Offshore Gas Research Articles

Power-from-Shore Optioneering for Integration of Offshore Renewable Energy in Oil and Gas Production

Despite the widespread usage of high-voltage alternating current (HVAC) for the connection of offshore wind farms (OWF), its use to power-from-shore (PFS) offshore oil and gas (O&G) production sites is often not feasible. Its limitations for long-distance subsea transmission are usually found at 50–70 km from shore and might be even shorter when compared commercially to a direct-current (DC) alternative or conventional generation. Therefore, this research paper aims to address the standardization of offshore transmission with a particular focus on the high-voltage direct current (HVDC) alternative. While the distance is typically not a limiting factor when using DC, and the voltages used are rather standard, the concept of power envelopes can be quite useful in addressing the high variability of offshore site power requirements and setting a design baseline that would lead to improved lead time. In this article, a full back and front-end genetic optioneering model purposely built from the ground up in Python language is used to #1 define up to three DC power envelopes that would cater to most of the candidate’s requirements and #2 provide the lowest cost variance. The results will demonstrate that this can be achieved at a minor overall cost expense.

A predicting method for the mechanical property response of the marine riser based on the simulation and data-driven models

The accurate and real-time prediction of the mechanical property response for the safety assessment of the marine riser is necessary during offshore oil and gas production. However, a finite element simulation is time-consuming, which obstructs the real-time monitoring and evaluation of the marine riser. Therefore, to obtain the real-time mechanical response of the marine riser, a predicting method based on the simulation and data-driven models is proposed. To obtain the prediction data, the finite element simulation model under the typical working conditions is established by the Abaqus software, and then the sensitivity analysis of influence factors is conducted due to the varied working conditions. The orthogonal experimental method is used to select the typical working conditions of the marine riser, and the selection of the sensitive influence factors is ensured based on the typical working conditions, the range analysis, and the grey relational method. To obtain enough training data, the Latin hypercube sampling method is used to enlarge the data for the analysis process. To find a more reliable prediction algorithm, four typical single surrogate models, which are the polynomial response surface model, the radial basis model, the kriging model, and the support vector machine regression model, are selected to establish a predicting model library. Meanwhile, a combining surrogate model, including the average weight surrogate model and the adaptive weight surrogate model, is established based on the combining weight to further improve the predicting accuracy. As a result, an optimal surrogate model is selected from the above four single and two combining surrogate models based on four evaluation criteria including the mean absolute percentage error, the mean absolute error, the root mean square error, and the goodness of fit. The cases show that the optimal surrogate model has a highly rapid response, with average relative errors are 8.17%, 3.42%, and 11.40% for the maximum bending moment, the maximum equivalent stress, and the maximum lateral deformation, respectively. In the above study, the accurate and reliable prediction method of the mechanical property responses will provide a theoretical basis for ensuring the safety of the marine riser.

CHARACTERIZATIONS AND CLASSIFICATION OF FORMATION WATER PRODUCED IN OILFIELDS

Formation water known as oilfield wastewater, produced water, associated water and brine; which generated in great volumes in onshore and offshore oil and gas production. As more and more world major oilfields mature, more water begins to be produced from oil producers because of aquifer encroachment and/or water injection. The evaluated characteristics of offshore oilfield produced water in oilfields is very important for petroleum engineering industry from both upstream and downstream activities, as well as is essential for both environmental assessment and reservoir management. This study has been conducted on two oilfields namely Sarir and Nafora for oil producing wells to distinguish the characterizations of the produced water. Also, the water characteristics are investigated in five gathering centers in Sarir oilfield. The study included the analysis of sixty water samples to determine the physiochemical characterizations. The data obtained from the chemical analysis were used to classify formation water and to determine the environmental deposition using Sulin's system. The results revealed that the type of formation water in both two fields are belonging to CaCl2 type and deep marine environment. The Stiff diagrams of the studied formation water of Sarir field were constructed for five gathering centers and compared with different patterns of Stiff diagrams. Most of the studied water exhibits a similarity of these patterns, but some of them show slightly deviation, this may be attributed to the type of formation and the source of brine.

