Unconventional shale plays have been a significant source of natural gas, gas condensates, and crude oil through much of North America. The Eagle Ford Shale in south Texas has been a prolific unconventional play since the mid-2000’s. It was deposited in the Gulf Coast basin along the southern rim of Texas. This play covers a vast area that stretches approximately 7 million acres (2.8 hectares) and extends from the College Station to the USA-Mexico Border near Del Rio. The majority of the Eagle Ford has been thoroughly studied and analyzed, however, there is much to learn about the basal member, the Maness Shale.
The Maness Shale was deposited 97 million years ago; it is the basal member of the Eagle Ford Group and lies directly above the Buda Limestone. The formation does not occur continuously throughout the entire Eagle Ford deposition and varies in thickness. Whereas the lateral extent still remains unknown, it has previously been mapped across the San Marcos Arch. The geophysical and geochemical properties of this member create drilling stability issues if encountered while drilling horizontal Eagle Ford wells. To further understand its geomechanical properties, two hand-held devices will be used on cores taken near the San Marcos Arch that contain the Maness Shale to determine rock strength variations of the Eagle Ford section. The Equotip Bambino is a micro-rebound hammer that provides hardness data values that can be used to estimate unconfined compressive strength. The dimpler is a micro-indentation device that infers rock strength by generating a “dimple” created by the tool and then measuring the depth and diameter of the dimple. These measurements are then correlated on graphs against the unconfined compressive strength for the regional Eagle Ford. The Maness has a neutron density range of 20-30%, indicating a high clay content. The x-ray diffraction (XRD) will be used to determine the content of the clay minerals. Geophysical well logs have been collected and correlated across the San Marcos Arch region; the initial maps identified the thickest Maness interval within the Karnes trough.

The sequence stratigraphy of Middle to Upper Pennsylvanian strata in the Appalachian Basin is complex, partly owing to the icehouse co-response to climate and sea level change during the late Paleozoic. The Breathitt Group resembles a traditional marine-to-terrestrial sequence stratigraphic model. The overlying Conemaugh Group also exhibits sequences, but they are more fluvial-dominated. Sequence stratigraphy largely presumes sea-level drive for sequences and accommodation. We present a model that is driven by both sea level and climate. We hypothesize that once the land surface is built up high enough above the water table, it is not required that sea level drop to induce valley incision, and in fact there is no evidence for a shelf slope break that would promote incision. Instead, we offer that climate change may be the main driver of valley incision.
This model is tested using strata in the Breathitt and Conemaugh Groups in the Northern and Central Appalachian Basin. Measured sections along a basin cross section in outcrop and 3D models built from UAV photographs help reveal this past environment to address the potential of climate change as a sequence driver.
The Breathitt to Conemaugh Group shift records a composite of sequences that are a progradational basin-fill and define a switch from a mixed marine and fluvial to fluvial fill. The Conemaugh sequences record upward shifts from a low-accommodation, valley-incised tributive to a high-accommodation, un-incised distributive systems tract. As a marine transgression tops the low-accommodation valleys below, it lays a basal peat which floods the tributive system. Next, the rivers in the distributive fluvial system prograde and push out the shore, as well as build a slope above sea level. This aggradation creates an elevated coastal prism. Continued progradation creates the elevation needed for valley incision, but this progradation need not cause incision, even if sea level falls. A climate change will eventually spur water table reduction owing to a locally drier climate, or an upstream water-sediment ratio change. Valley incision begins at that time, and possibly with no change in sea level. In this model, regression with or without sea level drop sets up the conditions needed for valley incision, but does not cause incision itself. Incision waits for adequate climate change to generate buffer valleys. The valleys record regression but are climate driven and do not have to define sea-level change.

