Swan Hills Research Articles

Reversible operation of solid oxide cells fed with syngas derived from underground coal gasification

Underground coal gasification (UCG) technology can directly convert coal resources to syngas underground, making it important for coal utilization. In this work, the power generation, CO2 electrolysis, and reversible operation of flat-tube solid oxide cells (SOCs) fueled with UCG syngas were studied. The factors affecting the performances of flat-tube solid oxide cells were investigated. Fueled with syngas (Swan Hills, Canada) at 750 °C, the flat-tube cell achieved a maximum power density of 329.4 mW cm−2 and a current density of 650.8 mA cm−2 at 1.4 V. 100-cycle (250 h) reversible operation of flat-tube SOCs running on syngas (Swan Hills) was accomplished. No carbon deposition on the surfaces of the cell fuel channels was detected. The syngas conversion in flat-tube cells was illuminated based on density functional theory calculations.

Reservoir evaluation of dolomitized Devonian strata in the Western Canada Sedimentary Basin: implications for carbon capture, utilization, and storage

Abstract Differentially dolomitized carbonate strata in the Western Canada Sedimentary Basin (WCSB) are increasingly targeted for carbon capture, utilization, and storage (CCUS), yet few studies have evaluated the petrophysical characteristics of these conventional hydrocarbon reservoirs for this purpose. To address this, this study uses drill-core analysis (sedimentology, diagenesis, pore morphology, and distribution), together with core-plug and production data, to evaluate the properties of five depleted oil and gas fields in the Middle to Upper Devonian Swan Hills Formation, Leduc Formation and Wabamun Group. The Swan Hills and Leduc formations are composed of reef, shoal, and lagoon deposits that are predominantly fossil-rich (e.g., stromatoporoid-dominated rudstones and boundstones). In contrast, the carbonate-ramp deposits of the Wabamun Group are fossil-poor, consisting instead of variably bioturbated carbonate mudstones, wackestones, and packstones. Replacement dolomitization is variable throughout each stratigraphic unit, but generally occurs within fossil-rich and/or heavily bioturbated intervals. Fracture densities are broadly comparable in limestone and dolostone. Porosity in the Swan Hills and Leduc formations is predominantly moldic and vuggy, occurring where fossils (e.g., stromatoporoids) are partially or fully dissolved. Pore space in the Wabamun Group is mostly restricted to intercrystalline porosity in burrows. In general, burial cements (e.g., calcite and dolomite) are volumetrically insignificant and only partially fill pores. Exceptions to this include porosity-occluding cements associated with fractures and breccias in the vicinity of faults. Dolomitization and depositional facies are found to exert a strong control on pore morphology, distribution, and interconnectivity. Porosity is principally controlled by the relative abundance of skeletal grains and by the presence of burrows. These highly porous facies acted as fluid pathways during burial diagenesis, resulting in their preferential dolomitization, solution enhancement of pre-existing pores, and creation of volume reduction-related porosity. The high CO2 storage capacity and low unplanned plume migration risk (due to depositional and/or diagenetic baffles) of dolomitized reefal reservoirs (e.g., Swan Hills and Leduc formations) make them more attractive targets for CCUS than those with limited capacity and/or potential migration pathways (e.g., fault-related fractures and breccias in the Wabamun Group). These results demonstrate that drill-core analysis, in combination with legacy data, can provide valuable insights into the factors that control reservoir CO2 injectivity, plume migration, and storage capacity.

Convective Versus Conductive Heat Flow in The Central Alberta Part Of The Western Canada Sedimentary Basin

Alberta, Canada, T6H 5X2. A detailed study of the hydrogeological and geothermal regimes in the Phanerozoic sequence of the Western Canada Sedimentary Basin was carried out for the Swan Hills and Cold Lake areas in central Alberta. The study was based on the examination, processing and interpretation of information from 6276 wells distributed over a total area of 39,500 km². The information processed refers to stratigraphic picks, chemistry of formation waters, drill stem tests and bottom hole temperatures. As a result, every stratigraphic unit is defined in terms of geometry and lithology, and characterized by appropriate hydraulic and thermal parameters. A sequence of eight major aquifer groups separated by eight aquitards and two aquicludes was identified. The fluid flow in the Paleozoic aquifers is mainly horizontal and regional in nature, being driven by the difference in hydraulic potential between the high areas in the foothills and the lowland areas in the prairies. The fluid flow in the Cretaceous aquifers is of regional to intermediate type, with a significant downward component. The fluid flow in the aquitards is vertical. The very low permeability of the strata is reflected in flow velocities on the order of magnitude of 1 cm/a and less. Dimensional analysis of heat transport processes in each hydrostratigraphic unit shows that convective heat transfer is negligible with respect to conductive heat transfer. The respective values of the Peclet number for heat flow in porous media areas are less than 10-2. In the Swan Hills and Cold Lakes areas the flow of the terrestrial heat flux from the crystalline Precambrian basement of the sedimentary basin to the atmosphere is controlled by the geometry and the changes in the thermal properties of the formations in the basin. The geothermal gradients for individual layers vary from 17 mK/m for sandstone units to 42 mK/m for shales. The integral geothermal gradient of the entire sedimentary column varies between 22 mK/m and 36 mK/m. The areal distribution of the integral geothermal gradient shows a strong correlation with stratigraphy and lithology.

