Extensive research has been conducted in numerous coalbed methane (CBM) basins; however, the Williston Basin (WB) remains largely unexamined due to the absence of CBM production despite large coal reserves. CBM in WB coalbeds has been reported, but there has been no systematic study on gas origin and distribution, or hydrogeochemical controls on gas generation to date. This study aims to determine differences in chemistry between groundwaters with and without the presence of CH₄ to better understand factors affecting CBM generation. Results reveal that shallow gas accumulations in WB coalbeds are microbial in origin and formed via CO₂ reduction. CBM is associated with Na-HCO₃ type groundwater with SO₄ concentrations<1 mmole/L due to cation exchange and sulfate reduction, respectively. These groundwaters occur in deeper units of the Fort Union Formation, underlying multiple coalbeds, suggesting that CH₄ is present in waters that have reacted extensively with formations containing low-rank (lignite) coals.

As the conventional reservoirs decrease in discovering, producing and reserving, unconventional reservoirs are more remarkable in terms of discovering, development and having more reserve. More fields have been discovered where Barnett Shale and Bakken Shale are the most recently unconventional reservoir examples. Shale reservoirs are typically considered self-sourcing and have very low permeability ranging from 10-100 nanodarcies. Over the past few decades, numerous research projects and developments have been studied, but it seems there is still some contention and misunderstanding surrounding shale reservoirs. One of the largest shale in the United State is the Bakken Shale play. This study will describe the primary geologic characteristics, field development history, reservoir properties,and especially production trends, over the Bakken Shale play. Data are available for over hundred wells from different companies. Most production data come from the Production Data Application (HDPI) database and in the format of monthly production for oil, water and gas. Additional 95 well data including daily production rate, completion, Pressure Volume Temperature (PVT), pressure data are given from companies who sponsor for this research study. This study finds that there are three Types of well production trends in the Bakken formation. Each decline curve characteristic has an important meaning to the production trend of the Bakken Shale play. In the Type I production trend, the reservoir pressure drops below bubble point pressure and gas releasingout of the solution. With the Type II production trend, oil flows linearly from the matrix into the fracture system, either natural fracture or hydraulic fracture. Reservoir pressure is higher than the bubble point pressure during the producing time and oil flows as a single phase throughout the production period of the well. A Type III production trend typically has scattering production data from wells with a different Type of trend. It is difficult to study this Type of behavior because of scattering data, which leads to erroneous interpretation for the analysis. These production Types, especially Types I and II will give a new type curve matches for shale oil wells above or below the bubble point.

The Upper Devonian-Lower Carboniferous Bakken Formation is present in the subsurface of the Williston Basin in northeastern Montana, North Dakota, southwestern Manitoba and southern Saskatchewan. In the southeastern corner of Saskatchewan, the Bakken Formation either conformably overlies the Upper Devonian Big Valley Formation or unconformably overlies the Torquay Formation, and is conformably overlain by the Lower Carboniferous Souris Valley (Lodgepole) Formation. The Bakken Formation typically includes three members: the lower and upper organic-rich black shale, and the middle calcareous/dolomitic sandstone and siltstone, which makes a “perfect” petroleum system including source rock, reservoir, and seal all within the same formation. According to detailed core analysis in the southeastern corner of Saskatchewan, the Bakken Formation is divided into eight facies, and one of which (Facies 2) is subdivided into two subfacies: Facies 1 (planar cross-stratified fine-grained sandstone); Facies 2A (wavy- to flaser-bedded very fine-grained sandstone); Facies 2B (thinly parallel-laminated very fine-grained sandstone and siltstone); Facies 3 (parallel-laminated very fine-grained sandstone and muddy siltstone); Facies 4 (sandy siltstone); Facies 5 (highly bioturbated interbedded very fine-grained sandstone and siltstone); Facies 6 (interbedded highly bioturbated sandy siltstone and micro-hummocky cross-stratified very fine-grained sandstone); Facies 7 (highly bioturbated siltstone); and Facies 8 (black shale). Our integrated sedimentologic and ichnologic study suggests that deposition of the Bakken occurred in two different paleoenvironmental settings: open marine (Facies 4 to 8) and brackish-water marginal marine (Facies 1 to 3). The open-marine facies association is characterized by the distal Cruziana Ichnofacies, whereas the brackish-water marginal-marine facies association is characterized by the depauperate Cruziana Ichnofacies. Isochore maps shows that both open-marine and marginal-marine deposits are widely distributed in this study area, also suggesting the existence of a N-S trending paleo-shoreline. The Bakken strata in this study area represent either one transgressive systems tract deposits or two transgressive systems tracts separated by a coplanar surface or amalgamated sequence boundary and transgressive surface. This surface has been identified in previous studies west-southwest of our study area, therefore assisting in high-resolution correlation of Bakken strata.

