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TitleDeterioration of oil quality during sample storage: are stored reservoir core samples a viable resource for oil viscosity determination?
AuthorBennett, B; Jiang, CORCID logo; Larter, S R
SourceFuel vol. 245, 2019 p. 115-121,
Alt SeriesNatural Resources Canada, Contribution Series 20180309
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf; html
Subjectsfossil fuels; geochemistry; mathematical and computational geology; petroleum resources; hydrocarbons; oil; reservoir rocks; core samples; sample storage; oil viscosities; statistical methods; organic geochemistry; bitumen; aromatic hydrocarbons; heavy oil; mass spectrometer analysis; Methodology; Quality control
Illustrationstables; profiles; chromatograms
ProgramGeoscience for New Energy Supply (GNES) Canadian Energy Geoscience Innovation Cluster (CEGIC)
Released2019 02 01
AbstractThe physical and chemical properties of oil residing in reservoir core samples are strongly susceptible to evaporative processes during storage. In a case study from the Peace River oil sands of Alberta, we performed dead oil viscosity measurements on oils recovered by mechanical extraction of fresh core, the equivalent cores stored for 7 months frozen plus 3 months at ambient conditions (time 1) and for 7 months frozen plus 8 months at ambient conditions (time 2). The dead oil viscosity of oil recovered from fresh core material (8100 cP at 20 °C) was more than an order of magnitude lower than that of the oil subsequently recovered from an equivalent core sample stored frozen for 7 months and then at ambient temperature for 8 months (313,500 cP at 20 °C). The evaporation of light hydrocarbons such as toluene and xylenes during storage is a continuous process responsible for progressive increase in dead oil viscosity. Meanwhile, when comparing the oils recovered from fresh core and aged core samples, the composition of the heavy (low volatility) hydrocarbons remains essentially the same. Because biodegradation is the primary control on oil viscosity and variation in hydrocarbon compositions for this oil sample suite, partial least squares models based on viscosity versus geochemical data may still be used to predict viscosity. Although the physical properties of the oil may be compromised during storage, the distributions of the high molecular weight components retain characteristics, similar to a bar code, that are inherited and representative of the original (fresh) core sample. Therefore, with the proviso that the distributions of high molecular weight components are comparable between fresh cores and aged cores, the viscosity of oil residing in stored core samples can be effectively restored by chemometric-based correlation methods.
Summary(Plain Language Summary, not published)
This study shows that both physical and chemical properties of oil residing in reservoir core samples are strongly susceptible to evaporative processes during storage. The main impact due to sample storage decay is on the volatile components through evaporative loss. Chemometric methods based on physical property measurements and geochemical data obtained from oils extracted from fresh cores may be used to effectively estimate oil properties of legacy core samples.

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