A facies- and sequence stratigraphy-based reservoir model for a carbonate reef complex: South Swan Hills oil pool, Alberta

We present a reservoir model for the South Swan Hills oilfield, Alberta, Canada, developed in a Devonian atoll reef, based on facies analysis and sequence stratigraphy. The analysis illustrates the complex reservoir geometries in such a reef, caused by facies variation from reef margin to reef interior and fluctuations in relative sea level. The latter resulted in cyclic deposition of facies and formation of field-scale sequence boundaries. The model is built on lithofacies analysis from high-resolution core descriptions that recorded lithologies, bioclast type and characteristics, and sedimentary structures. Core descriptions were correlated to well logs, enabling lithofacies to be mapped across the field. Lithofacies distributions permit definition of three distinct reef environments: a reef interior, a reef margin and a terminal shoal. Vertical variability is characterized using sequence stratigraphic interpretations. Two 3rd order and four 4th order sequence boundaries were identified and correlated across the reef. The analysis illustrates the complex reef geometries linked to facies variation from reef margin to reef interior and fluctuations in relative sea level. The latter resulted in cyclic deposition of facies and formation of field-scale unconformities. These and the intervening deposits represent the response to fluctuating sea level.The geological analysis was transformed into a 3-D geocellular model using a sequential indicator simulator. The simulator models lithofacies and, in turn, porosity and permeability distributions based on strong relationships between lithofacies and petrophysical properties for the three representative regions; the interior, margin and terminal shoal. The interior deposits formed forms the bulk of non-reservoir material in the centre of the reef build-up. The margin surrounded surrounds the interior and formed forms a continuous 1–2 km band of reservoir around it. Reservoir thickness is 20–30 m and primarily composed of reef flat deposits. The terminal shoal forms a reservoir body that caps the reef complex, but is disconnected from the bulk of the underlying reef by a thick layer of impermeable clay associated with a sequence boundary. The high-resolution realization displays the geometry and continuity of the reservoir and exposes demonstrates the compartmentalized and variable producibility of the atoll.

Vegetation recovery and edge effects of low impact seismic lines over eight-year period in boreal uplands of northern Alberta

As of the mid-1990 s, low impact seismic (LIS) line construction (<3 m wide) became common practice in western Canada and replaced construction of wider (5–10 m) conventional seismic lines, with the intention of mitigating the known negative environmental impacts (e.g., severe soil damage and minimal vegetation recovery) of these long, narrow corridors used by the Oil and Gas (O&G) industry for exploration. Though the apparent disturbance severity on LIS lines is lower compared to conventional lines and it is expected that succession would proceed more readily towards the conditions resembling pre-disturbance forested state in the upland boreal, there is little scientific evidence that supports this. Here, we assess environmental conditions, successional trajectories and potential edge effects extending into the adjacent forest from the LIS line edges three (2014) and eight (2019) years after their construction in 2011, in the southern upland boreal forest of Swan Hills region in northwestern Alberta, to determine if active restoration measures should be recommended. Soil moisture and light were higher on the lines compared to the adjacent forest. Bryophytes (particularly feathermosses associated with late-succession forests) recovered well within eight years of disturbance (attaining nearly 90 % cover in 2019, from a relatively low cover (∼25 %) on the lines in 2014, compared to ∼ 80–90 % in the adjacent forest in both years), while the shrub and herbaceous layers recovered minimally, and tree species were still mostly absent on these lines. Herbaceous species also had a lower cover in the ∼ 2 m zone away from the line edges compared to the interior 75 m away, indicating edge effects in both years. Our results indicate that LIS lines appear to possess a unique combination of similarities and differences to other common boreal disturbances (fire, harvest), resulting in the equally unique successional trajectories that do not generally follow patterns known to occur in upland boreal forests. Long-term monitoring is imperative to determine whether LIS lines will eventually return to the pre-disturbance conditions or whether human intervention will be required to promote the growth of the canopy cover, especially as they constitute part of the habitat for Woodland caribou, an important threatened wildlife species.