Methanol infrared spectral characteristics in offshore gas logging

Methanol infrared spectral characteristics in offshore gas logging. Methanol was found in the logging gases during offshore gas logging by infrared spectra. Logging gas spectra from over 300 offshore wells and 1,000 onshore wells were processed and analyzed, and methanol characteristics were prevalent in the offshore logging gases but not onshore logging gases. The spectra of instruments Alpha111829 and Alpha111834 are studied as examples. The methanol concentrations in some areas exceeded 1 vol%, seriously interfering with the other measurements of alkane gases. Moreover, there are rapid changes in the trends of methanol concentrations. It indicates that methanol does not originate from drilling fluid additives. The results of the correlation analysis show that there are no strong correlations between methanol and the other logging gas component concentrations. Therefore, methanol may be neither a judgmental indicator component gas for natural gas nor oil but a separate energy source. We believe methanol in the offshore logging gases originates from strata. The discovery and analysis of methanol in offshore logging gases are significant in atmospheric and marine environments, oil and gas exploration, geochemistry, and energy.

A review of the oceanographic structure and biological productivity in the southern Okhotsk Sea

The southern Okhotsk Sea is one of the best fishing grounds in Japan, and the biogeochemistry, primary productivity, and physical aspects of this region have been heavily researched. However, a comprehensive review of the literature has not been written since that by doctor Takatoshi Takizawa more than 40 years ago (1982). This review actualizes the share–ground knowledge of the influence of oceanographic conditions on the primary productivity of the area. This review includes topics from physical/chemical oceanography and hydrobiology, focusing on the complex oceanological structures that support the high primary productivity of the southern Okhotsk Sea. It is known that the formation of all water masses is ultimately a consequence of the seasonal interchange of the Soya Warm Current and the East Sakhalin Current. However, it was revealed that there may be over- or under-estimations in different material and heat fluxes among water masses, especially regarding the dense Soya Warm Current. Recent studies have investigated the formation mechanisms of different water masses using chemical tracers, particularly radionuclides. Although promising if properly combined with traditional techniques, more isotopes or compounds are required to derive further conclusions. In terms of biological aspects, the high seeding potential of Thalassiosira after sea ice melting has been featured by many authors, and it was considered as the reason for its highest abundance in spring. The total carbon mass flux, which is essential for scallop farming, is highest in April–June, normally 120–160 mg C m−2day−1. The total carbon mass flux is maximum (up to 1165 mg C m−2day−1) after the spring bloom peak, and the spring bloom is strongly linked to sea ice retreatment. It was identified that the routes of 134Cs towards the Intermediate Cold Water, the formation mechanism of the Cold Water Belt, and the solubilization process of sea ice-carried particulate Fe require further research. Three major potential threats were identified, including the appearance of alien toxic species, a decrease in sea ice production in the northern parts of the Okhotsk Sea, and offshore gas and oil drilling northeastern of the Sakhalin Island. Publicly available scientific knowledge about the biogeochemistry of the southern Okhotsk Sea and its relationship with its rich primary productivity was actualized to 2022, anticipating that this work will become the starting line for many early career scientists endeavoring in interdisciplinary studies.

Sand control screen selection for cased dual‐annulus gas offshore wells based on scaled laboratory tests

AbstractThis paper assessed and ranked several alternatives to control sand production in a well recompletion effort of offshore gas wells that have experienced massive sanding. The aim was to select an appropriate thru‐liner sand control system to increase well productivity. Four different screen types were evaluated, including a wire‐wrapped screen (WWS), slotted liner (SL), punched screen (PS), and a new multi‐layer open cell matrix polymer (OCMP) filter resembling gravel‐pack. The performance of screens regarding sand production and plugging was evaluated using a sand retention testing facility featuring a custom‐made device that mimics the unique well completion configuration. Further, a novel testing setup was constructed to assess the erosion potential of screens subject to high‐velocity gas and sand flow. All assessments were conducted under the representative actual well conditions. Laboratory tests indicate the superior performance of the OCMP filter compared to the other three options. Even though SL, WWS, and PS performed similarly in sanding, the WWS posed a higher erosion risk, with PS following in second place. The plugging tendency of the WWS was the least among all the options, whereas the PS had the highest tendency. Despite this, the WWS's sanding performance is expected to decline due to its vulnerability to erosion. Overall, the testing results indicated that the OCMP filter provides a promising solution to the issue of sand production in the gas wells being evaluated. However, the interaction of the OCMP filter with potential treatment chemicals in the wells should be tested before it can be used.

