Determination of in-situ Hydrocarbon Volumes in Liquid Rich Shale Plays

G. E. Michael
ConocoPhillips Houston

The determination of accurate in-situ oil and gas volumes is critical for unconventional “liquid-rich shale” (LRS) plays to determine total resource in-place and accurate recovery factors. Here, we present a methodology using geochemistry applied to pristine core samples to determine in-situ oil volume per volume of rock (bbls/acft), using open system Rock-Eval pyrolysis and solvent extract based geochemistry to determine the total hydrocarbon volume. An additional method is shown which attempts to correct for the mass of light oil lost due to evaporation during core recovery. The oil lost during core recovery is mostly low boiling point hydrocarbons less than C15 in the diesel and gasoline range compounds. The loss of this material can be estimated from the density of the hydrocarbon fluid in-place determined from a whole oil extract gas chromatogram or correlations to biomarker compounds. Examples of the methodology are shown for oil- and water-based drilled cores to assist in lateral well placement for enhanced liquid yields. The pyrolysis-based method (Rock-Eval pyrolysis) does a reasonable job of prediction of C6+ hydrocarbon volume and can be used to help constrain the recovery factor and determine the heterogeneity in resource density for optimization of development drilling. The next phase of understanding in-place fluids will require the quantification of gas in-place (C1-5) to obtain accurate gas-to-oil ratios.

AAPG Search and Discovery Article #90186 © AAPG Geoscience Technology Workshop, Hydrocarbon Charge Considerations in Liquid-Rich Unconventional Petroleum Systems, November 5, 2013, Vancouver, BC, Canada