Research Interests:
Research Interests:
Summary Strain relaxation in the Barre Granite and surrounding metasediments in Vermont, was measured by overcoring strain gauge rosettes bonded to outcrop surfaces. The average maximum expansion upon relieving 15.2 cm diameter cores... more
Summary Strain relaxation in the Barre Granite and surrounding metasediments in Vermont, was measured by overcoring strain gauge rosettes bonded to outcrop surfaces. The average maximum expansion upon relieving 15.2 cm diameter cores trends N55°W, while the average maximum expansion of 7.6 cm diameter cores coaxial with 15.2 cm cores trends N70°W. The maximum strain relief of the internal overcores
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
four sites in the Late Cambrian Keeseville member of the Potsdam sandstone indicates that compressive stresses were relieved upon overcoring with an average direction of maximum expansion of N78øW. These nine measurements also indicate... more
four sites in the Late Cambrian Keeseville member of the Potsdam sandstone indicates that compressive stresses were relieved upon overcoring with an average direction of maximum expansion of N78øW. These nine measurements also indicate that stress can be consistent in orientation over areas of tens of square kilometers. The average of three measurements at one site in the Nicholville member 11 km from the other four sites indicates a maximum expansion oriented N18øE. At several sites, residual strain was recovered when specimens free of boundary loads were overcored. We suggest that the residual strain measured in the Nicholville member may be related to a late Proterozoic (Hadrynian) or Early Cambrian stress field.
Research Interests:
Research Interests:
Description/Abstract Cross joints are late-formed fractures that extend across intervals between systematic joints and consistently terminate against pre-existing joints, which act as mechanical layer boundaries. The ratio of cross joint... more
Description/Abstract Cross joints are late-formed fractures that extend across intervals between systematic joints and consistently terminate against pre-existing joints, which act as mechanical layer boundaries. The ratio of cross joint spacing to layer thickness measured ...
Research Interests:
Research Interests:
Bedding-perpendicular joints confined to individual beds in interbedded sedimentary rocks commonly exhibit spacings which are proportional to the thickness of the jointed bed, and which vary according to lithology or structural position.... more
Bedding-perpendicular joints confined to individual beds in interbedded sedimentary rocks commonly exhibit spacings which are proportional to the thickness of the jointed bed, and which vary according to lithology or structural position. The mechanical explanation for this relationship is well understood when the joints are driven by far-field crack-normal tensile stresses, but poorly understood for cracks driven by elevated fluid
Research Interests:
Research Interests:
Analysis of two 3D surveys, available well data, published outcrop data and subsurface information, as well as production data available from the state of Pennsylvania, demonstrates that wide-azimuth seismic is sensitive to variations in... more
Analysis of two 3D surveys, available well data, published outcrop data and subsurface information, as well as production data available from the state of Pennsylvania, demonstrates that wide-azimuth seismic is sensitive to variations in fracturing at the scale of individual pads or even individual wells. These variations in fracturing begin to explain why production varies significantly, even locally, within the Marcellus Shale gas play. Rose diagrams from quantitative fracture analysis using azimuthal seismic velocity volumes were compared with published data from Appalachian black shale outcrops and subsurface fracture models proposed in various papers to validate the results from subsurface data. These analyses provided insight into the rock fabric and the presence of systematic joints that likely affect production. There was a strong correlation between the low anisotropy and low heterogeneity of anisotropy and high estimated ultimate recovery (EUR). Additionally, interpreted f...
Research Interests:
Research Interests: Geology()
()
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
Research Interests:
Research Interests: Geology()
()
... Select this article. BRIAN KILGORE and; R. DOUGLAS ELMORE. A study of the relationship between hydrocarbon migration and the precipitation of authigenic magnetic minerals in the Triassic Chugwater Formation, southern Montana. ...
Research Interests:
Research Interests:
Research Interests:
TABLE 1. CHARACTERISTICS OP SOLUTION CLEAVAGE INTENSITY TYPES Intensity ■type Average distance '.Shortening between accommodated cleavage эу cleavage Characteristics planes [from Table 2) Moderate Strong Very strong - Surfaces... more
TABLE 1. CHARACTERISTICS OP SOLUTION CLEAVAGE INTENSITY TYPES Intensity ■type Average distance '.Shortening between accommodated cleavage эу cleavage Characteristics planes [from Table 2) Moderate Strong Very strong - Surfaces generally of toothed, >5 cm ...
Research Interests:
Research Interests:
Research Interests:
Many traditional terms for fault-related rocks have undergone recent dynamic metamorphism under high-pressure discussions by various groups of specialists. A generally acceptable simplified framework encompassing these and associated... more
Many traditional terms for fault-related rocks have undergone recent dynamic metamorphism under high-pressure discussions by various groups of specialists. A generally acceptable simplified framework encompassing these and associated structural terms is now needed for many geologic, engineering, and legal purposes. Such a framework is proposed here, focusing on a rate-of-strain versus rate-of-recovery diagram and relating this framework to the products of brittle and ductile deformation along faults.
