Browsing by Author "Sanei, Hamed"

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    Characterization of the Lower Jurassic Gordondale Member in West-Central, Alberta, Canada, using Organic Geochemical and Petrophysical Methods
    (2017-12-12) Isinguzo, Nnenna; Clarkson, Christopher; Sanei, Hamed; Pederson, Per; Meyer, Rudi
    The organic-rich Lower Jurassic Gordondale Mudstone in the Western Canadian Sedimentary Basin, has exceptional unconventional hydrocarbon potential. This study integrates petrographic, organic and trace element geochemistry, and petrophysical techniques, to classify organic and mineral matter variations in the Gordondale, and their effects on unconventional reservoir quality. The depositional environment of the Gordondale is interpreted to range from dysoxic to euxinic bottom waters underling oxygenated, productive surface waters, with minimal detrital clastic input. Sulphur-rich solid bitumen is the predominant organic matter type, making up 90% of the total organic carbon (TOC) content. Fluid-like hydrocarbon residues (FHR) and light free hydrocarbons (LHC) comprise up to 3 vol. % of the whole rock. Solid bitumen has a negative (pore-occluding) effect on present day porosity, permeability, and specific surface area (SSA), while FHR covaries positively with these parameters. This relationship suggests that solid bitumen is detrimental to porosity and does not contribute significant organic porosity at its current level of thermal maturity.
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    Effect of thermal maturity on remobilization of molybdenum in black shales
    (Elsevier, 2016-09-01) Ardakani, Omid H.; Chappaz, Anthony; Sanei, Hamed; Mayer, Bernhard
    Molybdenum (Mo) concentrations in sedimentary records have been widely used as a method to assess paleo-redox conditions prevailing in the ancient oceans. However, the potential effects of post-depositional processes, such as thermal maturity and burial diagenesis, on Mo concentrations in organic-rich shales have not been addressed, compromising its use as a redox proxy. This study investigates the distribution and speciation of Mo at various thermal maturities in the Upper Ordovician Utica Shale from southern Quebec, Canada. Samples display maturities ranging from the peak oil window (VRo∼1%) to the dry gas zone (VRo∼2%). While our data show a significant correlation between total organic carbon (TOC) and Mo (R2=0.40, n=28, P<0.0003) at lower thermal maturity, this correlation gradually deteriorates with increasing thermal maturity. Intervals within the thermally overmature section of the Utica Shale that contain elevated Mo levels (20–81 ppm) show petrographic and sulfur isotopic evidence of thermochemical sulfate reduction (TSR) along with formation of recrystallized pyrite. X-ray Absorption Fine Structure spectroscopy (XAFS) was used to determine Mo speciation in samples from intervals with elevated Mo contents (>30 ppm). Our results show the presence of two Mo species: molybdenite Mo(IV)S2 (39±5%) and Mo(VI)-Organic Matter (61±5%). This new evidence suggests that at higher thermal maturities, TSR causes sulfate reduction coupled with oxidation of organic matter (OM). This process is associated with H2S generation and pyrite formation and recrystallization. This in turn leads to the remobilization of Mo and co-precipitation of molybdenite with TSR-derived carbonates in the porous intervals. This could lead to alteration of the initial sedimentary signature of Mo in the affected intervals, hence challenging its use as a paleo-redox proxy in overmature black shales.
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    Geochemistry, Diagenesis and Secondary Porosity Development of Late Jurassic-strata, Offshore Newfoundland, Canada
    (2021-12-15) Gordon, John Borthwick; Pedersen, Per; Sanei, Hamed; Ardakani, Omid; Ghanizadeh, Amin
    Hydrocarbon prospectively in siliciclastic reservoirs is dependant on many attributes. Two key factors are: (i) a complete understanding of the geochemical character of source rock organic matter (OM) and (ii) assessing reservoir quality of the reservoir rocks. These two key factors are the primary focus of the research completed in this thesis. In this thesis OM types and distribution, the hydrocarbon potential, thermal maturity of source rock intervals, and the diagenetic mechanisms that control anomalously high secondary porosity in sandstone reservoir intervals from Jurassic-aged, Late-Tithonian strata of the Central Ridge and Flemish Pass Basin, offshore Newfoundland, Canada are studied. This thesis comprises an integration of petrographic analysis, geochemical programmed pyrolysis, organic petrology, and machine learning algorithms from samples taken from cores, side wall cores (SWC), and drill cuttings that intersect the Kimmeridgian-aged to Tithonian-aged sandstones, siltstones, and mudstones of the Central Ridge and Flemish Pass Basin. The sandstone intervals in this area have well preserved anomalously high secondary porosity (>25%) in relative deeply buried (2-3 km) reservoirs. The deltaic sediments that envelop the sandstone bodies have OM-rich and/or OM-lean zones that are largely controlled by depositional environment. Applying a novel machine learning algorithm (Random Forest Analysis) highlights the high hydrocarbon potential zones with a high level of accuracy using wireline log data. A paragenetic sequence was constructed to understand the diagenetic events that control porosity development in the sandstone reservoirs and the relationship to the source rock intervals. Here the model was tested that the high secondary porosity development is caused by dissolution of carbonate cement by short-chained carboxylic acid (SCCA) generation during thermal maturation of OM in the bounding deltaic sediments and the interlaminated OM in the sandstone reservoirs.
