Draga Talinga - Academia.edu (original) (raw)

Papers by Draga Talinga

AGU Fall Meeting Abstracts, Dec 1, 2013

Following growth of the Canadian Cordillera during the Mesozoic, the southern Cordillera was subj... more Following growth of the Canadian Cordillera during the Mesozoic, the southern Cordillera was subject to extension during the Paleocene and Eocene that correlated with widespread volcanic activity in south-central British Columbia, including across much of the Nechako-Chilcotin plateau. In 2008, Geoscience BC acquired 330 km of deep vibroseis reflection profiles on the plateau, mostly over the Stikinia arc terrane, but also over its eastern contact with the oceanic Cache Creek terrane. All seven seismic reflection lines reveal a strongly reflective lower crust that extends from 7 to 9 s down to the Moho, which is defined by the downward termination of reflectivity at 11-12 s. In the uppermost crust, extension occurred by block faulting with faults soling into subhorizontal to shallowly dipping detachments above 10 km depth. Extension in the deeper upper and middle crust, which was partly controlled by antiforms likely related to earlier shortening, was accommodated on a network of anastomosing shear zones that sole out into the top of the reflective lower crust. The lower crustal reflections correlate with seismic P-wave velocities of 6.45-6.98 km/s, indicating that the reflective lower crust has a more mafic composition than the middle crust. As in other extensional settings, we suggest that this pervasive fabric of reflectors arises from the intrusion of mantle-derived basaltic magma into zones of ductile shearing, and that differentiation of these melts resulted in the widespread Paleocene to Eocene volcanism. Reflector dips indicate that extension was approximately east-west, consistent with north-northwest-trending horsts separated by basins filled with Paleocene to Eocene volcanic and volcaniclastic rocks. Résumé : Après la croissance de la Cordillère canadienne au Mésozoïque, la Cordillère sud a subi une extension durant le Paléocène et l'Éocène; cette extension était corrélée avec une activité volcanique étendue dans le centre-sud de la Colombie-Britannique, incluant à travers une grande partie du plateau Nechako-Chilcotin. En 2008, Geoscience BC a acquis 330 km de profiles vibrosismiques en profondeur sur le plateau, surtout au-dessus du terrane d'arc de Stikinia mais aussi par-dessus son contact est avec le terrane océanique de Cache Creek. Les sept lignes de sismique réflexion révèlent toutes une croûte inférieure fortement réflective qui s'étend depuis 7-9 s jusqu'au Moho, ce qui est défini par la terminaison vers le bas de la réflectivité à 11-12 s. Dans la croûte sommitale, l'extension s'est produite par le morcellement en bloc par des failles; les failles formant une semelle dans les détachements subhorizontaux ou avec un léger pendage, au-dessus de la profondeur de 10 km. L'extension dans les croûtes supérieure et médiane, plus profondes, partiellement contrôlée par des antiformes fort probablement reliés à un rétrécissement antérieur, était facilitée par un réseau de zones de cisaillement anastomosées qui forment une semelle sur le dessus de la couche inférieure réfléchissante. Les réflexions de la croûte inférieure correspondent à des vitesses de l'onde sismique P de 6,45-6,98 km/s, indiquant que la croûte inférieure réflective a une composition plus mafique que la croûte intermédiaire. Tout comme dans les autres environnements d'extension, nous suggérons que cette fabrique étendue des réflecteurs découle de l'intrusion de magma basaltique provenant du manteau dans des zones de cisaillement ductile, et que la différentiation de ces magmas a donné le volcanisme généralisé du Paléocène à l'Éocène. Les pendages des réflecteurs indiquent que l'extension était environ est-ouest, ce qui concorde avec des horsts de tendance nord-nord-ouest séparés par des bassins remplis de roches volcaniques et volcanoclastiques datant du Paléocène à l'Éocène. [Traduit par la Rédaction]

Caprock integrity is a critical safety issue oil-sands reservoirs, during thermal production with... more Caprock integrity is a critical safety issue oil-sands reservoirs, during thermal production with steam-assisted gravity drainage (SAGD). We present a method for in-situ anisotropic stress field characterization in the Clearwater Formation, which represents the caprock for the two Athabasca oil-sands reservoirs studied. The geomechanical parameters derived from seismic data are integrated with knowledge obtained from dipole sonic logs about formation's anisotropy. A key point in this method is the estimation of the normal fracture weakness parameter based on constraints on the compressional velocity of the intact rock, under the assumption of horizontal transverse isotropy. The constraints were necessary because not all the elastic moduli can be recovered using only density, compressional, and fast and slow shear wave data recorded in a borehole. The minimum (σ h), and maximum (σ H), horizontal stress were then expressed as a combination of the normal fracture weakness, Lamé parameters (incompressibility and shear modulus µ), and the vertical stress. The two principal horizontal stresses were further used to evaluate the differential horizontal stress ratio. Comparisons of minimum horizontal stress obtained from this method, with in-situ minimum horizontal stress estimated from injection testing at several wells, showed a very good consistency, with less than 0.3 MPa differences. Further away from the wells, the principal horizontal stresses (maximum and minimum) were predicted using Lamé parameters seismic volumes determined from PP-PS prestack inversion analysis. The differences between seismic and mini-frac estimations of minimum horizontal stress were within 0.05-0.6 MPa. The estimated stress field compared well with results from the amplitude variations with azimuth (AVAZ) inversion analysis. For example, the large differential horizontal stress ratio areas show high fracture density, and the fractures that are locally confined to areas of high stress ratio are oriented parallel to the direction of the regional maximum horizontal stress.