Research Interests:
This study presents a classification/characterization of Appalachian faults. Characterization factors include timing of movement relative to folding, metamorphism, and plutonism; tectonic position in the orogen; relations to existing... more
This study presents a classification/characterization of Appalachian faults. Characterization factors include timing of movement relative to folding, metamorphism, and plutonism; tectonic position in the orogen; relations to existing anisotropies in the rock masses; involvement of particular rock units and their ages, as well as the standard Andersonian distinctions. Categories include faults with demonstrable Cenozoic activity, wildflysch-associated thrusts, foreland bedding-plane thrusts, premetamorphic to synmetamorphic thrusts in medium- to high-grade terranes, postmetamorphic thrusts in medium- to high- grade terranes, thrusts rooted in Precambrian basement, reverse faults, strike-slip faults, normal (block) faults, compound faults, structural lineaments, faults associated with local centers of disturbance, and geomorphic (nontectonic) faults.
Research Interests:
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
ABSTRACT
Research Interests:
ABSTRACT
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Classic mapping of the Teton Anticline (Sawtooth Range, Montana) documented several fracture assemblages, believed to be related to fold development (i.e. Stearns 1964; Friedman and Stearns 1971). Based on mapping of Teton Anticline and... more
Classic mapping of the Teton Anticline (Sawtooth Range, Montana) documented several fracture assemblages, believed to be related to fold development (i.e. Stearns 1964; Friedman and Stearns 1971). Based on mapping of Teton Anticline and adjacent folds and thrust sheets during the summer of 2006, a number of observations apply to a reinterpretation of fracturing at Teton Anticline (Cannon et al.,
Research Interests:
... Terry Engelder This note serves as a warning that a re cently mutated virus, deviatoric stressitis, has infected many in the Earth science com munity. The good news is that this virus, nicknamed deveitis (dee vee' i-tis), is not... more
... Terry Engelder This note serves as a warning that a re cently mutated virus, deviatoric stressitis, has infected many in the Earth science com munity. The good news is that this virus, nicknamed deveitis (dee vee' i-tis), is not lethal and its victims can hope for a com plete recovery. ...
Research Interests:
ABSTRACT More than 2 × 104 m3 of water containing additives is commonly injected into a typical horizontal well in gas shale to open fractures and allow gas recovery. Less than half of this treatment water is recovered as flowback or... more
ABSTRACT More than 2 × 104 m3 of water containing additives is commonly injected into a typical horizontal well in gas shale to open fractures and allow gas recovery. Less than half of this treatment water is recovered as flowback or later production brine, and in many cases recovery is <30%. While recovered treatment water is safely managed at the surface, the water left in place, called residual treatment water (RTW), slips beyond the control of engineers. Some have suggested that this RTW poses a long term and serious risk to shallow aquifers by virtue of being free water that can flow upward along natural pathways, mainly fractures and faults. These concerns are based on single phase Darcy Law physics which is not appropriate when gas and water are both present. In addition, the combined volume of the RTW and the initial brine in gas shale is too small to impact near surface aquifers even if it could escape. When capillary and osmotic forces are considered, there are no forces propelling the RTW upward from gas shale along natural pathways. The physics dominating these processes ensure that capillary and osmotic forces both propel the RTW into the matrix of the shale, thus permanently sequestering it. Furthermore, contrary to the suggestion that hydraulic fracturing could accelerate brine escape and make near surface aquifer contamination more likely, hydraulic fracturing and gas recovery will actually reduce this risk. We demonstrate this in a series of STP counter-current imbibition experiments on cuttings recovered from the Union Springs Member of the Marcellus gas shale in Pennsylvania and on core plugs of Haynesville gas shale from NW Louisiana.
Research Interests:
ABSTRACT Between 2005 and 2014 in Pennsylvania, about 4000 Marcellus wells were drilled horizontally and hydraulically fractured for natural gas. During the flowback period after hydrofracturing, 2 to 4 x 10(3) m(3) (7 to 14 x 10(4)... more
ABSTRACT Between 2005 and 2014 in Pennsylvania, about 4000 Marcellus wells were drilled horizontally and hydraulically fractured for natural gas. During the flowback period after hydrofracturing, 2 to 4 x 10(3) m(3) (7 to 14 x 10(4) ft(3)) of brine returned to the surface from each horizontal well. This Na-Ca-Cl brine also contains minor radioactive elements, organic compounds, and metals such as Ba and Sr, and cannot by law be discharged untreated into surface waters. The salts increase in concentration to similar to 270 kg/m(3) (similar to 16.9 lb/ft(3)) in later flowback. To develop economic methods of brine disposal, the provenance of brine salts must be understood. Flowback volume generally corresponds to similar to 40% to 20% of the injected water. Apparently, the remaining water imbibes into the shale. A mass balance calculation can explain all the salt in the flowback if 2% by volume of the shale initially contains water as capillary-bound or free Appalachian brine. In that case, only 0.1%-0.2% of the brine salt in the shale accessed by one well need be mobilized. Changing salt concentration in flowback can be explained using a model that describes diffusion of salt from brine into millimeter-wide hydrofractures spaced 1 per m (0.3 per ft) that are initially filled by dilute injection water. Although the production lifetimes of Marcellus wells remain unknown, the model predicts that brines will be produced and reach 80% of concentration of initial brines after similar to 1 yr. Better understanding of this diffusion could (1) provide better long-term planning for brine disposal; and (2) constrain how the hydrofractures interact with the low-permeability shale matrix.
Research Interests: Geology()
()