Showing papers on "Submarine pipeline published in 2023"

Potential impact of offshore human activities on gray whales (Eschrichtius robustus)

Abstract: Gray whale (Eschrichtius robustus) reactions to offshore human activities have been relatively well studied compared to those of other mysticetes. Studies of short-term behavioural responses to underwater noise associated with aircraft, ships and seismic explorations indicate a 0.5 probability that whales will respond to continuous broadband noise when sound levels exceed ca 120dB2 and to intermittent noise when levels exceed ca 170dB, usually by changing their swimming course to avoid the source. Gray whales were ‘startled’ at the sudden onset of noise during playback studies, but demonstrated a flexibility in swimming and calling behaviour that may allow them to circumvent increased noise levels. Whales may be ‘harassed’ by noise from large commercial vessels, especially in shipping lanes or near busy ports. Gray whales sometimes change course and alter their swimming speed and respiratory patterns when followed by whalewatching boats. Conversely, some whales swim toward small skiffs deployed from whalewatching boats in breeding lagoons, seemingly attracted by the noise of idling outboard engines. Reported gray whale reactions to aircraft are varied and seem related to ongoing whale behaviour and aircraft altitude. Whale response to research involving tagging and biopsy sampling appears to be short term. Gray whales were seen swimming through surface oil from the Exxon Valdez oil spill along the Alaskan coast and showed only partial avoidance to natural oil seeps off the California coast. Laboratory tests suggest that gray whale baleen, and possibly skin, may be resistant to damage by oil, but spilled oil or oil dispersant in a primary feeding area could negatively affect gray whales by contaminating benthic prey. Gray whales are sometimes injured or killed in collisions with vessels or entanglement in fishing gear. Concern about the cumulative long-term impact of offshore human activities is particularly acute in the Southern California Bight, where many activities are often concurrent.

Comparison of the offshore distribution of southbound migrating gray whales from aerial survey data collected off Granite Canyon, California, 1979-96

Abstract: Aerial surveys provide an assessment of the offshore distribution of gray whales and an estimate of the proportion of whales that migrate beyond the visual range of shore-based observers. Six surveys were conducted concurrent with shore-based surveys during 1979, 1980, 1988, 1993, 1994 and 1996. Annual differences were tested for in the distribution of whales within an area 3 n.miles north and south of Granite Canyon, and it was found that the distributions within 3 n.miles of the shore differed by year but the shifts in the distribution were minor ( < 0.3 n.miles). The inshore ( < 2.25 n.miles) and offshore ( > 2.25 n.miles) distribution of gray whale pods did not differ significantly between survey years. An average of 4.76% (SE = 0.85%) of the whale pods were observed beyond 2.25 n.miles and only 1.28% (SE = 0.07%) beyond 3 n.miles.

Trends in dolphin abundance estimated from fisheries data: A cautionary note

Abstract: The previously published index of relative abundance of the northeastern offshore stock of spotted dolphins, the species most affected by the purse-seine fishery for tunas in the eastern Pacific Ocean, shows a decreasing trend in the last two decades despite dramatic reductions in incidental mortality since the early 1970s. To better understand the behaviour of this index, the effects of changes in data quality and methods of searching on estimation of relative abundance using current methodologies have been studied here. Changes in data quality since the late 1980s have led to a dramatic reduction in the proportion of sightings that are reported on or near the trackline. The decreasing trend in the index in the late 1970s and through the 1980s is strongly influenced by the fit of the detection function to the high proportion of sightings near the trackline that was present in the data during that time period. If this excess of sightings near the trackline is spurious, then much of the decreasing trend in the index over this time period is likely spurious. In addition, part of the decrease in the index in the late 1980s to mid-1990s is probably due to changes in data-collection biases that result from a dramatic increase in the amount of searching that is currently being carried out using helicopters as compared to high-powered binoculars. The results suggest that trends in bias associated with changes in data quality and fishery operations may have contributed to a trend in the index on the order of 1.0-1.5% per year, or approximately 25-33% of the maximum growth rate of the northeastern stock of offshore spotted dolphin. The pervasive nature of these sources of bias, and their potential magnitude relative to the maximum growth rates of the dolphin species involved, make use of this index in population growth models ill-advised. Fishery-derived indices such as these may be most useful for comparing trends in relative abundance between species, when the sources of biases are unlikely to be species-specific.

