Eastern Alberta Research Articles

Assessing Oil and Gas Plays in Facies-Cycle Wedges

Oil and gas potentials of formations in frontier areas can be assessed by comparison with formations in corresponding parts of facies-cycle wedges documented in producing areas. The transgressive-regressive facies-cycle wedge is a body of rock bounded above and below by regional unconformities or the tops of major nonmarine tongues. The ideal wedge includes, from base to top, facies successions from nonmarine, to coarse (sandstone or grain carbonate), to fine (marine shale or micrite), to coarse, and back to nonmarine. Five types of potential coarse reservoir plays, representing the wedge base, middle, top, edge, and subconformity positions, are identified by their distinctive vertical facies successions within this cycle. Different play types have different risks that can affect assessments. Least risky of sandstone plays are the transgressive wedge base, which is capped by marine shale that commonly is both a good source and seal, and the wedge middle, which is both underlain and overlain by thick shale. Most risky are the regressive wedge-top sandstones with no thick shale seal above and a typically poor-source shale beneath, and the wedge edge, which has no thick marine shales whatever. Subunconformity plays, which include any of the other wedge parts truncated beneath another wedge, have intermediate risks. Carbonate plays, with the exception of the wedge top, in general are riskier than their corresponding sandstone plays, probably because of more poorly developed porosity and permeability in the carbonate rocks. The exceptional wedge-top carbonate rocks have excellent leached porosity and anhydrite caps. The wedge classification contrasts different types of reefs for exploration purposes. Transgressive wedge-base reefs are encased in the overlying shale or micrite and are apt to be localized over unconformity topography. Wedge-middle reefs are both capped and underlain by shale, and many are localized by depositional topography. Typical regressive wedge-top reefs, which also may form at the edge of depositional slopes, overlie shale or micrite and commonly are capped by anhydrite and r d beds. Comparison based on wedge position considers the basic differences in source-reservoir-seal relations. Wedge position alone, however, cannot reflect all the other critical controls of oil and gas occurrence, such as source richness and maturation, reservoir quality, or trap capacity. Large variations in productivity thus can occur within any single play type. Accordingly, assessment procedures for new plays have three key steps: (1) selecting look-alike productive plays of the same wedge position; (2) scaling the potential hydrocarbon yields to compensate for obvious differences in thickness or areal extent; and (3) risking the results for the other factors that might render the new plays nonproductive. This study is based on stratigraphic cross sections from 80 producing basins of the free world. Selected examples are from the Eastern Venezuela, Alberta, Gulf Coast, Permian, and Paradox basins.

Deep Basin Gas Trap, Western Canada

Gas accumulations are distributed in a fashion similar to most other natural resources. The high-grade deposits are comparatively small. In general, as the grade decreases the size increases. Three of the largest sandstone gas fields in western North America are in low porosity-low permeability Cretaceous sandstone, in downdip structural locations, with porous water-filled reservoir rock updip. Examination of the details of these fields sets the stage for recognizing an enormous tight-sand gas trap in western Canada. The Mesozoic rock section, only 1,000 ft (300 m) thick on the shelf in eastern Alberta, thickens westward to over 15,000 ft (4,570 m) in the Deep Basin in front of the Foothills overthrusts. Most of the developed sandstone gas fields are in updip porosity traps, or minor structural traps, on the shelf. The porous, generally water-saturated sands of the shelf become less porous and permeable westward and downdip, passing from the water-bearing area with local gas traps through a transition zone to a gas-bearing area. This change is demonstrated by electrical resistivity logs and confirmed by drill-stem tests. Recent exploratory drilling in the Deep Basin has resulted in numerous discoveries in the area. Several hundred log analyses provide reliable data for measuring potential gas resources in the range of 400 Tcf. Recoverable gas at $2.00/Mcf net after royalty may reach 150 Tcf. The quantities of gas apparently present would be a major addition to the North American energy supply.

Unconventional Methods of Recovery of Bitumen And Related Research Areas Particular to the Oil Sands of Alberta