Multivariate and geochemical analyses of brines in Devonian strata of the Western Canada Sedimentary Basin for geothermal energy development

Geothermal favorability maps in the Western Canada Sedimentary Basin (WCSB) are focused on depth and temperature. The transfer of mass and heat by a geothermal system, however, depends on the brine's transport and thermodynamic properties, which are predominantly controlled by its solute geochemistry. As an ongoing attempt to identify, map, and model potential geothermal reservoirs in sedimentary formations in the WCSB, we collect brine samples from various databases and perform rigorous quality control to identify representative formation waters from the carbonate platforms and reefs of the Leduc and Swan Hills formations, and the sandstone of the Granite Wash and Gilwood formations. We carry out multivariate analysis on 1963 representative samples using major chemical components, i.e., sodium, potassium, calcium, magnesium, chloride, bicarbonate, sulfate, and brine's pH. Principal component and cluster analyses identify distinguishable hydrogeochemical groups and the corresponding influential constituents. We then examine the direct influence of fluid chemistry on the engineering aspects of geothermal energy development in terms of parasitic loads and geochemical risks. The high salinities and associated high densities in one of the groups generate significant parasitic loads, e.g., greater than 55% at 110 °C. The geochemical modeling in each group demonstrates the potential scaling risks of dolomite, calcite, and brucite. The geochemical approaches presented here can be applied to geothermal energy development in sedimentary basins around the world.

A Facies- and Sequence Stratigraphy-Based Reservoir Model for a Carbonate Reef Complex: South Swan Hills Oil Pool, Alberta

A Facies- and Sequence Stratigraphy-Based Reservoir Model for a Carbonate Reef Complex: South Swan Hills Oil Pool, Alberta

Burial dolomitization driven by modified seawater and basal aquifer‐sourced brines: Insights from the Middle and Upper Devonian of the Western Canadian Sedimentary Basin

AbstractDolomitization in the Western Canadian Sedimentary Basin has been extensively researched, producing vast geochemical datasets. This provides a unique opportunity to assess the regional sources and flux of dolomitizing fluids on a larger scale than previous studies. A meta‐analysis was conducted on stable isotope, strontium isotope (87Sr/86Sr), fluid inclusion and lithium‐rich formation water data published over 30 years, with new petrographic, X‐ray diffraction, stable isotope and rare‐earth element (REE+Y) data. The Middle to Upper Devonian Swan Hills Formation, Leduc Formation and Wabamun Group contain replacement dolomite (RD) cross‐cut by stylolites, suggesting replacement dolomitization occurred during shallow burial. Stable isotope, REE+Y and 87Sr/86Sr data indicate RD formed from Devonian seawater, then recrystallized during burial. Apart from the Wabamun Group of the Peace River Arch (PRA), saddle dolomite cement (SDC) is more δ18O(PDB) depleted than RD, and cross‐cuts stylolites, suggesting precipitation during deep burial. SDC 87Sr/86Sr data indicate contributions from 87Sr‐rich basinal brines in the West Shale Basin (WSB) and PRA, and authigenic quartz/albite suggests basinal brines interacted with underlying clastic aquifers before ascending faults into carbonate strata. The absence of quartz/albite within dolomites of the East Shale Basin (ESB) suggests dolomitizing fluids only interacted with carbonate strata. We conclude that replacement dolomitization resulted from connate Devonian seawater circulating through aquifers and faults during shallow burial. SDC precipitated during deep burial from basinal brines sourced from basal carbonates (ESB) and clastic aquifers (WSB, PRA). Lithium‐rich formation waters suggest basinal brines originated as residual evapo‐concentrated Middle Devonian seawater that interacted with basal aquifers and ascended faults during the Antler and Laramide Orogenies. These results corroborate those of previous studies but are verified by new integrated analysis of multiple datasets. New insights emphasize the importance of basal aquifers and residual evapo‐concentrated seawater in dolomitization, which is potentially applicable to other regionally dolomitized basins.