The Upper Devonian–Lower Mississippian Bakken Formation in the Williston Basin is estimated to have significant amount of technically recoverable oil and gas. The objective of this study is to identify differences in the character of the seismic response to Bakken interval between locations with high and poor production rates. The predicted seismic responses of the Bakken Formation will hopefully help achieve such discrimination from surface seismic recordings. In this study, borehole data of Bakken wells from both the Cottonwood and the Sanish Field were analyzed, including density information and seismic P and S wave velocities from Sonic Scanner logs. The Bakken Formation is deeper and thicker (and somewhat more productive) in the Sanish Field and is shallower and thinner in the Cottonwood Field. The Upper and Lower Bakken shale units are similar and can be characterized by low density, low P and S wave velocities and low Vp/Vs ratios. The Sonic Scanner data suggest that the Upper and Lower Bakken shales can be treated as VTI media while the Middle Bakken may be considered as seismically isotropic. Models of seismic response for both fields were constructed, including isotropic models and models with variations in VTI, HTI, and the combination of VTI and HTI in the Bakken intervals. Full offset elastic synthetic seismograms with a vertical point source were generated to simulate the seismic responses of the various models of Bakken Formation. This sensitivity study shows pronounced differences in the seismic reflection response between isotropic and anisotropic models. P-P, P-SV and SV-SV respond differently to anisotropy. VTI anisotropy and HTI anisotropy of the Bakken have different character. In particular, types of seismic data (P-P, P-SV, and SV-SV) and the range of source-receiver offsets that are most sensitive to variations in anisotropic parameters and fluid saturation were identified. Results suggest that bed thickness, anisotropy of the Upper and Lower Bakken shales, fractures/cracks and fluid fill in the fracture/cracks all influence the seismic responses of the Bakken Formation. The paucity of data available for “poorly” producing wells limited the evaluation of the direct seismic response to productivity, but sensitivity to potentially useful parameters was established. / text

In this thesis, the potential of enhanced geothermal system to provide adequate energy to a 10 MW electricity power plant from Prairie Evaporite Formation of Williston Basin was investigated. This formation partly consists of halite with low thermal resistance and high thermal conductivity, which translates into a lower drilling length to reach the desired temperature, comparing to other rock types. To this end, two numerical models with experimental data in south-west Manitoba (i.e. Tilston) and south-east Saskatchewan (i.e. Generic) were designed. The thermal reservoirs were located at 1.5 km (Tilston site) and 3 km (Generic site) with approximate thicknesses of 118 m. Considering an injection brine of 6% NaCl at 15°C, the final derived temperature at wellhead of the production wells were 43°C and 105°C respectively. Finally, the Generic site was concluded as a suitable candidate for electricity production by providing higher surfaced fluid temperature than the minimum of 80°C. / February 2017