An inventory and evaluation of unmanned aerial systems for offshore surveys of marine mammals

Abstract: A literature review, internet searches and communications with personnel working with unmanned aerial systems (UAS) were used to identify the capabilities of UAS throughout the world. We assessed their ability to replace manned aerial surveys for marine mammals, sea turtles and seabirds and to monitor, in real time, sea ice and other physical features that might influence marine mammal distribution. The vast majority of the systems identified were either too expensive or their capabilities did not meet minimum standards necessary to perform the tasks required of them in real time. Eight systems were identified that might be able to perform some of the desired tasks. Several other systems had similar capabilities but had not been tested or would require upgrades. Installation of high-definition (HD) video and better stabilisation systems would improve UAS performance. It is recommended that development of HD video with real-time data transmission and improved stabilisation systems for UAS be pursued and that side-by-side comparisons of a few of the best systems be conducted.

Drill Cuttings Disposal Efficiency in Offshore Oil Drilling

Abstract: The relevance of the study lies in the fact that with the depletion of conventional oil and gas reserves and an increase in the global demand for hydrocarbons, the focus of the industrial sector is gradually shifting towards the resources of the Arctic, which have tremendous potential for development. However, the current industrial policy has to take into account the concept of sustainable development, or harmony between economy, ecology, and society. Therefore, the extraction of raw materials must obey the principles of the circular economy, which aims to generate closed-loop cycles that maximize the use of the resources extracted and minimize waste generation so as not to destroy fragile ecosystems. It is necessary to drill wells for the discovery of a hydrocarbon deposit on the shelf, which entails the generation of a tremendous amount of complex waste., The use of disposal methods for drilling cuttings, which must be disposed of economically and with environmental reliability, is required to solve the problem. This study compares two methods of disposing of drilling waste. Statistical modeling results and a review of the literature show that the most effective method from both economic and environmental points of view is the thermomechanical cleaning of cuttings on site. This article discusses the advantages and disadvantages of both methods. It also evaluates drilling waste management prospects and opportunities for Russian offshore fields.

Vito Project: Host Construction and Commissioning

Abstract: In 2009, the Vito field was discovered in more than 1,200 m of water approximately 240 km offshore from New Orleans, Louisiana in the Gulf of Mexico (GoM). The project produces from reservoirs nearly 9,100 m below sea level. This paper provides the efficiencies in constructing the Vito FPS at a single fabrication yard, commissioning, and preparation for offshore installation. This paper is part of a Vito Project series at OTC 2023 and the other papers are listed in the references. The Vito Floating Production System (FPS) has a Lightship of 21,500 mt, Topside Lift Weight of 8,700 mt, and is 86 m Length × 86 m Width overall. Vito FPS fabrication at a single fabrication site included Hull Fabrication, Topside Fabrication, Living Quarters (LQ) Fabrication, Integration, and a majority of the Commissioning Scope. Key drivers to be successful at a single site included demonstratable safe execution, offshore fabrication quality capability, fabrication yard throughput availability, achievable integration execution plan, and competitive pricing. Following a transport to a readiness site adjacent to the Gulf of Mexico, four months of continued commissioning and preparation for offshore installation included the key activities of installation of the Temporary Living Quarters, riser and umbilical installation winches, tow-out and station-keeping rigging; de-preservation, final commissioning and verification of operability of key systems; aviation readiness and safety equipment verification; and final USCG inspections to obtain the Authorization to Proceed Offshore. The efficiencies identified and realized at the single fabrication site during the Vito FPS fabrication execution included focused safety at a single site, simplified quality weld procedures, single interface for detail engineering, simplified procurement delivery plan for Company Provided Items (CPI), efficient preservation strategy, single regulatory interface site, enhanced site team efficiencies in engineering and inspection, and simplified contracting at a single source. The readiness site integrated members of the Construction, Commissioning and Operation teams utilizing a single location to quickly mobilize various vendor teams for a final preparation for offshore installation without the constraints of remote offshore work. A key enabler to select the fabricator was their ability to complete a majority of the commissioning scope on the ground prior to integration of the complete Topside and Hull based on the single lift capability of the new 2 × 15,000 mt gantry cranes, which further increased the efficiency at the single fabrication site. 85% of the commissioning was completed by a Commissioning Management Contractor (CMC) prior to integration including load testing and dynamic commissioning of all the major rotating equipment.

Vito Project: Subsea System Goes Back to Basics

Abstract: In 2009, the Vito field was discovered in more than 4,000 ft of water approximately 150 miles offshore from New Orleans, Louisiana. The project produces from reservoirs nearly 30,000 feet below sea level. The project underwent major redesign to remain competitive, and this paper describes changes within the subsea system. This paper is part of a Vito Project series at OTC 2023, and the other papers are listed in the references. As the industry and market began to change in 2015, the project faced significant financial hurdles, and the project team decided to refresh the field development concept to reduce cost and simplify. This paper focuses on the subsea production system and some of the key decisions leading to the selected design and the approach the team used for making these decisions. It also discusses how the project execution model was established, and the modifications made during project execution to react to schedule challenges, the unprecedented impacts of COVID-19, and a tightening offshore market.

