Review of flow rate estimates of the Deepwater Horizon oil spill

Deep sea is the largest and likely the most biologically diverse ecosystem of the world, but it is also the most unknown. The Mediterranean Sea (< 1% of the ocean surface and contains only the 0.3% of its volume) is a hot spot of marine biodiversity containing ca 7.5% of the world marine biodiversity, associated with a multitude of habitats spreading from the coast to its dark portion (e.g., coral banks, seamounts, canyons, and hydrothermal vents). Its deep-sea ecosystems are increasingly subjected to direct anthropogenic impacts (including overfishing, chemical pollution, dumping, litter, and plastics), which are often over-imposed to the increasing effects of global change. Here, are illustrated the expected impacts of shifts in the main variables such as temperature, food supply, pH, and oxygen on the deep Mediterranean Sea ecosystems. One of the most consequences is related to shifts in the quality and quantity of the inputs of organic matter to the deep seafloor. The deep Mediterranean Sea is far more oligotrophic than other oceans at equal depths, and although deep-sea biota reacts to food shortage by increasing their efficiency in its use, a decrease in food availability can have dramatic effects on its food webs. The deep Mediterranean Sea is showing a clear rise of deep-water temperatures. In the last decades, deep-water warming is accelerating at unprecedented rates, causing a significant shift in biodiversity even for variations in the order of 0.1 °C. Higher temperatures increase deep-sea metabolism, thus exacerbating the effects of food limitation. Moreover, ocean acidification reduces the calcification capacity of corals and alters their metabolism. Although it can be expected that increasing temperatures might increase the potential spread of oxygen minimum zone, so far, only hypoxic events were reported in Mediterranean Sea. The analysis of potential ecosystem vulnerability indicates that the ecosystems that are most sensitive to global change are deep-water coral systems and deep-sea plains. In addition, deep-sea canyons are also likely increasingly subjected to physical disturbance as a result of the increase in the frequency and intensity of climate-driven episodic events. Available information also suggests that biodiversity and ecosystem functioning of the deep Mediterranean Sea is undergoing dramatic changes, which result in accelerated organic matter biogeochemical cycling, miniaturization of the organisms’ size, increased metabolism, dominance of the microbial components, and mortality rates of deep-sea biota. Given the high sensitivity of the Mediterranean Sea to global change in comparison with other oceanic regions, and the vulnerability of its deep-sea habitats/ecosystems, specific policy measures are needed to protect its biodiversity, restore damaged habitats, and increase deep-sea ecosystems resistance and resilience to the ongoing impacts of global change.

The goal of this paper is to review current impacts of human activities on the deep-sea floor ecosystem, and to predict anthropogenic changes to this ecosystem by the year 2025. The deep-sea floor ecosystem is one of the largest on the planet, covering roughly 60% of the Earth's solid surface. Despite this vast size, our knowledge of the deep sea is poor relative to other marine ecosystems, and future human threats are difficult to predict. Low productivity, low physical energy, low biological rates, and the vastness of the soft-sediment deep sea create an unusual suite of conservation challenges relative to shallow water. The numerous, but widely spaced, island habitats of the deep ocean (for example seamounts, hydrothermal vents and submarine canyons) differ from typical deep-sea soft sediments in substrate type (hard) and levels of productivity (often high); these habitats will respond differently to anthropogenic impacts and climate change. The principal human threats to the deep sea are the disposal of wastes (structures, radioactive wastes, munitions and carbon dioxide), deep-sea fishing, oil and gas extraction, marine mineral extraction, and climate change. Current international regulations prohibit deep-sea dumping of structures, radioactive waste and munitions. Future disposal activities that could be significant by 2025 include deep-sea carbon-dioxide sequestration, sewage-sludge emplacement and dredge-spoil disposal. As fish stocks dwindle in the upper ocean, deep-sea fisheries are increasingly targeted. Most (perhaps all) of these deep-sea fisheries are not sustainable in the long term given current management practices; deep-sea fish are long-lived, slow growing and very slow to recruit in the face of sustained fishing pressure. Oil and gas exploitation has begun, and will continue, in deep water, creating significant localized impacts resulting mainly from accumulation of contaminated drill cuttings. Marine mineral extraction, in particular manganese nodule mining, represents one of the most significant conservation challenges in the deep sea. The vast spatial scales planned for nodule mining dwarf other potential direct human impacts. Nodule-mining disturbance will likely affect tens to hundreds of thousands of square kilometres with ecosystem recovery requiring many decades to millions of years (for nodule regrowth). Limited knowledge of the taxonomy, species structure, biogeography and basic natural history of deep-sea animals prevents accurate assessment of the risk of species extinctions from large-scale mining. While there are close linkages between benthic, pelagic and climatic processes, it is difficult to predict the impact of climate change on deep-sea benthic ecosystems; it is certain, however, that changes in primary production in surface waters will alter the standing stocks in the food-limited, deep-sea benthic. Long time-series studies from the abyssal North Pacific and North Atlantic suggest that even seemingly stable deep-sea ecosystems may exhibit change in key ecological parameters on decadal time scales. The causes of these decadal changes remain enigmatic. Compared to the rest of the planet, the bulk of the deep sea will probably remain relatively unimpacted by human activities and climate change in the year 2025. However, increased pressure on terrestrial resources will certainly lead to an expansion of direct human activities in the deep sea, and to direct and indirect environmental impacts. Because so little is known about this remote environment, the deep-sea ecosystem may well be substantially modified before its natural state is fully understood.

