Lodgepole Formation Research Articles

Did sea level change drive carbon isotopic trends in the Madison Shelf? Sequence stratigraphy and carbon isotopes in the Mississippian Lodgepole Formation of southwest Montana

The Lower Mississippian Lodgepole Formation of Montana and Wyoming records one of the largest positive carbon isotopic excursions of the Phanerozoic. This globally recognized up to 7‰ increase in δ13Ccarb values occurs across the North American Kinderhookian-Osagean boundary (referred to as the KO excursion). It has been argued to reflect significant organic carbon burial, possibly linked to the onset of the Late Paleozoic Ice Age. Previously proposed correlations between carbon isotopic patterns and the sequence stratigraphic framework within these strata suggests that changes in sea level could have played a significant role in the expression and/or magnitude of the KO excursion in the Madison Shelf. This study explores the relationship between carbon isotopic values and sea level change at multiple scales. To accomplish this, we provide a comprehensive overview of the sedimentological and stratigraphic framework and address uncertainty about the number of sequences in the Lodgepole Formation. Our results support a three-sequence model for the Lodgepole Formation. Based on the number of sequences and the placement of sequence stratigraphic surfaces, we see little evidence of statistically significant correlation between carbon isotopic trends and the sequence stratigraphic framework. We argue that sea level change was not the primary driving mechanism for carbon isotopic trends in the Madison Shelf, nor the KO excursion. Instead, we support models that invoke global ocean anoxia and/or destabilization of the global carbon cycle due to land plants.

The history of Madison Group exploration and production in the North Dakota Williston Basin with an update on Madison Group source rocks

The Williston Basin has proven to be a global super basin in terms of oil production and reserves (Sonnenberg, 2020). Although recent production in the basin has been dominated by the Middle Member of the Bakken Formation, the Madison Group has yielded over a billion barrels of oil since 1951. The Madison Group consists of the Charles, Mission Canyon, and Lodgepole formations with various members in each. These formations are found in both the United States and Canada and led Williston Basin production until 2008. As with many petroleum plays, the Williston Basin enticed oil men for many decades with the prospect of oil before finally yielding to success. Success, which is so often accompanied by a bit of good fortune, is a matter of finances, persistence, and technology, ultimately paving the way to successful commercial wells. Many factors contributed to the ongoing production results in the basin and include seismic, horizontal drilling, and completion technologies, and of course, good geological assessments. The history of production in the basin is also detailed by the history of petroleum geochemistry. Source rock and oil geochemistry progressed from scratch tests, test tube pyrolysis, and standard physicochemical properties, such as API gravity, to detailed chemical investigations including high resolution gas chromatography and biomarker analysis.

Evolution of carbonate studies in the Rocky Mountain region over the past century

Just as the world’s population, knowledge in general, and the Rocky Mountain Association of Geologists (RMAG) have changed in major ways during the past 100 years, so too has the study and interpretation of carbonate rocks and reservoirs. The RMAG, a century old in 2022, has evolved from just 50 original charter members who held the organization’s first “meeting” in 1922, to its approximately 1800 members today. Thus, RMAG’s publications have helped document the evolution of carbonate rock studies, particularly those in the Rocky Mountain region. Key contributions have been made through RMAG’s hundreds of luncheon talks, through its quarterly technical publication, The Mountain Geologist, initiated in 1964, and the exceptionally comprehensive Geologic Atlas of the Rocky Mountain Region, published 50 years ago in 1972. In addition, since 1953 the RMAG has published field guides and symposia volumes focused on specific basins, types of reservoirs, and structural geology among other things. Many of these books contain papers focused on carbonate rock units in the Rockies. Analysis of the papers published in The Mountain Geologist each year from 1964 through 2021 reveals that a fairly consistent 10 to 15% of that journal’s articles each year deal directly with some aspect of carbonate rocks. Earlier papers in the 1960s and 1970s dealt mainly with outcrop studies and the correlation of specific carbonate units based on measured sections or the use of fossils to define facies and biostratigraphic units. During the 1980s emphasis shifted to refining carbonate depositional models and focusing more on carbonate diagenesis through detailed petrographic studies, isotopic analyses, cathodoluminescence, and scanning electron microscopy. The 1990s brought a shift to papers focused more on specific carbonate hydrocarbon reservoirs ranging from the peritidal dolomites in Cottonwood Creek Field to relatively deepwater Waulsortian mudmounds in the Mississippian Lodgepole Formation and the “basinal” chalks of the Niobrara Formation. The focus of carbonate studies shifted again in the early 2000s to the use of 3-D seismic data to better understand specific carbonate reservoirs and the increased interpretation of carbonate deposits within the context of sequence stratigraphy. The tools used to study carbonate rocks expanded even further over the past decade with more refined isotopic data, improved SEM studies, and the use of elemental data obtained with X-ray fluorescence analyses. No doubt the next decade will bring even more improvements in data collection methods and the interpretation of depositional and diagenetic processes that have impacted all Rocky Mountain carbonate deposits.

