Feely, M. (National University of Ireland Galway) | Costanzo, A. (National University of Ireland Galway) | Hunt, J. (National University of Ireland Galway) | Wilton, D. (Memorial University) | Carter, J. (Nalcor Energy)
Fluid inclusions are micron scale samples of aqueous and hydrocarbon fluids trapped in annealed microfractures developed during burial, or earlier in authigenic minerals
The Labrador Sea, extending from the Davis Strait in the north, through the Saglek Basin and down to the Hopedale Basin in the south, is one of the largest under-explored areas along the eastern Canadian Margin. Exploration of this region has focused on the continental shelf with 30 wells drilled during the 1970's and 1980's. Most of the wells targeted shelfal structural traps. No exploration has occurred in the slope and deepwater areas. From 2011 to 2015, long offset, broadband 2D seismic data (42,400 km) has been acquired by TGS-PGS in the slope and deepwater regions. The broadband image quality has led to the identification of significant new plays and leads in a region that was never before considered prospective. Several of these leads have the potential for large accumulations of oil and gas. The possibility for oil plays in the area is supported by the presence of natural oil seeps along the slope that were identified by satellite surveys in 2010. The long offset (8 km cable) seismic data has identified AVO anomalies on the far stacks. A new regional rock physics study (2014-15) has permitted the careful analysis of these AVO leads and this is helping to reduce exploration risk factors. The analysis shows the importance of the long offsets to identify and characterize these Class II AVO anomalies. In 2015, a seabed coring survey was conducted to target areas near the oil seeps and over large potential traps. Early results from this work are positive and analysis will continue through the spring of 2016. Heatflow measurements taken during the coring survey are providing inputs for a basin modelling study. In addition, several of the shelfal wells were resampled and fluid inclusion analysis was performed. Early results are showing the presence of liquid hydrocarbon inclusions. All of this work has led to the identification and analysis of large potential traps that could hold major oil accumulations. This paper will provide insights from the new seismic data and the recent studies and analyses to demonstrate this prospectivity.
Baffin Bay, northern Canada, represents the northernmost segment of rifting between Greenland and North America, and can be considered a northern extension of the Labrador Sea extinct rift system between Labrador and Greenland. Many questions remain about the nature of the crust beneath parts of Baffin Bay, although extinct spreading axes and a fracture zone have been previously identified based principally on gravity data. Existing deep seismic coverage over Baffin Bay is spatially limited and mostly concentrated in the north, although two regional 2-D transects span the region from the centre to the southern end of the bay. One of the regional 2-D refraction transects revealed a thick sedimentary package overlying oceanic crust along most of the profile, despite a lack of clear magnetic anomalies within Baffin Bay. To extrapolate the 2-D seismic refraction results offline and resolve the regional crustal structure across Baffin Bay, a constrained 3-D gravity inversion was undertaken. Bathymetry and depth to basement were used to constrain the 3-D inversion and the resolved crustal geometry from existing refraction lines was used to gauge the quality and reliability of the inverted model. The final inverted 3-D crustal structure model for Baffin Bay will provide useful constraints for basin studies and will shed light on its tectonic evolution.
