Geology of the Devonian Marcellus Shale--Valley and Ridge province, Virginia and West Virginia--a field trip guidebook for the American Association of Petroleum Geologists Eastern Section Meeting, September 28-29, 2011

Abstract

Detailed and reconnaissance field mapping and the results of geochemical and mineralogical analyses of outcrop samples indicate that the Devonian shales of the Broadtop Synclinorium from central Virginia to southern Pennsylvania have an organic content sufficiently high and a thermal maturity sufficiently moderate to be considered for a shale gas play. The organically rich Middle Devonian Marcellus Shale is present throughout most of the synclinorium, being absent only where it has been eroded from the crests of anticlines. Geochemical analyses of outcrop and well samples indicate that hydrocarbons have been generated and expelled from the kerogen originally in place in the shale. The mineralogical characteristics of the Marcellus Shale samples from the Broadtop Synclinorium are slightly different from the averages of samples from New York, Pennsylvania, northeast Ohio, and northern West Virginia. The Middle Devonian shale interval is moderately to heavily fractured in all areas, but in some areas substantial fault shearing has removed a regular "cleat" system of fractures.Conventional anticlinal gas fields in the study area that are productive from the Lower Devonian Oriskany Sandstone suggest that a continuous shale gas system may be in place within the Marcellus Shale interval at least in a portion of the synclinorium. Third-order intraformational deformation is evident within the Marcellus shale exposures. Correlations between outcrops and geophysical logs from exploration wells nearby will be examined by field trip attendees.

A novel prestack sparse azimuthal AVO inversion

“…The J1 and J2 joint sets make it favorable to drill horizontal wells for hydrocarbon production. While NNW/SSE (perpendicular to maximum horizontal stress direction) directional drilling drains the J1 sets, later hydraulic stimulation can cross-cut the J2 sets and deliver hydrocarbons (Engelder et al, 2009;Enomoto et al, 2011). High spatial variability of mineralogy, fracturing, and the limits of seismic resolution create a big challenge in reservoir characterization using conventional narrow azimuth data.…”

Active features along a “passive” margin: The intriguing interplay between Silurian–Devonian stratigraphy, Alleghanian deformation, and Eocene magmatism of Highland and Bath Counties, Virginia

“…In general, differential weathering in the southeastern Valley and Ridge province has resulted in northeast-trending mountain ridges that are underlain by resistant Silurian and Devonian sandstones, and valleys that are typically underlain by weak Devonian shales (e.g., Enomoto et al, 2012) or Ordovician carbonates (e.g., Diecchio, 1985Diecchio, , 1986. Smaller-scale, fault-related folds can add intriguing complexities to regional topographic patterns.…”

The impacts of Marcellus Shale gas drilling accidents on amphibians in a Pennsylvania fen

“…Receipt of contaminated surface and subsurface water from drilling-related accidents on private land in 2009 was documented in Alex Branch (Grant et al 2016;Campa et al 2018;Ulrich et al 2018), which flows through WMF, and thus, WMF would have received the same contaminated water. Therefore, we studied WMF to determine if those accidents may have affected the site, selecting a second wetland, Crystal Spring Bog (CSB, actually a fen), as a control site due to its upslope location (which helps protect it from surface spills) and its similar wetland habitat (based on initial site visits), underlying geology (Fleeger 1999;Enomoto et al 2012), and soils (poorly drained, mesic Typic Fragiaquults on 0-3% slope dominant at both sites) (https://websoilsurvey.sc.egov.usda.gov/App/ WebSoilSurvey.aspx.). This paper reports potential effects on amphibian populations at WMF, with water chemistry and habitat provided by vegetation being similar between WMF and CSB.…”