Black Gold

Author: Beth Hager

.S. Department of the Interior
U.S. Geological Survey
Fact Sheet 2008–3021
April 2008
National Assessment of Oil and Gas Fact Sheet
Assessment of Undiscovered Oil Resources in the Devonian-Mississippian Bakken Formation, Williston Basin Province, Montana and North Dakota, 2008
Printed on recycled paper
Introduction
The U.S. Geological Survey (USGS) completed an assessment
of the undiscovered oil and associated gas resources of the Upper Devonian–Lower Mississippian Bakken Formation in the U.S. portion of the Williston Basin of Montana and North Dakota and within the Williston Basin Province (fig. 1). The assessment is based on geologic elements of a total petroleum system (TPS) that include (1) source-rock distribution, thickness,
organic richness, maturation, petroleum generation, and migration; (2) reservoir-rock type (conventional or continuous), distribution, and quality; and (3) character of traps and time of formation with respect to petroleum generation and migration.
Detailed framework studies in stratigraphy and structural geology and the modeling of petroleum geochemistry, combined with historical exploration and production analyses, were used to aid in the estimation of the undiscovered, technically recoverable
oil and associated gas resources of the Bakken Formation in the United States. Using this framework, the USGS defined a Bakken-Lodgepole TPS (fig. 1) and seven assessment units (AU) within the TPS. For the Bakken Formation, the undiscovered oil and associated gas resources within six of these assessment units were quantitatively estimated (fig. 2, table 1). A conventional AU within the Lodgepole Formation was not assessed.
Bakken Formation and Bakken-Lodgepole Total Petroleum System
The Upper Devonian–Lower Mississippian Bakken Formation
is a thin but widespread unit within the central and deeper portions of the Williston Basin in Montana, North Dakota, and the Canadian Provinces of Saskatchewan and Manitoba. The formation
consists of three members: (1) lower shale member, (2) middle sandstone member, and (3) upper shale member. Each succeeding
member is of greater geographic extent than the underlying member. Both the upper and lower shale members are organic-rich marine shale of fairly consistent lithology; they are the petroleum source rocks and part of the continuous reservoir for hydrocarbons produced from the Bakken Formation. The middle sandstone member varies in thickness, lithology, and petrophysical properties, and local development of matrix porosity enhances oil production in both continuous and conventional Bakken reservoirs. Within
Using a geology-based assessment methodology, the U.S. Geological Survey estimated mean undiscovered volumes of 3.65 billion barrels of oil, 1.85 trillion cubic feet of associated/dissolved natural gas, and 148 million barrels of natural gas liquids in the Bakken Formation of the Williston Basin Province, Montana and North Dakota.the Bakken-Lodgepole TPS, the upper and lower shale members of the Bakken Formation are also the source for oil produced from reservoirs of the Mississippian Lodgepole Formation.
Geologic Model and Assessment Units
The geologic model used to define AUs and to assess the Bakken Formation resources generally involves thermal maturity of the Bakken shale source rocks, petrophysical character of the middle sandstone member, and structural complexity of the basin. Most important to the Bakken-Lodgepole TPS and the continuous
AUs within it are (1) the geographic extent of the Bakken Formation oil generation window (fig. 2), (2) the occurrence and distribution of vertical and horizontal fractures, and (3) the matrix porosity within the middle sandstone member. The area of the oil generation window for the Bakken continuous reservoir was determined by contouring both hydrogen index and well-log
resistivity values of the upper shale member, which is youngest and of greatest areal extent.
The area of the oil generation window for the Bakken
Formation was divided into five continuous AUs: (1) Elm
Coulee–Billings Nose AU, (2) Central Basin–Poplar Dome AU,
(3) Nesson–Little Knife Structural AU, (4) Eastern Expulsion Threshold AU, and (5) Northwest Expulsion Threshold AU. A sixth hypothetical conventional AU, a Middle Sandstone Member AU, was defined external to the area of oil generation.But what about Gold,I know that Oil is Black Gold,But what about Gold itself. Just ClickHere to find out about the Real Gold.


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