ABSTRACT

Unconventional reservoir performance is assessed and quantified via integration of compositional, rock fabric, and static mechanical property analyses that are routinely performed on drill core or cuttings. This approach has several limitations; for example, it can only be used where drill core and cuttings are available, and comprehensive analysis may be cost prohibitive at the full scale of a resource play. In this contribution, we propose a novel workflow that provides a robust correlation between compositional, mineralogical, and geomechanical properties of unconventional shale plays and wire-line log signature. Our approach enables the extrapolation of compositional and mechanical reservoir properties into areas in which drill core is lacking but wire-line logs are available. We illustrate our workflow using a case study from the Duvernay unconventional shale play in western-central Alberta (Canada). Our analysis reveals a high degree of correlation between core-measured mineral components and two wire-line logs: pulsed neutron spectroscopy (PNS) and spectral gamma ray (SGR). In particular, we show that PNS-derived calcium, aluminum, and silicon concentrations and SGR-derived thorium and potassium concentrations may be used to identify silica-rich, clay-rich, and carbonate-rich intervals, respectively, within the reservoir. We show that these intervals exhibit distinct mechanical properties, suggesting that they are also characterized by distinct hydraulic fracturing efficiency. Since well logs are generally more abundant than drill cores, our approach may prove critical in assessing predrill reservoir potential not only in the Duvernay but in similar unconventional plays worldwide.

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