Gething Formation Research Articles

New evidence for avian and small non-avian theropod ichnotaxa from the Lower Cretaceous of Canada: Implications for theropod ichnodiversity

A diverse continental ichnofauna from the Lower Cretaceous (Aptian) Gething Formation occurs at the Ninesting Creek site in northeastern British Columbia. Vertebrate tracks including Wupus and Saurexallopus are inferred to represent medium-sized (footprint length ∼10 cm) tridactyl avian and larger (footprint length ∼15–17 cm), gracile, tetradactyl non-avian theropod trackmakers respectively. Shape, length-to-width and divarication ratios, suggest two morphotypes that are distinct from the poorly known, and infrequently-cited, Gething Formation ichnogenera Columbosauripus and Irenichnites (footprint lengths ∼12.5 and ∼15.0 cm respectively). This suggests a diverse theropod ichnofauna representing size classes which are quite distinct from the better-known large theropod ichnogenus Irenesauripus with footprint lengths in the range of ∼38.0–53.5 cm. Thus, current evidence suggests that the ichnodiversity of smaller avian and non-avian theropod tracks (footprint length ∼<15.0 cm) outnumbers large ‘megatheropod’ morphotypes by about 7:1. The implications of this distribution are consistent with recently proposed palaeoecological models. The assemblage also includes probable pterosaur tracks and distinctive arcuate compound Archaeonassa-Lockeia traces, attributed to freshwater unionid bivalves. The trace fossils comprise a composite Mermia-Scoyenia Ichnofacies assemblage. Palaeoenvironmentally the site represents the low energy margin of an open lake basin or floodplain pond, or a fluvial point bar.

Reconstruction of brackish-water systems using an ichnological framework

This paper provides an overview of the history of ichnology from both Russian and international perspectives. However, the main purpose of the paper is to review how trace fossils can be used to discern the brackish-water sedimentary environments from their open-marine counterparts. A number of modern studies are presented, including: (1) Kouchibouguac Bay, New Brunswick, Canada; (2) Willapa Bay, Washington, USA; (3) Ogeechee River Estuary, Georgia, USA; and (4) Petitcodiac River estuary, New Brunswick, Canada. Cretaceous examples from the Western Canada Sedimentary Basin (i.e., McMurray Formation, AB, Canada and Gething Formation, British Columbia, Canada) are provided to test the models derived from the modern estuaries.

Vertebrate ichnites from the Boulder Creek Formation (Lower Cretaceous: middle to ?upper Albian) of northeastern British Columbia, with a description of a new avian ichnotaxon, Paxavipes babcockensis ichnogen. et isp. nov.

This is the first detailed report of vertebrate tracks from alluvial plain deposits of the Boulder Creek Formation (Lower Cretaceous: middle to ?upper Albian) from outcrop exposures in northeastern British Columbia. Several in situ dinosaur tracks observed in vertical section are described, as well as the recovery and description of an isolated track slab discovered in the Boulder Gardens recreation area south of Tumbler Ridge, British Columbia. The vertebrate ichnites consist of three small tridactyl theropod dinosaur prints, one tetradactyl ornithopod print, and 72 small tridactyl tracks of avian affinity which are described as a new ichnotaxon herein. The avian prints are small (under 30 mm length) and are characterised by a large divarication between digits II and III and comparatively lesser divarication between digits III and IV. The pace and stride are short and the pace angulation is high. The tracks are similar to those produced by extant shorebirds and the track-maker likely occupied a similar niche. The avian prints are described herein as a new ichnotaxon, Paxavipes babcockensis ichnogen. et isp. nov. Two of the theropod footprints are identified as Irenichnites gracilis, an ichnotaxon described in 1932 by C.M. Sternberg from the Lower Cretaceous (Aptian) Gething Formation near Hudson's Hope, British Columbia. One of the Irenichnites gracilis prints displays skin impressions associated with the digital pads of digit III and the metatarsal pad. This is the first record of skin impressions from prints of Irenichnites gracilis. The ornithopod track is partial and unidentifiable to a particular ichnotaxon, but displays skin impressions on the metatarsal pad and at the base of the second digit impression. The skin impressions from the ornithopod track differ from the Irenichnites gracilis skin impressions.