Palynologic delineation of the Devonian–Carboniferous boundary, West-Central Montana, USA

ABSTRACTCratonic depositional systems in the Central Montana Trough involve the Devonian--Carboniferous boundary (DCB), and reflect both subtle regional epeirogeny and significant global glacioeustatic controls. A palynologic analysis of the upper Three Forks, Sappington and lower Lodgepole formations was carried out at the classic Logan Gulch location in Horseshoe Hills. The lower Trident Member of Three Forks Formation yielded low-diversity cosmopolitan, long ranging phytoplankton and few spores species (LAs1), attributed to the middle Famennian. The upper part of the same green seaway shale yielded only leiosphaerids and Botryococcus (LAs2), along with an external mold of a clymenid ammonoid. Age-diagnostic spores Retispora lepidophyta, Verrucosisporites nitidus and Vallatisporites vallatus from middle Sappington siltstone (LAs3) indicated a Strunian LN Zone. Two more assemblages from upper Cottonwood Canyon Member (LAs4) and false Bakken (LAs5), in the lower Lodgepole Formation yielded scarce, poorly preserved spores. The presence of Waltzispora polita in LAs4 indicated a Tournaisan-Visean age.

Viscoplastic Deformation of the Bakken and Adjacent Formations and Its Relation to Hydraulic Fracture Growth

We report laboratory studies of the time-dependent deformation of core samples from four different formations in the Williston Basin—the Lodgepole Formation, the Middle and Lower Bakken Formations, and Three Forks Formation. The laboratory tests reveal varying amounts of viscoplastic deformation in response to applied differential stress. The time-dependent deformation is generally greater in rocks with higher clay and organic content and can be described by a power-law function. Because the magnitude of the creep strain is linearly proportional to the applied differential stress, we can utilize viscoelastic theory and geophysical logs to estimate the degree to which tectonic stress is affected by viscoplastic stress relaxation. We suggest that viscoplastic stress relaxation results in the Upper and Lower Bakken Formations acting as frac barriers during hydraulic fracture stimulation in the Middle Bakken, but the Lodgepole and the Three Forks Formations are not frac barriers.

Early Mississippian Orbital-Scale Glacio-Eustasy Detected From High-Resolution Oxygen Isotopes of Marine Apatite (Conodonts)

