with those of the base case. Moreover, the MR-N2 process exhibits enhanced energy efficiency compared to that of the various existing nitrogen expander-based processes. The energy savings of the proposed method varies between 3.2% and 61.7%, and the cycle capacity is 22.43% better than that of the SMR process.

Sensitivity analysis in the transient recovery voltage in an industrial power system✰

Transient Recovery Voltage (TRV) is one of the electromagnetic studies which shall be carried out to verify if the circuit breakers can withstand the transients imposed by the electrical system. Normally, the transient studies are performed only at the final phases of the electrical system design and if a problem exists mitigation measures shall be taken. In some cases, these measures imply in more costs and physical space in the electrical substations. In offshore units, the weight and space intended to be used are limited and if mitigation measures are necessary, it is important to know them as soon as possible. Therefore, this paper aims at verifying the influence of certain parameters on the transient recovery voltage of an industrial offshore electrical power system. Simulations are performed in a typical offshore installation and the effects on the different voltage levels (13.8 kV and 4.16 kV) are analysed. The results are intended to give a first approximation of the main parameters that affect the peak and rate of rise of the transient recovery voltage during the initial phases of the electrical system design.

Exact and heuristic algorithms for the fleet composition and periodic routing problem of offshore supply vessels with berth allocation decisions

This paper presents a branch-and-cut algorithm and an adaptive large neighborhood search (ALNS) heuristic for the periodic supply vessel planning problem (PSVPP) arising in the upstream offshore petroleum logistics chain. Platform supply vessels support the offshore oil and gas exploration and production activities by transporting all the necessary material and equipment back and forth between offshore units and an onshore supply base according to a delivery schedule. The PSVPP consists of solving a periodic vehicle routing problem and simultaneously determining an optimal fleet size and mix of heterogeneous offshore supply vessels, their weekly routes and schedules for servicing the offshore oil and gas installations, and the berth allocations at the supply base. The branch-and-cut algorithm considers a reduced formulation for the problem which performs much better than the complete one, and easily finds optimal solutions for the smaller and most of the clustered instances. The ALNS heuristic contains new features which include multiple starts and spaced local searches. These algorithms were tested on instances with up to 79 offshore units, providing better results than the best available.

Mud-Gas Breakthrough Equinor Develops Real-Time Reservoir-Fluid Identification

For all that logging-while-drilling has provided since its wide-spread adoption in the 1980s, there is one thing on the industry’s wish list that it could never offer: an accurate way to tell the difference between oil and gas. A new technology created by petrotechnicals at Equinor, however, has made this possible. The innovation could be thought of as a pseudo-log, but Equinor is describing it as a reservoir-fluid-identification system. Using an internally developed machine-learning model, it compares a database of more than 4,000 reservoir samples against the real-time analysis of the mud gas that flows up a well as it is drilled. Crunched out of the technology’s various hardware and software components is a prediction on the gas/oil ratio (GOR) that the rock being drilled through will have once it is producing. Since this happens in real time, it boils down to an alert system for when drillers are tapping into uneconomic pay zones. “This is something people have tried to do for 30 years - using partial information to predict entire oil and gas properties,” said Tao Yang. He added that “the data acquisition is rather cheap compared with all the downhole tools, and it doesn’t cost you rig time,” highlighting that the mud-gas analyzer critical to the process sits on a rig or platform without interfering with drilling operations. Yang is a reservoir technology specialist at Equinor and one of the authors of a technical paper (SPE 201323) about the new digital technology that was presented at the SPE Annual Technical Conference and Exhibition in October. He and his colleagues spent more than 3 years building the system which began in the Norwegian oil company’s Houston office as a project to improve pressure/volume/temperature (PVT) analysis in tight-oil wells in North America. It has since found a home in the company’s much larger offshore business unit in Stavanger. Offshore projects designed around certain oil-production targets can face harsh realities when they end up producing more associated gas than expected. It is the difference between drilling an underperforming well full of headaches and one that will pay out hundreds of millions of dollars over its lifetime. By introducing real-time fluid identification, Equinor is trying to enforce a new control on that risk by giving drillers the information they need to pull the bit back and start drilling a side-track deeper into the formation where the odds are better of finding higher proportions of oil or condensates. At the conference, Yang shared details about some of the first field implementations, saying that in most cases the GOR predictions made by the fluid-identification system were confirmed by traditional PVT analysis from the trial wells. Unlike other advancements made on this front, he also said the new approach is the first of its kind to combine such a large database of PVT data with a machine-learning model “that is common to any well.” That means “we do not need to know where this well is located” to make a GOR prediction, said Yang.

Dynamic Response of Drill Floor Considering Propagation of Blast Pressure Subsequent to Blowout

Explosions and fire have very critical safety hazard impacts on offshore oil and gas facilities since they are mostly located in remote areas and could induce serious environmental issues. Explosion risk assessment and structure blast analysis are essential for these production facilities, and research studies have been carried out. Explosion due to blowout during drilling operation is also a critical risk for drilling units, and this has not been researched much until the accident of the drilling unit in the Gulf of Mexico in 2010. This paper provides the risk and evaluation of explosion and structure under blast pressure during the drilling operation, whereas previous research studies have mainly been interested in process plants. This study suggests weight saving in drilling units through the consideration of the actual behavior of gas explosion. Weight saving is the priority of offshore unit design due to payload. This research also gives guidelines to select the material-grade-appropriate anti-explosion system through the comparison of several materials by design and result.

Molecular sieve change-out strategy to avoid production losses in offshore units

Molecular sieve change-out strategy to avoid production losses in offshore units

The assessment of impact damage caused by dropped objects on floating offshore structures

Offshore facilities are exposed to the risk of accidental damages caused by fire, explosion, dropped objects, extreme environmental events and vessel collision poses a big threat to the safety and operation. During any lifting work, either from a supply vessel to the installation or from within the installation or plant itself, there is a potential danger when objects are being lifted for a dropped object accident to take place. This paper introduces extensive dropped object analyses applied in the design of Floating Production Storage Offloading (FPSO) offshore units, where non-linear finite element analyses are performed using an explicit LS-DYNA tool. In the structural evaluation, the hull parts such as infill deck, galley, and main lay-down located on poop deck, and cargo deck are taken into account. The dropped objects study is to find out what happens to the FPSO hull structure if the heavy items are dropped. The drop object impact analyses show that even though some structural members were permanently deformed by drop loads, however, there was no failure taken place in accordance with the plastic strain criteria as per NORSOK Code. It is discovered that the pillars supporting the main lay-down area have not been suffered from buckling failure through examined reaction forces. Further, the impact resistance of a deck depends on the plate thickness and the size and spacing of the supporting stringers.