Managed-Pressure Drilling To Counteract Lost-Circulation and High-Pressure-Gas Zones: South Wapiti Red Rock Field

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 137428, ’Successful Use of Managed-Pressure Drilling To Counteract Lost-Circulation and High- Pressure-Gas Zones: A Case Study From the Red Rock South Wapiti Field in Grande Prairie, Alberta, Canada,’ by Hassan K. Malik, SPE, Raymond J. Litwin, SPE, and Bernard C. Jones, ConocoPhillips Canada, prepared for the 2010 Canadian Unconventional Resources &amp; International Petroleum Conference, Calgary, 19-21 October. The paper has not been peer reviewed. Use of heavy mud weight (MW) to control high-pressure (HP) -gas and lost-circulation zones at the same time is a challenge. The Red Rock field in the South Wapiti area in Alberta experienced this combination, which resulted in high operational costs, primarily caused by an additional casing string, high MW, and severe mud losses. On average, costs were 20% higher than anticipated, making this drilling program uneconomical. Introduction The Red Rock field is in the Deep basin of western Alberta, where much of the gas is found in low-porosity, low-permeability reservoirs deposited in an epicontinental seaway. The Deep basin is unique in that porous rocks are water saturated updip to the east and gradually become gas saturated and less porous downdip to the west. The Falher section (overlying the Gething formation) is overpressured in the area, but there is more confidence in predicting the presence on a broad scale. Coals are found throughout the Falher and Gething formations and must be considered. Historically, lost circulation has occurred in the Falher section at elevated MWs, also into several coal seams in a few cases. Recent wells have experienced kicks in the Bluesky, Gething, and Falher zones, which have driven MWs higher to manage risk. Further uphole, the Doe Creek and Dunvegan formations have been pinpointed as a main lost-circulation section in the area. Natural fractures exist in the wider area across this section, which supports the determination that these zones cause lost circulation. Red Rock Drilling Challenges Wells in this area are drilled with an invert-oil-based-mud (OBM) system, which is used in the field with consistent success in keeping reactive shales stable. The use of OBM systems, with high oil/water ratios, is costly in lost-circulation situations. Wellbore-strengthening materials have been used to varying degrees to mitigate losses while drilling the usual problem zones. This is seen when drilling into the Doe Creek and Dunvegan formations with low MWs (930–980 kg/m3) and losses are encountered. A regime of adding wellbore-strengthening materials before penetrating these zones helps heal the losses, and in several cases allowed the MW to be increased deeper in the well. This technique is an important tool in this area to drill through loss zones.

Preliminary assessment of ichnofacies in the Gething Formation of NE British Columbia

Abstract The Gething Formation in the Kahntah River–Ring/Border region of northeastern British Columbia is a variably thick, heterolithic succession of facies deposited in continental and marginal-marine depositional settings. This unit was deposited on the southwestern flank of the Keg River Highlands in the northern Western Canada Foreland Basin (approximately 58°N, 120°W). Although Gething Formation sandstone bodies are exploration targets further south, it is not considered to be a primary exploration target in the study area due largely to its complex and laterally discontinuous nature. However, in the study interval several of the lithofacies possess good reservoir properties, and the overlaying Wilrich Shale provides a potential stratigraphic seal. Hydrocarbon sources are available in both the Wilrich Shale and the Triassic Montney Formation into which the Gething Formation incises. An understanding of the overall palaeogeography and lithofacies distribution of the Gething Formation in the study area is necessary for efficiently exploiting these hydrocarbon resources and will facilitate characterization of other Gething Formation reservoirs that may flank the Keg River Highland to the east and west. Subsurface mapping in the area of Ring and Kahntah River gas fields shows that the Gething Formation in the study area occurs within three sinuous incised valleys that debouch southward into a large structural basin. In their northernmost (upstream) reaches, Gething Formation strata are dominated by unbioturbated, high-angle cross-bedded and current-ripple laminated upper-fine-grained sandstones, rich in organic detritus (primarily coal flakes). These are interpreted as fluvial channel and bayhead delta deposits. Lithofacies deposited in continental settings grade southwards into bioturbated, low- and high-angle cross-bedded, lower to upper-fine-grained sandstones with thin, bioturbated siltstone and mudstone intervals. Rhythmic bedding, mud flasers and mud/sand couplets characterize these lithofacies. The trace fossils Planolites, Skolithos, Cylindrichnus, Arenicolites, Teichichnus, and fugichnia are common. These strata are interpreted to represent brackish-water bay deposits. South of this, the Gething Formation is dominated by interstratified, sporadically bioturbated sand, silt and mud, sedimentologically similar to the aforementioned brackish channel deposits, but with more diverse and robust ichnofauna (the previous assemblage as well as large Thalassinoides, rare Helminthopsis and Phycosiphon). These deposits are ascribed to tidal channels in a larger, more marine bay.

