Geothermal Gradients, Hydrodynamics, and Hydrocarbon Occurrences, Alberta, Canada (original) (raw)
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Canadian Journal of Earth Sciences, 1985
A large number of bottom-hole temperature (BHT) data from Alberta (55 246 BHT from 28 260 wells) have been used to construct Paleozoic and Precambrian surface-temperature maps. A northward increase of average heat flow in Alberta results in higher subsurface temperatures at the Precambrian basement and at the top of the Paleozoic toward the north and northeast than at the same depths in the south and southeast. However, the temperature distribution at these surfaces is more depth dependent than gradient dependent, and so higher temperature values occur in the western part of the basin. As a result, good geothermal energy potential exists throughout the western half of the province, especially for regions west of the Calgary -Swan Hills -Grande Prairie -Rainbow Lake line. Through the central part of the basin, zones occur where the isotherms and the isopach lines of the Phanerozoic are parallel. These zones probably represent regions where little disturbance to heat transport by vertical water motion occurs. It is suggested that zones in the central part of the basin where such parallelism does not occur may represent areas where conductive transport of heat is perturbed by local, nonlateral fluid flow or zones with nonuniform heat contribution from the crystalline crust or upper mantle. The effect of hydrodynamics in the deeper sediments of the Paleozoic that lie below the BHT observations may also contribute to such zones.
Preliminary Geothermics of the Sedimentary Basins in the
1988
A new heat flow map has been constructed for northeastern British Columbia, using log-heading temperature records corrected for drilling disturbance, at depths ranging from 200 m to over 4000 m. Geothermal gradient varies from 20 to 90 mK/m (ºC/km). A significant regional trend of southward and southwestward decrease of geothermal gradient is observed in the map area. Effective thermal conductivity, based on an analysis of an evenly distributed network of wells throughout the area, shows variation in the range 1.2 to 2.4 W/mK. Very large variations of terrestrial heat flow, from 40 to 130 mW/m 2 , suggest a large imprint of highly variable heat generation in the upper crust. The lowest heat flow is observed in the southern part of the study area and especially in the southwest. The highest heat flow is in the north, with values commonly exceeding 100 mW/m 2 . However, lower heat flow values (<60 mW/ 2 ) are also observed in the north. In the deep western part of the basin, low heat flow in the south contrasts with high heat flow north of 59ºN. Reduced (deep) heat flow in the north is probably 10 to 20 mW/m 2 higher than the average of 33 mW/m 2 proposed previously. Higher regional reduced heat flow and higher than average heat generation (2-4 µW/m 3 ) of the basement rocks likely accounts for part of the northern high heat flow. It is estimated that the average temperature at a depth of 5 km is 180ºC; however, temperatures as high as 140 ºC are recorded at the much shallower depth of 2 km in the northern and northeastern part of the study area.
Geothermal exploration of Paleozoic formations in Central Alberta
Canadian Journal of Earth Sciences, 2013
Recent geothermal exploration indicated that the Cambrian Basal Sandstone Unit (BSU) in central Alberta could be a potential target formation for geothermal heat production, due to its depth and extent. Although several studies showed that the BSU in the shallower Western Canada Sedimentary Basin (WCSB) has good reservoir properties, almost no information exists from the deeper WCSB. This study investigated the petrography of the BSU in central Alberta with help of drill cores and thin sections from six wells. Porosity and permeability as important reservoir parameters for geothermal utilization were determined by core testing. The average porosity and permeability of the BSU is 10% and <1 × 10 −14 m 2 , respectively. A zone of high porosity and permeability was identified in a well located in the northern part of the study area. This study presents the first published geomechanical tests of the BSU, which were obtained as input parameters for the simulation of hydraulic stimulation treatments. The BSU has a relatively high unconfined compressive strength (up to 97.7 MPa), high cohesion (up to 69.8 MPa), and a remarkably high friction coefficient (up to 1.22), despite a rather low tensile strength (<5 MPa). An average geothermal gradient of 35.6°C/km was calculated from about 2000 temperature values. The temperature in the BSU ranges from 65 to 120°C. Results of this study confirm that the BSU is a potential geothermal target formation, though hydraulic stimulation treatments are required to increase the permeability of the reservoir.