Experimental and Numerical Study for Gas Release and Dispersion on Offshore Platforms

Accidental gas release is a major triggering event for the offshore oil and gas industry. This paper focuses on the experimental and numerical investigation for dispersion behavior of released gas on offshore platforms. For this purpose, an experimental system is designed and developed to investigate gas release and dispersion. A series of experiments are carried out, among which the scenarios with constant leakage rates and time-varying leakage rates are both emphasized. The gas concentrations at different sampling points are obtained to study the dispersion behavior and accumulation characteristics of the released gas. Furthermore, a numerical computational fluid dynamics model is established to replicate the experimental scenarios. Good agreement between experimental data and CFD simulation results is observed by calculating a series of statistical performance measures. The developed numerical model is subsequently utilized to investigate a gas release scenario on a practical offshore platform, in which a fully transient leakage rate is adopted considering the response of process protection measures. The developed numerical model could provide support for risk assessment and optimization of contingency plans against gas release accidents in offshore facilities.

Full-scale resonant bending fatigue testing of casing joints under bending moment load

The quality and reliability of oil casings play a pivotal role in the safety and efficiency of offshore oil and gas exploration. This study conducted research on resonant bending fatigue of 9-5/8-inch casing joints and established a systematic theoretical model for resonant bending fatigue based on the Euler–Bernoulli beam equation. The relationships between parameters affected by frequency and mode shape functions were deduced and solved to analyze the influence of wall thicknesses, length and weights at both ends of the specimen on the natural frequency of the resonant bending fatigue system. A full-scale fatigue test was then designed and conducted to investigate the circumferential stress distribution, reveal the stress amplitude–frequency response characteristics of the specimen, and explore resonance response behaviors under different excitation forces. This was done to establish a method for evaluating the oil casing life and obtain fatigue life characteristic curves of the specimen. A finite element model was employed to analyze the internal stress distribution of the coupling under bending moment load, considering the influence of material properties, thread lead angle and non-linear contact on casing joints. Finally, the fatigue life algorithm was summarized and compared by integrating the stress simulation results with the material properties of the specimen, elucidating the fatigue damage evolution process of casing joints. This research provides a significant engineering reference value for structural design optimization, fatigue testing and life analysis of oil casing threaded joints.

Simulation and experimental study on liner collapse of lined composite pipe

With the application of lined composite pipe in the offshore oil and gas transportation system, the instability and collapse problems of its liner has been paid more and more attention. In this paper, A nonlinear finite element model of elastic-plastic instability of the confined liner of lined composite pipe is established. Considering the initial out-of-roundness (δ0/R) defect, the instability configuration and displacement equilibrium path of the liner before and after critical buckling are considered, the δ0/R defect sensitivity and the relationship between D/t ratio of the liner are analyzed. Finally, the finite element solution and analytical solution are verified by experimental data in this paper and experimental data reported elsewhere. It is concluded that δ0/R defect relative to 1 % will reduce the critical instability load value by about 65 %. The relative error between finite element calculation results of instability critical load and experiment test measured load is 1.82 %. The experimental results are in good agreement with the finite element calculation results. Thus it can be seen that by using the nonlinear finite element model of elastic-plastic instability of the confined liner model established in this paper, not only the critical unstable load of the confined steel liner can be accurately solved, but also the cost of experiment test can be greatly saved. It provides a theoretical basis for the buckling-restrained design of lined composite pipe.

An approximated dynamic programming model for the supply vessel fleet sizing problem

The offshore oil and gas exploration and production activities heavily rely on a fleet of supply vessels, which play a crucial role in regularly providing necessary provisions from an onshore supply depot to the offshore installations. For Petrobras, the decision-making process concerning the number of supply vessels to be hired for the upcoming two years holds significant economic implications, given that the daily rates for a single supply vessel can soar to tens of thousands of USDs.In this study, we address the challenges of this heterogeneous fleet sizing problem by presenting an innovative approximated dynamic programming (ADP) model. The model takes into account the uncertainties associated with sea conditions and future demand, making it well-suited for real-world applications. To tackle this problem, we explored two types of approximate value functions: a piecewise linear concave value function and a neural network value function. Both methods underwent rigorous testing and demonstrated their capability to effectively address real-world problems. Consequently, our proposed method exhibits promising potential for practical implementation, allowing companies like Petrobras to accurately assess and determine the ideal fleet composition. By introducing this ADP model, we aim to provide valuable insights and solutions that enhance decision-making processes related to supply vessel fleet sizing in offshore operations. Through considering various uncertainties and complexities, our approach offers a robust and reliable framework to support critical economic decisions in this dynamic industry.

