Dissimilatory Fe(III) and Mn(IV) reduction.

A review of the braided-river depositional environment

Evaluating Fractured Reservoirs Reservoir Management Detecting And Predicting Fracture Occurrence and Intensity Analysis Of Anisotropic Reservoirs Analysis Procedures in Fractured Reservoirs Appendix A: List of Documented Fractured Reservoirs Appendix B: Procedures Checklist Appendix C: Averaging Techniques

Geologic Analysis of Naturally Fractured Reservoirs

Heat carried by ground water serves as a tracer to identify surface water infiltration, flow through fractures, and flow patterns in ground water basins. Temperature measurements can be analyzed for recharge and discharge rates, the effects of surface warming, interchange with surface water, hydraulic conductivity of streambed sediments, and basin-scale permeability. Temperature data are also used in formal solutions of the inverse problem to estimate ground water flow and hydraulic conductivity. The fundamentals of using heat as a ground water tracer were published in the 1960s, but recent work has significantly expanded the application to a variety of hydrogeological settings. In recent work, temperature is used to delineate flows in the hyporheic zone, estimate submarine ground water discharge and depth to the salt-water interface, and in parameter estimation with coupled ground water and heat-flow models. While short reviews of selected work on heat as a ground water tracer can be found in a number of research papers, there is no critical synthesis of the larger body of work found in the hydrogeological literature. The purpose of this review paper is to fill that void and to show that ground water temperature data and associated analytical tools are currently underused and have not yet realized their full potential.

http://www.geology.wisc.edu/~andy/GW_Heat%20as%20a%20Tracer.pdf

Heat as a ground water tracer.

Ichnology is the study of traces created in the substrate by living organisms. This is the first book to systematically cover basic concepts and applications in both paleobiology and sedimentology, bridging the gap between the two main facets of the field. It emphasizes the importance of understanding ecologic controls on benthic fauna distribution and the role of burrowing organisms in changing their environments. A detailed analysis of the ichnology of a range of depositional environments is presented using examples from the Precambrian to the recent, and the use of trace fossils in facies analysis and sequence stratigraphy is discussed. The potential for biogenic structures to provide valuable information and solve problems in a wide range of fields is also highlighted. An invaluable resource for researchers and graduate students in paleontology, sedimentology and sequence stratigraphy, this book will also be of interest to industry professionals working in petroleum geoscience.

Ichnology: Organism-Substrate Interactions in Space and Time

Sedimentary structures of ephemeral streams

The thermal resistance (or Bullard) method is used to judge the utility of petroleum well bottom‐hole temperature data in determining surface heat flow and subsurface temperature patterns in a sedimentary basin. Thermal resistance, defined as the quotient of a depth parameter Δz and thermal conductivity k, governs subsurface temperatures as follows: TB=T0+q0∑z=0BΔzk, where TB is the temperature at depth z=B, T0 is the surface temperature, q0 is surface heat flow, and the thermal resistance (Δz/k) is summed for all rock units between the surface and depth B. In practice, bottom‐hole and surface temperatures are combined with a measured or estimated thermal conductivity profile to determine the surface heat flow q0 which, in turn, is used for all consequent subsurface temperature computations. The method has been applied to the Tertiary Uinta Basin, northeastern Utah, a basin of intermediate geologic complexity—simple structure but complex facies relationships—where considerable well data are available. Bot...

Heat flow in the Uinta Basin determined from bottom hole temperature (BHT) data

Classifications of fine-grained sediments and sedimentary rocks are based on combinations of several criteria. These include: (1) texture, (2) fissility, (3) tectonic association or environment of deposition, (4) mineral composition, (5) color, (6) chemical composition and (7) degree of metamorphism. None of the classifications are generally used, however. For field studies, texture is the most significant property. The proportions of clay, silt and sand are used herein to define four major groups: claystone (clay), siltstone (silt), mudstone (mud) and sandstone (sand). Claystone, siltstone and sandstone are rocks containing more than 50 percent of clay-, silt- or sand-sized material, respectively. Mudstone contains less than 50 percent of clay, slit or sand. Silty and sandy are useful modifiers of claystone when clay-sized material is less than 75 percent but more than 50 percent. Clayey and sandy are used to modify siltstone when silt-sized material is less than 75 percent but more than 50 percent. The expression good sorting is applied to fine-grained clastic rocks that contain more than 90 percent silt or clay-sized material. Fair-sorted rocks contain 75 to 90 percent silt or clay. Poorly sorted siltstone or claystone contains less than 75 percent silt or clay. If fissile, fine-grained clastic rocks are so designated. The mineral composition of most fine-grained clastic rocks can be determined reliably with the petrographic microscope and by X-ray diffraction. Therefore, where possible, they should also be named according to one of the sandstone classifications and on the dominant clay mineral present. Color, bedding types and sedimentary structures, fossil content, type of cement and fissility should be included in complete descriptions. An example of a good field and laboratory description is: clayey siltstone, illite-subarkose, poor sorting, grayish red (5R4/2), dolomite cement, slabby, horizontal lamination, pelecypods.