Geothermal Assessment of Paleozoic Aquifers in the Central Alberta Basin, Canada
The Alberta Basin as foreland basin of the Rocky Mountains is known for its resources of oil, gas and coal. Due to its characteristic flexure of the foreland lithosphere this basin type deepens significantly towards the orogenic belt. These foreland deeps host potentially sedimentary layers containing hot fluids and structurally or facies controlled high permeability domains. Two focus regions are studied by well data analysis, 2D seismic sections, stress field analysis and temperature modeling. The study areas are located around the city of Edmonton in central Alberta (basin depth 1.8 – 3.5km) and in northeastern Alberta around the town of Peace River (basin depth 1.7 – 2.4 km). Extension and thickness of potential geothermal target formations is investigated by 3D structural geological modeling, and geostatistical methods are applied to analyze the distribution of porosity, permeability and temperature within these formations. For central Alberta, the medium to coarse grained Camb...
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Oxygen and carbon isotope measurements on authigenic carbonates and silicates from Sites 856, 857, and 858, drilled during Ocean Drilling Program Leg 139 at Middle Valley, Juan de Fuca Ridge, a sedimented seafloor spreading ridge, provide a record of present and past convective fluid circulation and high-temperature gradients associated with hydrothermal alteration and the deposition of massive sulfides. Oxygen isotope compositions of authigenic carbonates from the active hydrothermal field at Site 858 show vertical thermal gradients of 2.2°C/m in distal holes (Holes 858A and 858C) and up to 10°C/m at the central vent areas (Hole 858D). The higher thermal gradient is consistent with oxygen isotope data for Mg-rich authigenic clays and quartz, which yield isotope fractionation temperatures of approximately 265°C at 32 mbsf in Hole 858B. Extrapolation of this latter gradient to greater depths indicates temperatures of approximately 400°C at depths of 4(M•5 mbsf in the sedimentary sequence, approaching values that are sufficiently high to generate ore-forming fluids at these shallow depths. Furthermore, the calculated thermal gradients from the active vent area are similar to paleo-geothermal gradients recorded in the oxygen isotopic composition of carbonates from the relic hydrothermal field at Site 856, which are higher than the modern measured geothermal gradient. Carbon and oxygen isotope data of shallow carbonates at the active hydrothermal field are consistent with methane oxidation and, together with the presence of dolomite and Mg pore-water profiles, provide evidence for the advection of cold, oxidizing surface waters at shallow depths. From about 5 mbsf to the base of the cored section at Site 858 and throughout the hydrothermal reservoir at Site 857, the carbonate cement and nodules with δ 13 C values between-lO‰ and-25‰ reflect sulfate reduction and/or thermal decomposition of organic matter. The results of this isotope study, combined with pore-water and sediment geochemistry, delineate a system of large-scale convective hydrothermal circulation through the sedimentary sequence. In addition, smaller-scale fluid advection occurs in the shallowest part of the section. The oxygen isotope data imply an altered isotopic composition for the circulating fluid indicating that the reaction rates or fluid/rock interactions must be high relative to the fluid flux rates.
Numerical modeling of hydrothermal fluid flow in the Paleoproterozoic Thelon Basin, Nunavut, Canada
Journal of Geochemical Exploration, 2010
Several researchers have suggested that upward and lateral hydrothermal fluid flow was responsible for dolomitization of various Devonian and Mississippian reservoirs in the Western Canada Sedimentary Basin (WCSB) based on sedimentological, geochemical and diagenetic evidence. In this study, a numerical model was applied to investigate hydrothermal fluid flow in the Wabamun Group, Parkland field, northeastern British Columbia, Canada. Our numerical results indicate that faults play the most critical role in controlling hydrothermal fluid flow. They provide a pathway connecting the basement of the basin and overlying sedimentary layers. Upwelling fluid flow via faults may bring reactants and heat from underlying strata to shallow formations for diagenetic reactions (e.g. dolomitization and/or chertification) or forming ore deposits. Salinity distribution of formation water, permeability configuration of host rock and regional fluid flow are also important factors affecting hot and brine fluid flow and accompanying heat and mass distribution.