Japsen, Peter (Geological Survey of Denmark and Greenland) | Green, Paul F. (Geotrack International) | Bonow, Johan M. (Södertjörn University) | Hinchey, Alana M. (Geological Survey of Labrador and Newfoundland) | Wilton, Derek H. C. (Memorial University of Newfoundland)
The stratigraphic record along the continental margin of Labrador and Newfoundland provides ample evidence for vertical movements both prior to and after break-up. In the offshore domain, several major hiatuses punctuate the stratigraphic record. Along Labrador and the Grand Banks, Lower Cretaceous rocks rest on Paleozoic rocks or Precambrian basement in parts of the area. Onshore Labrador, the presence of a Cretaceous outlier on Precambrian basement adds to the evidence of one or more events of exhumation that has removed pre-Cretaceous sediments on a regional scale. Over much of the Labrador shelf, Miocene deposits are absent, and we show evidence based on vitrinite reflectance and sonic data that indicate that Miocene deposits of significant thickness may have been present prior to uplift and exhumation. We also present results from a pilot study comprising apatite fission-track analysis (AFTA) data that reveals a Phanerozic history involving a series of burial and exhumation episodes. The pilot study is a forerunner for a study of the onshore and offshore domain with three components. (1) A thermochronological study based on samples from outcrops and from onshore and offshore boreholes. (2) A stratigraphic landform analysis of the onshore study area based on mapping of denudation surfaces that will provide evidence of vertical motion using cross-cutting relationships between the denudation surfaces and stratigraphic constraints. (3) An integrated interpretation of the geological, geomorphological and thermochronological data to provide a coherent model of the timing and magnitude of the vertical movements along the margin both prior to and after break-up. Failure to account for greater depths of burial prior to exhumation may lead to serious underestimation of the petroleum resource maturity and to erroneous estimates of the timing of hydrocarbon generation. Uplift and exhumation may also lead to changes in migration routes and affect hydrocarbons present in reservoirs. Insights into the uplift history of a margin are important for understanding the source-to-sink system of sediment input into offshore basins.
Semi-submersible drilling platforms are typically moved off site given any threat of pack ice incursion. Operations in icy waters requires considerations of, amongst others, ice interations with the facility. The offshore industry will benefit from a standardized methodology to evaluate the capability of semi-submersibles in ice during drilling operations. Operators and drilling contractors are particularly interested in understanding how the drilling season may be extended into the shoulder season. This requires an understanding of variability in site-specific ice conditions throughout the year.
Ice load analysis is needed for semi-submersible rigs operating in ice prone regions to determine ice strengthening requirements. Ship-based ice class rules can be considered for the design loads of the pontoons in transit conditions, but there is no standardized methodology for determining ice loads for the operational conditions. This paper focusses on the operational phase, where loads act on the vertical-faced columns. ISO 19906 (2010) offers a framework for determining sea ice loads in the form of a deterministic equation that has been established for fixed structures mainly operating on a year-round basis. The results will generally be quite conservative for seasonal operations. Consideration of ice exposure, to account for the limited drilling season, is permitted by ISO 19906 using probabilistic approaches, though no specific guidance is provided. Seasonal operations can be planned to avoid the most severe winter conditions, allowing for a reduction of the design level ice conditions. This reduction in the severity of sea ice that impacts semi-submersible columns should be accounted for in determining design ice loads. This paper demonstrates application of an analytical approach to include exposure considerations to estimate extreme ice loads for various drilling season extensions.
An approach is demonstrated here for determining design sea ice loads to evaluate the capability of a semi-submersible in pack ice conditions. The approach considers the possibility of extended season drilling operations, rather than year-round operations, and may permit more efficient exploration in Arctic and sub-Arctic regions in the future. A study case is presented for a semi- submersible operating in the early ice season at a selected location in the Labrador Sea. The approach can be easily adopted for operations in other regions and other structure types, but is dependent on the availability of reliable data on ice conditions.
Wilton, Derek (Department of Earth Sciences, Memorial University of Newfoundland) | Burden, Elliott (Department of Earth Sciences, Memorial University of Newfoundland) | Greening, Adam (Yamana Gold Corp.)
The Ford’s Bight Diatreme is an apparently rare feature on the Precambrian coast of Labrador. Originally described as a Jurassic-Cretaceous sedimentary breccia cut by lamprophyric dykes, an early report of marine microfossils in the strata poses an interesting sedimentary and petroleum geology problem. In revisiting the area, the succession is now viewed as a rift related diatreme with a Cretaceous (ca. 137 Ma) radiometric age. In earlier work, this rock was dated from assemblages of poorly preserved Jurassic and early Cretaceous marine microfossils. Our own lengthy search for fossils in igneous rocks and clasts and carbonate matrix was fruitless. Some apparently carbonized debris is identified in microscopy and with some oddly shaped (non-biologic) microcrystalline structures seen under SEM. With an age and origin for this feature established from basic geology and radiometric dating, this therein leaves an unresolved petroleum exploration risk - and, namely, did Jurassic marine conditions cover this part of the Labrador coast before earliest Cretaceous volcanism?