Gas maturity and alteration systematics across the Western Canada Sedimentary Basin from four mud gas isotope depth profiles

Carbon isotope and molecular compositions of Mississippian to Upper Cretaceous mud gases have been examined from four depth profiles across the Western Canada Sedimentary Basin (WCSB). The profiles range from the shallow oil sands in the east ( R 0 = 0.25) to the very mature sediments in the overthrust zone to the west ( R 0 = 2.5). In the undisturbed WCSB, δ 13C 1– δ 13C 2 and δ 13C 2– δ 13C 3 cross-plots show three maturity and alteration trends: (1) pre-Cretaceous gas sourced from type II kerogen; (2) Cretaceous Colorado Group gas; and (3) Lower Cretaceous Mannville Group biodegraded gas. A fourth set of distinctly different maturity trends is recognized for Lower Cretaceous gas sourced from type III kerogen in the disturbed belt of the WCSB. Displacement of these latter maturity trends to high δ 13C 2 values suggests that the sampled gas was trapped after earlier formed gas escaped, probably as a result of overthrusting. Unusually 13C-enriched gas ( δ 13C 1 = −34‰, δ 13C 2 = −13‰, and δ 13C 3 = 0‰), from the Gething Formation in the disturbed belt, is the result of late stage gas cracking in a closed system. In general, gas maturity is consistent with the maturity of the host sediments in the WCSB, suggesting that migration and mixing of gases was not pervasive on a broad regional and stratigraphic scale. The ‘Deep Basin’ portion of the WCSB is an exception. Here extensive cross-formational homogenization of gases has occurred, in addition to updip migration along the most permeable stratigraphic units.

Evaluating the coalbed methane potential of the Gething coals in NE British Columbia, Canada: An example from the Highhat area, Peace River coalfield

Abstract Lower Cretaceous coals from the Gething Formation in the Highhat area of NE British Columbia were analyzed for gas content as part of an exploration program. Samples of continuous wireline core and cuttings were processed. Vitrinite reflectance and dry ash-free volatile matter both indicate that the rank of the coal is low volatile bituminous. The coals are well cleated and contain shear fractures, as seen in the core description and in the FMI logs. Coal cuttings were screened to remove a very fine fraction (− 200 mesh) and then treated in heavy liquid (SG 1.75 g/cm 3 ) to remove inorganic lithologies. For the cores, total gas content ranges from 516.9 to 876.8 scf/t (16.1–27.4 cm 3 /g; adb) with a mean value of 671.1 scf/t (20.9 cm 3 /g) at 20.5% ash (adb). For the cuttings, all desorbed gas was assigned to the + 200 mesh/float 1.75 SG weight fraction. On this recalculated basis, total gas content for the processed cuttings ranges from 651.8 scf/t (20.4 cm 3 /g) to a high value of 2083.6 scf/t (65.1 cm 3 /g; adb). Weight yields after screening/floating are generally low. For samples yielding very low values ( 3 /g; adb) with a mean value of 760.4 scf/t (23.8 cm 3 /g) at 15.5% ash (adb). The desorbed gas is predominantly methane (98–99%; air-free and acid-free basis) and average carbon dioxide is about 6%. Methane is thermogenic based on isotopic analysis. Methane adsorption isotherm analysis at reservoir conditions shows that the Gething coals are at least 95% gas saturated. Using 1300 m as a depth cut-off and an average gas content of 672 scf/t (21 cm 3 /g), GIP (gas-in-place) in the Highhat prospect area is estimated to be 270 bcf (billion cubic feet). This translates to 24.5 bcf/section (a section is equal to a square mile or 640 acres) for the 11 sections of land in the vicinity of the corehole or to 3 bcf/m/mile 2 . The low absolute permeability of the coals (0.5 md) is the main limiting factor for producibility and commercial development of the resource. Even at today's high natural gas prices, these coals are not economically viable.