Fracture analyses from 3D P-wave data were conducted for the Cabin Creek overthrust area in the A... more Fracture analyses from 3D P-wave data were conducted for the Cabin Creek overthrust area in the Alberta Foothills. Mapping event traveltime differences on prestack-migrated, limited source-receiver azimuth sections is a new developed method of fracture characterization. Good fold and azimuth/offset distribution allowed extension of the method to include cross-correlation of commonazimuth stacked data for both shallow and deep events. A second method applied was azimuthal traveltime inversion, based on moveout ellipticity. By using two different wide-azimuth processing techniques, the objective was to determine if the fracture model can be realized when some of the most critical parameters (matrix velocity and symmetry axis direction) are unknown. The orientations predicted are consistent within dipping Cretaceous strata, and correlate with fracture orientations from well data. The symmetry axis direction rotates with depth, and a fluid contact was interpreted within a Cretaceous fold. Analysis for sub-horizontal Jurassic, Paleozoic and Cambrian events showed both similarities and differences in the results.

Summary In this study we investigated a model for the estimation of pore pressure using compactio... more Summary In this study we investigated a model for the estimation of pore pressure using compaction trends and a modified Eaton’s method which considers effective stress. The region’s complexity required an understanding of the tectonic and depositional history prior to the interpretation of normal compaction trends and calibrations with formation pressure measurements. The pore pressure prediction model was then used to estimate the pore pressure distribution using results from simultaneous inversion of 3D seismic data. We integrated the results with a detailed structural and lithological model to evaluate the reservoir connectivity and the complex relationship between pressures, lithology and porosity distribution, structural framework, and fault geometry and sealing properties.

Canadian Journal of Earth Sciences, Apr 1, 2014

Across the Nechako-Chilcotin plateau of British Columbia, the distribution of Cretaceous sediment... more Across the Nechako-Chilcotin plateau of British Columbia, the distribution of Cretaceous sedimentary rocks, which are considered prospective for hydrocarbon exploration, is poorly known due to the surface cover of glacial deposits and Tertiary volcanic rocks. To constrain the subsurface distribution of these Cretaceous rocks, in 2008 Geoscience BC acquired seven long, up to 14.4 km, offset vibroseis seismic reflection lines across a north-northwest-trending belt of exhumed sedimentary rocks inferred to be part of the Taylor Creek Group. P-wave velocity models, which are consistent with sonic logs from nearby wells, have been estimated using three-dimensional first-arrival tomography to depths ranging from 1 to 4 km. Igneous basement can be identified on most lines using the 5.5 km/s isovelocity contour, which locates the top of the basement to an accuracy of ϳ400 m where its depth is known in exploration wells. There is no general distinction on the basis of seismic velocity between Cretaceous sedimentary and Paleocene-Eocene volcanic-volcaniclastic rocks, both of which appear to be characterized in the tomographic models by velocities of 3.0-5.0 km/s. The geometry of the igneous basement inferred from the velocity models identifies north-trending basins and ridges, which correlate with exposed rocks of the Jurassic Hazelton Group. Identified Cretaceous sedimentary rocks occur beneath less negative Bouguer gravity anomalies, but the original distribution of these rocks has been disrupted by later Tertiary extension that created north-trending basins associated with the most negative gravity anomalies. We suggest that Cretaceous sedimentary rocks, if deposited, could be preserved within these basins if the rocks had not been eroded prior to Tertiary extension. Résumé : À travers le plateau de Nechako-Chilcotin de la Colombie-Britannique, la distribution des roches sédimentaires du Crétacé, lesquelles sont considérées prometteuses pour l'exploration des hydrocarbures, est mal connue en raison des dépôts glaciaires et des roches volcaniques du Tertiaire qui recouvrent la surface. Afin de délimiter la distribution sous la surface de ces roches du Crétacé, Geoscience BC a acquis, en 2008, sept longues lignes décalées, de réflexion vibrosismique, atteignant 14,4 km, à travers une ceinture à tendance nord-nord-ouest de roches sédimentaires exhumées, qui feraient partie du Groupe de Taylor Creek. Les modèles de vitesse de l'onde P, concordant avec les diagraphies acoustiques provenant de puits avoisinants, ont été estimés au moyen de la tomographie tridimensionnelle des premières ondes arrivées à des profondeurs variant de 1 à 4 km. Le socle igné peut être identifié sur la plupart des lignes en utilisant le contour d'isovitesse de 5,5 km/s, ce qui situe le sommet du socle avec une précision de~400 m, où sa profondeur est connue dans les puits d'exploration. En se basant sur les vitesses sismiques, il n'y a pas de distinction générale entre les roches sédimentaires du Crétacé et les roches volcaniques-volcanoclastiques du Paléocène-Éocène; les deux ensembles de roches semblent être caractérisés dans les modèles tomographiques par des vitesses de 3,0 à 5,0 km/s. La géométrie du socle igné, inférée à partir des modèles de vitesse, identifie des bassins et des crêtes à tendance nord, qui correspondent à des roches en surface du Groupe de Hazelton (Jurassique). Les roches sédimentaires du Crétacé identifiées se trouvent sous les anomalies gravimétriques de Bouguer moins négatives; cependant, la distribution originale de ces roches a été perturbée plus tard par une extension au Tertiaire, qui a créé les bassins à tendance nord associés aux anomalies gravimétriques les plus négatives. Nous suggérons que les roches sédimentaires du Crétacé, si elles avaient été déposées, pourraient avoir été préservées dans ces bassins si la roche n'avait pas été érodée avant l'extension au Tertiaire. [Traduit par la Rédaction]

