Reef Trend Research Articles

An efficient deep learning-based workflow for CO2 plume imaging considering model uncertainties with distributed pressure and temperature measurements

Monitoring CO2 plumes throughout the operation of geologic CO2 sequestration projects is essential to environmental safety. The evolution of underground CO2 saturation can be predicted using high-fidelity numerical simulations. However, high-fidelity simulations can be prohibitively expensive to compute. As a result of recent developments in data-driven models, rapid predictions of the CO2 plume can now be made using readily available pressure and temperature measurements. This study presents a novel deep learning-based workflow for efficiently visualizing CO2 plumes in near real-time while considering their uncertainties.In our deep learning workflow, we visualize the CO2 plume images in the reservoir as a propagating saturation front, represented by ‘onset time’, using field measurements, including downhole pressure and temperature. At a given location, the ‘onset time’ is the calendar time when the CO2 saturation exceeds a certain threshold. Therefore, a single image of the CO2 front propagation is captured using the ‘onset time’ rather than storing multiple CO2 saturation images at different time steps. The use of ‘onset time’ significantly reduces memory and computational cost of deep learning-based framework, enabling large-scale field applications.We use a variational autoencoder-decoder (VAE) network to compress high dimensional ‘onset time’ images into low dimensional latent variables while considering uncertainties of the predicted images. The use of VAE and onset time, simplifies the overall neural network architecture and significantly enhances the training efficiency. To estimate the latent variables of the VAE network, we train a feed forward neural network model that incorporates available monitoring data such as downhole pressure and temperature measurements. The estimated latent variables are then fed into a trained decoder network to generate 3D onset time images, visualizing the propagation of CO2 plume in near real time.The proposed workflow is applied to both synthetic and field cases, where the field application is a large-scale geological carbon storage project in a carbonate reef reservoir in the Northern Niagaran Pinnacle Reef Trend in Michigan, USA. The field measurements include distributed temperature sensing (DTS) and distributed pressure responses from down-hole gauges along the monitoring well. The predicted CO2 plume images provided by the proposed workflow are shown to be consistent with the simulation results of traditional history matched model using genetic algorithm. Our deep learning-based framework can predict the CO2 front propagation in terms of onset time in seconds, making it well-suited for real time decision-making and operational optimization.

Concurrent 14. Presentation for: New imaging results and improved interpretation of Late Triassic depositional features within the Browse Basin, North West Shelf of Australia

Presented on Wednesday 18 May: Session 14 The Maxima 3D is located approximately 300 km from the north-west coast of Australia, within the Brecknock–Scott Reef anticlinal trend, at the margin of the Scott Plateau and Caswell Sub-basin. The survey was acquired with eight overlapping swaths in and around the Scott Reef, which is a large carbonate build-up on the present-day seafloor. The area within and around the reef trend represents a significant challenge for imaging, involving complex survey acquisition, very shallow to deep water depths and strong velocity distortion associated with the present-day carbonate build-up. In light of this, CGG undertook a reprocessing test of a swath of the Maxima 3D, to apply the latest processing techniques and demonstrate the potential imaging uplift in a very challenging area. The enhanced data swath has led to a step change in interpretation capabilities for the data, resulting in the identification of what is inferred to be a Late Triassic, isolated reef build-up, on a structural high that developed contemporaneous with early basin formation. These Late Triassic reefal build-ups have been identified by CGG within a number of large complexes, through a comprehensive review of the Triassic prospectivity potential, and represent an emerging play type for the North West Shelf. To access the presentation click the link on the right. To read the full paper click here

Emerging marine protected areas of eastern Indonesia: Coral reef trends and priorities for management