Abstract Stratigraphic and geochemical studies from tropical through polar latitude records now recognize that the late Paleozoic ice age (LPIA) began earlier and ended later than traditionally thought and was characterized by discrete, My-scale intervals of increased glacial ice volumes that were separated by My-scale intervals of diminished ice volumes. Whereas the onset of LPIA glaciation now is recognized to have started as early as the Late Devonian, the continuity and patterns of glaciation in the > 15 My interval between this onset date and the well-documented mid-Carboniferous portion of the LPIA are less well understood. This study utilizes detailed cyclostratigraphic and δ18O records from Lower Mississippian (mid Tournaisian) tropical marine deposits and conodont apatite to argue that in addition to evidence for a discrete, My-scale early LPIA glaciation, there is compelling evidence for superimposed high-frequency (orbital-scale) glacial–interglacial climate oscillations driving glacio-eustasy and changes in sea-surface temperature (SST). Cyclostratigraphic evidence includes the development of asymmetric (progressive shallowing) and symmetric (deepening followed by shallowing) subtidal cycles in the Tournaisian Woodhurst Member of Lodgepole Formation which record repeated high-frequency water-depth changes from below storm wave base to above fairweather wave base. δ18O values from samples originating from six cycles range from 17.8‰ to 21.6‰, and intracycle trends record progressive increases in isotopic values from the deepest-water facies (at cycle base for asymmetric cycles or mid cycle for symmetric cycles) into the shallower-water cycle caps. Four of the cycles record average intracycle isotopic shifts of 1.4‰, and two cycles record shifts of ≥ 2.5‰. These co-varying trends between interpreted water-depth and δ18O changes are consistent with the hypothesis that the water-depth changes were controlled by orbital-scale glacio-eustasy. Assuming that the observed intracycle δ18O shifts represent the combined effects of ice-volume and SST changes, calculated glacio-eustatic magnitudes were < 50 m with tropical SST changes of < 4°C. Cycles recording ≥ 2.5‰ shifts may reflect additional SST cooling related to intensification of coastal upwelling during the onset of glacial stages. Orbital-scale glacio-eustatic interpretations imply that in addition to overall long-term Early Mississippian cooling and glaciation, the mid Tournaisian was characterized by superimposed high-frequency orbital-scale climate changes which controlled marked changes in glacial ice volumes, eustatic sea levels, coastal-upwelling intensities, and tropical SSTs. These long-term and superimposed short-term climate changes highlight the dynamic nature of the early LPIA and are reminiscent of climate patterns observed for Cenozoic and Late Ordovician greenhouse-to-icehouse climatic transitions.

Microseismic joint location and anisotropic velocity inversion for hydraulic fracturing in a tight Bakken reservoir

To improve the accuracy of microseismic event locations, we developed a new inversion method with double-difference constraints for determining the hypocenters and the anisotropic velocity model for unconventional reservoirs. We applied this method to a microseismic data set monitoring a Middle Bakken completion in the Beaver Lodge area of North Dakota. Geophone arrays in four observation wells improved the ray coverage for the velocity inversion. Using an accurate anisotropic velocity model is important to correctly assess the height growth of the hydraulically induced fractures in the Middle Bakken. Our results showed that (1) moderate-to-strong anisotropy exists in all studied sedimentary layers, especially in the Upper and Lower Bakken shale formations, where the Thomsen parameters ([Formula: see text] and [Formula: see text]) can be greater than 0.4, (2) all the events selected for high signal-to-noise ratio and used for the joint velocity inversion are located in the Bakken and overlying Lodgepole formations, i.e., no events are detected in the Three Forks formation below the Bakken, and (3) more than half of the strong events are in two clusters at approximately 100 and 150 m above the Middle Bakken. Reoccurrence of strong, closely clustered events suggested activation of natural fractures or faults in the Lodgepole formation. The sensitivity analysis for the inversion results showed that the relative uncertainty in parameter [Formula: see text] is larger than other anisotropy parameters. The microseismic event locations and the anisotropic velocity model are validated by comparing synthetic and observed seismic waveforms and by S-wave splitting.