Stratigraphy, structure and tectonic history of the Pink Mountain Anticline, Trutch (94G) and Halfway River (94B) map areas, northeastern British Columbia

Abstract Pink Mountain Anticline stands out in front of the foothills of northeastern British Columbia (57°N, 123°W). Geologic mapping and prestack depth-migrated seismic sections show that it is localized above and west of a northwest-trending subsurface normal fault. Along with isopach maps these data demonstrate episodic normal movement on the fault during deposition of the Carboniferous Stoddart Group, Triassic Montney Formation and possibly the Jurassic–Cretaceous Monteith–Gething formations. West of this fault, during Laramide compression, a pair of backthrusts nucleated on either side of a minor east–west trending Carboniferous fault and propagated across it in an en echelon pattern. One backthrust ramped laterally across the area and separated the Pink Mountain and Spruce Mountain structures, both of which are contained within a 30+ km long pop-up structure above the Besa River Formation decollement. Glomerspirella fossils confirm the existence of the Upper Jurassic Upper Fernie Formation and Upper Jurassic to Lower Cretaceous Monteith Formation at Pink Mountain.

Controls on Methane Adsorption Capacity of Lower Cretaceous Coals from Northeastern British Columbia, Canada: Part 2—Effect of Temperature, Pressure, Maceral Composition, and Mineral Matter on Adsorption

The effect of temperature, pressure, maceral composition, and mineral matter on the methane adsorption of coals from the Gething Formation was examined. Data was compared with coals from the Gates Formation in the same area and with coals from Australia. Adsorption capacity in the Gething coals appears to be moderately to strongly affected by the vitrinite (and pseudovitrinite) content and mineral matter, which does not only have a diluting effect, but also acts negatively on gas adsorptive capacity. Another explanation for the high gas adsorption capacity in the Gething coals may be related to the presence of free gas, which is more common when coals are below equilibrium moisture in a gas-saturated stratigraphy. Both Gething and Gates coals show an increase in gas-holding capacity, with increasing pressure as a function of vitrinite/inertinite ratio. Such an increase is absent in coals from the Bulli Seam, Sydney Basin, Australia.

Controls on Methane Adsorption Capacity of Lower Cretaceous Coals from Northeastern British Columbia, Canada: Part 1—Geology, Rank Variation, and Adsorption Isotherms

This study examines the high-pressure methane adsorption capacity of coals in the Gething Formation, Peace River coalfield, northeastern British Columbia, Canada. The Gething coals have higher than expected methane adsorptive capacity based on their rank. For example, at 1,000 m depth and 1.7% Ro,max methane adsorption capacity ranges from 22–27 cc/g (daf) (700–870 scf/ton), whereas gas content estimated using the Eddy curves and the Ryan Equation is about 17 cc/g (daf) (545 scf/ton). This study also describes the geology, regional rank variations, maceral composition, and coal quality characteristics of the Gething coals in an attempt to rationalize the adsorption isotherm data of the coals.

ABSTRACT: Sequence Stratigraphy of the Gething and Bluesky Formations, Western Canada Sedimentary Basin: Prediction of Systems Tract Development, Reservoir Performance and Deep Basin Conditions

ABSTRACT: Sequence Stratigraphy of the Gething and Bluesky Formations, Western Canada Sedimentary Basin: Prediction of Systems Tract Development, Reservoir Performance and Deep Basin Conditions

Abstract: Influence of the Pre-Cretaceous Unconformity on the Development of Fluvial to Marginal Marine Reservoirs, Cretaceous Bluesky and Gething Formations, Dahl-Buick Creek Areas, British Columbia&amp;nbsp;

Abstract: Influence of the Pre-Cretaceous Unconformity on the Development of Fluvial to Marginal Marine Reservoirs, Cretaceous Bluesky and Gething Formations, Dahl-Buick Creek Areas, British Columbia&amp;nbsp;