Wilton, Derek (Earth Sciences, Memorial University) | Feely, Martin (National University of Ireland) | Carter, James (Nalcor Energy - Oil & Gas) | Costanzo, Alessandra (National University of Ireland) | Hunt, Jon (National University of Ireland)
MLA-SEM analyses can quantitatively define the modal mineralogy of detrital components in a variety of sample material including offshore well cuttings such that the possible source(s) of the detrital material might be ascertained. The MLA data can be queried for combinations of detrital minerals that might reflect a specific source terrane (e.g., igneous suite, metamorphic complex,
Wei, Lixin (National Marine Environmental Forecasting Center) | Ma, Jing (National Marine Environmental Forecasting Center) | Sun, Hulin (National Marine Environmental Forecasting Center) | Qin, Ting (National Marine Environmental Forecasting Center)
In this study, the NASA GISS ModelE atmospheric circulation model was employed to investigate winter atmospheric response to specified sea ice anomalies. Two sensitivity experiments were conducted, one used 10-yr linear trend field of winter sea ice in the high latitude north from 40°N to 90°N (Atrend) as the boundary forcing, and the other one used 10-yr linear trend field of winter sea ice in the north Pacific sector (Ptrend, 60-80°N,30°W-45°E). Our simulation results show that the winter sea ice anomalies lead to strong response in wintertime atmospheric circulation and the influence is mainly in the mid- and high latitude of northern hemisphere. Atrend excites atmospheric response resembling AO/NAO or Northern Hemisphere annular mode, along with strengthened westerly winds, which are unfavorable for the longitudinal heat exchange in high latitude. Ptrend leads to a pattern that is quite different from AO/NAO, characterized by weakened westerly winds, which are favorable for the longitudinal heat exchange in mid- and high latitude. The changes induced by sea ice anomalies influence the weather and climate in northern hemisphere.
The Arctic region has experienced significant changes in recent times, which are more severe when compared with other regions. As one of the most important climate factors in polar region, sea ice is undergoing dramatic change. Satellite observations (1979 to present) indicate that Arctic sea ice cover has declined over recent decades. The decline has been especially steep since 2002 (e.g., Comiso et al., 2008; serreze et al., 2007; Stroeve et al., 2005; 2007), and two record minima occurred in 2007 an 2012 (Francis, 2013).The declining trend in sea-ice extent is -0.40x106km2 per decade in March and -0.89x106km2 per decade in September from 1979-2013 (Miles et al., 2014; GAO Yongqi et al., 2015). The observed reduction in sea-ice extent is even faster than that simulated by most numerical models (Stroeve et al., 2012)
The sea ice in Arctic significantly affects the interaction between atmosphere and ocean. Firstly, the high albedo of sea ice greatly cuts the absorption of short wave radiation, making polar region the source of cold air in the global climate system. Secondly, the low thermal conductivity of sea ice dramatically decreases the exchange of heat, moisture and momentum between atmosphere and ocean. Thirdly, the forming and melting of sea ice change the perpendicular structure of upper sea water, e.g. the forming and melting of sea ice significantly affect the salinity of the upper sea water, and also influence the global oceanic thermohaline circulation. Through complex feedback process, sea ice change can affect the large-scale atmospheric circulation. Deser et al. (2000) pointed out that the winter sea ice decrease of Greenland Sea goes with the decrease of surface pressure and 500hPa height and the increase of surface air temperature. Several Chinese scholars have pointed out that the Arctic sea ice can affect the temperature and precipitation patterns in China through changing storm tracks and subtropical high pressure in northwest Pacific (Fang and Wallace, 1994; Wu et al., 1999, 2001, 2004; Liu et al., 2007).