Canadian Journal of Earth Sciences, 2007
Detailed fluid geochemistry studies on hydrothermal quartz veins from the Rouyn-Noranda and Val-d'Or areas along the transcrustal Cadillac Tectonic Zone (CTZ) indicate that unmineralized (with respect to gold) sections of the CTZ contained a distinct CO 2 -dominated, H 2 S-poor hydrothermal fluid. In contrast, both gold mineralized sections of the CTZ (e.g., at Orenada #2) and associated higher order shear zones have a H 2 O-CO 2 ± CH 4 -NaCl hydrothermal fluid. Their CO 2 /H 2 S ratios indicate H 2 S-rich compositions. The Br/Cl compositions in fluid inclusions trapped in these veins indicate that hydrothermal fluids have been equilibrated with the crust. Oxygen isotope ratios from hydrothermal quartz veins in the CTZ are consistently 2‰ more enriched than those of associated higher order shear zones, which are interpreted to be a function of greater fluid/rock ratios in the CTZ and lower fluid/rock ratios, and more efficient equilibration of the hydrothermal fluid with the wall rock, in higher order shear zones. An implication from this study is that the lower metal endowment of the transcrustal CTZ, when compared with the higher metal endowment in higher order shear zones (ratio of about 1 : 1000), may be the result of the lack of significant amounts of H 2 O-H 2 S rich fluids in most of the CTZ. In contrast, gold mineralization in the higher order shear zones appear to be controlled by the high H 2 S activity of the aqueous fluids, because gold was likely transported in a bisulfide complex and was deposited during sulfidation reactions in the wall rock and phase separation in the quartz veins.
Bulletin of Canadian Petroleum Geology, 2001
The northeastern GaspE Peninsula is divided into two distinct tectono-stratigraphic domains: Cambro-Ordovician rocks of the Humber and Dunnage zones, to the north, and Siluro-Devonian rocks of the GaspE Belt, to the south. The northeastern part of the GaspE Belt is being investigated for its hydrocarbon potential. This area is dissected by major NW-trending faults that divide the study area into three tectonic domains: the northern, central and southern blocks. During the Late Silurian-Early Devonian Salinic disturbance, the faults were active as synsedimentary normal faults. Faults were reactivated as dextral strike-slip faults during the Middle Devonian Acadian Orogeny. Regional Acadian folds are ENE-to E-trending. Locally, NW-trending folds related to the Salinic disturbance occur close to the faults. Because of their total organic carbon content (TOC), the Cambro-Ordovician rocks were considered to be more likely source rocks than rocks of the Siluro-Devonian Gaspd Belt before maturation. Good source rock intervals are locally present in the York River Formation, in all the tectonic blocks of the study area. These beds are rich in organic matter, are marginally mature and of limited extent. Based on TOC and Rock-Eval analyses, the Indian Point and Forillon formations show significant thicknesses of fair source rocks in some wells of the central block where most oil indications and seeps occur. Our results indicate that these source rocks have the highest hydrocarbon potential. A new calibration is proposed between the reflectance of collotelinite (standard vitrinite) and that of chitinozoans and solid bitumen, which are more common than vitrinite in marine successions of the GaspE Belt. Interpretation of reflectance analysis indicates that thermal maturation in the GaspE Belt succession is primarily related to burial and occurred during deposition of the GaspE Sandstones. Maximum burial is contemporaneous with Acadian ENE-to Etrending folding and pre-dates strike-slip faulting. Oil and condensate in Indian Point and Forillon formations were mostly produced before the Acadian deformation, but after the Salinic disturbance. Potential source rocks of the York River Formation generated some oil during and after Acadian deformation. RI~SUMI~ Le NE de la GaspEsie est divisE en deux domaines tectono-stratigraphiques distincts: les roches cambro-ordoviciennes des zones de Humber et de Dunnage au nord et les roches siluro-dEvoniennes de la ceinture de GaspE au sud. La partie NE de la ceinture de GaspE est investiguEe pour son potentiel en hydrocarbures. Cette region est traversEe par des failles majeures d'orientation NO qui divisent la region en trois domaines tectoniques: les blocs nord, central et sud. Celles-ci ont agi en failles normales durant la sedimentation tardi-silurienne-dEvonienne prEcoce pendant la pulsation salinique et ont rejouE en failles de dEcrochement dextre durant l'orogEnie acadienne au DEvonien Moyen. Les plis rEgionaux acadiens sont de direction ENE h E. Localement, des plis d'orientation NO, associEs ~ la pulsation salinique, sont spatialement associEs g des failles de mame orientation. D'apr~s leur contenu en carbone organique total, les roches cambro-ordoviciennes ont probablement EtE de meilleures roches mires que les roches siluro-dEvoniennes de la ceinture de Gasp6 avant leur maturation. Dans les trois blocs tectoniques, des roches mbres sont observEes localement dans la Formation de York River. Celles-ci sont toutefois d'extension limitEe et marginalement matures. D'aprbs les analyses de carbone organique et de Rock-Eval, des roches mbres d'Epaisseurs plus importantes, mais de qualitE moyenne, s'observent dans les formations d'Indian Point et de Forillon du bloc central, 1~ ol) la majoritE des indices d'huile sont observds. Nos rEsultats indiquent que ces roches mires ont dEj~ gEnErE la majeure pattie de leur potentiel en hydrocarbures.