Indonesian coral reefs are under pressure from illegal, unregulated and unreported fishing, the use of destructive fishing practices, land-based pollution, coastal development and climate change. Marine protected areas (MPAs) are necessary to allow habitat recovery and fish stock replenishment. Through the United States Agency for International Development Sustainable Ecosystems Advanced Project (2016–2021), Indonesia worked to improve fisheries productivity and sustainable livelihoods within the three provinces of Maluku, North Maluku and West Papua, where 13 new coral reef MPAs were designed for multiple use, with a zoning system to support biodiversity conservation and sustainable fisheries. At the time of writing in mid-2021, regulations to prohibit fishing within the no-take areas (NTAs) were not yet implemented. This paper presents baseline and trends in percent coral cover and reef fish density and biomass in the MPAs. In 2020, overall coral cover had increased from 42% to 45% across all MPAs. The average target fish biomass across all NTAs had declined from 1709 ( ± 176 SE) kg per hectare in 2017 to 884 ( ± 76 SE) kg per hectare in 2020, representing a significant decline of about 48%. Large and significant declines in many target fish families across multiple MPAs are reflective of unsustainable levels of exploitation. It is evident that management plans need to be implemented with adequate enforcement and stakeholder engagement to stem the decline of target species and to secure livelihoods for local fishing communities.

New imaging results and improved interpretation of Late Triassic depositional features within the Browse Basin, North West Shelf of Australia

The Maxima 3D is located approximately 300 km from the north-west coast of Australia, within the Brecknock–Scott Reef anticlinal trend, at the margin of the Scott Plateau and Caswell Sub-basin. The survey was acquired with eight overlapping swaths in and around the Scott Reef, which is a large carbonate build-up on the present-day seafloor. The area within and around the reef trend represents a significant challenge for imaging, involving complex survey acquisition, very shallow to deep water depths and strong velocity distortion associated with the present-day carbonate build-up. In light of this, CGG undertook a reprocessing test of a swath of the Maxima 3D, to apply the latest processing techniques and demonstrate the potential imaging uplift in a very challenging area. The enhanced data swath has led to a step change in interpretation capabilities for the data, resulting in the identification of what is inferred to be a Late Triassic, isolated reef build-up, on a structural high that developed contemporaneous with early basin formation. These Late Triassic reefal build-ups have been identified by CGG within a number of large complexes, through a comprehensive review of the Triassic prospectivity potential, and represent an emerging play type for the North West Shelf.

Monitoring Migration of Injected CO2 at a Northern Niagaran Pinnacle Reef Via Distributed Temperature Sensing (DTS) and Behind-Casing Sensors

Conventional reservoir monitoring techniques in Carbon Capture & Storage (CCS) and CO2-Enhanced Oil Recovery (EOR) sites include surface and bottomhole pressure and temperature monitoring at injection and monitoring wells, along with flow rate measurements of injected CO2. In this paper, novel monitoring techniques involving a realtime distributed temperature sensing (DTS) system and multi-depth behind-casing pressure and temperature sensors are evaluated at a CO2-EOR reef in the Northern Niagaran Pinnacle Reef Trend (NNPRT). Data from these monitoring technologies are evaluated for the purpose of monitoring bottomhole conditions in response to injection of CO2 at a nearby injection well and monitoring migration of injected CO2 within the storage formation after the monitoring well was converted to an injection well.

Zone specific trends in coral cover, genera and growth-forms in the World-Heritage listed Ningaloo Reef

On coral reefs, changes in the cover and relative abundance of hard coral taxa often follow disturbance. Although the ecological responses of common coral taxa have been well documented, little is known about the ecological responses of uncommon coral taxa or of coral morphological groups across multiple adjacent reef zones. We used Multivariate Auto-Regressive State-Space modelling to assess the rate and direction of change of hard coral cover across a variety of coral genera, growth forms, and susceptibility to bleaching and physical damage covering multiple reef zones at northern Ningaloo Reef in Western Australia. Trends were assessed between 2007 and 2016, during which multiple episodic disturbances occurred including cyclones and a heatwave. We provide evidence of zone specific trends, not only in total hard coral cover, but also in taxonomic and morphological groups of corals at Ningaloo Reef. Declines in total coral cover on the reef flat corresponded with declines in fast growing corals, particularly Acropora. In contrast, total coral cover on the reef slope and inshore (lagoon) did not undergo significant change, despite divergent trajectories of individual genera. Importantly, we also show that changes in the composition of coral assemblages can be detected using a morphological based approach when changes are not evident using a taxonomic approach. Therefore, we recommend that future assessments of coral reef trends incorporate not just standard metrics such as total coral cover, but also metrics that provide for detailed descriptions of trends in common and uncommon taxa and morphological groups across multiple reef zones.