&amp;lt;p&amp;gt;Deep-sea oil releases from accidents during offshore exploratory drilling or production are of particular concern, as the potential for such accidents increases with the expansion of the offshore industry to more extreme environments. During the 2010 Deepwater Horizon, huge amounts of oil were released into the Gulf of Mexico, adversely affecting marine wildlife. What prevented a worse outcome was the ability of nature to biodegrade oil. &amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;To this end, the community oi spill model MEDSKIL-II has been modified to incorporate biodegradation kinetics of dissolved oil and oil droplets dispersed in the water column. Biodegradation of oil can be modelled by Monod kinetics or as a first order decay process. The kinetics of oil particles size reduction due to the microbe-mediated degradation at water-oil particle interface is represented by the shrinking core model. Furthermore, a Lagrangian plume module has been developed and coupled to MEDSLIK-II, for predicting the fate of the spill until reaching the sea surface. The Lagrangian plume model is represented by elements that trace the plume&amp;amp;#8217;s trajectory. Each Lagrangian element represents a mixture of water, oil and gas. Changes in the mass and composition of the element are accounted for by the turbulent entrainment of ambient water, leakage of gas bubbles and oil droplets from the plume, dissolution of gas in seawater, and formation or disintegration of gas hydrates. The motion of the element is computed from the conservation equations for mass, momentum, and buoyancy. Biodegradation kinetics are also represented in the model, to enhance prediction of fate and transport of deep-sea spills.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;A novel sampling apparatus was designed for the collection of indigenous microbial populations from the deep Eastern Mediterranean Sea, maintaining &amp;lt;em&amp;gt;in situ&amp;lt;/em&amp;gt; pressure throughout the entire process of retrieval and experimentation to determine microbial oil degradation. Seawater samples were collected on board the R/V Aegaeo (Hellenic Centre for Marine Research) on 2-29-2020, off Southeast Crete, Greece. The High Pressure (HP) Sampler collected seawater between 600 to 1000 m depth. A known volume of the collected sample was transferred via a piston pump, without pressure disruption, into a HP-Reactor, at 10 MPa pressure and was incubated with crude oil at plume concentration for 77 days at &amp;lt;em&amp;gt;in situ&amp;lt;/em&amp;gt; temperature (14&amp;lt;sup&amp;gt;&amp;amp;#959;&amp;lt;/sup&amp;gt;C). Iranian light crude oil bioremediation was monitored for 35 days, and then the effect of dispersant addition (1:25 v/v COREXIT 9500) was observed until day 77. Kinetic analysis was used to estimate the degradation rates of hydrocarbon compounds, which were incorporated into the integrated modified MEDLSLIK-II model to simulate the effect of biodegradation on the fate and transport of subsurface spills for the Sea of Crete. Several scenarios have been considered to include the different laboratory data and oceanographic fields (water density, currents) for the area. To our knowledge, this is the first modelling effort incorporating area-specific data for biodegradation capacity of hydrocarbon degrading consortia to predict the fate of deep-water oil releases in the Eastern Mediterranean Sea.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;lt;strong&amp;gt;Acknowledgement: &amp;lt;/strong&amp;gt;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;This research was funded by the GSRT and HFRI projects DEEPSEA, GA No 1510 and HEALMED, GA No 1874.&amp;lt;/p&amp;gt;

