|Title||Étude géomécanique régionale de la Formation de Macasty et de sa couverture d'après les puits pétroliers et gaziers de l'Ile d'Anticosti, Province de Québec
|Source||Geological Survey of Canada, Open File 7907, 2015, 114 pages, https://doi.org/10.4095/296885 (Open Access)|
|Publisher||Natural Resources Canada|
|NTS||12E; 12F/04; 12F/05; 22H/16|
|Lat/Long WENS||-64.5000 -61.5000 50.0000 49.0000|
|Subjects||geophysics; structural geology; stratigraphy; well logging; well log analyses; wells; seismic waves; hydraulic fracturing; fractures; acoustic surveys; reservoirs; stratigraphic correlations;
statistical analyses; Macasty Formation; Jupiter fault; Mingan Formation; English Head Formation; Vauréal Formation; Silurian; Ordovician|
|Illustrations||location maps; tables; stratigraphic columns; plots; profiles|
|Program||Shale Reservoir Characterization, Geoscience for New Energy Supply (GNES)|
|Released||2015 11 18|
|Abstract||This project is part of a larger study initiated by the Geological survey of Canada, Quebec section (GSCQuebec), and which deals with the evaluation of the geomechanical parameters of the Macasty
Formation and its caprock on Anticosti Island to better understand their spatial variability and their controls.|
This study enabled to document the geomechanical properties of the Macasty Formation and its caprock at a regional scale on Anticosti
Island, based on the available petrophysical logs from the oil and gas wells drilled on the island and through a calibration with data from a reference well, the well Petrolia/Corridor, Anticosti, Chaloupe No. 1 (D020). This well is the only one on
the island for which an acoustic log of the S wave is available at the present time, and in the absence of laboratory data this log is required to establish the various geomechanical parameters.
A series of calibration tests was conducted in a
first time so as to determine the best method to generate a synthetic acoustic log of the S wave for each of the wells considered. On the basis of the available regional data and the parameters required for the calibrations, eight oil and gas wells
were selected for the regional geomechanical study.
At the scale of the well, the results highlight the presence of clear mechanical contrasts between the Macasty Formation and the overlying and underlying formations. In a context of hydraulic
fracturing these mechanical contrasts are reflected in the existence of barriers to the propagation of hydraulic fractures outside the Macasty Formation. Furthermore, the analysis of two wells located on both sides of a regional-scale fault, the
Jupiter Fault, reveals that the vicinity of the fault does not affect significantly the mechanical properties of the caprock.
At a regional scale the results demonstrate a remarkable homogeneity from a well to another, except in the South-central
part of the island where a barrier to the hydraulic fractures is identified stratigraphically higher in the caprock rather than immediately above the Macasty Formation. In this specific case the phenomenon can be real or correspond to an artifact
related to methodological limitations of the study, and it is not possible to decide on the basis of currently available data.
The calibrations necessary for this study are based on the raw acoustic log of the S-wave of the sole well D020.
Therefore, in the future it is recommended to confirm the robustness of the method and the results presented here by comparing them with data which may be eventually collected in new wells.
In the scope of exploration and exploitation of
unconventional reservoirs on Anticosti Island it is also particularly desirable to examine the impact that may have structural discontinuities -- faults interpreted on seismic and natural fractures networks documented at surface -- on the integrity
of the caprock of the Macasty Formation.
|Summary||(Plain Language Summary, not published)|
This work is performed in the scope of a larger study focusing on the potential impacts on groundwater aquifers related to shale oil development on
Anticosti Island (Province of Quebec). The purpose of this study is to estimate the geomechanical properties of the caprock of the Macasty Formation based on petrophysical logs at the scale of the entire island using all available well logs. Eleven
well logs have been studied covering the entire island, this suite includes well D-20 that was used to construct the S wave log unavailable for all the other well (DP 7892). A complete vertical geomechanical profile has been successfully established
for all eleven wells. The results confirm that the caprock of the Macasty Formation provides an effective seal and a barrier to the propagation of hydraulic fractures, thus providing a regional good protection for the shallow groundwater aquifers in
the study area.