|Title||Caprock integrity of the Carboniferous Frederick Brook Shale analyzed by oil and gas well logs: McCully gas field and Elgin area, New Brunswick|
|Source||Geological Survey of Canada, Open File 8203, 2017, 120 pages, https://doi.org/10.4095/299664 (Open Access)|
|Publisher||Natural Resources Canada|
|NTS||21H/11; 21H/12; 21H/13; 21H/14|
|Area||Elgin; McCully; Sussex|
|Lat/Long WENS|| -66.0000 -65.0000 46.0000 45.5000|
|Subjects||engineering geology; fossil fuels; environmental geology; geophysics; structural geology; stratigraphy; petroleum resources; gas fields; reservoir rocks; fluid migration; oil wells; gas wells;
observation wells; gas; hydraulic fracturing; bedrock geology; lithology; sedimentary rocks; shales; evaporites; dolomites; structural features; fractures; fracture analyses; faults; geophysical logging; well logging; well log analyses; rock
mechanics; mechanical analyses; petrophysics; stress analyses; pore pressures; groundwater resources; aquifers; environmental impacts; Magdalen Basin; Moncton Subbasin; McCully gas field; Horton Group; Albert Formation; Frederick Brook Member; Hiram
Brook Member; Dawson Settlement Member; Bloomfield Formation; Memramcook Formation; Windsor Group; Pictou Group; Cumberland Group; Mabou Group; Sussex Group; Weldon Formation; Ridge Brook Formation; Dutch Valley Formation; Mill Brook Formation;
McQuade Brook Formation; Jordan Mountain Fault; Berry Mills Fault; Penobsquis Fault; Urney fault; Clover Hill Fault; Waterford Fault; Ward Creek Fault; sedimentary cover; elasticity; Young's modulus; Poisson's ratio; brittleness; lithostatic
pressure; Phanerozoic; Paleozoic; Permian; Carboniferous; Devonian; Precambrian|
|Illustrations||location maps; geological sketch maps; stratigraphic charts; cross-sections; 3-D diagrams; tables; cross-plots; histograms; geophysical logs; plots; profiles; graphs; correlation sections|
|Program||Shale Gas - New Brunswick aquifers, Environmental Geoscience|
|Program||Program of Energy Research and Development
|Released||2017 01 26|
This study allowed to establish the geomechanical properties of the Carboniferous Frederick Brook Member (Albert Formation, Horton Group) and its Carboniferous-Permian cover
succession, based on petrophysical log data from available oil and gas wells, both at the scale of individual wells and at the regional level, for the McCully gas field and the adjacent area of Elgin.
The Young's modulus, the Poisson's ratio, two
brittleness indexes as well as the intensity of the minimum horizontal principal stress were defined. The representativeness of the results derived from the raw logs has been verified by calculating synthetic parameters for additional wells whose
dataset was incomplete, and by the comparison of the log results to independent laboratory data.
At the scale of the individual well the results highlight the presence of net eomechanical contrasts between the Frederick Brook Member and the
overlying Hiram Brook Member, as well as within the cover succession above these two units. In a context of hydraulic fracturing these mechanical contrasts translate into the existence of barriers that would limit the propagation of hydraulic
fractures outside the Frederick Brook Member.
At the regional scale it was noted that the same geomechanical contrasts than those recognized at the well scale are present and confirmed the homogeneity of the mechanical properties within the
McCully gas field as well as between this field and the Elgin area. The latter area geologically stands out however, by the absence of evaporite deposits in the Windsor Group.
Further work is recommended in order to better understand the role
played by natural fractures - if present - in the possible migration paths through the caprock of the Frederick Brook Member shale. As such it would be relevant to examine the natural fracturing patterns using available geological data and to
implement one or more observation wells out of the drilling pads, following the subsurface trajectory of the deviated wells that have been hydraulically fractured, in order to highlight the migration or the absence of migration of fluids in the
geological medium at distance from the surface casing of the wells.
|Summary||(Plain Language Summary, not published)|
This study establishes the geomechanical properties of the Frederick Brook Member (Albert Formation, Horton Group) and the overlying
Carboniferous-Permian succession based on petrophysical log data from oil and gas wells. The area of interest encompasses the McCully gas field and the adjacent area of Elgin near the town of Sussex, New Brunswick. At the scale of the well, the
results highlight the presence of clear geomechanical contrasts between the Frederick Brook Member and the overlying Hiram Brook Member, as well as within the cover succession above these two units. In a context of hydraulic fracturing, these
mechanical contrasts translate into the existence of barriers that limit the propagation of hydraulic fractures. At the regional scale, it has been possible to observe the same geomechanical contrasts than those recognized at the well scale and to
confirm the homogeneity of the mechanical properties within the McCully gas field, as well as between this field and the Elgin area.