Canadian Journal of Earth Sciences, Apr 1, 2014

Following growth of the Canadian Cordillera during the Mesozoic, the southern Cordillera was subj... more Following growth of the Canadian Cordillera during the Mesozoic, the southern Cordillera was subject to extension during the Paleocene and Eocene that correlated with widespread volcanic activity in south-central British Columbia, including across much of the Nechako-Chilcotin plateau. In 2008, Geoscience BC acquired 330 km of deep vibroseis reflection profiles on the plateau, mostly over the Stikinia arc terrane, but also over its eastern contact with the oceanic Cache Creek terrane. All seven seismic reflection lines reveal a strongly reflective lower crust that extends from 7 to 9 s down to the Moho, which is defined by the downward termination of reflectivity at 11-12 s. In the uppermost crust, extension occurred by block faulting with faults soling into subhorizontal to shallowly dipping detachments above 10 km depth. Extension in the deeper upper and middle crust, which was partly controlled by antiforms likely related to earlier shortening, was accommodated on a network of anastomosing shear zones that sole out into the top of the reflective lower crust. The lower crustal reflections correlate with seismic P-wave velocities of 6.45-6.98 km/s, indicating that the reflective lower crust has a more mafic composition than the middle crust. As in other extensional settings, we suggest that this pervasive fabric of reflectors arises from the intrusion of mantle-derived basaltic magma into zones of ductile shearing, and that differentiation of these melts resulted in the widespread Paleocene to Eocene volcanism. Reflector dips indicate that extension was approximately east-west, consistent with north-northwest-trending horsts separated by basins filled with Paleocene to Eocene volcanic and volcaniclastic rocks. Résumé : Après la croissance de la Cordillère canadienne au Mésozoïque, la Cordillère sud a subi une extension durant le Paléocène et l'Éocène; cette extension était corrélée avec une activité volcanique étendue dans le centre-sud de la Colombie-Britannique, incluant à travers une grande partie du plateau Nechako-Chilcotin. En 2008, Geoscience BC a acquis 330 km de profiles vibrosismiques en profondeur sur le plateau, surtout au-dessus du terrane d'arc de Stikinia mais aussi par-dessus son contact est avec le terrane océanique de Cache Creek. Les sept lignes de sismique réflexion révèlent toutes une croûte inférieure fortement réflective qui s'étend depuis 7-9 s jusqu'au Moho, ce qui est défini par la terminaison vers le bas de la réflectivité à 11-12 s. Dans la croûte sommitale, l'extension s'est produite par le morcellement en bloc par des failles; les failles formant une semelle dans les détachements subhorizontaux ou avec un léger pendage, au-dessus de la profondeur de 10 km. L'extension dans les croûtes supérieure et médiane, plus profondes, partiellement contrôlée par des antiformes fort probablement reliés à un rétrécissement antérieur, était facilitée par un réseau de zones de cisaillement anastomosées qui forment une semelle sur le dessus de la couche inférieure réfléchissante. Les réflexions de la croûte inférieure correspondent à des vitesses de l'onde sismique P de 6,45-6,98 km/s, indiquant que la croûte inférieure réflective a une composition plus mafique que la croûte intermédiaire. Tout comme dans les autres environnements d'extension, nous suggérons que cette fabrique étendue des réflecteurs découle de l'intrusion de magma basaltique provenant du manteau dans des zones de cisaillement ductile, et que la différentiation de ces magmas a donné le volcanisme généralisé du Paléocène à l'Éocène. Les pendages des réflecteurs indiquent que l'extension était environ est-ouest, ce qui concorde avec des horsts de tendance nord-nord-ouest séparés par des bassins remplis de roches volcaniques et volcanoclastiques datant du Paléocène à l'Éocène. [Traduit par la Rédaction]

Interpretation, Nov 1, 2019

One of the challenges encountered during the life cycle of an oil-sand thermal-production reservo... more One of the challenges encountered during the life cycle of an oil-sand thermal-production reservoir is the prediction of the formation pore pressure and in situ stress regime during the assessment phase of the reservoir development and, more importantly, during the development phase. We have investigated the state of formation pore pressure and stress in the overburdenrepresented by the Clearwater Formation, Grand Rapids Formation, and Colorado Groupof a preproduction oil-sands reservoir situated in the Athabasca Basin of Alberta, Canada. Our methodology integrates pressure data from piezometers, stress data from mini-frac (MF), dipole sonic logs, and elastic properties obtained from multicomponent 3D seismic inversion data. It combines the Terzaghi effective stresses with the Schoenberg and Sayers elastic stiffness matrix for horizontal transversely isotropic fractured materials. The total principal stresses (vertical, minimum, and maximum horizontal stresses) are expressed as functions of the normal fracture weakness (anisotropic correction factor), formation pore pressure, seismic data (Lamé constants), and the Biot-Willis coefficient. The effective principal stresses are estimated from the equivalent total principal stresses and the formation pore pressure multiplied by the Biot-Willis coefficient. On all three overburden intervals analysed, the relations between principal stresses indicate a normal stress regime. The estimated total minimum horizontal stress matches the MF values within 10%. The formation pore pressure, along with the 3D seismically derived estimates of the total and effective principal stresses, allows for better assessment of the caprock integrity and for operational savings based on a reduced number of MF tests. It can also be used for stress estimation within the formations hosting aquifers, which is so important for thermal production. Understanding the subsurface on the reservoir area is important for efficient production, but knowing the subsurface of the overburden is equally important for reducing potential issues due to production.

Interpretation, Feb 1, 2019

In the Athabasca Basin of Alberta, Canada, the Lower Cretaceous McMurray Formation reservoir is o... more In the Athabasca Basin of Alberta, Canada, the Lower Cretaceous McMurray Formation reservoir is overlain by the Clearwater Formation, a regionally continuous layer composed predominantly of shales with interbedded mudstones. The shales form the reservoir caprock and have the role of blocking the vertical migration of the steam from thermal oil production by confining the stresses and the deformations. We have developed a new method for the 3D seismic reconstruction of the anisotropic stress field, which accounts for the formation pore pressure and the effective stress. We integrated anisotropy estimated from dipole sonic logs with formation pore pressure data from piezometers and elastic properties obtained from multicomponent seismic inversion. The method combines the Terzaghi effective stress with the Schoenberg and Sayers elastic stiffness matrix for horizontal transversely isotropic (HTI) fractured materials. The key points of this method are the estimation of the formation pore pressure in the abnormal regime of the Clearwater Formation, the normal fracture weakness parameter (based on constraints on the compressional velocity of the intact rock under the HTI assumption), and the 3D seismic anisotropic stress field. We expressed the total vertical stress as the weight of the overlying formations, and the total minimum and maximum horizontal stresses as a combination of the total vertical stress, normal fracture weakness, formation pore pressure, Biot-Willis coefficient, and Lamé elastic constants. The effective principal stresses are estimated from the equivalent total principal stresses and the formation pore pressure multiplied by the Biot-Willis coefficient. We observed excellent consistency between the calculated total minimum horizontal stress and mini-frac values. This new method for the 3D seismic reconstruction of the anisotropic stress field allows for the assessment of the caprock integrity and for operational savings based on a reduced number of mini-frac measurements, and it can be used for time-lapse stress estimation within the thermal production reservoir.