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    The impact of organic matter deposition and pre-oil window diagenetic transformation on commonly utilized thermal maturity indicators
    (2021-08-19) Synnott, Dane Patrick; Pedersen, Per Kent; Dewing, Keith; Fowler, Martin; Sanei, Hamed; Larter, Stephen; Curiale, Joseph
    Despite decades of research on organic matter deposition, alteration, and preservation, the processes affecting and altering organic matter at low maturity are relatively poorly understood. Processes that affect deposition of organic matter, such as wildfires, or influence its preservation after deposition, such as diagenetic clay catalyzed transformation, can reduce the reliability of commonly applied thermal maturity proxies. This thesis integrated organic geochemistry and petrographic examination of samples from the Upper Cretaceous in Western Canada and the Canadian Arctic Islands to better understand processes that altered organic matter during deposition and early diagenetic. Samples from the Upper Cretaceous Kanguk Formation of the Canadian Arctic Islands have abundances of pyrogenic polycyclic aromatic hydrocarbon compounds and combustion-related organic macerals that show a distinct trend of increasing wildfire influence from the Turonian to the Campanian. This trend corresponds with increasing amounts of terrigenous organic matter in the marine Sverdrup Basin, in addition to increasing angiosperm-derived biomarkers. High rates of terrigenous organic matter deposition, accelerated by wildfires, have an important impact on the preservation of organic matter in a marine basin, as observed through degradation trends correlated to elevated primary productivity. A stratigraphically-controlled thermal maturity transect of samples ranging from eogenesis up to the peak of catagenesis was collected from the Upper Cretaceous Western Canadian Sedimentary Basin and examined using integrated organic geochemistry and organic petrology. The diagenetic transformation of hopanoid and steroid compounds was investigated, and key chemical transformations were calibrated to a maturity level. This investigation demonstrated that early clay-catalyzed backbone rearrangement in both hopanoid and steroid compounds has a profound impact on the hopanoid and steroid composition at higher maturity levels as well as on commonly applied thermal maturity indicators. A detailed calibration was completed, producing a correlation between a wide variety of common geochemical and optical thermal maturity indicators. Although each indicator has drawbacks, thirteen proxies are found to be effective, and a multi-disciplinary approach is recommended.
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    Organic matter preservation during early diagenesis and implications for potential hydrocarbon generation, a study of the immature Belle Fourche and Second White Specks formations, central Alberta, Canada
    (2017) Synnott, Dane Patrick; Pedersen, Per Kent; Dewing, Keith; Sanei, Hamed; Fowler, Martin
    The Cenomanian to Early Turonian Belle Fourche and Second White Specks formations in central Alberta are composed of organic rich mudstones deposited under changing depositional conditions. Processes that take place during deposition or during early diagenesis, can have important implications on the eventual hydrocarbon potential of the rock following burial. These processes include the deposition of allochthonous refractory organic matter, as well as the bacterial degradation of autochthonous organic matter during diagenesis. The analysis of these processes in this study has revealed important impacts on the source rock properties of these formations, including elevation of the reflectance of oil prone organic matter, dilution of the measured total organic carbon by refractory organic matter, and insights into the methodologies, which may be used to quantify these impacts. This work has demonstrated that traditional screening techniques must be closely examined in order to account for the impact of these processes.
