Skip Nav Destination Article Navigation. Close mobile search navigation Article navigation. Volume 36, Number 5. Previous Article Next Article. Article Navigation. Research Article May 01, Google Scholar. AAPG Bulletin 36 5 : Article history first online:.
This content is PDF only. However, some rocks from each Phanerozoic period are preserved in the basin. These strata record several cycles of marine transgressions that filled the basin, followed by marine regressions that drained the basin.
Sloss defined six inter-regional rock-stratigraphic units that were traceable across the North American craton and named them sequences. One of the example areas Sloss used when he first proposed the sequence concept was the Williston Basin. Figure 5. Extent of the Williston Basin with major North Dakota structures shown.
Figure 6. Generalized stratigraphic column for the Williston Basin with gas producing horizons shown in red and oil producing horizons shown in blue. More recently, Sloss' sequence concept changed to a depositional sequence concept that is based upon the identification of sequences on seismic data Mitchum, Vail, and Thompson, The study of depositional sequences on seismic data has become known as seismic stratigraphy and is used worldwide as a major tool in exploration for oil and natural gas.
Vail, Mitchum, and Thompson a; b also recognized that depositional sequences record regional relative sea level changes which, if coincident with relative changes in many regions, are probably of global extent. They noted three orders of cycles and identified a number of cycles. They identified two first-order cycles, also called super cycles, that were million years long and fourteen second-order cycles that lasted for 10 to 80 million years Fig.
They also identified more than 80 third-order cycles, each lasting from 1 to 10 million years, but did not consider the pre-Jurassic cycles to be of global extent as the data came largely from North America.
Most of the hydrocarbons are produced from rocks deposited during the Paleozoic Era Fig. Since the initial discovery, the Madison Group Mississippian has produced the most oil, but significant volumes have also been found in the Red River Ordovician and Duperow Devonian formations Table 1.
Natural gas had been produced from other Cretaceous sands in Dickey and LaMoure counties and from glacial drift in Bottineau County, but none is produced from these strata now. Figure 7. Modified from Fowler and Nisbet, Structural Geology The Williston Basin, compared to many basins worldwide, is a structurally simple basin. It is roughly circular, deepest in its center, and the strata become both shallower and thinner towards its margins.
It is a large basin, covering approximately , square miles over parts of North Dakota, South Dakota, and Montana and parts of the adjacent Canadian provinces of Saskatchewan and Manitoba. The basins deepest point is thought to be near Williston, ND where the Precambrian surface is more than 16, feet below the surface. The earliest rocks are difficult to study because the Lower Phanerozoic and Precambrian rocks are not exposed at the surface in North Dakota and only a few wells have penetrated these rocks.
Our present understanding of the early geologic history of the basin is pieced together from outcrops in adjacent states and provinces, from seismic data, and from the limited well data. The Superior Craton is Archean in age and consists mainly of granites and greenstones that were emplaced between 2. Rocks of the Wyoming Province are gneissic, or banded to lenticular feldspar and quartz-rich rocks, and are approximately the same age as rocks from the Superior Craton.
Between these two cratons, under most of western North Dakota, lies the Trans-Hudson orogen, which is composed of oceanic material from an early rifting event within the Superior Craton. Green et al, Rocks from the island-arc complexes are between 1. Figure 8. Structural elements in the vicinity of the Williston Basin Modified from Green et al, The internal structural geology of the two provinces and the orogen can be very complex, as are the structural relationships between them.
Our limited ability to either sample the rocks or to seismically image them restricts our ability to determine how the Williston Basin formed. The early structural history of the basin has had an impact on later Phanerozoic deposition, but the extent of that impact is not always known.
Although subsurface data is limited, in Beaver Lodge Field on the Nesson anticline, it can be demonstrated from well control that within a few miles, there are hundreds of feet of topographic relief on the Precambrian surface Fig. The relief on the basement surface is either an erosional remnant of a granite knob or is a horst block formed by movement along vertical to near-vertical faults. Most of the structural deformation during the Phanerozoic Eon in North Dakota probably resulted from the subsidence of the Williston Basin.
The main evidences of structural deformation in the basin are folding and faulting. The best evidence of folding in North Dakota is the anticlinal and synclinal structures that were formed.