Interpretation, 2019

One of the challenges encountered during the life cycle of an oil-sand thermal-production reservo... more One of the challenges encountered during the life cycle of an oil-sand thermal-production reservoir is the prediction of the formation pore pressure and in situ stress regime during the assessment phase of the reservoir development and, more importantly, during the development phase. We have investigated the state of formation pore pressure and stress in the overburden — represented by the Clearwater Formation, Grand Rapids Formation, and Colorado Group — of a preproduction oil-sands reservoir situated in the Athabasca Basin of Alberta, Canada. Our methodology integrates pressure data from piezometers, stress data from mini-frac (MF), dipole sonic logs, and elastic properties obtained from multicomponent 3D seismic inversion data. It combines the Terzaghi effective stresses with the Schoenberg and Sayers elastic stiffness matrix for horizontal transversely isotropic fractured materials. The total principal stresses (vertical, minimum, and maximum horizontal stresses) are expressed a...

Interpretation, 2018

In the Athabasca Basin of Alberta, Canada, the Lower Cretaceous McMurray Formation reservoir is o... more In the Athabasca Basin of Alberta, Canada, the Lower Cretaceous McMurray Formation reservoir is overlain by the Clearwater Formation, a regionally continuous layer composed predominantly of shales with interbedded mudstones. The shales form the reservoir caprock and have the role of blocking the vertical migration of the steam from thermal oil production by confining the stresses and the deformations. We have developed a new method for the 3D seismic reconstruction of the anisotropic stress field, which accounts for the formation pore pressure and the effective stress. We integrated anisotropy estimated from dipole sonic logs with formation pore pressure data from piezometers and elastic properties obtained from multicomponent seismic inversion. The method combines the Terzaghi effective stress with the Schoenberg and Sayers elastic stiffness matrix for horizontal transversely isotropic (HTI) fractured materials. The key points of this method are the estimation of the formation pore...

SEG Technical Program Expanded Abstracts 2014, 2014

We present a case study of oil sands reservoir characterization using resistivity and density sei... more We present a case study of oil sands reservoir characterization using resistivity and density seismic volumes estimated from multicomponent seismic data. In the Athabasca Oil Sands region of Alberta, the Lower Cretaceous McMurray Formation is the reservoir. In this reservoir the sand can be differentiated from shale based on density. The sands could be wet or bitumen bearing and resistivity proved to be the only property which can differentiate between the two kinds of sands. We estimated resistivity from multicomponent 3D seismic data integrated with cores and wells data. Our workflow includes petrophysical analysis, joint PP-PS prestack inversion and neural network analysis. Joint PP-PS prestack inversion produces very good estimates of the elastic properties: P-and S-wave velocities and density. Neural network analysis is used for density and resistivity estimation. In all neural network analyses the most significant seismic attributes include converted-wave information. Key problems solved include excellent pay characterization, correct flank water mapping and accurate identification of high versus low oil saturation in zones with high salinity bitumen sand.

Proceedings 76th EAGE Conference and Exhibition 2014, 2014

The Lower Cretaceous McMurray Formation reservoir used in this study is located in the Athabasca ... more The Lower Cretaceous McMurray Formation reservoir used in this study is located in the Athabasca basin, of the Northern Alberta, Canada. High resolution multicomponent 3D seismic data, along with core and well data were processed using the most advanced workflows in order to image the reservoir heterogeneity. These workflows include petrophysical analysis, joint PP-PS inversion and neural network analysis. Three inversions using PP and PS seismic data are analyzed and compared. The joint PP-PS inversion of the prestack seismic data produces the best estimates of P-impedance, S-Impedance and density, allowing for excellent reservoir characterization. Neural network analysis is used to enhance the resolution of the elastic properties estimated from joint PP-PS prestack inversion, and to estimate petrophysical and engineering properties such as porosity, resistivity and saturation. In all neural network analyses the most significant seismic attributes include converted-wave information. Some of the results are: 1. converted-wave seismic data have a major role in oil-sands reservoir characterization; 2. estimated density seismic volume shows a good separation of the two bitumen sands; 3. P-wave velocity seismic allows better mapping of the McMurray top; 4. estimated resistivity allows not only to differentiate the reservoir from the non-reservoir but also bitumen sand from water sand.

cspg.org

Fracture analyses from 3D P-wave data were conducted for the Cabin Creek overthrust area in the A... more Fracture analyses from 3D P-wave data were conducted for the Cabin Creek overthrust area in the Alberta Foothills. Mapping event traveltime differences on prestack-migrated, limited source-receiver azimuth sections is a new developed method of fracture characterization. Good fold and azimuth/offset distribution allowed extension of the method to include cross-correlation of commonazimuth stacked data for both shallow and deep events. A second method applied was azimuthal traveltime inversion, based on moveout ellipticity. By using two different wide-azimuth processing techniques, the objective was to determine if the fracture model can be realized when some of the most critical parameters (matrix velocity and symmetry axis direction) are unknown. The orientations predicted are consistent within dipping Cretaceous strata, and correlate with fracture orientations from well data. The symmetry axis direction rotates with depth, and a fluid contact was interpreted within a Cretaceous fold. Analysis for sub-horizontal Jurassic, Paleozoic and Cambrian events showed both similarities and differences in the results.

