The impacts of effective stress and CO₂ sorption on the matrix permeability of shale reservoir rocks [The impacts of CO₂ sorption and effective stress on the matrix permeability of shale reservoir rocks]

Journal Article · Tue May 02 00:00:00 EDT 2017 · Fuel

DOI:https://doi.org/10.1016/j.fuel.2017.04.103· OSTI ID:1369242

Wu, Wei ^[1]; Zoback, Mark D. ^[2]; Kohli, Arjun H. ^[3]

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1. Nanyang Technological Univ. (Singapore)
2. Stanford Univ., Stanford, CA (United States)
3. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)

We assess the impacts of effective stress and CO₂ sorption on the bedding-parallel matrix permeability of the Utica shale through pressure pulse-decay experiments. We first measure permeability using argon at relatively high (14.6 MPa) and low (2.8 MPa) effective stresses to assess both pressure dependence and recoverability. We subsequently measure permeability using supercritical CO₂ and again using argon to assess changes due to CO₂ sorption. We find that injection of both argon and supercritical CO₂ reduces matrix permeability in distinct fashion. Samples with permeability higher than 10^–20 m² experience a large permeability reduction after treatment with argon, but a minor change after treatment with supercritical CO₂. However, samples with permeability lower than this threshold undergo a slight change after treatment with argon, but a dramatic reduction after treatment with supercritical CO₂. These results indicate that effective stress plays an important role in the evolution of relatively permeable facies, while CO₂ sorption dominates the change of ultra-low permeability facies. The permeability reduction due to CO₂ sorption varies inversely with initial permeability, which suggests that increased surface area from hydraulic stimulation with CO₂ may be counteracted by sorption effects in ultra-low permeability facies. As a result, we develop a conceptual model to explain how CO₂ sorption induces porosity reduction and volumetric expansion to constrict fluid flow pathways in shale reservoir rocks.

• Research Organization: SLAC National Accelerator Lab., Menlo Park, CA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-76SF00515
• OSTI ID: 1369242
• Journal Information: Fuel, Vol. 203, Issue C; ISSN 0016-2361
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
shale matrix
permeability evolution
supercritical CO2
effective stress
hydraulic fracturing