Effect of sand production on physical properties and fracturing development of gas hydrate reservoir

Offshore gas hydrates are being focused on as an unconventional energy source. The susceptibility of marine hydrate reservoirs to sand emergence makes them unsuitable for long-term exploitation. This research delves into the particle-transport law in hydrate reservoirs, revealing that sand blockage hinders long-term exploitation, and proposes a reservoir modification strategy to establish high-permeability channels, thereby enhancing production. After 110 days of mining, the range of porosity and permeability below the initial value was approximately 8.5 m. The study further optimizes reservoir modification parameters under sand blockage, suggesting that a balance between fracture and reservoir blockage can be achieved with a fracture half-length of 20 m, leading to increased production. It also highlights that the slow decomposition of blocked hydrate and the accumulation of decomposed methane gas in the upper part of the reservoir can be leveraged to increase production by providing a high permeability channel for free gas, concluding that maintaining long-term high permeability is crucial for hydrate reservoir fractures.

Trajectory simulation of 3D-printed container models based on CFD

Subsea pipelines are a cost-effective and reliable way to transport hydrocarbons in offshore oil and gas development. However, dropped objects can pose a hazard and cause damage to the pipes. Among them, the container is a relatively common structure in maritime transportation, and its falling process is likely to cause potential danger. In this paper, computational fluid dynamics (CFD) is used to calculate the relevant hydrodynamic coefficients of the different container models at different drop angles. This study validates the CFD-derived results by comparing drop test results with CFD simulation results, including the total flow time, landing location, and number of spatial flips, etc. In addition, the consistency between the simulated added mass coefficient (Ca) & drag coefficient (Cd) and the reference values of DNV-RP-F107 (2010) also demonstrates the reliability and precision of the CFD technique. The results show that the agreement between CFD-simulated Ca and the values provided by DNV-RP-F107 (2010) as well as the theoretical values outlined by Clauss et al. (1992) validates the precision of CFD simulation.

A Fresh Look at the South Australian Onshore Otway Basin (Insights from Dem's Petroleum Systems Model Project)

The Otway Basin is one of the best known Mesozoic rift basins that span the southern coastline of Australia and has both on and offshore gas production and oil discoveries. 104 petroleum and 6 geothermal wells have drilled since the 1890s. In 1987 Katnook 1 discovered economic gas in the Penola Trough (the most significant hydrocarbon province in the SA part of the basin to date), further drilling led to more discoveries and construction of a processing plant.

Failure Mode And Effect Analysis On Risk Management At An Oil And Gas Survey Company In Indonesia

Asia is the second highest number of work accidents in the world after Africa. There are over 30% of major accidents experienced in the oil and gas industry triggered by inadequate maintenance. The fatal accidents in oil and gas accident increased from 2019 to 2022 in Indonesia. This qualitative study aims to analyze the risks that may occur in offshore oil and gas survey activities at Company X, an oil and gas survey company in Indonesia using Failure Mode and Effect Analysis (FMEA). Company X is a company that provides survey activities for oil and gas as the main service. Primary data are collected by interviewing the vessel manager, an Executive, and three employees involved in offshore oil and gas surveys. The FMEA steps are transcribing the answers, arranging them to make them easier to understand, providing a severity rating, setting the occurrence, detection rating, calculate the Risk Priority Number (RPN), prioritizing activities work that has highest RPN value, for determining long-term improvement strategies. The study reveals that the RPN for working accident turned out to be the highest from all risks which is 175 points, meaning that this risk has the highest ranking and need a mitigation as soon as possible. The recommended actions for this risk are regular maintenance for audits and inspections and upgrading FFA (Fire Fighting Appliances) and LSA (Life Saving Appliances) equipment.

