|Title||Delta-13C, delta-18O and 87Sr/86Sr isotope composition of Montney Formation carbonate phases: implications for the nature of diagenetic fluids|
|Author||Liseroudi, M H; Ardakani, O H; Sanei, H; Pedersen, P K; Spencer, R J;
Wood, J M|
|Source||Geoconvention 2019, technical program; 2019 p. 1 Open
|Links||Online - En ligne (PDF, 147
|Alt Series||Natural Resources Canada, Contribution Series 20180340|
|Meeting||Geoconvention 2019; Calgary; CA; May 13-15, 2019|
|File format||pdf (Adobe® Reader®)|
|Province||British Columbia; Alberta|
|NTS||84E/05; 84E/06; 84E/11; 84E/12; 84E/13; 84E/14; 94H/06; 94H/07; 94H/08; 94H/09; 94H/10; 94H/11; 94H/14; 94H/15; 94H/16|
|Lat/Long WENS||-121.5000 -119.0000 58.0000 57.2500|
|Subjects||fossil fuels; geochemistry; sedimentology; Science and Technology; petroleum resources; hydrocarbons; gas; isotopic studies; carbon isotopes; oxygen isotopes; strontium strontium ratios; bedrock
geology; lithology; sedimentary rocks; siltstones; carbonate; calcite; dolomites; diagenesis; reservoir fluids; source areas; petrographic analyses; burial history; Montney Formation; Phanerozoic; Mesozoic; Triassic|
|Program||Geoscience for New Energy Supply (GNES) Shale Reservoir Characterization|
|Released||2019 05 01|
|Abstract||The Montney Formation, western Canada's leading unconventional tight gas play, is a siltstone-dominated reservoir with a complex diagenetic history. Previous diagenetic studies of the Montney Formation
are mainly centered on the effect of diagenesis on reservoir quality and porosity evolution with minimal application of isotopic studies to address water-rock interaction and origin of diagenetic fluids in this Formation. This study presents
preliminary results of petrographic studies and bulk stable isotope data from calcite and dolomite plus bulk 87Sr/86Sr ratio analyses to investigate the nature of the diagenetic fluid(s) and geochemical processes involved during diagenesis of the
Montney Formation in western Alberta and northeastern BC. |
Petrographic studies show that dolomite occurs as ferroan zoned and non-ferroan pore-filling cement, mostly nucleated on rounded detrital grains. Calcite exists as non-ferroan to ferroan
pore-filling, ferroan replacive, and non-ferroan poikilotopic cement. The delta-13C and delta-18O values of dolomite range from -6.5 to 0.4 permille (V-PDB) and -2.8 to -7.8 permille (V-PDB), respectively. Calcite exhibits similar delta-13C values to
dolomite ranging from -0.1 to -7.1 permille (V-PDB) with a narrower range of delta-18O values varying from -6.0 to -9.5 permille (V-PDB). The preliminary 87Sr/86Sr isotope composition of three measured samples varies from 0.7105 to 0.7111.
and oxygen isotope composition of both calcite and dolomite are depleted in comparison to the reported range of delta-13C and delta-18O for the Triassic marine calcite and dolomite. This suggests that the isotopic composition of the Montney Formation
carbonates is strongly influenced by diagenetic fluids that originated from source(s) other than the Triassic seawater derived pore water. Calcite and dolomite from northeastern BC are more depleted in 18O correlating with elevated burial temperature
of the Montney Formation in this region. The 18O -depleted dolomite from the area of lower burial temperature in western Alberta is likely linked to hydrothermal activity. Negative delta-13C values of both calcite and dolomite are probably indicative
of diagenetic fluids depleted in 13C derived from decomposition of organic matter during burial. Preliminary 87Sr/86Sr ratio analysis also suggests that Montney Formation carbonate phases were formed from fluids enriched in radiogenic Sr isotope.
Further work is underway to determine the strontium isotopic composition of individual phases. This may further confirm contribution of fluids other than coeval Triassic pore water to precipitation of carbonates in the Montney Formation.
|Summary||(Plain Language Summary, not published)|
This study presents preliminary results of petrographic studies and bulk stable isotope data from calcite and dolomite plus bulk 87Sr/86Sr ratio analyses
to investigate the nature of the diagenetic fluid(s) and geochemical processes involved during diagenesis of the Montney Formation in western Alberta and northeastern BC.