Green development strategy of offshore wind farm in China guided by life cycle assessment

Abstract: Offshore wind power contributes to the decarbonization of the power system; however, its green development faces many challenges, including environmental impact concerns, scale limitations, and grid parity to go carbon neutral. This study applies life cycle assessment (LCA) to evaluate the potential environmental impact of China's first high-power prototype windfarm. The environmental impact of the wind farm is more sensitive to steel, copper, and electricity usage. The recycling of waste turbines can be a solution to reduce the environmental impacts of not only the wind farm but also other entities such as metal producers. Overall, this wind farm case can reduce energy consumption and greenhouse gas emissions by 9.23 MJ and 767.9 g CO 2 -eq for 1 kWh electricity produced, respectively. Guided by LCA results, green development strategies that include toward the deep sea, promote industrial upgrading and synergy, and advance demonstration projects are discussed in the offshore wind power industry.

Data Assimilation Using High‐Frequency Radar for Tsunami Early Warning: A Case Study of the 2022 Tonga Volcanic Tsunami

Abstract: High-frequency (HF) radar monitors the sea surface current velocity and provides information for tsunami early warning. SeaSondeR, an HF ocean radar system in the eastern Tsugaru Strait, Japan, measured the tsunami-induced current velocity during the 2022 Tonga volcanic tsunami. As an air-coupled tsunami, the generating mechanism was complex, making it difficult to predict coastal tsunamis using traditional early warning methods. We adopted the tsunami data assimilation (DA) approach, which reconstructs the tsunami wavefield using offshore data and does not require source information, to forecast the coastal tsunami waveforms. Observations from the HF radar and offshore bottom pressure gauges (OBPGs) were used as the input for tsunami DA. The assimilation process started at 09:00 (UTC, hereafter) and forecasts were made at 14:00 and 15:00. The surface current velocity recorded by the HF radar reached the maximum (∼0.25 m/s) at 13:00, which corresponded to a negative phase of ∼2 cm sea level variation observed by OBPGs. We compared the forecasted waveforms with the observed waveforms at Hakodate and Shimokita tide gauges. The assimilation results obtained using HF radar showed a better performance in tsunami forecasting than those using OBPG in this case study. At 14:00, the forecasting accuracy indices were 91% and 67% for the next 2 and 6 hr, respectively. At 15:00, it was 63% and 70% for the next 2 and 6 hr, respectively. We suggest that HF radar could be a good supplement to OBPG for tsunami early warning purposes.

A regional geological overview of the upper permian zechstein supergroup (z1 to z3) in the sw margin of the southern north sea and onshore eastern england

Abstract: The Upper Permian Zechstein Supergroup has the potential to play an important role in the UK's future energy production and energy transition. However the Supergroup is comparatively poorly understood in the UK, particularly the link between the onshore and offshore geology. In this paper we re‐evaluate available data in order to present a consistent regional interpretation of the Z1 to Z3 Zechstein Supergroup cycles. This review is based on an interpretation and re‐evaluation of 620 offshore wells located in the UK portion of the SW Southern North Sea and 83 onshore wells located in Yorkshire and Lincolnshire (eastern England). The Zechstein Supergroup was interpreted in each well, and the data was used to compile seven SW‐NE oriented correlation panels which show the development of the Supergroup in the study region. Five isopach maps for key formations in the Zechstein Supergroup were created, together with depositional environment maps for each of the main Zechstein carbonate formations. In combination, these regional‐scale maps and diagrams have resulted in a consistent interpretation of the Zechstein Supergroup over an area which extends from the onshore outcrop in the west to the UKCS boundary in the Southern North Sea in the east.

Control of screw pile installation to optimise performance for offshore energy applications

Abstract: Screw piles can be used as foundations for offshore energy applications, thanks to their silent mode of installation and considerable uplift capacity, although a significant upscaling of onshore dimensions is necessary. However, the crowd (vertical) force necessary to install upscaled screw piles was previously shown to be far too great for practical installation. Although guidance recommends that the pile's vertical displacement must be one helix pitch (helix height) per each pile revolution, it is shown in this paper that a lower vertical displacement per revolution can significantly reduce the necessary crowd force during installation or even generate some pull-in. In addition, it was shown that the uplift stiffness and capacity of the pile were enhanced by this installation process, at a shallow (relative) depth in sand. This paper gathers 19 centrifuge tests, with varying screw pile geometries (shaft diameter, base shape), sand relative density and advancement rates. A predictive framework for the pull-in potential of a given pile geometry was proposed to assess its ability to be installed with a reduced crowd force.