Late Ordovician Red River strata of southeastern Saskatchewan were deposited in a broad epicontinental sea. In the lower part, the Yeoman and Herald formations comprise two cycles of carbonateevaporite sequences. Although these units possess an overall layer-cake aspect, thickness variations especially in the Herald Formation show that accumulation was affected by syndepositional flexure, differential subsidence and displacement of fault-bounded blocks. The mainly laminated dolomudstones and anhydrites of the Lake Alma and Coronach members of the Herald Formation were deposited under relatively tranquil conditions. These units host different kinds of synsedimentary deformation features, interpreted to have been induced by earthquakes generated because of movements along basement faults thought to have been oriented orthogonally NE−SW and NW−SE. The low-energy environmental setting was conducive to preserving these features, referred to as seismites.<p> The variety of seismites in the Herald Formation is related to the varying rheology of the carbonate or evaporite sediment, as well as shaking intensity. Brittle and quasi-brittle failure is represented by faults, microfaults, shear-vein arrays and pseudo-intraclastic breccias, mostly in dolomudstones which must have been stiff at the time of deformation. Plastic behaviour is recorded by soft-sediment deformation, comprising a family of features that includes loop bedding, folded laminae and convolute bedding. Indeed, these structures in enterolithic anhydrite are more reasonably interpreted as due to deformation than crystal growth, volume expansion and displacement, the more usual explanations. Sediment shrinkage and concomitant fluidization are recorded by dikelets containing injected carbonate mud or granular gypsum, the latter now preserved as anhydrite. Evidence for wholesale liquefaction, however, was not observed. These rheological differences were caused by the primary nature of the sediment plus modifications due to early diagenesis and burial confinement. Shaking intensity is difficult to gauge, but it is presumed that a minimum of VI on the modified Mercalli scale was required to produce these features. Consequently, shaking of lesser magnitude was probably not recorded.<p> The geographic distribution of seismites should reflect the location of basement faults presumed to have been active during deposition, and indeed there is a concentration adjacent to the known location of syndepositonal fault lineaments. In addition, the stratigraphic distribution of seismites records higher frequencies of activity of these same faults. These distributions show that earthquake-induced ground motion was common during deposition of the Lake Alma Member in southeastern Saskatchewan but less so during deposition of the Coronach Member.<p> Seismites serve as proxies for the activity of relatively nearby syndepositional faults making up the tectonic fabric of sedimentary basins. They also point to basement features that, if re-activated, can induce fracture porosity or influence subsurface fluid flow. Syndepositional tectonism undoubtedly had a much more profound influence on many successions than is presently accepted, and its effects are more widespread than currently appreciated.

The Upper Devonian-Lower Mississippian Bakken Formation has recently become a prolific producer of light gravity oil in southeastern Saskatchewan since the advent of horizontal drilling and multi-stage hydraulic fracture technologies, which has resulted in an increase in geological studies within the area. However, the Bakken Formation of west-central Saskatchewan has been producing heavy oil since the 1950s, and has comparatively received much less attention than its southeastern counterpart. The Bakken Formation is the youngest member of the Three Forks Group and unconformably overlies the Big Valley Formation. In west-central Saskatchewan, the Bakken Formation can be conformably overlain by the Mississippian carbonates of the Madison Group or unconformably overlain by the Lower Cretaceous Mannville Group. A tripartite subdivision is applied to the Bakken Formation, with a mixed clastic/carbonate Middle Member deposited between Lower and Upper Black Shale Members. Based on detailed core description, eight facies have been defined for the Bakken Formation of west-central Saskatchewan: Facies 1 (Lower and Upper Black Shale members), Facies 2 (bioturbated siltstone/sandstone), Facies 3 (wave-rippled sandstone), Facies 4 (bioclastic grainstone), Facies 5 (interbedded mudstone, siltstone, and very fine-grained sandstone), Facies 6 (very fine- to fine-grained sandstone), Facies 7 (bioturbated siltstone/sandstone), and Facies 8 (massive and brecciated siltstone). Deposition of the Bakken Formation in west-central Saskatchewan occurred under either open-marine or marginal-marine conditions. Facies association 1 (open-marine interval), which is made up of F1 through F4, is characterized by the distal Cruziana Ichnofacies. It was deposited within a wave-dominated shallow-marine depositional environment. Facies association 2 (marginal-marine interval), which is comprised of F5 through F8, shows scarce biogenic structures, most likely as a result of brackish-water conditions. Geological mapping (structure surface and isopach) of the facies and facies associations has aided in illustrating their lateral distribution. However, mapping of the overlying Mississippian carbonates and sub-Mesozoic unconformity shows that post-Mississippian erosion was a controlling factor in the distribution and preservation of Bakken Formation deposits, which creates uncertainty when interpreting geological maps and stratigraphic cross-sections. Although post-Mississippian erosion causes problems when reconstructing the depositional history and stratigraphic architecture of the Bakken Formation, it illustrates the importance of not performing stratigraphic studies within a vacuum, only focusing on the formation of interest. Rather, underlying and overlying units must be studied to see whether or not the unit of interest’s deposition and distribution has been affected by pre- and post-depositional events.