AGU Fall Meeting Abstracts, Dec 1, 2013

Following growth of the Canadian Cordillera during the Mesozoic, the southern Cordillera was subj... more Following growth of the Canadian Cordillera during the Mesozoic, the southern Cordillera was subject to extension during the Paleocene and Eocene that correlated with widespread volcanic activity in south-central British Columbia, including across much of the Nechako-Chilcotin plateau. In 2008, Geoscience BC acquired 330 km of deep vibroseis reflection profiles on the plateau, mostly over the Stikinia arc terrane, but also over its eastern contact with the oceanic Cache Creek terrane. All seven seismic reflection lines reveal a strongly reflective lower crust that extends from 7 to 9 s down to the Moho, which is defined by the downward termination of reflectivity at 11-12 s. In the uppermost crust, extension occurred by block faulting with faults soling into subhorizontal to shallowly dipping detachments above 10 km depth. Extension in the deeper upper and middle crust, which was partly controlled by antiforms likely related to earlier shortening, was accommodated on a network of anastomosing shear zones that sole out into the top of the reflective lower crust. The lower crustal reflections correlate with seismic P-wave velocities of 6.45-6.98 km/s, indicating that the reflective lower crust has a more mafic composition than the middle crust. As in other extensional settings, we suggest that this pervasive fabric of reflectors arises from the intrusion of mantle-derived basaltic magma into zones of ductile shearing, and that differentiation of these melts resulted in the widespread Paleocene to Eocene volcanism. Reflector dips indicate that extension was approximately east-west, consistent with north-northwest-trending horsts separated by basins filled with Paleocene to Eocene volcanic and volcaniclastic rocks. Résumé : Après la croissance de la Cordillère canadienne au Mésozoïque, la Cordillère sud a subi une extension durant le Paléocène et l'Éocène; cette extension était corrélée avec une activité volcanique étendue dans le centre-sud de la Colombie-Britannique, incluant à travers une grande partie du plateau Nechako-Chilcotin. En 2008, Geoscience BC a acquis 330 km de profiles vibrosismiques en profondeur sur le plateau, surtout au-dessus du terrane d'arc de Stikinia mais aussi par-dessus son contact est avec le terrane océanique de Cache Creek. Les sept lignes de sismique réflexion révèlent toutes une croûte inférieure fortement réflective qui s'étend depuis 7-9 s jusqu'au Moho, ce qui est défini par la terminaison vers le bas de la réflectivité à 11-12 s. Dans la croûte sommitale, l'extension s'est produite par le morcellement en bloc par des failles; les failles formant une semelle dans les détachements subhorizontaux ou avec un léger pendage, au-dessus de la profondeur de 10 km. L'extension dans les croûtes supérieure et médiane, plus profondes, partiellement contrôlée par des antiformes fort probablement reliés à un rétrécissement antérieur, était facilitée par un réseau de zones de cisaillement anastomosées qui forment une semelle sur le dessus de la couche inférieure réfléchissante. Les réflexions de la croûte inférieure correspondent à des vitesses de l'onde sismique P de 6,45-6,98 km/s, indiquant que la croûte inférieure réflective a une composition plus mafique que la croûte intermédiaire. Tout comme dans les autres environnements d'extension, nous suggérons que cette fabrique étendue des réflecteurs découle de l'intrusion de magma basaltique provenant du manteau dans des zones de cisaillement ductile, et que la différentiation de ces magmas a donné le volcanisme généralisé du Paléocène à l'Éocène. Les pendages des réflecteurs indiquent que l'extension était environ est-ouest, ce qui concorde avec des horsts de tendance nord-nord-ouest séparés par des bassins remplis de roches volcaniques et volcanoclastiques datant du Paléocène à l'Éocène. [Traduit par la Rédaction]

Caprock integrity is a critical safety issue oil-sands reservoirs, during thermal production with... more Caprock integrity is a critical safety issue oil-sands reservoirs, during thermal production with steam-assisted gravity drainage (SAGD). We present a method for in-situ anisotropic stress field characterization in the Clearwater Formation, which represents the caprock for the two Athabasca oil-sands reservoirs studied. The geomechanical parameters derived from seismic data are integrated with knowledge obtained from dipole sonic logs about formation's anisotropy. A key point in this method is the estimation of the normal fracture weakness parameter based on constraints on the compressional velocity of the intact rock, under the assumption of horizontal transverse isotropy. The constraints were necessary because not all the elastic moduli can be recovered using only density, compressional, and fast and slow shear wave data recorded in a borehole. The minimum (σ h), and maximum (σ H), horizontal stress were then expressed as a combination of the normal fracture weakness, Lamé parameters (incompressibility and shear modulus µ), and the vertical stress. The two principal horizontal stresses were further used to evaluate the differential horizontal stress ratio. Comparisons of minimum horizontal stress obtained from this method, with in-situ minimum horizontal stress estimated from injection testing at several wells, showed a very good consistency, with less than 0.3 MPa differences. Further away from the wells, the principal horizontal stresses (maximum and minimum) were predicted using Lamé parameters seismic volumes determined from PP-PS prestack inversion analysis. The differences between seismic and mini-frac estimations of minimum horizontal stress were within 0.05-0.6 MPa. The estimated stress field compared well with results from the amplitude variations with azimuth (AVAZ) inversion analysis. For example, the large differential horizontal stress ratio areas show high fracture density, and the fractures that are locally confined to areas of high stress ratio are oriented parallel to the direction of the regional maximum horizontal stress.