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    Regional Diagenesis and Fluid Flow Study of the Early Triassic Montney Formation as Related to H2S Generation
    (2021-08) Haghnazar Liseroudi, Mastaneh; Pedersen, Per; Sanei, Hamed; Qing, Hairuo; Henderson, Charles; Spencer, Ronald; Haeri Ardakani, Omid
    The regional diagenetic evolution of the Early Triassic Montney Formation was investigated using detailed petrographic techniques (optical and SEM/EDXS/CL) and multiple bulk and in-situ isotope geochemical data to address the nature of diagenetic fluids, water/rock interaction, and geological, geochemical, and structural processes controlled the formation of sulfates (anhydrite and barite), sulfides (H2S and pyrite), and carbonates (calcite and dolomite). According to the results of this study, the Montney Formation contains both early and late diagenetic anhydrite and late barite cement mainly formed by the Montney Formation pore water and incursion of structurally-controlled Devonian-sourced hydrothermal sulfate-rich fluids. Three pyrite forms, i.e., framboidal, recrystallized, and coalesced with distinct δ34S values, were identified. The sulfur isotope composition of anhydrite/barite, H2S, and pyrite demonstrates both microbial and thermochemical sulfate reduction (MSR and TSR) controlled the diagenetic sulfur cycle of the Montney Formation. The present-day produced-gas H2S was dominantly originated from the in-situ thermochemical sulfate reduction process and partially migrated from underlying formations. The Montney Formation is also comprised of three and four generations of early to late calcite (C1-C3) and dolomite (D1-D4) cement, respectively. Bulk δ13C and δ18O values, and 87Sr/86Sr isotope ratios of carbonate cement suggest water/rock interaction between hot basinal brines, Precambrian metasediments, and siliciclastics in the basin. Moreover, hydrothermal fluids as well as burial diagenesis appear to have contributed to the formation of carbonate cement. The overall diagenetic evolution of the Montney Formation was controlled by intraformational (Montney Formation pore water), and cross-formational fluid flow driven by hydrothermal activities and tectonic evolution of the Canadian Cordillera.
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    The Evolution of Petrophysical Properties During Thermal Maturation, as a Function of Various Hydrocarbon Fractions Comprising the Total Organic Carbon Content
    (2018-05-16) Clarke, Katherine; Pedersen, Per; Clarkson, Christopher R.; Pedersen, Per Kent; Sanei, Hamed; Meyer, Rudi; Tutolo, Benjamin M.
    Rock Eval pyrolysis is a standard industry technique used to evaluate the hydrocarbon-generating potential of a formation by quantifying its total organic matter content and thermal maturity. By utilizing a new Rock Eval procedure (ESH Rock Eval), in which the heating rate is slowed down over an extended temperature range, different hydrocarbon components are more easily distinguished due to enhanced peak resolution. The impacts of these various hydrocarbon types on reservoir quality is evaluated by observing the evolution of organic matter and petrophysical properties during pyrolysis. With the elution of the free hydrocarbons in the sample (S1 peak in Rock Eval), petrophysical properties do not notably change. However, significant changes occur after the S2a and S2b peaks, which correspond to the pyrolysis of pervasive, fluid-like hydrocarbon residue (FHR) which coats mineral grains, and the remaining organic matter (solid bitumen) that resides in the larger pore spaces in the samples, respectively. This work was evaluated utilizing core and drill cuttings samples from the Montney, Duvernay and Doig Formations from the Western Canadian Sedimentary Basin.
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    Unconventional Hydrocarbon Potential of a Middle Triassic Source Rock in the West-Central Sverdrup Basin, Canadian Arctic Archipelago
    (2015-09-01) Kondla, Danielle; Clarkson, Christopher R.; Sanei, Hamed
    Organic-rich Middle Triassic strata of the Sverdrup Basin have been identified as source rocks; however their potential as a self-sourced, unconventional hydrocarbon reservoir has not been examined. This study uses a combination of organic and inorganic geochemical, petrographic, and petrophysical techniques to provide insights into the hydrocarbon potential and reservoir characterization. Factors influencing organic matter (OM) distribution during deposition are established to develop an understanding of the depositional system. Effects from diagenesis and thermal maturation are investigated to reveal the present reservoir conditions. Suboxic to anoxic bottom waters and minimal clastic dilution conditions associated with the base of regressive systems tracts are favorable for high primary OM preservation. OM in the thermally mature interval of the studied strata is dominated by solid bitumen, which has a negative effect on reservoir quality by occluding porosity. However, this interval does have capacity to generate oil and gas.