Due to the logistical challenges and the dynamic nature of fluvial systems, studying modern point bar deposits over formative time periods is difficult. Seasonal and annual changes in precipitation can greatly influence the rate at which deposition is recorded. The lack of accurate sediment-package dating makes it difficult to compare sedimentation rates to actual chronostratigraphic events such as floods. This study combines photogrammetry, mapped surface migration, a survey of sediment elevation change, a trench, and water discharge rates to develop a more complete understanding of how a point bar forms on an annual scale. The Powder River, Montana, USA, which has little influence from engineering, offers a unique opportunity to study a seasonally exposed point bar and how its internal architecture and surface features form through time.
The study area is along the Powder River between Moorhead, Montana, USA, and Broadus, Montana, USA. The Powder River is a northward flowing, meandering river that is sourced from the Bighorn Mountains in northeast Wyoming, USA and is a tributary to the Yellowstone River. Point bar PR141A, the focus of this study, is the result of the neck cut-off of point bar PR141 during a 50 year flood in 1978. The sediment elevation survey is conducted annually, with a few exceptions, at centimeter scale to determine sediment elevation change and the building and erosion of the point bar. The survey is applied to the architectural-element analysis of the sediment packages within the point bar to compare time with sediment deposition.
This study reconstructs the growth of point bar PR141A, its discrete accretionary architecture at the scale of years, and determines the inter-relationship between annual flooding events and bar accretion. The sediment survey timeline shows that on average the river builds one accretionary body per yearly flood cycle. On occasion, the river builds multiple bodies during the year or can take several years to build one accretion set. The change in the accretion set building period is attributed to changes in river flow. The continual change of deposit direction, grain size distribution, erosion, and reshaping of the bar surface between accretion events leads to fragmentation of the point bar body, vastly different from the textbook model of a point bar. The detailed study of how a modern point bar forms lends insight into the fragmentation of fluvial hydrocarbon reservoir bodies.

The Eagle Ford Shale (EFS) was deposited on the South Texas Shelf in the Late Cretaceous, during a time of widespread marine transgression. With industry interest in the EFS, an understanding of the geology and depositional environment of these rocks is imperative to maximize well results. For the study, a section of the EFS was measured and described in detail in Heath Canyon, Brewster County, Texas. Lithostratigraphy, biostratigraphy, and mechanical stratigraphy were determined via outcrop and elemental composition was determined from sample collection and lab analysis. Data suggests the EFS was deposited in a potentially anoxic environment below storm-wave base on the South Texas Shelf.

Quantifying source-to-sink sediment flux for stratigraphic systems is critical for accurate basin models, but all available methods are hampered by low precision and most require data not readily attained by common subsurface studies. The Fulcrum approach uses the variables of channel bankfull thickness and grain size to calculate sediment bankfull discharge and converts this to an annual sediment volume. The Fulcrum approach uses commonly collected data but similarly yields only approximate flux estimates. In order to calculate a more precise source-to-sink estimate for long basin durations, the amount of time the fluvial systems runs at bankfull flow and the annual proportion of sediment discharged during this bankfull flow must also be determined. By categorizing fluvial systems by attributes such as drainage area and paleoclimate at the time of discharge, a more specified and accurate bankfull flow duration and total bankfull sediment discharge is estimated. We constructed a database that stores and categorizes these data and a user interface (RAFTER: River Analogue and Fulcrum Transport Estimates Repository) to query and display this data. Daily stream gauge data spanning decades is used in conjunction with measured bankfull values from literature to populate the datasets for the database and derive stream specific data attributes. This bankfull flux searchable database evaluates stream gauge data for modern fluvial systems according to classes such as climate setting and is also a useful tool for identifying analog stream data scaled to drainage basin and channel size. It evaluates designated parameters of days within a year that the river runs at bankfull flow, as well as the yearly proportion of sediment discharged over bankfull duration. The database can thus yield a more accurate value for duration at bankfull flow and sediment discharge at bankfull from modern rivers that can be used as an analog for stratigraphic rivers with interpreted climate and size parameters. Results show a key breakdown in bankfull duration, with arid and tropical rivers on the order of a fraction of a day per year, boreal climates tending to be an order of magnitude longer, and temperate climates still longer. Categorizing stratigraphic rivers by known climate and other parameters can lower the total error in sediment flux from paleohydrology by a geometric factor.