Evaluating Risk After a Hazardous Waste Treatment Plant Released Persistent Organic Pollutants: Part 3, Aboriginal Health Risk and Impact

On 16 October 1996, a malfunction at the Swan Hills Special Waste Treatment Center (SHSWTC) in Alberta, Canada, released an undetermined quantity of persistent organic pollutants (POPs) into the atmosphere, including polychlorinated biphenyls, dioxins, and furans. The circumstances of exposure are detailed in Part 1, Background and Policy Issues. An ecologically based, staged health risk assessment was conducted in two parts with two levels of government as sponsors. The first, called the Swan Hills Study, is described in Part 2. A subsequent evaluation, described here in Part 3, was undertaken by Health Canada and focused exclusively on Aboriginal residents in three communities living near the lake, downwind, and downstream of the SHSWTC of the area. It was designed to isolate effects on members living a more traditional Aboriginal lifestyle. Aboriginal communities place great cultural emphasis on access to traditional lands and derive both cultural and health benefits from “country foods” such as venison (deer meat) and local fish. The suspicion of contamination of traditional lands and the food supply made risk management exceptionally difficult in this situation. The conclusion of both the Swan Hills and Lesser Slave Lake studies was that although POPs had entered the ecosystem, no effect could be demonstrated on human exposure or health outcome attributable to the incident. However, the value of this case study is in the detail of the process, not the ultimate dimensions of risk. The findings of the Lesser Slave Lake Study have not been published previously and are incomplete.

Evaluating Risk After a Hazardous Waste Treatment Plant Released Persistent Organic Pollutants. Part 2. Ecotoxicology and Human Health Risk

On 16 October 1996, a malfunction at the Swan Hills Special Waste Treatment Center (SHSWTC) in Alberta, Canada, released an undetermined quantity of persistent organic pollutants to the atmosphere, including PCBs, PCDDs and PCDFs. The circumstances of exposure are detailed in Part 1, Background and Policy Issues. An ecologically based, staged health risk assessment was conducted in two parts with two levels of government as sponsors. The first, called the Swan Hills Study, is described in this part, which was conducted by the Government of Alberta to evaluate the human health risks, primarily by determining contaminant levels in wild game and fish and in serum of residents of the area to reflect body burden. A diet and activity survey was conducted by telephone to determine and to inform an initial advisory on consumption of country foods. A subsequent evaluation, called the Lesser Slave Lake Study, focused exclusively on Aboriginal residents in the area and is presented in Part 3 of this case study. Because this is a case study and not a research report, the findings are presented as they became available at the time of the study.

Evaluating Risk After a Hazardous Waste Treatment Plant Released Persistent Organic Pollutants. Part 1. Background and Policy Issues

On 16 October 1996, a malfunction at the Swan Hills Special Waste Treatment Center (SHSWTC) in Alberta, Canada, released an undetermined quantity of persistent organic pollutants to the atmosphere. An ecologically based, staged health risk assessment was conducted to evaluate the human health risk, the findings of which are presented in Part 2, on Ecotoxicology and Human Health Risk. The incident resulted in the largest fine for an environmental infraction in Alberta history up to that time. Despite the incident, the province of Alberta has continued to subsidize the facility and has kept it in operation, with changes in management. The policy rationale is that if the facility were not available, accumulation and possible diversion of hazardous waste into illegal disposal alternatives would threaten the environment much more than operation of the plant. This case study illustrates an ecological approach to risk assessment and an attempted culturally sensitive approach to risk management. Incidents in which people are exposed to toxic substances do not occur in a social vacuum. Risk management strategies must be adapted to groups with different cultural values and expectations. Community and individual responses to such incidents, and the development of health advisory messages, may depend on presenting information on exposure and risk in terms consistent with cultural patterns among subpopulations in the community.

Subsurface faults inferred from reflection seismic, earthquakes, and sedimentological relationships: Implications for induced seismicity in Alberta, Canada

Abstract Given the recent induced seismic activity in Alberta, identification of subsurface faults and areas of structural complexity has become increasingly important in improving our understanding of the controls on induced seismic events. Using a 3D geological model supplemented with 2D and 3D reflection seismic data, several basement-bounded and basement-rooted faults, which extend upward and into the Devonian strata, are identified in areas coincident with increased seismic activity. The presence of faults in the study area was confirmed through a statistically significant correlation of high-quality seismic event data from historical and recent (1970–2016) induced earthquakes in Alberta to the edge of the Devonian-aged Swan Hills platform. Along with the identification of faults using reflection seismic and earthquake hypocenter data, a review of the role of pre-existing structure on depositional patterns that has been previously used to infer deep structure in this area, is also presented in this study. Several pre-existing extensional and/or transtensional style faults in the deeper strata and shallow basement of the study area are consistent with structure influencing the sedimentation of the overlying stratigraphy. Therefore, a better understanding of genetic fault-reef associations and the relationship to overlying strata may aid in identification of fault locations, style, and orientation. Considering the advancement of proper avoidance strategies during the planning stages of unconventional resource development or storage, this paper demonstrates the use of geological knowledge and relationships to identify areas comprising faults that may be prone to reactivation.

