The McMurray Formation of northern Alberta in Canada contains multiscale complex geologic features that were partially formed in a fluvial-estuarine depositional environment. The inclined heterolithic strata deposited as part of fluvial point bars contain continuous centimeter-scale features that are important for flow characterization of steam-assisted gravity drainage processes. These channels are common, extensive, and imbricated over many square kilometers. Modeling the detailed facies in such depositional systems requires a methodology that reflects heterogeneity over many scales. This article presents an object-based facies modeling technique that (1) reproduces the geometry of multiscale geologic architectural elements seen in the McMurray Formation outcrops and (2) provides a grid-free framework that models these geologic objects without relating them to a grid system. The grid-free object-based modeling can be applied to any depositional environment and allows for the complete preservation of architectural information for consistent application to any gridding scheme, local grid refinements, downscaling, upscaling, drape surface, locally variable azimuths, property trend modeling, and flexible model interaction and manipulation. Features millimeters thick or kilometers in extent are represented very efficiently in the same model.
Added on 30 June, 2013
Bulletin E P Note
The petroleum trap for the Athabasca oil sands has remained elusive because it was destroyed by flexural loading of the Western Canada Sedimentary Basin during the Late Cretaceous and Paleocene. The original trap extent is preserved because the oil was biodegraded to immobile bitumen as the trap was being charged during the Late Cretaceous. Using well and outcrop data, it is possible to reconstruct the Cretaceous overburden horizons beyond the limit of present-day erosion. Sequential restoration of the reconstructed horizons reveals a megatrap at the top of the Wabiskaw-McMurray reservoir in the Athabasca area at 84 Ma (late Santonian). The megatrap is a four-way anticline with dimensions 285 x 125 km (177 x 78 mi) and maximum amplitude of 60 m (197 ft). The southeastern margin of the anticline shows good conformance to the bitumen edge for 140 km (87 mi). To the northeast of the anticline, bitumen is present in a shallower trap domain in what is interpreted to be an onlap trap onto the Canadian Shield; leakage along the onlap edge is indicated by tarry bitumen outliers preserved in basement rocks farther to the northeast. Peripheral trap domains that lie below the paleospillpoint, in northern, southern, and southwestern Athabasca, and Wabasca, are interpreted to represent a late charge of oil that was trapped by bitumen already emplaced in the anticline and the northeastern onlap trap. This is consistent with kimberlite intrusions containing live bitumen, which indicate that the northern trap domain was charged not before 78 Ma. The trap restoration has been tested using bitumen-water contact well picks. The restored picks fall into groups that are consistent both with the trap domains determined from the top reservoir restoration and the conceptual charge model in which the four-way anticline was filled first, followed by the northeastern onlap trap, and then the peripheral trap domains.
Added on 28 February, 2014
Explorer Director’s Corner
You don’t have to spend much time around the oil and natural gas industry to understand that it is political.
Added on 01 August, 2013
Explorer Division Column EMD
Every six months, chairs of the Energy Minerals Division committees convene and report on developments in the areas they cover. In this column, we highlight important observations from these recent reports.
Added on 01 February, 2014
The AAPG Energy Minerals Division covers many scientific disciplines and interests – and because previous EXPLORER articles featured shale gas and oil shale, this quarter will focus on highlights from this year’s EMD November Mid-Year Meeting Commodity Reports.
Added on 01 February, 2013
Recount: The U.S. Geological Survey offers a new estimate of the world’s undiscovered conventional oil and gas resources.
Added on 01 September, 2012
A world-class technical program is in place for the AAPG International Conference and Exhibition in Singapore.
Added on 01 September, 2012
Explorer Policy Watch
I first wrote about the Keystone XL pipeline in this column back in September 2010. At the time, the project was nearing the end of a review by the U.S. Department of State for a Presidential Permit.
Added on 01 February, 2012
Explorer President’s Column
I can remember hearing, way back in 1977, the president of a major oil company that I worked for say that the United States had run out of oil and gas – there was not much left to find and develop.
Added on 01 March, 2013
Explorer Regions and Sections
Concepts and technologies developed for liquid-rich unconventional plays in North America are on the verge of being exported worldwide.
Added on 01 October, 2013