Fracture analyses from 3D P-wave data were conducted for the Cabin Creek overthrust area in the A... more Fracture analyses from 3D P-wave data were conducted for the Cabin Creek overthrust area in the Alberta Foothills. Mapping event traveltime differences on prestack-migrated, limited source-receiver azimuth sections is a new developed method of fracture characterization. Good fold and azimuth/offset distribution allowed extension of the method to include cross-correlation of commonazimuth stacked data for both shallow and deep events. A second method applied was azimuthal traveltime inversion, based on moveout ellipticity. By using two different wide-azimuth processing techniques, the objective was to determine if the fracture model can be realized when some of the most critical parameters (matrix velocity and symmetry axis direction) are unknown. The orientations predicted are consistent within dipping Cretaceous strata, and correlate with fracture orientations from well data. The symmetry axis direction rotates with depth, and a fluid contact was interpreted within a Cretaceous fold. Analysis for sub-horizontal Jurassic, Paleozoic and Cambrian events showed both similarities and differences in the results.

Summary In this study we investigated a model for the estimation of pore pressure using compactio... more Summary In this study we investigated a model for the estimation of pore pressure using compaction trends and a modified Eaton’s method which considers effective stress. The region’s complexity required an understanding of the tectonic and depositional history prior to the interpretation of normal compaction trends and calibrations with formation pressure measurements. The pore pressure prediction model was then used to estimate the pore pressure distribution using results from simultaneous inversion of 3D seismic data. We integrated the results with a detailed structural and lithological model to evaluate the reservoir connectivity and the complex relationship between pressures, lithology and porosity distribution, structural framework, and fault geometry and sealing properties.

Canadian Journal of Earth Sciences, Apr 1, 2014

Across the Nechako-Chilcotin plateau of British Columbia, the distribution of Cretaceous sediment... more Across the Nechako-Chilcotin plateau of British Columbia, the distribution of Cretaceous sedimentary rocks, which are considered prospective for hydrocarbon exploration, is poorly known due to the surface cover of glacial deposits and Tertiary volcanic rocks. To constrain the subsurface distribution of these Cretaceous rocks, in 2008 Geoscience BC acquired seven long, up to 14.4 km, offset vibroseis seismic reflection lines across a north-northwest-trending belt of exhumed sedimentary rocks inferred to be part of the Taylor Creek Group. P-wave velocity models, which are consistent with sonic logs from nearby wells, have been estimated using three-dimensional first-arrival tomography to depths ranging from 1 to 4 km. Igneous basement can be identified on most lines using the 5.5 km/s isovelocity contour, which locates the top of the basement to an accuracy of ϳ400 m where its depth is known in exploration wells. There is no general distinction on the basis of seismic velocity between Cretaceous sedimentary and Paleocene-Eocene volcanic-volcaniclastic rocks, both of which appear to be characterized in the tomographic models by velocities of 3.0-5.0 km/s. The geometry of the igneous basement inferred from the velocity models identifies north-trending basins and ridges, which correlate with exposed rocks of the Jurassic Hazelton Group. Identified Cretaceous sedimentary rocks occur beneath less negative Bouguer gravity anomalies, but the original distribution of these rocks has been disrupted by later Tertiary extension that created north-trending basins associated with the most negative gravity anomalies. We suggest that Cretaceous sedimentary rocks, if deposited, could be preserved within these basins if the rocks had not been eroded prior to Tertiary extension. Résumé : À travers le plateau de Nechako-Chilcotin de la Colombie-Britannique, la distribution des roches sédimentaires du Crétacé, lesquelles sont considérées prometteuses pour l'exploration des hydrocarbures, est mal connue en raison des dépôts glaciaires et des roches volcaniques du Tertiaire qui recouvrent la surface. Afin de délimiter la distribution sous la surface de ces roches du Crétacé, Geoscience BC a acquis, en 2008, sept longues lignes décalées, de réflexion vibrosismique, atteignant 14,4 km, à travers une ceinture à tendance nord-nord-ouest de roches sédimentaires exhumées, qui feraient partie du Groupe de Taylor Creek. Les modèles de vitesse de l'onde P, concordant avec les diagraphies acoustiques provenant de puits avoisinants, ont été estimés au moyen de la tomographie tridimensionnelle des premières ondes arrivées à des profondeurs variant de 1 à 4 km. Le socle igné peut être identifié sur la plupart des lignes en utilisant le contour d'isovitesse de 5,5 km/s, ce qui situe le sommet du socle avec une précision de~400 m, où sa profondeur est connue dans les puits d'exploration. En se basant sur les vitesses sismiques, il n'y a pas de distinction générale entre les roches sédimentaires du Crétacé et les roches volcaniques-volcanoclastiques du Paléocène-Éocène; les deux ensembles de roches semblent être caractérisés dans les modèles tomographiques par des vitesses de 3,0 à 5,0 km/s. La géométrie du socle igné, inférée à partir des modèles de vitesse, identifie des bassins et des crêtes à tendance nord, qui correspondent à des roches en surface du Groupe de Hazelton (Jurassique). Les roches sédimentaires du Crétacé identifiées se trouvent sous les anomalies gravimétriques de Bouguer moins négatives; cependant, la distribution originale de ces roches a été perturbée plus tard par une extension au Tertiaire, qui a créé les bassins à tendance nord associés aux anomalies gravimétriques les plus négatives. Nous suggérons que les roches sédimentaires du Crétacé, si elles avaient été déposées, pourraient avoir été préservées dans ces bassins si la roche n'avait pas été érodée avant l'extension au Tertiaire. [Traduit par la Rédaction]