Detecting changes in the distribution of calling bowhead whales exposed to fluctuating anthropogenic sounds

Abstract: This paper describes an analysis approach designed to detect the effects of fluctuating anthropogenic underwater sound on the distribution of calling bowhead whales (Balaena mysticetus) during migration. The anthropogenic sounds in this case were associated with an offshore oil production island (Northstar Island) in the Beaufort Sea northwest of Prudhoe Bay, Alaska, but the method has wider applicability. In autumn, bowhead whales migrate westward at varying distances offshore where some are exposed to Northstar sounds. Anthropogenic effects, if present, were hypothesised to be most pronounced in the southern (proximal) part of the migration corridor. Underwater sound levels were measured continuously ca. 500m from Northstar, and locations of calling whales were determined by a seafloor array of directional acoustical recorders. Weighted quantile regression related the 5th quantile of offshore call distance to anthropogenic sounds and other covariates. Case weights were inversely proportional to both probability of detection and location uncertainty. Due to potential dependencies in call locations, block permutation of uncorrelated whale call clusters was used to assign significance levels to coefficients in the quantile regression model. Statistical model selection was used to determine the anthropogenic sound measures most correlated with the 5th quantile of offshore call distances, after allowing for natural within-season variation quantified by day–night changes, distance of the call east or west of Northstar, and date. Data used to illustrate the method were collected over 29 days in September 2003 and included 25,176 bowhead calls. The estimated offshore distance of the 5th quantile call was 0.67km (95% confidence interval 0.31 to 1.05km) farther offshore when tones associated with Northstar were recorded in the 10–450Hz band during the 15 minutes just prior to each call. The method has been applied successfully to similar data collected near Northstar in other years, and may be useful in other studies that simultaneously collect data on animal locations and fluctuating stimuli.

Cold ridge formation mechanisms on the Agulhas Bank (South Africa) as revealed by satellite-tracked drifters

Abstract: The formation of the cold ridge, a seasonal mid-shelf upwelling feature on the Agulhas Bank, is investigated from a combination of satellite-tracked surface drifters, in situ current and temperature data, as well as satellite sea surface temperature (SST) and chlorophyll-a (Chl-a). The observational data showed coastal upwelling along the Tsitsikamma coast to be induced by the easterly wind in austral summer, with a coexistent westward flowing coastal current. Under this wind and current regime, surface drifters moved west and onto the mid-shelf with the cold water, thereafter following the southward-curved 100 m isobath. Satellite observations in March–April 2008 showed increased south-westward advection of wind-driven upwelled water during an Agulhas Current intrusion that resulted in the formation of a classically shaped cold ridge. Also of interest was the passing of a Natal Pulse along the south-eastern shelf edge of the Agulhas Bank in July 2007. This generated a large cyclonic eddy in the Agulhas Bight with an attendant warm water plume that swept over the adjacent shelf. Two idle drifters positioned on the mid-shelf at the time, immediately west of the Natal Pulse, were rapidly advected offshore along the curved 100 m isobath, confirming the long-thought association of the cold ridge with an Agulhas Bight cyclone. A moored current meter adjacent to the Tsitsikamma coast (1.5 km offshore) showed the effect of the Natal Pulse on the nearshore. Drifter trajectories show accelerated south-westward flow on the offshore side of the cold ridge and recirculation towards the east on its shoreward side. These findings strongly support the Westward Transport Hypothesis where squid paralarvae are advected westward from the inshore breeding grounds, to the food maxima on the interior of the central Agulhas Bank, to improve their chances of survival and can therefore have important implications for the management of the South African chokka squid fishery.

A note on the release and tracking of a rehabilitated pygmy sperm whale (Kogia breviceps)

Abstract: A stranded, rehabilitated 220cm female pygmy sperm whale was radiotracked from 31 May-4 June 1994 after its release in the Gulf Stream off Cape Canaveral, Florida. The whale moved directly off the continental shelf and headed northward within a corridor bounded by the shelf break and the eastern edge of the Gulf Stream. It moved offshore up to 32 n.miles from the shelf break during the late afternoons and nights and headed back toward the shelf break during the day. The average travelling speed was 3.0kts, and ranged from 0-6kts. Speeds were greatest offshore of the shelf break (4.7kts), where the speed of the Gulf Stream was the greatest, and both travelling speeds and Gulf Stream speeds decreased with distance offshore. The whale did not appear, however, to be drifting passively with the current. Diving duration varied significantly with light levels. The whale made long dives ( > 8min) at night and on overcast days when squid are known to be closer to the surface. During clear days, the whale’s dives were significantly shorter, typically less than five minutes (n = 841). Although these results come from only a single, rehabilitated animal, the four days of data provided the first information on pygmy sperm whale movements and diving behaviour at sea: how its behaviour was influenced by time of day, oceanographic features, and environmental conditions, and how the whale’s surfacing behaviour could allow survey estimates to be adjusted for diving whales missed along the trackline.