Factors Affecting Downhole Scale Deposition: North Dakota Bakken Formation

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 140977, ’Field Study of the Physical and Chemical Factors Affecting Downhole Scale Deposition in the North Dakota Bakken Formation,’ by Lawrence M. Cenegy, SPE, Clyde A. McAfee, SPE, and Leonard J. Kalfayan, SPE, Hess Corporation, prepared for the 2011 SPE International Symposium on Oilfield Chemistry, The Woodlands, Texas, 11-13 April. The paper has not been peer reviewed. Oil recovery from the North Dakota Bakken formation has increased nearly 100-fold over the last 5 years. For one North Dakota operator with 150 Bakken producing wells, 22 of the wells have experienced at least one event of severe calcium carbonate scaling in the pump and production tubing, leading to well failure. A study showed that 82% of those wells failed during early production (i.e., less than 20,000 bbl of water produced and 2 years production); after this point, failures became increasingly rare. This rate correlated with transient alkalinity spikes in the water analyses and was attributed to fracturing-fluid flowback. Simulated blending of fracturing and formation waters demonstrated that during this period, it was most important to maintain a high level of scale inhibitor. Introduction The Bakken formation is within the Williston basin in western North Dakota and northeastern Montana in the USA and in southern Saskatchewan and southwestern Manitoba in Canada, as shown in Fig. 1. Discovered in 1953, the formation contains three key layers: an upper shale member (approximately 25 ft thick) that separates it from the Mississippian Lodgepole formation, a middle sandstone and silty-sandstone member (approximately 35 to 90 ft thick), and a lower shale member (approximately 50 ft thick) that separates it from the Devonian Three Forks formation. While the upper and lower shale members are rich in organic matter, the middle sandstone layer is most often produced economically because of its greater porosity. Bakken production occurs from approximately 8,000- to 11,000-ft vertical depth, with temperatures up to 240°F and pressures of 5,500 to 6,000 psi. The oil gravity is 39 to 46°API. Background Horizontal drilling is used to exploit reserves because the middle member is a relatively thin layer. Wells completed with 10,000-ft laterals are common. This method allows access to more oil-producing zones; however, the low permeability of the Bakken middle member requires effective hydraulic fracturing for production. Initially, the opera-tor conducted only “scour frac” operations, in which a single, high-rate fracturing treatment was pumped into the horizontal open hole without controlled placement. The result was cracking of the formation at its weakest point rather than a distribution of multiple propped fractures along the wellbore. Often, the result was excessive fracture-height growth and water incursion from other formations. Newer fracturing technology enables pinpoint multizone fracturing of the horizontal section. Pinpoint fracturing uses openhole packers and ball-actuated sliding sleeves to isolate targeted intervals. The operator applies such a system to fracture a mini-mum of 18 zones per lateral in a continuous operation.

Silicification in Mississippian Lodgepole Formation, northeastern flank of Williston basin, Manitoba, Canada

Five types of replacement silica are recognized in the Lower Mississippian Virden Member carbonates on the northeastern flank of Williston basin: microcrystalline quartz, chalcedonic quartz, anhedral megaquartz, euhedral megaquartz, and stringy megaquartz. Silica tends to replace various bioclasts, and all except the stringy megaquartz also occur as non-replacive void-filling cement or as silica forming chert nodules and silicified limestone. Although crinoids, brachiopods, corals, bryozoans, molluscs, trilobites, forams, and ostracodes are present in the sediments studied, only the first three show evidence of silicification. Crinoids are commonly replaced by microcrystalline quartz whereas brachiopods typically by spherules of length slow chalcedony. Coalesced spherules, often in concentric rings (beekite rings), may form sheet-like masses on the surface of corals and brachiopods. Although bryozoans are common in the Virden Member, none showed any evidence of silicification. The difference in the susceptibility to silicification may be related to the shell microstructure, biological group, size of organism, skeletal mineralogy, and organic content of the bioclasts. Biogenic silica derived from the dissolution of siliceous sponge spicules is considered to be the most likely silica source for silicification. Most silica is believed to be released during early diagenesis before the sediments were deeply buried. The Virden Member carbonate may have experienced two episodes of replacement, the first affecting the bioclasts, the second producing silicified limestone and chert nodules.