Dynamically Installed Anchors (DIAs) refer to anchors which can embed themselves by free-fall from a specified height above the seabed. They have been widely regarded as the most promising deepwater anchor concept in terms of several advantages over other anchors. First, it is economical because of ease fabrication, quick installation, and no requirement from external source of energy. Second, the installation cost is less depend on the water depth. Finally, the holding capacity is less sensitive to the soil undrained shear strength profile since higher seabed soil shear strength permit less penetration depths and vice versa. However, a degree of uncertainty still exists in relation to predicting the embedment depth and subsequent pull-out capacity especially the inclined pull-out capacity.
The pull-out capacity of DIAs can be dominated by the vertical or horizontal failure mechanisms or a combination of the two. When the combination controls, the DIAs are referred to as being under the inclined pull-out failure. This paper focuses on the inclined pull-out failure of DIAs. A series of finite element analysis on pull-out resistance of DIAs in normally consolidated clay was carried out. First, the numerical results were validated through experimental results and analytical empirical results. A proper method to model the inclined pull-out of DIA is illustrated. Then, a methodology for evaluating the inclined pull-out capacity of DIA is proposed based on the numerical parametric study. This method is capable of predicting pull-out capacity of DIA for various embedment depths and DIA aspect ratios. Finally, the design procedure for DIA is proposed.
Ahmed, Aziz (Department of Civil and Environmental Engineering, National University of Singapore) | Qian, Xudong (Department of Civil and Environmental Engineering, National University of Singapore) | Tian Peng, Benjamin Xia (Keppel Offshore & Marine Technology Centre) | Chen, Zhuo (Keppel Offshore & Marine Technology Centre) | Choudhary, Ankit (Keppel Offshore & Marine Technology Centre) | Hussain, Anis (Keppel Offshore & Marine Technology Centre)
The Arctic is an exciting frontier in the oil and gas exploration regime. A number of studies estimate that the Arctic holds about one fourth of the all undiscovered oil and gas reserves in the world. This implies a forthcoming race for the oil and gas exploration in this pristine and fragile region. Due to their relatively small environmental footprint and versatility, floating platforms have strong potential in becoming the most suitable exploration and production option for a wide range of water depths. However, compared to fixed platforms in the Arctic, research and developments associated with the application of floating platform in the arctic is extremely rare. Based on extensive literature review, this paper aims to provide a starting point towards the development of site specific floating platform solution for oil and gas exploration and production in the arctic.
The literatures studied include research works and industrial reports since the 70's and 80's to current on-going developments. The topics reviewed comprise suitable deployment regions for the arctic floaters as well as a wide variety of floaters both in conceptual and deployment phase. This paper also briefly presents various approaches to predict the effect of ice load on floaters as well as some literature review on ice management and oil spill response. The focus of this review paper comprise of theoretical, experimental as well as practical research and developments in the field of arctic floaters both by academics and industrial experts.
The Arctic region is protected by increasingly stringent local and international maritime laws and environmental protection laws and calls for extreme caution from engineering perspective in developing oil and gas exploration systems. This paper points towards the best practices to safely approach the oil and gas exploration in the Arctic based on academic research findings and industrial experiences. Comparison of the wide variety of floaters conceptualized or developed for the Arctic, aids the new studies on the similar theme to set onto the right course. Accumulation of several empirical, semi empirical and analytical methods for the prediction ice loads on a floater assists in a quick estimation of ice loads on the floaters. This section also points towards several competing detailed assessment methodologies to predict dynamic ice loads on the floaters. The literature reviews of ice management and oil spill responses make the reader aware of the resources to identify the recent developments in these fields.
Based on systematic and focused literature review of a wide range of academic studies and industrial reports, this paper briefly assimilates the state of the art on arctic floaters. This review paper targets to infer some useful initial information, on the future development projects involving floaters for oil and gas exploration in the Arctic.