The giant Cano Limon field was discovered in July 1983. The discovery was the culmination of a 3-yr exploration effort by Occidental involving 4000 km of dynamite seismic, 20 stratigraphic tests from 396 to 1,067 m deep, and 12 exploratory wells. Prior to Oxy's entering the area, there had been 61 exploratory wells drilled with meager results, namely two fields with total reserves of about 20 million bbl of light oil and one field with reserves of 90 million bbl of 13.6{degree} API oil-none of which were commercial. The Llanos basin was known for its abundant excellent reservoir sandstones and opinions varied as to whether there was adequate source rock. The major problem had been defining traps. Except for the very young folding along the Andean front, the known structural traps were sparse and subtle. Most of the exploration had been done in the western part of the basin near the basin deep or in the Andean foothills. Occidental took a very large acreage position east of the area of past exploration efforts and found an exception to the small fault closures known elsewhere in the basin. This exception, the Cano Limon area, is dominated by major early Tertiary northeast-southwestmore » strike-slip faulting. Concurrent folding in combination with fault sealing formed the Cano Limon field and other much smaller fields in the area. The Cano Limon field, encompassing 3,570 ha, contains an estimated 1.8 billion bbl of oil in place, of which 1.6 billion bbl are expected to be recovered with the very strong natural water drive. The bulk of the oil is in deltaic sandstones of the Eocene Mirador formation with additional reservoirs in the Upper Cretaceous. The average porosity of the Mirador is about 25%, the permeability is about 5 d, and water saturation is about 23%. Individual well flow rates have exceeded 20,000 BOPD. The average oil gravity is 29.5{degree} API, with a GOR of 8 ft3/bbl and sulfur content of 0.41%. Current production is about 230,000 bbl/day.« less

The term ‘deep ocean’ typically describes any marine ecosystem located at depths higher than 500 m. This environment is characterised by an elevated hydrostatic pressure, an average temperature of 2–4 °C, the absence of sunlight and the scarce availability of organic food. Specific organisms are associated with the deepest areas, and pressure‐adapted animals as well as microorganisms inhabit these peculiar ecosystems. It is difficult to understand how we do not know much about deep sea compared to space environment, despite the fact that its distance from the ocean surface is relatively short. With no doubt, the deep‐sea biodiversity is still mostly unseen and important benefits to human health and industrial activities will be available in the future from more extensive studies on this fascinating environment. Key Concepts: The deep sea is the world's largest ecosystem. The deep‐sea biodiversity is still mostly unseen. The less diversity of animals with increasing depths is mainly due to the hydrostatic pressure, as well as to a larger competition for food coupled with a lower basal metabolism. Further insights into the natural traits of deep‐sea will lead to important benefits to human health and industrial applications. Despite the fact that the distance of deep‐sea from the ocean surface is much shorter than that between Earth and space, the abyssal environment is far to be well known.

This report describes the application of a computer model to simulate reservoir depletion and oil flow from the Macondo well following the Deepwater Horizon blowout. Reservoir and fluid data used for model development are based on (1) information released in BP's investigation report of the incident, (2) information provided by BP personnel during meetings in Houston, Texas, and (3) calibration by history matching to shut-in pressures measured in the capping stack during the Well Integrity Test. The model is able to closely match the measured shut-in pressures. In the simulation of the 86-day period from the blowout to shut in, the simulated reservoir pressure at the well face declines from the initial reservoir pressure of 11,850 pounds per square inch (psi) to 9,400 psi. After shut in, the simulated reservoir pressure recovers to a final value of 10,300 psi. The pressure does not recover back to the initial pressure owing to reservoir depletion caused by 86 days of oil discharge. The simulated oil flow rate declines from 63,600 stock tank barrels per day just after the Deepwater Horizon blowout to 52,600 stock tank barrels per day just prior to shut in. The simulated total volume of oil discharged is 4.92 million stock tank barrels. The overall uncertainty in the simulated flow rates and total volume of oil discharged is estimated to be + or - 10 percent.

Prevalence of temperate viruses in deep South China Sea and western Pacific Ocean

Towards an Ecosystem-Based Marine Spatial Planning in the deep Mediterranean Sea.