Production Casing Performance In a Thermal Field

Abstract High temperature steaming of wells can cause plastic yielding of the production casing. However, when properly designed and installed these casing strings will last the full life of a thermal project. Inferior designs or installations can cause significant well problems ranging from wellhead growth and settling to buckled or parted casing. Since 1979, Shell Canada limited has been operating a thermal project in the Peace River/Cadotte Lake area. Steam injection temperatures have been as high as 335 ° C, but only two of the 286 steamed wells have incurred thermal induced casing failures. Three additional casing failures were caused by corrosion. Some 10 to 15 other wells have experienced wellhead settling (casing contraction). Several wellheads have gone down 25 to 50 cm, requiring wellhead and piping modifications but casing integrity has been maintained. This paper discusses the casing and cement designs used historically, field observations and explanations for the casing "shrinking" phenomena and the field testing of K-55 grade casing. Shell Canada Limited's current design utilizes K-55 premium connection casing with class G thermal 1,880 kg/m3 and 1,400 kg/m3 weight cements. Introduction Shell Canada Limited has operated a steam injection project at Peace River since 1979. The production zone is an unconsolidated sandstone of the Lower Cretaceous Gething formation. This bitumen reservoir is 550 m from surface with an average pay thickness of 25 m. The bitumen gravity is 8 - 10 ° API with a viscosity at reservoir conditions of 200 Pa.s. The bitumen saturation decreases with depth in the zone. At bitumen saturations below 65%, the water phase is mobile and allows steam injection below fracture pressures. Most, but not all the wells drilled have a mobile bottom water layer. The primary recovery process has been a pattern steam drive. Dedicated injection wells were utilized, however all wells were initially steamed and produced to establish bitumen mobility and communication between wells. In 1993, four horizontal wells were drilled to evaluate the Enhanced Steam Assisted Gravity Drainage Process (ESAGD). Since then, 25 horizontal wells have been drilled for ESAGD or cyclic steaming bitumen recovery. All of these wells have used K-55 casing with premium connections. Casing designs have varied from NM-80 LT&amp;C, L-80 VAM, L-80 OBTC (oversize buttress threaded and coupled), and most recently K-55 NS-CC premium connection. Between 1979 and 1997, there were five casing failures at the Peace River complex. One was a buckled casing string, another was a parted connection and the remaining three were due to corrosion. Ten to 15 wells have had casing "contraction," causing the wellhead to settle 10 to 50 cm. The casing/wellhead movement is not a failure but can impose additional operating expenses and difficulty. In general, the casing performance has been satisfactory, as the above failures can be explained and continued reliability from the existing casing strings is anticipated. Casing Design An understanding of the stresses imposed on the casing during thermal operations is needed to properly design the casing and evaluate its performance.

Coalbed methane potential in northeast British Columbia, Gates and Gething formations

Coalbed methane potential in northeast British Columbia, Gates and Gething formations

Dinosaur footprints with skin impressions from the Cretaceous of Alberta and Colorado

Cretaceous dinosaur footprints discovered in the J Sandstone of the South Platte Formation (Dakota Group) in Colorado and the St. Mary River Formation of southwestern Alberta exhibit the first reported foot pad skin impressions of large ornithopods. The Canadian tracks occur as sandstone casts preserved in mudstones, whereas the Colorado tracks are natural impressions in a sandstone bed overlain by shale. The South Platte Formation tracks occur as impressions in a widespread "dinoturbated" sandstone bed representing low-gradient, delta plain – coastal plain facies assemblages associated with the upper member of the group, the J Sandstone. Only one of the many iguanodontid trackways exhibits good skin impressions.The St. Mary River Formation palaeoenvironment is interpreted as an anastomosed fluvial system that flowed northeast over a low-gradient floodplain from Montana. Footprints, often preserved in trackways, were left as dinosaurs walked across lake and marsh sediments that were relatively well drained or in various stages of dewatering. The quality of preservation is variable, depending on the properties of the substrate, and only one hadrosaur footprint includes clear casts of skin patches on the bottom of the footprint. Similar track-rich facies assemblages, representing lowland coastal plain and deltaic environments, are found in both the Lower (Gething Formation, British Columbia) and Upper Cretaceous (Mesa Verde, Colorado) successions of western North America. Few substrates of these depositional environments were suitable for the preservation of skeletal remains, so the information derived from tracks is palaeontologically significant.