Many other unnamed anticlinal structures exist in the basin, but only some of them have been proven to be oil-producing. The other primary evidence of structural deformation is faulting, and faults are less well documented in North Dakota. Some faults, like those on the west flank of the Cedar Creek anticline Clement, and the Heart River fault Chimney et al. Clement shows faults to be steeply dipping, almost vertical, and reports that faults along the Cedar Creek anticline have undergone recurrent near-vertical and wrench movements.
He also reports that the displacement direction along some of these faults changed over time. The inferred faults probably have similar characteristics to the larger faults on the Cedar Creek anticline, that is they dip nearly vertically, may have a component of wrenching, have undergone recurrent movements, and the direction and magnitude of displacement has changed over time.
However, it is unlikely that most faults will be proven to exist because the near-vertical dip makes them difficult to intersect or image. Figure 9. Note the relief on the Precambrian surface and the missing Deadwood section over the Precambrian high.
Features that are frequently interpreted to be present in the Williston Basin are lineaments. A lineament is the surface expression of a basement block boundary or fault Brown and Brown, The magnitude of individual displacements may not have been great, but the displacement was at least sufficient to have affected local deposition and erosion patterns.
These local patterns often control where oil is trapped. Stratigraphy and Petroleum Characteristics Basement Rocks Precambrian Basement is the crust of the earth extending from the base of sedimentary cover down to the Mohorovicic discontinuity, or all Precambrian rocks.
Phanerozoic deposition in the Williston Basin began on a surface of weathered basement rocks. The Precambrian is subdivided into two eons. The older is the Archeozoic Eon, from between 4 to 2. The geology of the Precambrian rocks underlying the Williston Basin is complex, consisting of many juxtaposed, fault-bounded lithostructural domains Peterman and Goldich, Green et al suggested that the basement rocks in western North Dakota formed in an orogenic belt, or linear deformed area, called the Trans-Hudson orogen that lies between the Archean Superior and Wyoming Provinces Fig.
More recently, Baird and others reported another, previously unknown block under western North Dakota which they named the Dakota block. They interpreted the block to be an Archean continental fragment because of similarities in its reflection geometry to Archean crustal material exposed in the Glennie domain in Canada. In general, basement rocks do not produce oil in North Dakota, but one well in Newporte Field did produce oil from fractured Precambrian rocks.
The Cambrian sea transgressed eastward into an embayment on the edge of the Cordilleran shelf Carlson, ; Lochman-Balk, , and deposited siliciclastic sediments, sands and shales, as the dominant sediment type in North Dakota. During Lower Ordovician, carbonate sediments began to be deposited in the center of the basin, which was now formed and had begun to subside LeFever et al. Figure Location of oil and gas wells producing from the Cambrian Deadwood and Ordovician Winnipeg formations.
Equivalent strata are thought to have covered a much greater area, once extending at least as far as Nebraska to the south and southeast, but later erosion has removed much of the strata.
Deposition was continuous across the Ordovician-Silurian boundary and sedimentation continued at least until Middle Silurian. The top of the sequence is a major erosional unconformity that has removed an unknown amount of strata.
All of these formations were deposited in marginal to shallow marine environments. The Black Island Formation has two members Thompson, The lower member is comprised of two lithofacies, a lower red-bed lithofacies containing quartz arenites and "clayshales", and an upper green quartz wacke. The upper member is also comprised of two lithofacies, a quartz arenite and green quartz wackes.
The Icebox Formation, an organic-rich green shale, is thought to be a source rock for Lower Paleozoic reservoirs Dow, ; Williams, The Roughlock Formation is predominantly a nodular limestone and is transitional with the overlying Red River Formation LeFever et al, In both areas, production is from Black Island sandstones and natural gas is the dominant hydrocarbon produced.
The Red River Formation, the basal unit of the group, has been subdivided into two informal members. The lower member is the lower two-thirds of the formation and is composed of fossiliferous and selectively dolomitized limestones.
The upper member includes four dolomitized porosity zones; the "D", "C", "B", and "A" zones, in ascending order Carroll, The upper three zones are capped by anhydrite beds while the "D" zone is not Fig. The anhydrites are widespread, as they are present across most of western North Dakota and eastern Montana, and they are present in the center of the basin Fig.