In view of the problem of high risk and high cost of deep-sea crude oil export technology, this paper starts with the problem that DPST (Dynamic Positioning Shuttle Tanker) in Brazil's one deep sea project compulsorily be used in offloading operation. From coordinating and participating in the comparison and selection of offloading schemes from CNOOC and individual partners, to the raising of technical proposal CTV (Cargo Transfer Vessel) and subsequent carrying out of ship design, construction, sea trial and until actual application, this paper fully discusses and verifies CTV's correctness and adaptability. As the world's first unique technological solution for the offloading issue. its excellent security and low cost advantages will assure CTV a greater role in the field of deep sea oil offloading and other marine areas.

In this chapter after a brief review of historical oil spills and their impacts on the environment and economy, several oil spills with major impacts are reviewed. The chapter begins with an introduction followed by methods of detection of oil spills and determination of the size and thickness of slicks with satellite remote sensors. Then several major oil spills caused by oil tankers are reviewed followed by oil spills caused by offshore exploration and production activities. Among these oil spills two incidents are reviewed in more detail. These two spills are the 1991 oil spill in the Persian Gulf as a result of the Iraq invasion of Kuwait and the 2010 BP oil spill in the Gulf of Mexico (GOM) as a result of a blowout in the Macondo exploratory well due to a flawed well plan. In the Gulf War between 6 and 8 million barrels of oil were spilled, and the cleanup efforts continued for more than two decades. In the GOM accident about 5 million barrels of oil flew into the sea for a period of nearly three months. Although much of the oil was recovered, the damage to the ecosystems is not yet fully done. As the BP oil spill is the most recent and significant environmental event, and with the availability of data in the public domain, much of this chapter is devoted to this accident, its occurrence, the amount of oil spilled, its trajectory and simulation by NOAA, chronological data, and specifications of the Macondo well and its reservoir fluids.

AimDispersal and environmental gradients shape marine microbial communities, yet the relative importance of these factors across taxa with distinct sizes and dispersal capacity in different ocean layers is unknown. Here, we report a comparative analysis of surface and deep ocean microbial beta diversity and examine how these patterns are tied to oceanic distance and environmental gradients.LocationTropical and subtropical oceans (30°N–40°S).Time period2010–2011.Major taxa studiedProkaryotes and picoeukaryotes (eukaryotes between 0.2 and 3 μm).MethodsBeta diversity was calculated from metabarcoding data on prokaryotic and picoeukaryotic microbes collected during the Malaspina expedition across the tropical and subtropical oceans. Mantel correlations were used to determine the relative contribution of environment and oceanic distance driving community beta diversity.ResultsMean community similarity across all sites for prokaryotes was 38.9% in the surface and 51.4% in the deep ocean, compared to mean similarity of 25.8 and 12.1% in the surface and deep ocean, respectively, for picoeukaryotes. Higher dispersal rates and smaller body sizes of prokaryotes relative to picoeukaryotes likely contributed to the significantly higher community similarity for prokaryotes compared with picoeukaryotes. The ecological mechanisms determining the biogeography of microbes varied across depth. In the surface ocean, the environmental differences in space were a more important factor driving microbial distribution compared with the oceanic distance, defined as the shortest path between two sites avoiding land. In the deep ocean, picoeukaryote communities were slightly more structured by the oceanic distance, while prokaryotes were shaped by the combined action of oceanic distance and environmental filtering.Main conclusionsHorizontal gradients in microbial community assembly differed across ocean depths, as did mechanisms shaping them. In the deep ocean, the oceanic distance and environment played significant roles driving microbial spatial distribution, while in the surface the influence of the environment was stronger than oceanic distance.

E&amp;P Notes (January 2021)

Environmental viromes reveal the global distribution signatures of deep-sea DNA viruses

Chapter 12 - Fates of petroleum compounds from the Deepwater Horizon oil spill

Over two‐thirds of the surface of the earth is covered by oceans, which have an average depth of about 3800 m. As each drop of ocean water contains > 105 cells, the > 1030 microbial cells in the ocean represent the largest reservoir of microbes on earth (Whitman et al., 1998). Communities of bacteria, archaea, protists and unicellular fungi account for most of the oceanic biomass and metabolism. Marine microbes are known to play an essential role in the global cycling of nitrogen, carbon, oxygen, phosphorous, iron, sulfur and trace elements (Karl, 2007).