Abstract

MORENO-ENRIQUEZ, Angee et al. Assessment of the original gas volume in situ in unconventional gas-shale reservoirs through multiple models worldwide and its analogy to a Colombian formation. Bol. geol. [online]. 2022, vol.44, n.2, pp.109-123.  Epub July 18, 2022. ISSN 0120-0283.  https://doi.org/10.18273/revbol.v44n2-2022005.

The gas can be present in the source rock, either as free gas in the porous medium, free gas in natural fractures or as gas adsorbed, which can represent up to 85% of the total volume present in the reservoir. Different inquiries have been pointed by professionals in the oil and gas industry about whether all the necessary parameters are considered in the quantification of the original gas in place volume, in order to mitigate the uncertainty in its estimation. The objective of this research is to study the main methods and correlations used to quantify the gas that is adsorbed by the rock, to finally estimate the total gas. With that said, multiple adsorption models were studied with information from the literature, in order to determine which models had the least deviation, comparing to the laboratory data. Likewise, using the characteristics of the La Luna Formation in Colombia, an analogy is proposed to estimate the possible reserves of this formation. The results showed that the models with a greater number of parameters involved presented a better fit with the laboratory data, however, models such as the three-parameter Langmuir model or the Jovanovic model were very close to the real values. This guarantees a smaller error in the calculation of the total gas.

Keywords : Isotherms; Source rock reservoirs; Geochemistry.

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