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. In this presentation we present methodology using geochemistry applied to pristine core samples to determine in-situ oil volume per volume of rock (bbls/acft). This methodology uses 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 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 by knowing the density of the hydrocarbon fluid in-place which can be estimated from the whole oil extract gas chromatogram or estimated from relationships based on 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.
When exploiting LRS plays it is important to determine the oil in-place. This is important to understand the potential size of a resource base that a company is pursuing for exploration, but is also important in development and exploitation. Ultimately, in order to calculate the recovery factor and expected ultimate recovery it is necessary to know the drained rock volume per well and the in-place hydrocarbon density in that volume. The actual drained rock volume is still a matter of research, but this paper works to quantify the hydrocarbon density. Current methodologies for calculating the oil in place use some form of measured or log calculated rock porosity and a measured water saturation and hydrocarbon saturation. This method, tied to Dean Stark type extractions for determination of oil saturation, works best for higher permeability reservoirs but is suspect for shales (Noble et al., 1997). In addition, water saturation measurement is not an easy measurement and addition of clay bound water may overestimate water saturation.