Upper Devonian to Lower Mississippian conodont biostratigraphy of uppermost Wabamun Group and Palliser Formation to lowermost Banff and Lodgepole formations, southern Alberta and southeastern British Columbia, Canada: Implications for correlations and sequence stratigraphy

Research Article| December 01, 2010 Upper Devonian to Lower Mississippian conodont biostratigraphy of uppermost Wabamun Group and Palliser Formation to lowermost Banff and Lodgepole formations, southern Alberta and southeastern British Columbia, Canada: Implications for correlations and sequence stratigraphy David I. Johnston; David I. Johnston 103 - 3017 Blakiston Drive NW, Calgary, AB T2L 1L7, johnstda@shaw.ca Search for other works by this author on: GSW Google Scholar Charles M. Henderson; Charles M. Henderson Department of Geoscience, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, charles.henderson@ucalgary.ca Search for other works by this author on: GSW Google Scholar Michael J. Schmidt Michael J. Schmidt ConocoPhillips Canada, 401 9th Avenue SW, Calgary, AB T2P 2H7, Mike.J.Schmidt@conocophillips.com Search for other works by this author on: GSW Google Scholar Bulletin of Canadian Petroleum Geology (2010) 58 (4): 295–341. https://doi.org/10.2113/gscpgbull.58.4.295 Article history received: 23 Sep 2009 accepted: 02 Nov 2010 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation David I. Johnston, Charles M. Henderson, Michael J. Schmidt; Upper Devonian to Lower Mississippian conodont biostratigraphy of uppermost Wabamun Group and Palliser Formation to lowermost Banff and Lodgepole formations, southern Alberta and southeastern British Columbia, Canada: Implications for correlations and sequence stratigraphy. Bulletin of Canadian Petroleum Geology 2010;; 58 (4): 295–341. doi: https://doi.org/10.2113/gscpgbull.58.4.295 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of Canadian Petroleum Geology Search Advanced Search Abstract Biostratigraphic analysis of conodont faunas from the Upper Devonian Wabamun Group, the Upper Devonian to Lower Mississippian Exshaw Formation and the Lower Mississippian Banff Formation in southern Alberta has shown that significant hiatuses may exist within the Late Devonian Big Valley and equivalent upper Costigan Member of the Palliser Formation and within the Early Mississippian lower Banff and Lodgepole formations. Minor hiatuses occur in the Late Devonian to Early Mississippian Exshaw Formation between the lower and upper members and between the equivalent lower black shale and middle sandstone members of the Bakken Formation. All of these hiatuses are interpreted to have been the result of forced regression due to uplifts. Biostratigraphic data and stratigraphic evidence derived from mapping suggest an erosional high existed at about the position of the Fifth Meridian in southwestern Alberta, as indicated by the repeated removal of Upper Devonian to Lower Mississippian strata in this area. The only other tectonic elements that may have influenced sedimentation and distribution patterns of these strata are possible deep-seated basement faults beneath the position of the Early Cretaceous Cutbank channel and the Sweetgrass Arch.The lower part of the Big Valley Formation and upper Costigan Member may represent one major episode of deposition, whereas the upper part of these units, the Exshaw Formation and the lower and middle members of the Bakken Formation appear to represent another depositional event. At least two depositional events may be represented in the lower Banff and Lodgepole formations in the study area. The depositional events and hiatuses documented in the study area generally correlate with similar events in western North America and globally. However, discordance between events in our study area and elsewhere probably reflect the masking effect of local tectonism. Correspondingly, one transgressive-regressive sequence may be recognized in the lower part of the Big Valley and upper Costigan Member. The upper part of these units, the Exshaw Formation and the lower and middle members of the Bakken Formation are interpreted as a single transgressive-regressive sequence, contrary to previous interpretations. One complete sequence and a portion of another are recognized in the lower Banff and Lodgepole formations.Many of the unconformities may be linked to Antler orogenesis, which also would have affected subsidence rates. Changes in subsidence rates interacting with eustatic sea level changes produced the stratigraphic framework and distribution of units observed in the study area. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Spatial variation of Bakken or Lodgepole oils in the Canadian Williston Basin

