is currently country manager for Chemostrat Inc. based in Houston, Texas. Prior to joining Chemostrat in 2000, Milly gained a B.Sc. degree (geology) from the University of Leicester, United Kingdom (2000). Milly is also currently studying for a Ph.D. in Houston.

No abstract

Incised valleys are a ubiquitous feature of the Lower Cretaceous Mannville Group of the Western Canada Sedimentary Basin. The Basal Quartz, a member of the Lower Mannville Formation, is present in two north-south-oriented subparallel valley-form systems in southern Alberta, the western valley form termed the Taber-Cutbank Valley and the eastern valley form termed the Whitlash Valley. This paper details the application of chemostratigraphy to discriminate between the three informal lithostratigraphic units of the Basal Quartz, namely the Horsefly, the Bantry-Alderson-Taber (BAT), and the Ellerslie units in these valley forms. In the Taber-Cutbank Valley, the Horsefly, BAT, and Ellerslie units each have unique chemostratigraphic signatures that enable them to be readily differentiated using inorganic geochemical data. The changes in elemental chemistry that allow this differentiation are inferred to reflect changes in sediment provenance, paleoclimate, and surface residence time. The whole-rock geochemistry of the Horsefly unit, the basal unit of the fill, is demonstrated to remain relatively constant longitudinally in the Taber-Cutbank Valley, therefore demonstrating, when compared to the vertical changes in geochemistry, that temporal or stratigraphic changes are of a greater magnitude than longitudinal changes within in a single valley form. The whole-rock geochemistry of the Horsefly unit in the two valley forms, which in previous studies has been demonstrated to be homotaxial by conventional stratigraphic techniques, is markedly different between the two valley forms. The geochemical differences suggest that the Horsefly unit was subjected to more prolonged and/or intense weathering in the eastern Whitlash Valley than in the western Taber-Cutbank Valley, and that the provenance of the Horsefly unit is fundamentally different between the two valley systems. The application of chemostratigraphy to the Basal Quartz of the Lower Mannville Formation demonstrates that the technique can be utilized as a viable correlation tool in low-accommodation incised-valley settings; however, it is most effective when the whole-rock geochemical data are placed in a regional context by integration with a detailed stratigraphic framework. Once chemostratigraphy is used in conjunction with these other data streams, the differences in geochemistry of the Horsefly unit between the Whitlash and Taber-Cutbank Valleys can be used to infer that the Horsefly unit deposited in the two valleys are two homotaxial, not coeval subunits.

In recent years shale resource plays have become increasingly important. However, understanding the controls on reservoir quality in shale formations is still in its infancy, despite thousands of well penetrations. Using examples from several shale resource plays, including the Haynesville, the Eagle Ford and the Muskwa formations, this paper demonstrates how inorganic whole rock geochemical data that are primarily obtained to provide stratigraphic correlations can be used to model mineralogy, model TOC, determine paleoredox facies, recognize zones of biogenic silica and aid with sequence stratigraphic interpretations. The primary application of whole rock geochemical data to date has been providing stratigraphic correlation based around changes through time in elemental composition, i.e. chemostratigraphy. Stratigraphic correlation is of paramount importance for temporally and geographically constraining other reservoir characteristics. In addition to classic chemostratigraphy, the whole rock geochemical data provide information about terrigenous inputs, which can be used to help elucidate transgressive – regressive cycles and thereby help with understanding sequence stratigraphic correlations. Reservoir quality in shale is dependent largely on mineralogy. Major element concentrations determined for chemostratigraphy can be used to model most mineral phases, including quartz, clay (semi quantitative abundance of kaolinite, illite and chlorite), calcite, dolomite, feldspars, pyrite and apatite. By adding select trace elements, typically U and Ni, the TOC contents can also be modeled. Furthermore, it will be demonstrated how by combing SiO2 concentrations with elements derived from terrigenous sources, it is possible to recognize zones where biogenic silica is present. Paleoredox plays an important role in determining TOC values. Consideration of redox-sensitive elements, such as V, Ni, Th, U and Mo provides a means to determine the degree of anoxia during deposition. Using examples from the Haynesville Shale, it will be shown how anoxia is determined and how it varies laterally within the basin. The methodologies shown in this paper are readily exportable to any shale resource play. The results can be generated from core, side-wall core and cuttings samples, providing a rapid, cost effective means to assess shale in a well-bore penetration.

No abstract