|Title||Influence of drilling technique on a borehole geophysical dataset - a case study in New Brunswick|
|Licence||Please note the adoption of the Open Government Licence - Canada
supersedes any previous licences.|
Cartwright, T; Brewer, K; Lavoie, D; Rivard, C|
|Source||Geological Survey of Canada, Scientific Presentation 116, 2020, 1 sheet, https://doi.org/10.4095/321967 Open Access|
|Publisher||Natural Resources Canada|
|NTS||21H/11; 21H/12; 21H/13; 21H/14|
|Lat/Long WENS|| -65.5833 -65.2500 45.8333 45.6667|
|Subjects||geophysics; environmental geology; stratigraphy; hydrogeology; fossil fuels; Science and Technology; Nature and Environment; groundwater resources; aquifers; groundwater pollution; petroleum resources;
hydrocarbons; gas; reservoir rocks; fluid migration; stratigraphic analyses; boreholes; drilling techniques; observation wells; geophysical logging; bedrock geology; lithology; sedimentary rocks; clastics; conglomerates; sandstones; siltstones;
mudstones; core samples; drill core analyses; Maritimes Basin; Mabou Group; Phanerozoic; Paleozoic; Permian; Carboniferous; Devonian|
|Illustrations||location maps; geoscientific sketch maps; photographs; geophysical logs; stereonets|
|Program||Environmental Geoscience Shale Gas - New Brunswick aquifers|
|Released||2020 03 20|
Over the past eight years, the Geological Survey of Canada (GSC) in collaboration with different partners has been investigating potential upward fluid migration pathways from deep
shale and tight sandstone gas reservoirs to shallow aquifers in regions of eastern Canada (Raynaud et al., 2016, Rivard et al., 2017, Rivard et al., 2018). As part of the bedrock aquifer studies underway in Sussex, New Brunswick, the GSC drilled,
geophysically logged, and hydrogeologically tested 14 bedrock observation wells (50 to 130 m in depth).
The study area is located within a sedimentary sub-basin of the Upper Devonian to Permian Maritimes Basin. The shallow observation wells
intersect the bedrock units of the Mabou Group which consist of interbedded fine to coarse-grained, fluvial to continental, clastic units including conglomerate, sandstone, siltstone and mudstone (St. Peter and Johnson, 2009). Rapid and irregular
lateral facies changes are the norm in these deposits and lateral persistence of marker beds across the study area was not observed (Crow et al., 2017).
Boreholes were advanced using a combination of hammer and diamond drilling techniques. In four
locations, hammer and diamond drilled boreholes were co-located 4 m to 6 m apart, providing a unique opportunity to assess how drilling methods influence a downhole geophysical dataset in this geological setting. The suite of logs included fluid
temperature/conductivity, heat pulse flow meter, optical and acoustic televiewers, acoustic caliper, video camera, gamma-gamma density, guard resistivity, full waveform sonic, and spectral gamma. This poster presents some comparisons of the logs
collected in the side-by-side boreholes.
Differences between the datasets raise questions on the ultimate benefits and drawbacks of interpreting geomechanical (e.g. moduli) and hydrogeological (e.g transmissivity) parameters for critical projects
in wells with different wall roughness conditions. While drilling hammered boreholes is less expensive and time consuming than coring holes, are there potential trade-offs with data quality? Leveraging the placement of adjacent boreholes, this
question is examined in the context of a terrestrial, clastic sedimentary bedrock setting. This work is developing knowledge to support design choices for future GSC groundwater studies.
|Summary||(Plain Language Summary, not published)|
This work examines how differences in borehole wall roughness caused by different drilling techniques can influence a borehole geophysical dataset. This
poster presents some comparisons of logs collected in side-by-side boreholes drilled with diamond (smooth wall) and hammer (rough wall) drilling techniques. Differences between the datasets raise questions on the ultimate benefits and drawbacks of
interpreting geomechanical (e.g. moduli) and hydrogeological (e.g transmissivity) parameters for critical projects in wells with different wall roughness conditions. This work is developing knowledge to support design choices for future Geological
Survey of Canada groundwater studies.