A comparison of carbon dioxide storage resource estimate methodologies for a regional assessment of the Northern Niagaran Pinnacle Reef Trend in the Michigan Basin

The Northern Niagaran Pinnacle Reef Trend has more than 800 identified Silurian-aged pinnacle reefs in the Michigan Basin. The reefs have a long history of oil and gas production, gas storage, and more recently successful CO2-enhanced oil recovery (EOR) operations. These fields provide an excellent opportunity to evaluate the geologic variability in complex carbonate reservoirs and its impact on carbon capture, utilization, and storage feasibility. A comprehensive database was built that identifies reefs and links key reservoir attributes to each field. Novel methodologies and techniques were developed to analyze hundreds of fields for CO2 storage and EOR options. This included a regional static earth model to compute volumetric-based resource estimates, fluid substitution to estimate storage resources from oil and gas production, and proximity analysis–based weighting of reefs to predict reservoir performance metrics and estimate EOR. Lastly, an enhanced storage scenario of maximizing a reef’s storage potential at the end of a CO2-EOR life cycle was evaluated.

Assessment of CO2‐enhanced oil recovery and associated geologic storage potential in the Michigan Northern Pinnacle Reef Trend

AbstractThis paper provides an improved estimate of CO2‐EOR (where CO2 is carbon dioxide and EOR is enhanced oil recovery) and CO2 storage potential for depleted oil fields in Michigan's northern pinnacle reef trend (NPRT). Our methodology is based on capturing data on reservoir performance from reefs currently undergoing CO2‐EOR operations in the NPRT (referred to as ‘monitored reefs’), and then applying them to other reefs within the NPRT (referred to as ‘catalog reefs’). For each monitored reef, we calculate fractional primary recovery, fractional incremental EOR recovery, net utilization ratio, and storage efficiency factor. The corresponding incremental oil recovery from EOR, storage capacity until end of EOR, and total CO2 injection needs are then estimated for each catalog reef and combined (over all monitored reefs) using a weighted averaging procedure. These weights are related to a statistical similarity measure that is calculated between each monitored reef and each catalog reef based on a number of variables related to production data, formation type, or descriptive geologic attributes. For the entire NPRT catalog of 383 reefs as used in this study, our results indicate 118 million (MM) stock tank barrels (STB) (1.88 × 107 Sm3) of incremental oil from EOR operations, corresponding to 49 MM metric tons (MT) of CO2 storage and 266 MM MT of total CO2 injection. However, approximately one‐third of the reefs provide two‐thirds of the potential for CO2‐EOR and geologic storage, assuming an economic threshold of 0.5 MM STB (80 000 Sm3) of incremental oil from EOR. © 2020 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons, Ltd.

Pulsed Neutron Capture Logging: Monitoring Co2 Breakthrough in Multiple Co2-Eor Fields

Pulsed neutron capture (PNC) well logging technology was utilized in the large-scale, long-term CO2-EOR Midwest Regional Carbon Sequestration Partnership (MRCSP) to monitor CO2 breakthrough in the Michigan Niagaran reef trend. Comprehensive tool response modeling and assessment of pre- and post-CO2 injection PNC data were performed to evaluate oil, gas, and water saturation changes and potential CO2 breakthrough in monitored reefs. An examination of the different phases of the program and monitoring data are presented.