Canadian Journal of Earth Sciences, Apr 1, 2014

Following growth of the Canadian Cordillera during the Mesozoic, the southern Cordillera was subj... more Following growth of the Canadian Cordillera during the Mesozoic, the southern Cordillera was subject to extension during the Paleocene and Eocene that correlated with widespread volcanic activity in south-central British Columbia, including across much of the Nechako-Chilcotin plateau. In 2008, Geoscience BC acquired 330 km of deep vibroseis reflection profiles on the plateau, mostly over the Stikinia arc terrane, but also over its eastern contact with the oceanic Cache Creek terrane. All seven seismic reflection lines reveal a strongly reflective lower crust that extends from 7 to 9 s down to the Moho, which is defined by the downward termination of reflectivity at 11-12 s. In the uppermost crust, extension occurred by block faulting with faults soling into subhorizontal to shallowly dipping detachments above 10 km depth. Extension in the deeper upper and middle crust, which was partly controlled by antiforms likely related to earlier shortening, was accommodated on a network of anastomosing shear zones that sole out into the top of the reflective lower crust. The lower crustal reflections correlate with seismic P-wave velocities of 6.45-6.98 km/s, indicating that the reflective lower crust has a more mafic composition than the middle crust. As in other extensional settings, we suggest that this pervasive fabric of reflectors arises from the intrusion of mantle-derived basaltic magma into zones of ductile shearing, and that differentiation of these melts resulted in the widespread Paleocene to Eocene volcanism. Reflector dips indicate that extension was approximately east-west, consistent with north-northwest-trending horsts separated by basins filled with Paleocene to Eocene volcanic and volcaniclastic rocks. Résumé : Après la croissance de la Cordillère canadienne au Mésozoïque, la Cordillère sud a subi une extension durant le Paléocène et l'Éocène; cette extension était corrélée avec une activité volcanique étendue dans le centre-sud de la Colombie-Britannique, incluant à travers une grande partie du plateau Nechako-Chilcotin. En 2008, Geoscience BC a acquis 330 km de profiles vibrosismiques en profondeur sur le plateau, surtout au-dessus du terrane d'arc de Stikinia mais aussi par-dessus son contact est avec le terrane océanique de Cache Creek. Les sept lignes de sismique réflexion révèlent toutes une croûte inférieure fortement réflective qui s'étend depuis 7-9 s jusqu'au Moho, ce qui est défini par la terminaison vers le bas de la réflectivité à 11-12 s. Dans la croûte sommitale, l'extension s'est produite par le morcellement en bloc par des failles; les failles formant une semelle dans les détachements subhorizontaux ou avec un léger pendage, au-dessus de la profondeur de 10 km. L'extension dans les croûtes supérieure et médiane, plus profondes, partiellement contrôlée par des antiformes fort probablement reliés à un rétrécissement antérieur, était facilitée par un réseau de zones de cisaillement anastomosées qui forment une semelle sur le dessus de la couche inférieure réfléchissante. Les réflexions de la croûte inférieure correspondent à des vitesses de l'onde sismique P de 6,45-6,98 km/s, indiquant que la croûte inférieure réflective a une composition plus mafique que la croûte intermédiaire. Tout comme dans les autres environnements d'extension, nous suggérons que cette fabrique étendue des réflecteurs découle de l'intrusion de magma basaltique provenant du manteau dans des zones de cisaillement ductile, et que la différentiation de ces magmas a donné le volcanisme généralisé du Paléocène à l'Éocène. Les pendages des réflecteurs indiquent que l'extension était environ est-ouest, ce qui concorde avec des horsts de tendance nord-nord-ouest séparés par des bassins remplis de roches volcaniques et volcanoclastiques datant du Paléocène à l'Éocène. [Traduit par la Rédaction]

Interpretation, Nov 1, 2019

One of the challenges encountered during the life cycle of an oil-sand thermal-production reservo... more One of the challenges encountered during the life cycle of an oil-sand thermal-production reservoir is the prediction of the formation pore pressure and in situ stress regime during the assessment phase of the reservoir development and, more importantly, during the development phase. We have investigated the state of formation pore pressure and stress in the overburdenrepresented by the Clearwater Formation, Grand Rapids Formation, and Colorado Groupof a preproduction oil-sands reservoir situated in the Athabasca Basin of Alberta, Canada. Our methodology integrates pressure data from piezometers, stress data from mini-frac (MF), dipole sonic logs, and elastic properties obtained from multicomponent 3D seismic inversion data. It combines the Terzaghi effective stresses with the Schoenberg and Sayers elastic stiffness matrix for horizontal transversely isotropic fractured materials. The total principal stresses (vertical, minimum, and maximum horizontal stresses) are expressed as functions of the normal fracture weakness (anisotropic correction factor), formation pore pressure, seismic data (Lamé constants), and the Biot-Willis coefficient. The effective principal stresses are estimated from the equivalent total principal stresses and the formation pore pressure multiplied by the Biot-Willis coefficient. On all three overburden intervals analysed, the relations between principal stresses indicate a normal stress regime. The estimated total minimum horizontal stress matches the MF values within 10%. The formation pore pressure, along with the 3D seismically derived estimates of the total and effective principal stresses, allows for better assessment of the caprock integrity and for operational savings based on a reduced number of MF tests. It can also be used for stress estimation within the formations hosting aquifers, which is so important for thermal production. Understanding the subsurface on the reservoir area is important for efficient production, but knowing the subsurface of the overburden is equally important for reducing potential issues due to production.

Interpretation, Feb 1, 2019

In the Athabasca Basin of Alberta, Canada, the Lower Cretaceous McMurray Formation reservoir is o... more In the Athabasca Basin of Alberta, Canada, the Lower Cretaceous McMurray Formation reservoir is overlain by the Clearwater Formation, a regionally continuous layer composed predominantly of shales with interbedded mudstones. The shales form the reservoir caprock and have the role of blocking the vertical migration of the steam from thermal oil production by confining the stresses and the deformations. We have developed a new method for the 3D seismic reconstruction of the anisotropic stress field, which accounts for the formation pore pressure and the effective stress. We integrated anisotropy estimated from dipole sonic logs with formation pore pressure data from piezometers and elastic properties obtained from multicomponent seismic inversion. The method combines the Terzaghi effective stress with the Schoenberg and Sayers elastic stiffness matrix for horizontal transversely isotropic (HTI) fractured materials. The key points of this method are the estimation of the formation pore pressure in the abnormal regime of the Clearwater Formation, the normal fracture weakness parameter (based on constraints on the compressional velocity of the intact rock under the HTI assumption), and the 3D seismic anisotropic stress field. We expressed the total vertical stress as the weight of the overlying formations, and the total minimum and maximum horizontal stresses as a combination of the total vertical stress, normal fracture weakness, formation pore pressure, Biot-Willis coefficient, and Lamé elastic constants. The effective principal stresses are estimated from the equivalent total principal stresses and the formation pore pressure multiplied by the Biot-Willis coefficient. We observed excellent consistency between the calculated total minimum horizontal stress and mini-frac values. This new method for the 3D seismic reconstruction of the anisotropic stress field allows for the assessment of the caprock integrity and for operational savings based on a reduced number of mini-frac measurements, and it can be used for time-lapse stress estimation within the thermal production reservoir.