There are two opposing schools of thought that infer either the Bakken Formation or the Lodgepole Formation as the primary source rock for the Madison-reservoired oils in the Canadian Williston Basin. A recent geochemical study revealed evidence indicating the existence of significant mixing of Bakken and Lodgepole oils in the Madison reservoirs. To investigate the geographic distribution of the oil compositions, we employed a multivariate statistical method to extract source and maturity-specific geochemical signatures from a geochemical data set for spatial analysis. Oil mixing appears to be geographically dependent and restricted by a northeast-southwest–striking zone (Torquay-Rocanville trend) in southeast Saskatchewan. Thus, fracture or fault systems are inferred to have provided high-permeability zones allowing Bakken-derived oil to migrate upward across the Lodgepole Formation. The areas without significant fault or fracture systems favor lateral oil migration along porous beds, restricting Bakken-derived oil accumulation to pools in Bakken reservoirs and Lodgepole-derived oils to occur primarily in overlying reservoir beds of the Madison Group.

VP/VS characterization of a heavy-oil reservoir

This article demonstrates a VP/VS application for a heavy oil field near Plover Lake, Saskatchewan, where Nexen has applied both hot and cold production methods. Plover Lake Field is about 8 km east of the Alberta-Saskatchewan border and about 320 km north of the Canada-U.S. border. Oil sands of the Devonian-Mississippian Bakken Formation are found in NE-SW trending shelf-sand tidal ridges that can be up to 30 m thick, 5 km wide, and 50 km long. Overlying Upper Bakken shales are preferentially preserved between sand ridges. The Bakken Formation is disconformably overlain by Lodgepole Formation carbonates (Mississippian) and/or clastics of the Lower Cretaceous Mannville group. Since sandstones have larger S-wave velocities (and hence lower VP/VS ratios) than shales, VP/VS maps should help to identify thickening sand layers within the target zone. We also intend to examine changes within the reservoir due to cold production. Unlike the steam injection processes used in enhanced heavy oil recovery, cold prod...

Facies associations, sedimentary cyclicity and compartmentalization of the MC-1 Member (Mississippian), Tilston Field, southwestern Manitoba

ABSTRACT The sedimentary rocks of the Mississippian Mission Canyon-1 (MC-1) Member (Tilston Beds) of the Tilston Field, southwestern Manitoba, Canada, were deposited on a low-relief carbonate platform along the northeastern margin of the Williston Basin. Three oil pools occur in the Tilston Field: Mission Canyon 1 A (MC-1 A), Mission Canyon 1 C (MC-1 C) and Mission Canyon 1 D (MC-1 D). The rocks of the MC-1 Member are broken into five facies associations, which stack to form five shallowing-upward subtidal carbonate cycles (TB1, TB3 to TB6) and one shallowing- to deepening-upward subtidal carbonate cycle (TB2). Each cycle was deposited in water depths that varied from fair weather wave base to slightly below storm wave base. Well log analysis of the uppermost Lodgepole Formation indicates at least four shallowing-upward subtidal carbonate cycles (L1 to L4). Argillaceous-rich wackestone to mudstone intervals occur in the basal part of each cycle. Each cycle of the MC-1 Member and uppermost Lodgepole Formation can be correlated across the study area. The MC-1 Member and Lodgepole cycles show a trend of increasing total porosity and decreasing argillaceous content from south to north across the Tilston Field. Cycles TB4 and TB5 have the lowest argillaceous content and the highest porosity, and are the main oil producing units in the Tilston Field. The lack of argillaceous material and the relatively high porosity suggests that reservoir compartmentalization is highly unlikely across the TB4 to TB5 boundary. In contrast, the basal parts of cycles TB3 to TB1 and L1 to L4 are argillaceous rich and characterized by fair total porosity. It is likely that these argillaceous-rich zones form barries to the vertical movement of fluids, thus compartmentalizing the aquifer. In the absence of vertical fractures, the dominant drive mechanism in the Tilston Field oil pools is likely to be edge water drive. Progressive erosional truncation of the MC-1 Member cycles to the north, combined with the presence of two structural saddles, effectively reduces the areal support of the edge water aquifer from south to north. The MC-1 A Pool is likely to have the strongest aquifer support, whereas the MC-1 D Pool has the weakest aquifer support. Significant differences in horizontal well productivity can be partially attributed to the relative strength of the aquifer in each pool. End_Page 244------------------------