Skeletal reconstruction and life restoration of Sauropelta (Ankylosauria: Nodosauridae) from the Cretaceous of North America

A skeletal reconstruction and life restoration are presented for the Early Cretaceous nodosaurid ankylosaur Sauropelta edwardsi. This composite is based on several partial skeletons having armor preserved in situ from the Lower Cretaceous Cloverly Formation of Wyoming and Montana. Comparison of foot morphology with that of the ichnofossil Tetrapodosaurus borealis, from the Lower Cretaceous Gething Formation of British Columbia, suggests that the footprint is that of Sauropelta. A hypothesis is presented suggesting that most ankylosaurs are found on their backs because of bloating.

Regional Inventory of Peace River Oil Sands, Alberta, Canada: ABSTRACT

The Peace River oil sands of northwestern Alberta contain an estimated 92 billion bbl of bitumen trapped in an updip pinch-out of the Lower Cretaceous Bluesky and Gething Formations. The geologic reservoir characteristics of the Peace River oil sands are being mapped on a regional scale through the use of core and geophysical logs. Four wells per township are used wherever possible. A computerized data file on each well consists of basic well data, tops of the Bluesky and Gething Formations, and oil sand reservoir and the underlying pre-Cretaceous unconformity, and a coded lithology log. The lithology log is kept simple due to the limits of geophysical log interpretation but attempts to quantify sand, shale, interbedded sand and shale, oil, and water. Logs have been calib ated wherever possible with core control. Because the data are stored as a log of the well, a wide variety of useful maps can be generated by the computer. These include maps showing structure, sand/shale ratios, gross and net pay thicknesses, basal water, top water, lean zones, and uninterrupted pay. Recognition of four major facies including continental, tidal flat, shoreline and shallow marine, and tidal channel deposits has led to the proposal of an estuarine model for sedimentation within the Gething Formation. Isopach maps from the top of the Bluesky and Gething Formations down to the pre-Cretaceous unconformity show a regional southeast to northwest drainage trend on the unconformity surface. Similar trends are seen in the main sand bodies. Coordination of computer-generated maps with the facies model highlights areas which satisfy specific criteria that may be critical in determining the applicability of a particular in-situ recovery method. End_of_Article - Last_Page 543------------

Developments In The Peace River Coalfield Northeast British Columbia

Introduction In response to a rapidly growing steel industry in Japan and to an increasing extent in Korea, coal production in British Columbia has risen from 773,000 tonnes in 1969 to 11,690,000 tonnes in 1981 (Fig. 1). The production figures for 1981 show coal running a close second in value, only to copper. As a result of escalating prices and predicted diminishing supplies of petroleum and natural gas, a renewed interest has been taken in coal as a source of thermal energy. The existence of coal in the Peace River country was first noted around 1800 by Alexander McKenzie. Mining commenced in 1908 and continued intermittently until 1964 with approximately 90,000 tonnes produced at 4 small mines on the Peace and Pine Rivers for local use. The main production in the province during this period, however, was from the Vancouver Island Coalfields and the Crowsnest Coalfield. Since 1970, companies operating in the Crowsnest Coalfield have built up the constantly increasing trade with Japan, primarily in metallurgical coal. About 15% of the production is now sold as thermal coal. The coals of the Peace River generally are similar to those of the southeastern coalfields, and vary from a high volatile " A" bituminous to a low volatile bituminous with some semi-anthracite. About 20% of the northeastern coal will be used for thermal purposes. Whereas the major portion of current exports go to Asia with minor quantities to Europe, North and South America and Canada; the entire initial production of exports through Prince Rupert will be destined for Japan, commencing in 1983 (Fig. 2). Major exploration in the foothills of the Northern Rocky Mountains did not commence until the latter part of the 1960's due mainly to inaccessibility and access to markets. Since 1969, exploration has taken place, predominantly on the Sukunka and Quintette properties. In late 1972, a moratorium on the issuance of coal licenses was declared which lasted until February 10, 1978. In 1974 the license boundaries were re-draughted onto petroleum and natural gas grid system, and reassigned in northeastern British Columbia. Since the lifting of the moratorium, a substantial number of licenses were applied for and granted throughout British Columbia. These trebled in area over the subsequent two years, and reached a total for the province of one million hectares in 1980 (including freehold). Since then the figures have dropped to 580,000 hectares in licenses and 160,000 in freehold, bringing the total area under steady exploration to 740,000 hectares, of which 422,617 hectares is in the Peace River Country. Geology (Fig. 3) The Peace River coalfield of northeastern British Columbia is exposed along the Rocky Mountain foothills; it is some 600 kilometres in length and varies from 20 to 30 kilometres in width. Nearly all the coal licenses, however, lie between the Peace River and the Alberta border, as the coal seams in the northern half appear to be thin and discontinuous. The coal occurs in the Gates Member of the Commotion Formation, which overlies the Moosebar Formation, and, as well, in the Gething Formation which underlies this formation (Fig. 4).