Interpretation, 2019

One of the challenges encountered during the life cycle of an oil-sand thermal-production reservo... more One of the challenges encountered during the life cycle of an oil-sand thermal-production reservoir is the prediction of the formation pore pressure and in situ stress regime during the assessment phase of the reservoir development and, more importantly, during the development phase. We have investigated the state of formation pore pressure and stress in the overburden — represented by the Clearwater Formation, Grand Rapids Formation, and Colorado Group — of a preproduction oil-sands reservoir situated in the Athabasca Basin of Alberta, Canada. Our methodology integrates pressure data from piezometers, stress data from mini-frac (MF), dipole sonic logs, and elastic properties obtained from multicomponent 3D seismic inversion data. It combines the Terzaghi effective stresses with the Schoenberg and Sayers elastic stiffness matrix for horizontal transversely isotropic fractured materials. The total principal stresses (vertical, minimum, and maximum horizontal stresses) are expressed a...

Interpretation, 2018

In the Athabasca Basin of Alberta, Canada, the Lower Cretaceous McMurray Formation reservoir is o... more In the Athabasca Basin of Alberta, Canada, the Lower Cretaceous McMurray Formation reservoir is overlain by the Clearwater Formation, a regionally continuous layer composed predominantly of shales with interbedded mudstones. The shales form the reservoir caprock and have the role of blocking the vertical migration of the steam from thermal oil production by confining the stresses and the deformations. We have developed a new method for the 3D seismic reconstruction of the anisotropic stress field, which accounts for the formation pore pressure and the effective stress. We integrated anisotropy estimated from dipole sonic logs with formation pore pressure data from piezometers and elastic properties obtained from multicomponent seismic inversion. The method combines the Terzaghi effective stress with the Schoenberg and Sayers elastic stiffness matrix for horizontal transversely isotropic (HTI) fractured materials. The key points of this method are the estimation of the formation pore...

SEG Technical Program Expanded Abstracts 2014, 2014

We present a case study of oil sands reservoir characterization using resistivity and density sei... more We present a case study of oil sands reservoir characterization using resistivity and density seismic volumes estimated from multicomponent seismic data. In the Athabasca Oil Sands region of Alberta, the Lower Cretaceous McMurray Formation is the reservoir. In this reservoir the sand can be differentiated from shale based on density. The sands could be wet or bitumen bearing and resistivity proved to be the only property which can differentiate between the two kinds of sands. We estimated resistivity from multicomponent 3D seismic data integrated with cores and wells data. Our workflow includes petrophysical analysis, joint PP-PS prestack inversion and neural network analysis. Joint PP-PS prestack inversion produces very good estimates of the elastic properties: P-and S-wave velocities and density. Neural network analysis is used for density and resistivity estimation. In all neural network analyses the most significant seismic attributes include converted-wave information. Key problems solved include excellent pay characterization, correct flank water mapping and accurate identification of high versus low oil saturation in zones with high salinity bitumen sand.

Proceedings 76th EAGE Conference and Exhibition 2014, 2014

The Lower Cretaceous McMurray Formation reservoir used in this study is located in the Athabasca ... more The Lower Cretaceous McMurray Formation reservoir used in this study is located in the Athabasca basin, of the Northern Alberta, Canada. High resolution multicomponent 3D seismic data, along with core and well data were processed using the most advanced workflows in order to image the reservoir heterogeneity. These workflows include petrophysical analysis, joint PP-PS inversion and neural network analysis. Three inversions using PP and PS seismic data are analyzed and compared. The joint PP-PS inversion of the prestack seismic data produces the best estimates of P-impedance, S-Impedance and density, allowing for excellent reservoir characterization. Neural network analysis is used to enhance the resolution of the elastic properties estimated from joint PP-PS prestack inversion, and to estimate petrophysical and engineering properties such as porosity, resistivity and saturation. In all neural network analyses the most significant seismic attributes include converted-wave information. Some of the results are: 1. converted-wave seismic data have a major role in oil-sands reservoir characterization; 2. estimated density seismic volume shows a good separation of the two bitumen sands; 3. P-wave velocity seismic allows better mapping of the McMurray top; 4. estimated resistivity allows not only to differentiate the reservoir from the non-reservoir but also bitumen sand from water sand.

cspg.org

Fracture analyses from 3D P-wave data were conducted for the Cabin Creek overthrust area in the A... more Fracture analyses from 3D P-wave data were conducted for the Cabin Creek overthrust area in the Alberta Foothills. Mapping event traveltime differences on prestack-migrated, limited source-receiver azimuth sections is a new developed method of fracture characterization. Good fold and azimuth/offset distribution allowed extension of the method to include cross-correlation of commonazimuth stacked data for both shallow and deep events. A second method applied was azimuthal traveltime inversion, based on moveout ellipticity. By using two different wide-azimuth processing techniques, the objective was to determine if the fracture model can be realized when some of the most critical parameters (matrix velocity and symmetry axis direction) are unknown. The orientations predicted are consistent within dipping Cretaceous strata, and correlate with fracture orientations from well data. The symmetry axis direction rotates with depth, and a fluid contact was interpreted within a Cretaceous fold. Analysis for sub-horizontal Jurassic, Paleozoic and Cambrian events showed both similarities and differences in the results.