Bakken/Madison petroleum systems in the Canadian Williston Basin. Part 2: molecular markers diagnostic of Bakken and Lodgepole source rocks

The uppermost Devonian-Mississippian Bakken Formation black shale and the Mississippian Lodgepole Formation carbonate represent two of the most important source rocks in the Canadian Williston Basin. Quantitative analyses of both saturated and aromatic hydrocarbon fractions reveal significant differences in the relative distributions and absolute concentrations for a wide range of molecular markers between the extracts of the two source units. Among others, the Bakken shales are characterized by their high relative abundance of trimethyl aryl and diaryl isoprenoids likely derived from green sulfur bacteria Chlorobiaceae. In contrast, the Lodgepole carbonates at similar maturity levels display a C 35 homohopane prominence and abundant benzohopanes, ring-D monoaromatic 8,14-secohopanes and a tetracyclic monoaromatic hydrocarbon. The distinctive nature of molecular marker “fingerprints” diagnostic of the two source rocks is clearly related to their different organic inputs and depositional environments. Additionally, the large difference in the absolute concentrations of these compounds observed in both source units may potentially lead to biased geochemical interpretations if strictly conventional, saturate-based biomarker approaches were used for oil-oil and oil-source correlation.

Abstract: Sequence Stratigraphic Framework, Sedimentology, and Diagenesis of Waulsortian Mounds of the Lodgepole Formation (Mississippian) in the Dickinson Field Complex, Williston Basin, North Dakota&nbsp;

Abstract: Sequence Stratigraphic Framework, Sedimentology, and Diagenesis of Waulsortian Mounds of the Lodgepole Formation (Mississippian) in the Dickinson Field Complex, Williston Basin, North Dakota&nbsp;

Abstract: A Comparison Study of Mississippian Mounds in the Lodgepole Formation of Montana and North Dakota&amp;nbsp;

Abstract: A Comparison Study of Mississippian Mounds in the Lodgepole Formation of Montana and North Dakota&amp;nbsp;

Abstract :Sequence Stratigraphic Framework of the Lower Mississippian Lodgepole Formation, Williston Basin: Carbonate Ramp Sedimentation in a Starved Basin Setting

Abstract :Sequence Stratigraphic Framework of the Lower Mississippian Lodgepole Formation, Williston Basin: Carbonate Ramp Sedimentation in a Starved Basin Setting

A Comparison of the Rates of Hydrocarbon Generation from Lodgepole, False Bakken, and Bakken Formation Petroleum Source Rocks, Williston Basin, U.S.A.: ABSTRACT

Recent successes in the Lodgepole Waulsortian Mound play have resulted in the reevaluation of the Williston Basin petroleum systems. It has been postulated that hydrocarbons were generated from organic-rich Bakken Formation source rocks in the Williston Basin. However, Canadian geoscientists have indicated that the Lodgepole Formation is responsible for oil entrapped in Lodgepole Formation and other Madison traps in portions of the Canadian Williston Basin. Furthermore, geoscientists in the U.S. have recently shown oils from mid-Madison conventional reservoirs in the U.S. Williston Basin were not derived from Bakken Formation source rocks. Kinetic data showing the rate of hydrocarbon formation from petroleum source rocks were measured on source rocks from the Lodgepole, False Bakken, and Bakken Formations. These results show a wide range of values in the rate of hydrocarbon generation. Oil prone facies within the Lodgepole Formation tend to generate hydrocarbons earlier than the oil prone facies in the Bakken Formation and mixed oil/gas prone and gas prone facies in the Lodgepole Formation. A comparison of these source rocks using a geological model of hydrocarbon generation reveals differences in the timing of generation and the required level of maturity to generate significant amounts of hydrocarbons.