Classification of Fine-grained Sedimentary Rocks

Lacustrine deposits can be recognized through the use of a variety of criteria that include physical chemical and biologic aspects of sedimentary rocks Because large lakes closely resemble shallow epicontinental seas in physical properties large differences in lithologic characteristics sequences facies relations sedimentary struc tures paleocurrentpatterns and other physical parameters are not to be expected Comparisons of these fea tures in lacustrine and epicontinental rocks indicate the scarcity of significant diagnostic differences In contrast fluvial and lacustrine environments differ considerably in physical aspects and the two environments can be differentiated on the basis of the physical characteristics of the rocks Large lakes and epicontinental seas differ mainly in size chemistry and biota Size differences are evident few lakes exceed 10 000 sq mi in area Regional stratigraphic and paleogeographic relations are useful therefore in distinguishing former lakes and seas Geochemical differences are more definitive however Normal sea water has been relatively constant in composition for most of geologic history and changes related to evaporation precipitation or dilution are predictable In contrast the chemistry of lacustrine water is not uniform but is determined almost wholly by the lithology and climate of the hydrographic basin The geochemical character of lakes therefore differs widely from onearea to another and rarely approximates that of sea water Accordingly lakes and seas can differ in authigenic and diagenetic minerals The products of evaporite cycles are especially useful forenvironmental interpretation Marine and nonmarine environments commonly are distinguished by their faunas Paleontologic differentia tion of nonmarine environments is uncertain however and requires further study Despite the qualifications mentioned here reconstructions of lacustrine environments can be made with con fidence Lacustrine or marine environments can be differentiated from fluvial environments on the basis of physical properties of the deposits Lakes and seas can then be differentiated by geochemical and biologic criteria

Criteria for Recognizing Lacustrine Rocks

Spheroidal (cannon ball) calcite-cemented concretions, some of gigantic size, were studied from three Cretaceous shelf sandstone units: Ferron, Frontier, and Second Frontier. The concretions have diameters between 2 cm and 6 m; those larger than 40 cm in diameter in the Ferron and Frontier have septarian structure. Rare concretions in the Second Frontier with cone-in-cone also have septaria. The pattern of carbon and oxygen isotopic data and intergranular volume (IGV) data across concretions indicate that concretion growth was complex; not all concretions grew progressively from their centers toward their edges. In many concretions displacive fascicular-optic high-Mg calcite (FOC) precipitated simultaneously throughout the concretions (pervasive growth pattern), although the earliest cementation was concentrated in and near their centers. Remaining pores were subsequently filled by poikilotopic calcite of lower Mg content. Displacive FOC cement in the bodies of concretions and in cone-in-cone structure, and the large IGV values, indicate that these carbonate phases formed at burial depths no greater than tens of meters. IGV values indicate that spar cement continued to depths of at least 50 m and possibly deeper. The association of organic matter and microbial structures, or microbial byproducts, with displacive FOC and cone-in-cone calcite raises the possibility that biogenic processes were responsible for the apparently rapid growth of the displacive calcite. The oxygen isotope composition of pore waters was fairly uniform (in the range of 18O of -4 to -6‰ SMOW) during 80% of concretion growth but became even more depleted in 18O during the last stage of growth and during septarian fracture filling, ranging into values as depleted as -14‰ SMOW. 13C in calcite is negative (-4 to -18‰ V-PDB) but variable, reflecting a range of microbial processes under both oxidizing and reducing conditions. Earlier calcites fall mostly in the range of -10 to -16‰ V-PDB; relatively later calcite, in veins and on concretion margins, is more enriched in 13C. Fe and Mn concentrations in calcites have a rough positive correlation with higher 13C values. The concentration of Mg, derived from seawater and altered volcanic rock fragments, covaries positively with the degree of meteoric influence: lower Mg contents correlate positively with relatively depleted 18O values. 87Sr/86Sr values are typical of Sr derived from coeval seawater or marine skeletal debris. Growth of concretions 4 to 6 m in diameter, apparently in < 5 My, requires some spatial localization of growth sites by a self-organization process, and probably a large supply of carbonate shells in the original sediment. Elongation of larger concretions in the plane of bedding suggests that advective rather than diffusive supply of cement components dominated late in concretion growth history. Concretions formed close to the tops of parasequence boundaries.

M. Dane Picard

Papers

Sedimentary structures of ephemeral streams

Heat flow in the Uinta Basin determined from bottom hole temperature (BHT) data

Classification of Fine-grained Sedimentary Rocks

Criteria for Recognizing Lacustrine Rocks

Calcite-Cemented Concretions in Cretaceous Sandstone, Wyoming and Utah, U.S.A.