Self-adaptive early warning of undesirable gas-liquid flow pattern in offshore oil and gas pipeline-riser system

It is an important function of submarine pipeline flow assurance system to monitor undesirable gas-liquid flow patterns in pipeline in real time, and release early warning ahead of the formation of these flow patterns. In order to tackle the problem of existing method that requires a large training set, and A method of self-adaptive early warning of transition to unstable regime is developed based on transient experiment of gas-liquid two-phase flow performed on a 150-m-long laboratorial pipeline-riser system. The responses of different differential pressure signals were investigated first, so as to pick out the optimum ones used for early warning. Then, the long-short time memory (LSTM) neural network combined with empirical mode decomposition (EMD) was adopted to judge transient condition. In the next step, a series of EMD-LSTM models were trained in order to predict whether undesirable flow pattern would occur, and the warning would be released if the result was ‘yes’. Within the range of experiments, all transient cases were correctly judged. The principles of proposed method were then tested and verified by data from a longer laboratorial pipeline-riser system and an offshore oil field, indicating good adaptability of the method.

Dynamic modeling and rotation control for flexible single-link underwater manipulator considering flowing water environment based on modified morison equation

Flexible single-link underwater manipulator (FSLUM) can be installed in autonomous underwater vehicles, it can carry out underwater tasks such as offshore oil and gas exploration, underwater cable maintenance as well as fishery farming and fishing. The design and development of the FSLUM are of great significance for ocean exploration and development. The FSLUM is affected by the underwater interference torque during underwater tasks in the flowing water environment, which will greatly affect the operational accuracy. In addition, many nonlinear factors such as the flexibility of the transmission system and the two-dimensional deformation of flexible links will aggravate the control difficulty of the FSLUM. An improved sliding mode control (SMC) strategy based on neural network identification is proposed to enhance the FSLUM's control accuracy. Neural networks are proposed to identify uncertain components including underwater interference and flexible nonlinear terms, so as to advance the control law design accuracy. Firstly, the FSLUM dynamic equations coupled with underwater interference torque considering multiple nonlinear factors are established according to the assumed mode method (AMM). A modified Morison equation is proposed to abbreviate the underwater interference torque in flowing water environments. Next, the control law of improved neural network sliding mode control (NNSMC) strategies are proposed according to the Lyapunov stability theorem, so as to ensure closed-loop stability of the FSLUM. Finally, the results of simulation and prototype tracking control experiments show that the improved NNSMC strategy has high tracking accuracy.

Assessing damage and predicting future risks: A study of the Schilling Titan 4 manipulator on work class ROVs in offshore oil and gas industry

This article undertakes a comprehensive investigation of the damage incurred by the Schilling-manufactured Titan 4 seven-function manipulator during the period of 2017–2022. This particular manipulator stands as the most widely employed equipment on work class remotely operated vehicles (ROVs) globally. The article delves into a detailed discussion of ROVs in general, with a specific focus on those belonging to the work class category. Furthermore, the manipulator is dissected into its constituent elements, as delineated by the manufacturer, and each individual component is subjected to separate evaluation. The damages that were encountered are described in detail, along with the corresponding repair processes.To quantify the likelihood of future damage to the various manipulator elements over the subsequent five-year period, the obtained damage results are inputted into the Geogebra program. This enables the calculation of the probability of damage occurrence for each individual component.The research findings are ultimately summarized and juxtaposed with the real-life experiences of ROV operators, which are captured through a meticulously designed questionnaire. The questionnaire is carefully constructed to elicit valuable insights from the operators regarding the most common faults or defects observed in the Titan 4 manipulator.It is important to note that this manipulator-focused investigation is based on the author's first-hand experience as a ROV Supervisor in the offshore oil and gas industry. The combination of practical expertise and the empirical data gathered from the questionnaire responses ensures a comprehensive and well-rounded examination of the Titan 4 manipulator and its associated operational challenges.