A preliminary statistical model for hydraulic fracture‐induced seismicity in the Western Canada Sedimentary Basin

AbstractWe characterize the statistical relationship between hydraulic fracturing and seismicity in western Canada by using the concept of cellular seismicity. We determine the regionally averaged probability that hydraulic fracture operations will be associated with M ≥ 3 seismicity within a 10 km grid cell. This rate is 0.01 to 0.026 at the 95th percentile confidence limit. Monte Carlo simulations confirm that the observed correlations are extremely unlikely (≪1%) to have been obtained by chance. Proximity to a disposal well and proximity to the Swan Hills Formation, which has been suggested as a proxy for basement controlled faults, appear to increase the likelihood that hydraulic fracturing will trigger seismicity.

Evolution of Li-enriched oilfield brines in Devonian carbonates of the south-central Alberta Basin, Canada

There is a long and extensive history of study regarding the origins and characteristics of brines within the Alberta Basin of Canada. This study focuses on the origins of Li-enriched (>50 mg/kg) brines of the late Devonian Swan Hills, Nisku and Leduc Formations of the southwestern Alberta Basin. Available data show that two Li-enriched brines having distinctly different geochemical characteristics, and thus distinct evolutionary histories, exist within the late Devonian carbonates of the southwestern Alberta Basin. Li-enriched brine of the Swan Hills Formation appears to have been formed by dissolution of halite and mixing with Li-enriched fluids expelled from Precambrian crystalline basement. The degree of mixing between Swan Hills brines and meteoric water is unknown. Formation of Li-enriched brines in the Nisku and Leduc Formations could be explained by preferential dissolution of Li-enriched late-stage evaporite minerals, likely from the middle Devonian Prairie Evaporite Formation, into evapoconcentrated late Devonian seawater. Dense Li-enriched brine migrated downward into the underlying early Devonian Winnipegosis Formation and then westward in response to westward tilting beginning in Jurassic time. Li-enriched brine was then diluted by mixing with meteoric water driven into the Devonian of the southwestern Alberta Basin in response to hydraulic gradients created by the effects of Laramide tectonics.

Secondary anhydrites in deeply buried Devonian carbonates of the Alberta Basin, Canada

Observations from about 500 drill cores from Devonian reefs and carbonate platforms in the Alberta Basin, Canada, reveal that the Upper Devonian strata across this basin contain about 20 petrographically distinct types of anhydrite that can be placed into two groups: ‘primary’ and ‘secondary’ anhydrites. ‘Primary’ anhydrites formed syndepositionally in essentially unlithified sediments, either directly from evaporitic brines or within a few years to perhaps hundreds of years during very shallow burial (centimeters to meters). In contrast, ‘secondary’ anhydrites formed in essentially lithified sediments at burial depths of meters to thousands of meters. Some secondary anhydrites formed from gypsum at depths of less than about 600–1,100 m, others formed directly as anhydrite at greater depths. Some remobilized anhydrite invaded sour gas fields in which anhydrite had been removed previously by thermochemical sulfate reduction. In the Leduc, Swan Hills, and Nisku reefs and platform carbonates of the Alberta subsurface, and in the strata surrounding these carbonates, no primary anhydrites have been found. Rather, a few types of secondary anhydrite predominate. The sources appear to be threefold: (1) brines migrating from Middle to Late Devonian evaporite-bearing strata; (2) seawater and mesohaline brines that formed gypsum and/or anhydrite as a by-product of dolomitization; (3) redistribution of both primary and secondary anhydrites, in some cases demonstrably after maximum burial and sour gas formation. These findings are of interest to the petroleum industry because anhydrites often reduce porosity and permeability significantly.

Tracking chiral polychlorinated biphenyl sources near a hazardous waste incinerator: Fresh emissions or weathered revolatilization?