Journal of Geophysical Research: Solid Earth, 1994
Apatite separated from 47 Cretaceous and Tertiary drill core and surface samples from the foreland basin strata of the Western Canada Sedimentary Basin (WCSB) have been analyzed for their apatite fission track (AFT) age and confined track length distribution. Thermal histories of the fission track data were then estimated using a constrained random search inversion technique based on the Durango apatite annealing model. Most importantly, this technique provides an estimate of the peak postdepositional temperature experienced by each sample with error bounds determined by the precision of the fission track data. Most apatite samples retain at least some tracks that formed prior to the time of maximum Cenozoic burial, assumed to be coincident with maximum temperature. Seven apatite samples were fully annealed during burial, during or following the Laramide Orogeny, and provide a minimum age of 42 Ma for heating. Lower Cretaceous samples from near the deformation front were fully annealed and attained temperatures of at least 119ø-138øC during maximum burial. In contrast, stratigraphically equivalent samples at the northeastern end of the transect near the Cold Lake heavy oil and tar sand deposits did not exceed 80øC. Paleogeothermal gradients calculated using bounded estimates of the peak temperatures experienced by the samples, together with maximum burial estimates from coal moisture studies, range from-20øC/km near the deformation front to as high as 60øC/km near the cratonic edge of the basin. This variation has the same trend as present geothermal gradients, which range from-30øC/km to 45øC/km, but indicates a greater contrast at the end of the Laramide. The results are consistent with the concept of heat transport by basinal scale fluid flow.
Cinématique et modélisation pétrolière des zones externes des montagnes Rocheuses de l'Alberta à l'ouest de Calgary -Cet article résume les principaux résultats d'une étude intégrée utilisant les données pétrolières de surface et de subsurface, réalisée avec les outils de modélisation pétrolière récemment développés à l'IFP, le long d'un transect recoupant le front des Rocheuses canadiennes de l'Alberta, entre Banff et Calgary. Dans toutes chaînes de montagnes, les compressions sont à l'origine d'un important raccourcissement tectonique, mais aussi d'importants mouvements verticaux impliquant de fortes érosions. Dans un premier temps, nous avons calculé les profils d'érosion, à partir de puits réels ou fictifs, grâce à une modélisation thermique avec le logiciel 1D Genex-Gentec. Ces profils ont permis de reconstruire la géométrie antécompression du bassin flexural crétacé de l'Alberta. Dans un deuxième temps, une modélisation cinématique et thermique directe du front des Rocheuses a été entreprise avec le logiciel 2D Thrustpack. Elle a fourni : -les géométries du bassin depuis les stades préorogéniques jusqu'au stade actuel, en passant par le stade du « bassin flexural » et les différentes étapes de plissement et de chevauchement ; -les fenêtres de maturité des différentes roches mères paléozoïques et mésozoïques en considérant un transfert thermique purement conductif. Ces géométries ont ensuite été utilisées comme conditions aux limites du logiciel Ceres pour modéliser les mouvements et les pressions de fluides, ainsi que la migration des hydrocarbures et leur piégeage dans les anticlinaux. Les résultats de cette étude améliorent considérablement notre compréhension de la chronologie de la genèse et du piégeage des hydrocarbures dans les réservoirs gréseux du Crétacé, et surtout, dans les réservoirs carbonatés du Dévonien-Carbonifère, à partir des roches mères du Crétacé et du Dévonien-Carbonifère.