Abstract A review was carried out of certain unconventional and untried methods of recovery of bitumen from the tar sands of Alberta. Future areas of research which might provide abreak through with regard to the potential application of these methods have been described. Preliminary laboratory investigations have been described out on the interfacial properties of heavy crudes in the presence of chemically treated waters. The result of this review show that there is a significant amount of research work that must be carried cut dealing with the physics and chemistry of interfaces, and fluid flow through a bituminous oil sand. In addition, the fundamental basic physical properties of interfaces, disturbed oil sands, including electrical and/or thermal properties, and chemical reaction behaviour at high pressures and temperatures, should be investigated. Further studies should be made of sub-surface mining techniques supplemented by external sources of energy, bitumen processing and upgrading techniques, and the utilization of by-products. The interfacial properties were found to be a function of crude oil composition, particularly of the surface-active constituents of the crudes. A new foaming technique was used to concentrate the surface-active agents contained in heavy viscous crude oils, and the dependence of interfacial properties on the surface-active constituents of the crude oil was studied. Introduction IN 1974, it was estimated that the in-place crude bitumen of the oil sands of Alberta (not including the heavy-oil areas of eastern Alberta) were at the proven level of 895 billion barrels. Of this, it was estimated that surface mining could result in the recovery of some 38 billion barrels; no proved recoverable reserves could as yet be assigned to in-situ methods of recovery techniques. From the standpoint of exploitation, it is generally concluded that surface mining is only applicable in areas where the overburden thickness is less than 150 feet and potentially feasible in-situ methods of recovery are probably only applicable where overburden thicknesses exceed some 700 feet. The reserves between 150 and some 700 feet are economically exploitable by current methods; however, some new and untried methods might be applicable here. This paper proposes, in part, to briefly review and describe these largely untried bitumen exploitation proposals, and to occasionally indicate future areas of investigation and research which could lead to a better assessment of their potential applicability. Secondly, some aspects of currently used or at least pilot tested extraction processes will also be discussed. Finally, attention will be focused on the urgent need for broad basic research leading to a better knowledge and understanding of the physical and chemical properties of the tar sands, in particular of the interfacial properties of the bitumen-sand-additives system under various conditions. General Review of Recovery Techniques Figure I, illustrates schematically the processes of in-situ and surface methods of recovery, and the bitumen upgrading common to both.

Search for elaphostrongyline parasites in cervids from Alberta.

No elaphostrongyline parasites were found in the cranial cavities of 140 while-tailed deer, 20 mule deer, and 37 moose from Alberta. No larvae with dorsal caudal spines were found in white-tailed deer feces from eastern Alberta, but spined larvae indistinguishable from those of Parelaphostrongylus spp. were found in mule-deer feces from western Alberta. These results suggest that P. tenuis is not found in Alberta and that the larvae from mule deer may represent a metastrongyloid, probably a species of Parelaphostrongylus, that is not found in the cranial cavity as an adult.

Application of Geochemistry to Stratigraphic Problems in Lower Cretaceous of Western Canada

The detrital sediments that form the Lower Cretaceous series of the Interior Plains of western Canada were sampled at close vertical intervals in fourteen widely spaced sections in Alberta and western Saskatchewan. The soda and potash contents of these samples were determined and then corrected to a carbonate-free basis. logs are plotted for each section and show that throughout the area studied the series can be separated into three stratigraphic divisions, each of distinctive soda content. The lower division is poor in soda. The middle division is principally composed of sediments that are rich in sodic igneous detritus, and which interfinger with low-soda strata in the eastern part of the area. The upper soda division consists of sediments that have a low to intermediate soda content. Samples of different grain size, such as sand and shale, share a distinctively similar soda content if they come from the same division or sediment suite. Thus chemical contacts may be traced from section to section without being affected by the lateral facies changes from sand to shale that are so common in the Lower Cretaceous. The potash content of the series is controlled by grain size variations to a much greater extent than soda, and thus this oxide is much less useful for stratigraphic correlation. Correlations made on the basis of the chemical data are related to the different stratigraphic units into which the series has been divided in different parts of the area. Compositional variation between the sediment suites is ascribed principally to varying provenance, rather than to influences within the depositional basin. Plots showing regional chemical variation within the middle division indicate a western derivation for the highly sodic detritus and an eastern derivation for the soda-poor sediments, with the two suites mixing in eastern Alberta and western Saskatchewan. The upper division shales show a consistent decrease in potash and an increase in soda away from the presumed western shoreline of the time. Chemical methods of correlating detrital sediments appear to be useful, particularly when applied to shales or to mixed assemblages that include shales. The rapid development of more efficient methods of analyzing rocks makes the application of geochemical methods to stratigraphic studies increasingly attractive.

Keewatin end moraines in Alberta, Canada

The outermost Keewatin moraines, within sight of the Rocky Mountains, are as youthful topographically as is the Late Wisconsin Altamont terminal moraine in eastern Alberta and western Saskatchewan. Differences in outline of the ice front, however, indicate that all moraines west of the Altamont are the product of an earlier advance. The moraine pattern records a southern Alberta convexity or lobe, limited on the west by the foothills of the Rocky Mountains and on the south by the Arctic Ocean-Gulf of Mexico divide. A complicated succession of melt-water dischargeways and associated glacial lakes is intimately related to the moraine succession. Escape of all this drainage was across the divide and to the Missouri River in Montana. Correlation of discontinuous moraine units is possible because drainage held close to the edge of the Keewatin ice sheet as it retreated down the slope of the Great Plains. Moraine outside (higher than) any one drainage channel thus is older than moraine inside (lower than) the channel.

Oil and Gas Possibilities of Eastern Alberta

Oil and Gas Possibilities of Eastern Alberta

Correction: Notes from Eastern Alberta

Correction: Notes from Eastern Alberta

Notes from Eastern Alberta

Notes from Eastern Alberta