The Swan Hills Treatment Centre (SHTC), located in central Alberta, is the primary facility in Canada for incinerating polychlorinated biphenyls (PCBs). Past studies have shown significant contamination by PCBs and other pollutants of the immediate surrounding region. However, it is unclear whether the major source of contamination to the region's atmosphere is historical release incidents or long-term emissions. To answer this question, concentrations of PCBs and enantiomer fractions of several PCB congeners were determined in soil and air, via polyurethane foam passive samplers, over several seasons between 2005 and 2008. Concentrations in both media were highest for samples collected closest to the SHTC, demonstrating a concentration profile typical of a point source. Enantiomer analysis revealed racemic profiles in air for all congeners, while soil was significantly nonracemic for PCB 95, indicating significant microbial degradation of this congener. However, the primary source of this congener, and likely others, in the surrounding atmosphere is recent and continual releases from the SHTC, rather than the release of weathered PCBs previously deposited to local soils. In addition, enantiomer compositions for PCBs 95 and 149 yielded minimum biotransformation half-lives of 25 and 97 years, respectively, suggesting an expected gradual decline in the region's PCB load once fresh inputs cease.

Modelling and mapping topographic variations in forest soils at high resolution: A case study

This article examines the utility of a digitally derived cartographic depth-to-water (DTW) index to model and map variations in drainage, vegetation and soil type and select soil properties within a forested area (40 ha) of the Swan Hills, Alberta, Canada. This index was derived from a LiDAR (Light Detection and Ranging) derived digital elevation model (DEM), with at least 1 ground return per m 2. The resulting DTW pattern was set to be zero along all DEM-derived flow channels, each with a 4 ha flow-initiation threshold. Soil type (luvisol, gleysol, mesisol), drainage type (very poor to excessive), vegetation type (hydric to xeric) and forest floor depth were determined along hillslope transects. These determinations conformed more closely to the DEM-derived log 10(DTW) variations ( R 2 > 60%) than to the corresponding variations of the widely used topographic wetness index (TWI) ( R 2 < 25%). Setting log 10(DTW) thresholds to represent the wet to moist to dry transitions between vegetation, drainage and soil type enabled a high-resolution mapping of these types across the study area. Also determined were soil moisture content, coarse fragment and soil particle composition (sand, silt, clay), pH, total C, N, S, P, Ca, Mg, K, Fe, Al, Mn, Zn, and available Ca, Mg, K, P and NH 4, by soil layer type and depth. Most of these variables were also more correlated with log 10(DTW) than with TWI, with and without soil layer depth as an additional regression variable. These variables are, therefore, subject to topographic controls to at least some extent, and can be modelled and mapped accordingly, as illustrated for soil moisture, forest floor depth and pH across the study area, from ridge tops to depressions. Further examinations revealed that the DEM-produced DTW and TWI patterns complemented one another, with DTW delineating soils in relation to local water-table influences, and with TWI delineating where the water would flow and accumulate.

Gully erosion in the Swan Hills, Alberta

Deforestation related to development work in the Swan Hills oilfield has resulted in gullying in road ditches, power lines and pipelines, right-of-ways and on well sites. The study of a large number of these gullies developed in clay and soft shale has made it possible to establish a nomograph to locate erosion control check dams. More importantly, the study suggests research avenues to determine the resistance of poorly consolidated material to erosion by running water.

Depositional facies analysis and modeling of the Judy Creek reef complex of the Upper Devonian Swan Hills, Alberta, Canada: Reply

Depositional facies analysis and modeling of the Judy Creek reef complex of the Upper Devonian Swan Hills, Alberta, Canada: Reply

Depositional facies analysis and modeling of the Judy Creek reef complex of the Upper Devonian Swan Hills, Alberta, Canada: Discussion

2nd revised manuscript received February 17, 2010 Jack Wendte The article of Ma et al. (2009) in the September 2009 issue of the Bulletin fails to provide credible evidence or to cite references to support the stratigraphic framework and facies analysis on which their numerical modeling of the Judy Creek reef complex is based. Ma et al. (2009) subdivide the reef into a lower rimmed reef phase, consisting of the R1, R2, R3, and R4 cycles, and an upper ramp-bounded shoal complex, consisting of the R5A, R5B, and R5C cycles (p. 1238, 2d and 3d paragraphs). However, they do not present evidence or cite references to support these subdivisions. In the Wendte (1992) article, I subdivided the reef reservoir into two main phases of growth, an underlying rimmed-reef phase approximately 43 m (∼140 ft) thick and an overlying ramp-bounded shoal complex, up to 30 m (100 ft) thick, separated by a subaerial unconformity that I termed R4. The top of the ramp-bounded shoal complex …