Exploring the grounds for cyber resilience in the hyper-connected oil and gas industry

This paper explores the offshore oil and gas industry as a case of an industry operating in demanding conditions with an imminent potential for catastrophic failure, undergoing major transformations driven by advances in digital technologies while being exposed to an increasingly aggressive threat landscape due to geopolitical changes. It is also a case of cyber-physical systems with tight couplings between digital changes which might be incited from virtually anywhere, and real-world, physical consequences. The exploration is aimed at understanding, based on interviews, to which extent the existing cyber security practices in the industry carries the potential to be strengthened by the application of resilience principles. An enhanced level of cyber security, denoted cyber resilience, is regarded as a crucial part for the industry to become able to close a strategic agility gap, in which they are at risk of falling behind in their response repertoire, becoming stuck and stale while trying keep up with an increasing rate of shocks through classical modelling and simulation. Resilience is, however, a concept with many meanings, originating from a diversity of academic discourses. The paper demonstrates the usefulness of analyzing the empirical data through an analytical framework of cyber resilience, a “resilience ABC”, accommodating a crucial distinction between robustness and resilience founded on adaptive capacities. Moreover, we find that closing the strategic agility gap requires a cyber resilience approach that is a mix of robustness and adaptive capacity, and that the gradual shift towards more emphasis on adaptive capacity requires a fundamental shift from seeing resilience-as-outcome as just an epiphenomenon of existing practice. In contrast, we see adaptive capacity as resilience-as-process, a phenomenon to study on its own terms. This also implies that cyber resilience management must move beyond a sheer assimilation with risk management. As access to real incident data may be limited, we also advocate the idea of training on scenarios at the boundaries of robustness.

A real-time drilling parameters optimization method for offshore large-scale cluster extended reach drilling based on intelligent optimization algorithm and machine learning

Offshore large-scale cluster extended reach wells (ERWs) are widely used to develop offshore oil & gas resources. Due to the complex downhole environments and complicated geological conditions, drilling parameters real-time optimization is challenging in offshore large-scale cluster ERWs drilling. In this paper, a real-time drilling parameters optimization method for offshore large-scale cluster extended reach drilling based on an intelligent optimization algorithm and machine learning (IOA-ML) is proposed. The method takes ROP as the objective function, establishes a ROP model based on long short-term memory (LSTM) neurons, and obtains drilling parameters optimization results asynchronously by combining the genetic algorithm, differential evolution algorithm, and particle swarm algorithm. The results show that ROP has been improved by 33.33% on average after the optimization by this real-time intelligent optimization method with an optimization time within 60s, which meets the requirements of real-time optimization of drilling parameters.

Sedimentary architecture and evolution of a Quaternary sand-rich submarine fan in the South China Sea

Investigating the sedimentary architecture and evolution of sand-rich submarine fans is vital for comprehending deep-water sedimentary processes and enhancing the success rate of hydrocarbon resource exploration. Recent drilling activities in the Qiongdongnan Basin, northern South China Sea, have unveiled significant gas hydrate and shallow gas potential. However, exploration in this area faces substantial challenges due to the limited understanding of sandy reservoirs. Leveraging extensive newly acquired extensive 3D seismic data (~9000 km2) and well data, our study reveals five distinct deep-water depositional systems in the Quaternary Ledong Formation, including a submarine fan system, mass transport deposits, deepwater channel-levee systems, slope fans, and hemipelagic sediments. Notably, the targeted sand-rich submarine fan lies within the abyssal plain, situated at a water depth of 1300-1700 m. This fan exhibits a unique tongue-shape configuration and a SW-NE flow direction within the plane and spans an expansive area of ~2800 km2 with maximum length and width reaching 140 km and 35 km, respectively. Vertically, the fan comprises five stages of distributary channel-lobe complexes, progressing from Unit 1 to Unit 5. Their distribution ranges steadily increase from Unit 1 to Unit 3, followed by a rapid decrease from Unit 4 to Unit 5. Our results suggest that the occurrence and evolution of the submarine fan are primarily controlled by sea level fluctuation, confined geomorphology, and sediment supply. Specifically, sea level fluctuation and sediment supply influenced the occurrence of the submarine fan. Concurrently, the confined geomorphology in the abyssal plain provided accumulation space for sediments and shaped the fan into its distinct tongue-like form. In contrast to the deepwater channels within the deepwater channel-levee systems, the distributary turbidite channels within the submarine fan are marked by lower erosion depth with “U” shapes, greater channel width, and higher ratios of width to depth. The comparative analysis identifies turbidite channels as the focal points for offshore gas hydrate and shallow gas exploration in the Qiongdongnan Basin. Furthermore, the temporal evolution of submarine fan offers valuable insights into Quaternary deep-water sedimentary processes and hydrocarbon exploration within shallow strata of marginal ocean basins.