Rank and Petrographic Composition of Selected Jurassic - Lower Cretaceous Coals of British Columbia, Canada

ABSTRACT Rank and composition of Jurassic - Lower Cretaceous coals from four localities in the Crowsnest and Peace River Coalfields of British Columbia are described. The coals obtained from the Crowsnest Coalfield represent so called needle coals from the Elk Formation of the Kootenay Group, whereas coals of the Peace River Coalfield were obtained from the Gorman Creek and Bickford Formations of the Minnes Group and from the Gething Formation of the Bullhead Group. Rank, determined by vitrinite reflectance measurements, ranges from subbituminous C in the Crowsnest Coalfield to medium volatile bituminous in the Peace River Coalfield. Composition was determined by maceral analysis. Results indicate that, in general, coals from the Elk Formation in the south and from the Gorman Creek and Bickford Formations in the north are characterized by moderate to high concentrations of macerals of the liptinite group (alginite, sporinite and cutinite) and very small amounts of semifusinite and inerts. This maceral composition, together with occurrences of boghead (algal-rich) and cannel (spore-rich) layers associated with mainly unstructured vitrinite, is interpreted as an indication of a reed swamp to open-water swamp depositional environment. In certain parts of the Peace River Coalfield, increase of rank with depth (Hilt's Law) is masked by maceral composition. In some sections there is no rank change with increase in depth; instead, vitrinite reflectances are controlled by the total amount of liptinites in a given coal sample. The reflectance of vitrinite decreases gradually with increase in liptinite content. This effect is interpreted as being caused by diffusion of bituminous substances out of the liptinite macerals into the surrounding vitrinites. Coking and liquefaction properties of the coal are discussed. It can be demonstrated that low- to intermediate-rank coals from the Crowsnest and Peace River Coalfields, characterized by high amounts of so-called reactive macerals (vitrinite and liptinite), are excellent feed coals for liquefaction. They are, however, too low in rank and too rich in reactive macerals to produce a strong coke. Good coking properties are predicted for the higher-rank coals from the Peace River Coalfield, which are characterized by increasing amounts of inert macerals.

Diagenetic Sequence, Oil Migration, and Reservoir Quality in Peace River Oil Sands, Northwestern Alberta: ABSTRACT

Extensive deposits of heavy oil occur in updip pinch-out of the Bluesky and Gething Formations (Lower Cretaceous) of northwestern Alberta. In-situ extraction technologies require a detailed knowledge of porosity, permeability, and mineralogy within the reservoir and the effect of diagenesis on these properties. Marine sands in the upper part of the Gething Formation are composed predominantly of quartz and chert with lesser amounts of clastic carbonate, rock fragments, and feldspar. Emplacement of heavy oil forming the Peace River oil sands effectively stopped or slowed diagenesis. Thin-section petrography and scanning electron microscopy provide the means of establishing a diagenetic sequence and of timing of oil migration. Three wells with abundant core have been chosen to illustrate the relations among diagenesis, hydrocarbon migration, and reservoir quality. Authigenic minerals, in their probable order of emplacement, include pyrite, quartz overgrowths, feldspar overgrowths, kaolinite, and illite. Kaolinite and illite are most abundant in the water sands. An unusual secondary carbonate mineral, dawsonite. NaAlCO3(OH)2, occurs in only the richest oil sands but the timing of its deposition is in question. Secondary porosity was formed after feldspar overgrowths but before deposition of kaolinite. Oil migration took place after part of the kaolinite formed. Diagenesis is an ongoing process and the various stages probably continued until migration of oil into the reservoir. Porosity is better in the good oil sands than in the water sands. Permeability is reduced by the heavy oil. End_of_Article - Last_Page 626------------