Two depositional models have been proposed to explain the origin of the dolomites and capping anhydritesin the upper Red River Formation. In the first model, the marine waters in the central Williston Basin evaporated to the point that a sabkha developed there Carroll, while in the second model, all deposition occurred in subtidal environments Kendall, The data can be interpreted to fit either model, hence the controversy.
Stratigraphy of the upper Red River Formation The letters correspond to informally named porosity zones. Modified from Carroll, In the sabkha model, the "D" zone strata were deposited in a subtidal to intertidal environment and the basal strata of the "C", "B", and "A" zones were deposited in a subtidal environment.
The upper strata of the "C", "B", and "A" zones were deposited in a broad supratidal environment, or sabkha Carroll, In this model, a series of marine transgressions deposited subtidal to intertidal sediments during the basal phase of each cycle, were followed by a marine regression. In the cases of the "C", "B", and "A" zones, the regression dried out the basin. Dolomitization in the upper three zones was different - penecontemporaneous with deposition.
The anhydrites were deposited in the high-evaporation environment of the sabkha. The sabkha model requires that sabkha progradation continued until the center of the basin was completely filled. In the second model of upper Red River sedimentation, deposition occurred in a subtidal environment. In this model, the dolomites and anhydrites were deposited during periods of basin restriction and increasing water salinity Kendall, Below are publications associated with this project.
Filter Total Items: Year Published: Assessment of undiscovered conventional oil and gas resources in the lower Paleozoic of the Williston Basin Province, Using a geology-based assessment methodology, the U.
Schenk, Christopher J. View Citation. Schenk, C. Geological Survey Fact Sheet —, 2 p. Year Published: Assessment of undiscovered conventional oil and gas resources of upper Paleozoic strata in the Williston Basin Province, Using a geology-based assessment methodology, the U. Geological Survey Fact Sheet —, 4 p. Year Published: Assessment of undiscovered gas resources in the Williston Basin Province, Using a geology-based assessment methodology, the U. Year Published: Assessment of undiscovered oil and gas resources in the Pennsylvanian Tyler Formation of the Williston Basin Province, Using a geology-based assessment methodology, the U.
Year Published: Assessment of undiscovered continuous oil and gas resources in the Heath Formation, central Montana and western North Dakota, Using a geology-based assessment methodology, the U. Drake, Ronald M. Drake, R. Year Published: U. Geological Survey assessments of continuous unconventional oil and gas resources, to From to , the U. Geological Survey U. Continuous Resources Assessment Team, , U. Geological Survey assessments of continuous unconventional oil and gas resources, to U.
Since the discovery of the Williston Basin in ; the successful drilling, casing, and cementing of Basin wells through various salt sequences has been an area of continuing challenge and technological improvement.
These salt intervals vary in thickness and depth of burial and are present in Triassic through Devonian age rock. Their enlargement during drilling due to dissolution and well borehole erosion, and the ensuing poor cement jobs have further resulted in widespread casing collapse in the Basin over time due to plastic salt movement creep and transverse loading point loading.
Previous work on the subject includes case studies and papers targeting casing design, cement design and cementing practices, drilling fluid design, and drilling practices. Recent work by R. Hackney essentially revamped traditional casing design practices across salts, and a 1.
Also, several papers have been presented in the realm of drilling fluid design. A paper by Earl and Nahm described the use of chemical salt precipitation inhibitors to maintain the supersaturation of salt muds, and work by E. Rike described Gulf Oil Company's use of a relaxed filtrate invert mud in one field of the Williston Basin.
Although these recommendations differ, the authors agree that the use of an inhibitive mud is necessary to reduce hole enlargement through massive salt sections. This leads to another commonly held maxim and the central thought of this paper. In order to protect the investment an operator makes in a Williston Basin well, it is necessary to drill a well bore conducive to successful cementation of production casing.
It is also necessary that this be accomplished in a cost effective manner. Since cost restraints differ from operator to operator and drilling program to drilling program, this paper does not serve to recommend one type drilling fluid system over another.
Sign In or Register.
0コメント