Regional Jurassic sediment depositional architecture, Browse Basin: Implications for petroleum systems

The Browse Basin hosts considerable gas and condensate resources, including the Ichthys and Prelude fields that are being developed for liquefied natural gas (LNG) production. Oil discoveries are sub-economic. This multi-disciplinary study integrating sequence stratigraphy, palaeogeography and geochemical data has mapped the spatial and temporal distribution of Jurassic to earliest Cretaceous source rocks. This study allows a better understanding of the source rocks contribution to the known hydrocarbon accumulations and charge history in the basin, including in underexplored areas. The Jurassic to earliest Cretaceous source rocks have been identified as being the primary sources of the gases and condensates recovered from accumulations in the Browse Basin as follows: - The Lower–Middle Jurassic J10–J20 (Plover Formation) organic-rich source rocks have been deposited along the northeast-southwest trending fluvial-deltaic system associated with a phase of pre-breakup extension. They have charged gas reservoired within J10–J20 accumulations on the Scott Reef Trend and in the central Caswell Sub-basin at Ichthys/Prelude, and in the Lower Cretaceous K40 supersequence on the Yampi Shelf. - Late Jurassic–earliest Cretaceous J30–K10 source rocks are interpreted to have been deposited in a rift, north of the Scott Reef Trend and along the Heywood Fault System (e.g. Callovian–Tithonian J30–J50 supersequences, lower Vulcan Formation). The J30–K10 shales are believed to have sourced wet gas reservoired in the K10 sandstone (Brewster Member) in the Ichthys/Prelude and Burnside accumulations, and potentially similar plays in the southern Caswell Sub-basin. - The organic-rich source rocks observed in the Heywood Graben may be associated with deeper water marine shales with higher plant input into the isolated inboard rift. They are the potential source of fluids reservoired within the Crux accumulation, which has a geochemical composition more closely resembling a petroleum system in the southern Bonaparte Basin.

Regional Variability of Michigan Niagaran Reefs and the Impact on CO2 Storage Resources

There are over 800 identified Silurian-aged (Niagaran) pinnacle reefs in the Northern Niagaran Pinnacle Reef Trend (NNPRT) of the Michigan Basin. These fields provide an opportunity to evaluate the geologic variability in complex carbonate reservoirs and its impact on carbon dioxide (CO2) storage configurations. Analyses of the reefs included: 1) geologic characterization using wireline logs, whole core, and production records; 2) assessment of enhanced oil recovery (EOR)/carbon capture, utilization, and storage (CCUS) feasibility and comparison between the reefs via simplified modeling; and 3) estimates of CO2 storage resources across the NNPRT. A comprehensive dataset collected on this project was used to identify trends in the NNPRT and to characterize variability while also providing a resource and guide for future CCUS activities. New methodologies and techniques were developed to analyze hundreds of fields. These methods include image analysis techniques to statistically derive porosity indicators and to quantify diagenetic features in whole core using computerized tomography (CT) scan data as well as petrophysical techniques for complex carbonates to identify reefs better suited for CCUS. Results from simplified modeling and storage resource calculations were used to rank the reefs by CCUS feasibility. Future geomechanical anayses will assess the effectiveness of CCUS in reefs.

From oil field to geothermal reservoir: assessment for geothermal utilization of two regionally extensive Devonian carbonate aquifers in Alberta, Canada

