Abstract
Extended Slow Heating (ESH) pyrolysis is applied to assess oil fractions in reservoir rocks. It
offers a novel approach to estimate oil saturation, as presented by a case study from the Nini West oilfield
(Danish North Sea). This method enables cost-effective saturation estimation from minimal sample sizes,
using cleaned core plugs to evaluate cleaning efficiency and adjust for porosity underestimation due to
incomplete cleaning. ESH involves gradual pyrolysis of 50 mg dry, ground samples (100–650 °C at
10 °C/min) using a HAWK Pyrolysis and TOC analyser calibrated against oils with known gravity and API
standards. Hydrocarbon release is continuously measured during pyrolysis, and oil fractions were defined
based on their densities. ESH-derived oil saturation and API values aligned with direct measurements,
confirming the method’s reliability. Saturation values in scCO₂-flooded plugs were significantly lower,
suggesting that lighter hydrocarbons were removed, leaving heavier, immobile fractions (solid
bitumen/asphaltenes), although with minor quantities. The study, combining ESH, chromatography,
porosity measurements, and cleaning techniques, reveals that solid bitumen and asphaltenes remain post-
scCO2 flooding and cleaning. ESH is a rapid and effective method for determining oil composition,
saturation, and API gravity. Its low sample requirement allows for spatial oil composition analysis from
cuttings, offering advantages over traditional core analysis methods.
offers a novel approach to estimate oil saturation, as presented by a case study from the Nini West oilfield
(Danish North Sea). This method enables cost-effective saturation estimation from minimal sample sizes,
using cleaned core plugs to evaluate cleaning efficiency and adjust for porosity underestimation due to
incomplete cleaning. ESH involves gradual pyrolysis of 50 mg dry, ground samples (100–650 °C at
10 °C/min) using a HAWK Pyrolysis and TOC analyser calibrated against oils with known gravity and API
standards. Hydrocarbon release is continuously measured during pyrolysis, and oil fractions were defined
based on their densities. ESH-derived oil saturation and API values aligned with direct measurements,
confirming the method’s reliability. Saturation values in scCO₂-flooded plugs were significantly lower,
suggesting that lighter hydrocarbons were removed, leaving heavier, immobile fractions (solid
bitumen/asphaltenes), although with minor quantities. The study, combining ESH, chromatography,
porosity measurements, and cleaning techniques, reveals that solid bitumen and asphaltenes remain post-
scCO2 flooding and cleaning. ESH is a rapid and effective method for determining oil composition,
saturation, and API gravity. Its low sample requirement allows for spatial oil composition analysis from
cuttings, offering advantages over traditional core analysis methods.
| Original language | English |
|---|---|
| Title of host publication | 38th International Symposium for the Society of Core Analysts (SCA) , Hannover, Lower Saxony, Germany, 25-29 August 2025 (Session Laboratory Core Analysis) |
| Publisher | Society of Core Analysts |
| Number of pages | 11 |
| DOIs | |
| Publication status | Published - 2025 |
Programme Area
- Programme Area 3: Energy Resources
- Programme Area 5: Nature and Climate
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