A Two-Dimensional Regional Basin Model of Williston Basin Hydrocarbon Systems

Institut Francais du Petrole's two-dimensional model, temispack, is used to discuss the functioning of petroleum systems in the Williston basin along a 330-km-long section, focusing on four regional source intervals: Ordovician Yeoman formation, Lower Devonian Winnipegosis Formation, Upper DevonianuLower Mississippian Bakken Formation, and Mississippian Lodgepole formation. Thermal history calibration against present temperature and source rock maturity profiles suggests that the Williston basin can be divided into a region of constant heat flow of about 55 mW/m2 away from the Nesson anticline, and a region of higher heat flow and enhanced thermal maturity in the vicinity of the Nesson anticline. Original kinetic parameters used in the calibration were derived or each of the four source rocks from Rock-Eval yield curves. Bakken overpressures are entirely due to oil generation, not compaction disequilibrium. Very low Bakken vertical permeabilities range from 0.01 to 0.001 nd are matched against observed overpressures, whereas Bakken porosities based on the model and confirmed by measurements are inferred to be also unusually low, around 3%. Mature Bakken shales do not seem to have reached hydraulic fractionation thresholds, except perhaps locally in regions of extensional tectonic stress. Hydraulic fracturing cannot be viewed as a pervasive mechanism driving Bakken oil expulsion. Our expulsion model confirms the high residual Bakken oil saturations and explains the low residual S1/TOC by the low Bakken shale porosities. Approximately 85% of the oil generated in the Bakken shales is predicted to have been expelled out of Bakken strata, which agrees with observed S1/TOC trends. Madison Group accumulations at the subcrop edge are found to be fed by Lodgepole-sourced oil only, in particular by the rich middle Lodgepole interval. These accumulations probably result from a three-dimensional migration pattern. Madison accumulations in the Nesson anticline are found to be fed mostly by Lodgepole-sourced oil mixed with minor amounts of Bakken-sourced oil. The vast majority of the expelled Bakken oils are lost in the Madison Group at very low saturations. This explains the low conventional oil resource associated with Bakken sources by recent geochemical studies. Expulsion and migration occurred no earlier than the atest Cretaceous-Paleocene in the Yeoman and no earlier than the Eocene in other source rocks, consistent with temporal controls on oil migration. Flow models show no restriction to expulsion and migration of Yeoman oil. This suggests a potential undiscovered oil resource in Ordovician and Silurian strata of Williston basin, northeast of the Nesson anticline.

Basin Configuration and Depositional Trends in the Mission Canyon and Batoliffe beds, U.S. Portion of the Williston Basin: ABSTRACT

Construction of Mission Canyon and Ratcliffe depositional trends utilizing shoreline models and anhydrite edge maps shows a significant change in basin configuration associated with regional sea level changes. Sea level highstand, which began during deposition of the Scallion member of the Lodgepole Formation, was punctuated by two lowstand events. The first occurred during deposition of the MC-2 anhydrite (Tilston). During this lowstand event, the width of the carbonate basin decreased significantly. With sea level rise, a broad basin formed with carbonate and evaporate ramp deposition (Lands, Wayne, Glenburn and Mohall members). The top of the Mohall contains evidence of the second lowstand event. This event introduced quartz sand detritus into the basin (Kisbey Sandstone). Because of sea level lowstand, Sherwood and younger Mission Canyon beds were deposited during highstand in a narrower carbonate basin. Funneling of marine currents and tides in this basin created higher energy shoreline and shoal deposits than those commonly found in older Mission Canyon sediments. The top of the Mission Canyon (Rival) was capped by a deepening event or transgression which enlarged the basin and created broad Ratcliffe ramp systems similar to those that existed during Glenburn and Mohall deposition. By utilizing sequence stratigraphy and mappingmore » shoreline trends and basin configuration, reservoir and trap geometries are identified, and exploration success is improved.« less