The Lea Park formation is an equivalent of the Upper Cretaceous Milk River and Pakowki formations of southern Alberta. Upper Cretaceous sediments of the Prairie Provinces are derived from land masses which bordered the Western geosyncline. Redistribution of Upper Cretaceous non-marine sediments from the seaward margin of deltas by epeiric sea currents resulted in the deposition of marine sand lenses within the mud-bottomed basin. Palaeontological criteria are the most helpful for distinguishing these marine from other non-marine environments. The Lea Park formation consists, between Lloydminster and Battleford, of four stratigraphic units. The basal shale unit contains the Epistomina caracolla microfauna. Overlying it is a shale characterized by Verneuilina bearpawensis. This is followed by a sand and sandstone facies with a marine megafauna. The fourth and highest member in the Lea Park formation is of marine shale. Upward the Lea Park formation passes into the Ribstone Creek, a brackish water arenite formation. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Rocks of the Lower Cretaceous Blairmore formation extend over the whole of southern Saskatchewan. Along outcrop areas in western Manitoba, the Blairmore has undergone erosional truncation. Equivalent beds are found over almost the entire western interior plains of Canada and the United States. in southern Saskatchewan and adjacent western Manitoba the formation consists principally of fine to coarse quartzose sandstone, shale, salt and pepper sandstone, lignite, clay ironstone, kaolinite shale, and various mixtures of shaly sandstone and sandy shale. The Blairmore of the area is divided into five areal units and related to adjacent, more thoroughly studied areas. The divisions are: Mannville, Kootenai, Dakota, Swan River, and Ashville areas. The stratigraphy of each area is described and environment and source areas discussed. Oil in commercial quantities has been found in the Blairmore formation. The most likely areas of future exploration are suggested. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Two experimental seismic surveys were collected in the 1991 LITHOPROBE Trans-Hudson Orogen (THO) data acquisition program. The purpose of the coincident dynamite and vibroseis reflection surveys was to compare crustal images obtained using high-fold low-energy and low-fold high-energy sources. On single-fold field records, signal amplitudes from explosive sources are consistently 50 dB higher than on the corresponding vibroseis records. The vibroseis final stack exhibits better defined upper-crustal reflectivity due primarily to the higher fold. However, at lower-crustal and Moho levels, the dynamite data provides images which are equal or superior to those obtained from the vibroseis data. The dynamite source not only allowed deeper signal penetration but also succeeded in mapping of a number of subcrustal reflections not identified in previous vibroseis data. These new seismic images indicate that the crustal root is not simple depression on the upper-mantle as was inferred initially but a broad (3 s) zone of reflectivity that dips west and extends more than 10 km below the younger regional Moho. Moreover, the dynamite data also indicates that diffraction patterns, detected at lower crustal and Moho depths, have large apertures which permitted proper migration of these lower crustal events. Four vibroseis expanding spread profiles (ESP) were also acquired during the data acquisition program to obtain more detailed and accurate velocity structure. These profiles, with a maximum offset of 18 km, were centered on areas where prominent crustal reflectivity was detected by the regional vibroseis survey. The small source stepout distance (100 m) generated high-fold ($>$30) data. Extensive modeling was carried out to estimate the offset range within which each traveltime approximation and velocity analysis technique may be implemented. The results reveal that velocity estimation becomes more robust and accurate when crustal seismic surveys utilize longer offsets than commonly used. These larger source-receiver separations, however, must be generally limited to offset/depth ratios not exceeding 1.5 when conventional velocity analysis techniques, based on the hyperbolic moveout assumptions, are implemented. Besides the semblance method two velocity estimators adapted to crustal studies, namely the covariance and the $\tau$ - p techniques, were tried. The former yielded the highest resolution followed by the semblance and the $\tau$ - p methods. Resolution of the semblance estimator for a maximum offset of 36 km is equal to that of the covariance method with a corresponding offset of 18 km for mid-crustal reflectors. The advantages provided by the long-offset data acquisition include increased S/N ratio and a greater number of traces with sufficiently large moveouts whichimproved velocity resolution, especially below mid-crustal depths. To achieve similar advantages in a regional crustal reflection survey would require the adoption of longer spread lengths than those presently implemented in standard data acquisition procedures.

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Understanding the stratigraphic architecture of geologically complex reservoirs, such as the heavy oil deposits of Western Canada, is essential to achieve an efficient hydrocarbon recovery. Borehole and 3-D seismic data were integrated to define the stratigraphic architecture and generate 3-dimensional geological models of the Mannville Group in Saskatchewan. The Mannville is a stratigraphically complex unit formed of fluvial to marine deposits. Two areas in west-central and southern Saskatchewan were examined in this study. In west-central Saskatchewan, the area corresponds to a stratigraphically controlled heavy oil reservoir with production from the undifferentiated Dina-Cummings Members of the Lower Cretaceous Mannville Group. The southern area, although non-prospective for hydrocarbons, shares many similarities with time-equivalent strata in areas of heavy oil production. Seismic sequence stratigraphic principles together with log signatures permitted the subdivision of the Mannville into different packages. An initial geological model was generated integrating seismic and well-log data Multiattribute analysis and neural networks were used to generate a pseudo-lithology or gamma-ray volume. The incorporation of borehole core data to the model and the subsequent integration with the lithological prediction were crucial to capture the distribution of reservoir and non-reservoir deposits in the study area. The ability to visualize the 3-D seismic data in a variety of ways, including arbitrary lines and stratal or horizon slicing techniques helped the definition of stratigraphic features such as channels and scroll bars that affect fluid flow in hydrocarbon producing areas. Small-scale heterogeneities in the reservoir were not resolved due to the resolution of the seismic data. Although not undertaken in this study, the resulting stratigraphic framework could be used to help construct a static reservoir model. Because of the small size of the 3-D seismic surveys, horizontal slices through the data volume generally imaged only small portions of the paleogeomorphologic features thought to be present in this area. As such, it was only through the integration of datasets that the geological models were established.

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