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TitleImproved models for estimating TOC in shale resource play: an example from Duvernay Formation, Western Canada Sedimentary Basin
AuthorWang, P; Chen, Z; Pang, X; Hu, K; Sun, M
SourceCanadian Society of Petroleum Geologists, Canadian Society of Exploration Geophysicists, Joint Annual Meeting, Abstracts 2015.
Year2015
Alt SeriesEarth Sciences Sector, Contribution Series 20140396
PublisherCanadian Society of Petroleum Geologists
MeetingCSPG GeoConvention 2015; Calgary; CA; May 4-8, 2015
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceAlberta; British Columbia
AreaDuvernay Formation
Subjectseconomic geology; organic materials; modelling; source rocks; shales; petrogenesis; petroleum; Western Canada Sedimentary Basin (WCSB); total organic content (TOC); Devonian
ProgramShale-hosted petroleum ressource assesment, Geoscience for New Energy Supply (GNES)
LinksOnline - En ligne
AbstractDetermination of total organic content (TOC) is essential in source rock study and unconventional shale resource play evaluation (Jarvie et al., 2007; Rokosh et al., 2012). Indirect method, such as the petrophysical approach, does not require laboratory test and can provide a fast, convenient and cost efficient means for TOC estimation when well log data are available. Among the publically available approaches, the deltalogR method proposed by Passey et al. (1990) is proven to be useful and widely accepted. In the recent source rock evaluations in the Western Canada Sedimentary Basin (WCSB) and elsewhere, we found that mineral composition and rock texture of the organic rich shales vary considerably from play to play. With fixed parameters pertaining to mineral composition, compaction and rock texture, the original deltalogR method may result in biased estimates when the target source rock differs significantly from the one that was used to derive the equations. Other limitations of the deltalogR method include restricted ranges of resistivity and sonic transit time because a linear approximation of the ratio of resistivity to porosity logs and inconvenience of converting commonly used thermal indicators, such as Ro% or Tmax to LOM.
This study attempts to improve the deltalogR method by 1) introduce flexible petrophysical parameters specific to the target source rock and drop the linear approximation, 2) replace LOM with commonly used thermal indicator Tmax, and 3) include additional log curve (Gamma Ray) to improve TOC estimation. We present the models with an application example from the Devonian Duvernay shale of WCSB to demonstrate the improved deltalogR method. The TOC estimates derived from the revised models (sonic- and density-based models) show much high correlation coefficients (R2 = 84% and 86% respectively) with the measured TOCs from core samples, as compared with R2 of 67% and 59% for sonic- and density-based models respectively from the original deltalogR method.
Summary(Plain Language Summary, not published)
Determination of total organic content (TOC) is essential in source rock study and unconventional shale resource play evaluation. In the recent source rock evaluations in the Western Canada Sedimentary Basin (WCSB) and elsewhere, we found that mineral composition and rock texture of the organic rich shales vary considerably from play to play. With fixed parameters pertaining to mineral composition, compaction and rock texture, the original ?logR method may result in biased estimates when the target source rock differs significantly from the one that was used to derive the equations. This study attempts to improve the ?logR method. We present the models with an application example from the Devonian Duvernay shale of WCSB to demonstrate the improved ?logR method.
GEOSCAN ID295737