Abstract. The Canadian province of Alberta has one of the highest per capita CO2-equivalent emissions in Canada, predominantly due to the industrial burning of coal for the generation of electricity and mining operations in the oil sands deposits. Alberta's geothermal potential could reduce CO2 emissions by substituting at least some fossil fuels with geothermal energy.The Upper Devonian carbonate aquifer systems within the Alberta Basin are promising target formations for geothermal energy. To assess their geothermal reservoir potential, detailed knowledge of the thermophysical and petrophysical rock properties is needed. An analogue study was conducted on two regionally extensive Devonian carbonate aquifers, the Southesk-Cairn Carbonate Complex and the Rimbey-Meadowbrook Reef Trend, to furnish a preliminary assessment of the potential for geothermal utilization. Samples taken from outcrops were used as analogues to equivalent formations in the reservoir and correlated with core samples of the reservoir. Analogue studies enable the determination and correlation of facies-related rock properties to identify sedimentary, diagenetic, and structural variations, allowing for more reliable reservoir property prediction.Rock samples were taken from several outcrops of Upper Devonian carbonates in the Rocky Mountain Front Ranges and from four drill cores from the stratigraphically equivalent Leduc Formation and three drill cores of the slightly younger Nisku Formation in the subsurface of the Alberta Basin. The samples were analyzed for several thermophysical and petrophysical properties, i.e., thermal conductivity, thermal diffusivity, and heat capacity, as well as density, porosity, and permeability. Furthermore, open-file petrophysical core data retrieved from the AccuMap database were used for correlation.The results from both carbonate complexes indicate good reservoir conditions regarding geothermal utilization with an average reservoir porosity of about 8 %, average reservoir permeability between 10−12 and 10−15 m2, and relatively high thermal conductivities ranging from 3 to 5 W m−1 K−1. The most promising target reservoirs for hydrothermal utilisation are the completely dolomitized reef sections. The measured rock properties of the Leduc Formation in the subsurface show no significant differences between the Rimbey-Meadowbrook Reef Trend and the Southesk-Cairn Carbonate Complex. Differences between the dolomitized reef sections of the examined Leduc and Nisku Formation are also minor to insignificant, whereas the deeper basinal facies of the Nisku Formation differs significantly.In contrast, the outcrop analogue samples have lower porosity and permeability, likely caused by low-grade metamorphism and deformation during the Laramide orogeny that formed the Rocky Mountains. As such, the outcrop analogues are not valid proxies for the buried reservoirs in the Alberta Basin.Taken together, all available data suggest that dolomitization enhanced the geothermal properties, but depositional patterns and other diagenetic events, e.g., fracturing, also played an important role.

Domal, thrombolitic, microbialite biostromes and associated lithofacies in the Upper Albian Devils River Trend along the northern, high-energy margin of the Maverick Basin

The Lower Cretaceous Devils River Trend on the northeast margin of the Maverick Basin in southwest Texas contains unique deposits of large domal, thrombolitic, microbial biostromes that have not been identified elsewhere in the Albian of the onshore Gulf of Mexico. These microbial biostromes are overlain by microbial-dominated, moderate-energy grainstones to mud-free rudstones. Above the grainstone to rudstone section is a hiatus (the Albian-19, high-frequency-sequence maximum flooding surface), and above this hiatus are large caprinid rudist bioherms. The overall setting for these carbonate deposits is the moderate- to high-energy north rim of the intraplatform Maverick Basin that is approximately 150 mi (240 km) behind the Stuart City Reef Trend. Four levels of description are necessary to describe the biostromes: (1) megalevel (overall external form)—domal biostromes, (2) macrolevel (larger internal form or layering)—sinuous convex-up layers within domes, (3) mesolevel (basic growth morphology—clotted thrombolites [subvertical to vertical]), and (4) microlevel (microbialite basic texture)—microbial peloids and mesoclots (clots of microbial-mediated material—mainly packed clusters of dark, micritic peloids). The thrombolitic peloids and mesoclots are arranged in digitate to randomly branching growth forms. The thrombolites are very microporous. Growth-framework cavities with sediment fill are common and are filled with mesoclots, peloids, clasts, miliolids, ostracods, echinoid fragments, bivalve fragments, and gastropods. The microbial biostrome is not continuous but has gaps (channels) filled with microbial-dominated grainstone and mud-free rudstones. The microbial-dominated grainstone and mud-free rudstone strata above the microbial biostrome are continuous, although irregularly bedded, with some beds being cross-stratified, and they are composed of fossiliferous, peloidal, mesoclot grainstone with abundant biota encrusted in a microbial coating. The domal, thrombolitic, microbialite biostrome is interpreted to have been deposited on a moderate-energy, semirestricted intraplatform rim at the northeast edge of the Maverick Basin during a higher order transgression. The microbial-dominated strata may have been associated with high nutrient concentrations and initial low sedimentation rates, followed by low to moderate sedimentation rates. The microbial-dominated grainstones and mud-free rudstones above were laid down in a moderate-energy environment during continued transgression. A sharp break exists with the shelf-interior, high-frequency highstand cycle above, which contains abundant rudist bioherms but no microbialites. Most of the primary megapores (growth-framework cavities and interparticle pores) are cemented with equant calcite. Nano- and micropores are extremely abundant within the microbial-related strata. These deposits would make good microporous reservoirs in the subsurface.

PEBBLES IN THE TARKWAIAN BANKET CONGLOMERATE: INFERENCE OF GOLD GRADE AND PALEO-TRANSPORT DIRECTION

TarkwaianBanket conglomerateat Tarkwa area contains rounded to sub-rounded quartz pebbles ofwhich theB reef horizon haslarger pebble sizes, showed preferred northeast-southwest orientation with their longest axes in the north to northwest andprobably ofSEpaleo-transport direction. Interestingly, samplesfrom zones with pebblestrending in northeast-southwest directionshave higher gold grades.Pebbles ofthe B reef,trendtowards the northwestand probably came from the east,and characterizehighest average gold gradeof 2.50 g/t whilethose with the averagetrendof SW were associatedwithlowest average gradeof 1.95 g/t. Pebbles in theC reef trend towards the north to northwest and could have travelledfrom the east; those withthe averagetrendof SEhad a higheraverage grade of 1.12 g/t compared tothelower grade variety of 0.73 g/t which trends NW.

Static Earth Modeling of Diverse Michigan Niagara Reefs and the Implications for CO2 Storage

The northern Michigan Niagara reef trend has more than 700 reefs at various stages of the production lifecycle. Five reefs were selected for static earth modeling that display differences in abundance of limestone and dolomite, salt plugging, and compartmentalized, separate pod scenarios. These resulting static earth models demonstrate the efficacy of a new, integrated approach to reservoir evaluation, as well as illustrating the diversity of the geology and diagenesis, and how this complexity influences reservoir potential and behaviour. The developed geologic modeling approaches will be generalized to implement a regional assessment of CO2 storage across the reef complex.

Developing Best Practices for Evaluating Fluid Saturations with Pulsed Neutron Capture Logging Across Multiple Active CO2-EOR Fields

The Midwest Regional Carbon Sequestration Partnership (MRCSP) is leading an extensive study and monitoring effort of large-scale carbon dioxide (CO2) injection and storage during enhanced oil recovery (EOR) in depleted oil fields in the Michigan Niagara Reef Trend. Detailed monitoring of caprock and reservoir zones is vital for understanding oil, gas, and water saturations and potential migration of CO2. Baseline and repeat pulsed neutron capture (PNC) logs were collected as part of the monitoring effort and study for these storage sites. An overview of the development and enhancement of best practices for PNC logging in complex EOR fields is presented.

Stratigraphy of the Middle Devonian Keg River and Prairie Evaporite formations, northeast Alberta, Canada

Stratigraphy of the Middle Devonian Keg River and Prairie Evaporite formations, northeast Alberta, Canada

New insights into the petroleum prospectivity of the Browse Basin: the results of a multi-disciplinary study

The Browse Basin hosts large gas accumulations, some of which are being developed for conventional liquefied natural gas (LNG). Extensive appraisal drilling has been focused in the central Caswell Sub-basin at Ichthys and Prelude, and along the extended Brecknock-Scott Reef Trend; whereas elsewhere the basin remains underexplored. To provide a better understanding of regional hydrocarbon prospectivity, the sequence stratigraphy of the Cretaceous succession and structural framework were analysed to determine the spatial relationship of reservoir and seal pairs, and those areas of enhanced source rock development. The sequence stratigraphic interpretation is based upon a common North West Shelf stratigraphic framework that has been developed in conjunction with industry, and aligned with the international time scale. Sixty key wells and 2D and 3D seismic data have been interpreted to produce palaeogeographic maps and depositional models for the Cretaceous succession. Geochemical analyses have characterised the molecular and stable isotopic signatures of fluids and correlated them with potential source rocks. The resultant petroleum systems model provides a more detailed understanding of source rock maturity, organic richness and hydrocarbon-generation potential in the basin. The model reveals that many accumulations have a complex charge history, with the mixing of hydrocarbon fluids from multiple Mesozoic source rocks, including the Lower–Middle Jurassic J10–J20 supersequences (Plover Formation), Upper Jurassic–Lowermost Cretaceous J30–K10 supersequences (Vulcan Formation), and Lower Cretaceous K20–K30 supersequences (Echuca Shoals Formation). Burial history and hydrocarbon expulsion models, applied to these Jurassic and Cretaceous supersequences, suggest that numerous petroleum systems are effective within the basin. For example, hydrocarbons are interpreted to have been generated from several source pods within the southern Caswell Sub-basin with migration continuing onto the Yampi Shelf, an area of renewed exploration interest.

Coral injuries observed at Mesophotic Reefs after the Deepwater Horizon oil discharge

Pathologies in over 400 octocoral and antipatharian colonies were quantified in the aftermath of the DWH oil discharge. Observations were made in September 2011 at water depths of 65–75m in the Pinnacle Reef trend area offshore from Mississippi and Alabama, Gulf of Mexico, using a digital macro camera deployed from an ROV to examine the coral populations for injury at two principal sites: Alabama Alps Reef (AAR) and Roughtongue Reef (RTR). Taxa observed to exhibit injury included gorgonian octocorals Hypnogorgia pendula, Bebryce spp., Thesea nivea, and Swiftia exserta, the antipatharian Antipathes atlantica, and the sea whips Stichopathes sp., and Ellisella barbadensis. The most common type of injury was a biofilm with a clumped or flake-like appearance covering sea-fan branches. Extreme injuries were characterized by bare skeletons, broken and missing branches. Comparing the 2011 results to previous photo surveys of the same study sites between 1997 and 1999, we found significantly more occurrences of injury in 2011 among taxa with growth forms >0.5m. We hypothesize that Tropical Storm Bonnie facilitated and accelerated the mixing process of dispersant-treated hydrocarbons into the water column, resulting in harmful contact with coral colonies at mesophotic depths. Analysis of total polycyclic aromatic hydrocarbon (tPAH) concentrations in sediments at AAR and RTR found levels elevated above pre-discharge values, but orders of magnitude below toxicity thresholds established for fauna in estuarine sediments. The tPAH concentrations measured in octocoral and echinoderm tissue samples from AAR and RTR were detectable (mean values ranged from 51 to 345ppb); however, bioeffect thresholds do not currently exist with which to evaluate the potential harm these levels may cause. Our findings indicate that coral injuries observed in 2011 may have resulted from an acute, isolated event rather than ongoing natural processes.

Effect of secondary oil migration distance on composition of acidic NSO compounds in crude oils determined by negative-ion electrospray Fourier transform ion cyclotron resonance mass spectrometry

The acidic and neutral NSO compounds in a series of Duvernay-sourced oils in Canada, which are believed to have migrated extensively over relatively long distances such as along the Rimbey-Meadowbrook reef trends, were characterized by negative-ion electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Heteroatomic compounds were characterized according to their class (number of nitrogen, oxygen and sulfur heteroatoms), degree of aromaticity [rings plus double bonds (DBE)] and carbon number distribution. The N1, N1O1, N1O2, N1S1, O1 and O2 classes were identified in Duvernay-sourced oils. With increasing migration distance, the relative abundance of O2, N1O1 and N1O2 showed a significant decrease, while the O1 class increased from <10% to nearly 30% of the total. With increasing migration along the Rimbey-Meadowbrook reef trend, pyrrolic nitrogen compounds (N1 class) shows an enrichment of alkylcarbazoles (DBE=9) relative to alkylbenzocarbazoles (DBE=12), and of higher homologous relative to the lower homologous. O1 compounds show a relative enrichment of those with low DBE values. Additionally, the N1O1 and N1S1 compounds show a relative enrichment of those with high DBE values, and of higher homologues compared to the lower homologues, indicating great potential for developing new migration indices.