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Constraints on upward migration of hydraulic fracturing fluid and brine.

Flewelling SA, Sharma M - Ground Water (2013)

Bottom Line: Recent increases in the use of hydraulic fracturing (HF) to aid extraction of oil and gas from black shales have raised concerns regarding potential environmental effects associated with predictions of upward migration of HF fluid and brine.Consequently, the recently proposed rapid upward migration of brine and HF fluid, predicted to occur as a result of increased HF activity, does not appear to be physically plausible.Unrealistically high estimates of upward flow are the result of invalid assumptions about HF and the hydrogeology of sedimentary basins.

View Article: PubMed Central - PubMed

Affiliation: Gradient, 20 University Road, Cambridge, MA 02138; msharma@gradientcorp.com.

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Related in: MedlinePlus

(A) Normalized permeability of Wilcox Shale from (Kwon et al. 2001), assuming that effective stress is the difference between lithostatic pressure and hydrostatic pressure. The bulk density of overburden and water were assumed to be 2300 kg m−3 and 1000 kg m−3, respectively. k0 in this case would be the permeability at the land surface (i.e., when effective stress is zero); (B) relative permeability estimated from Equation 2. k0 in this case would be the permeability for water-saturated rock. In gas-rich shales, pore space is predominantly occupied by gas and oil; therefore, the permeability to water is reduced by orders of magnitude.
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fig03: (A) Normalized permeability of Wilcox Shale from (Kwon et al. 2001), assuming that effective stress is the difference between lithostatic pressure and hydrostatic pressure. The bulk density of overburden and water were assumed to be 2300 kg m−3 and 1000 kg m−3, respectively. k0 in this case would be the permeability at the land surface (i.e., when effective stress is zero); (B) relative permeability estimated from Equation 2. k0 in this case would be the permeability for water-saturated rock. In gas-rich shales, pore space is predominantly occupied by gas and oil; therefore, the permeability to water is reduced by orders of magnitude.

Mentions: Permeability is partly dependent on effective stress, which controls the amount of compaction and fracture apertures in a given rock layer. Both the void space and connectivity decrease as effective stress increases, thereby restricting flow and lowering permeability. (Kwon et al. 2001) provided a pressure-permeability relationship for the Wilcox Shale based on laboratory experiments, k = k0[1 − (Pe/P1)m]3, where k0 is on the order of 10−17 m2, P1 is 19.3 (±1.6) MPa, m is 0.159 (±0.007), and Pe is the effective stress (Pe = Pc − χPp, where Pc is the overburden stress, Pp is fluid pore pressure, and χ is a constant that is approximately one for shales; Kwon et al. 2001). This relationship is plotted in Figure 3A. Note that the relationship of (Kwon et al. 2001) is for horizontal permeability (for flow parallel to bedding), which is typically higher than vertical permeability (for flow perpendicular to bedding). (Kwon et al. 2001) indicate that permeability decreases by 4 orders of magnitude as effective stress increases to 12 MPa (e.g., conditions that may be encountered at depths >1000 m).


Constraints on upward migration of hydraulic fracturing fluid and brine.

Flewelling SA, Sharma M - Ground Water (2013)

(A) Normalized permeability of Wilcox Shale from (Kwon et al. 2001), assuming that effective stress is the difference between lithostatic pressure and hydrostatic pressure. The bulk density of overburden and water were assumed to be 2300 kg m−3 and 1000 kg m−3, respectively. k0 in this case would be the permeability at the land surface (i.e., when effective stress is zero); (B) relative permeability estimated from Equation 2. k0 in this case would be the permeability for water-saturated rock. In gas-rich shales, pore space is predominantly occupied by gas and oil; therefore, the permeability to water is reduced by orders of magnitude.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4321062&req=5

fig03: (A) Normalized permeability of Wilcox Shale from (Kwon et al. 2001), assuming that effective stress is the difference between lithostatic pressure and hydrostatic pressure. The bulk density of overburden and water were assumed to be 2300 kg m−3 and 1000 kg m−3, respectively. k0 in this case would be the permeability at the land surface (i.e., when effective stress is zero); (B) relative permeability estimated from Equation 2. k0 in this case would be the permeability for water-saturated rock. In gas-rich shales, pore space is predominantly occupied by gas and oil; therefore, the permeability to water is reduced by orders of magnitude.
Mentions: Permeability is partly dependent on effective stress, which controls the amount of compaction and fracture apertures in a given rock layer. Both the void space and connectivity decrease as effective stress increases, thereby restricting flow and lowering permeability. (Kwon et al. 2001) provided a pressure-permeability relationship for the Wilcox Shale based on laboratory experiments, k = k0[1 − (Pe/P1)m]3, where k0 is on the order of 10−17 m2, P1 is 19.3 (±1.6) MPa, m is 0.159 (±0.007), and Pe is the effective stress (Pe = Pc − χPp, where Pc is the overburden stress, Pp is fluid pore pressure, and χ is a constant that is approximately one for shales; Kwon et al. 2001). This relationship is plotted in Figure 3A. Note that the relationship of (Kwon et al. 2001) is for horizontal permeability (for flow parallel to bedding), which is typically higher than vertical permeability (for flow perpendicular to bedding). (Kwon et al. 2001) indicate that permeability decreases by 4 orders of magnitude as effective stress increases to 12 MPa (e.g., conditions that may be encountered at depths >1000 m).

Bottom Line: Recent increases in the use of hydraulic fracturing (HF) to aid extraction of oil and gas from black shales have raised concerns regarding potential environmental effects associated with predictions of upward migration of HF fluid and brine.Consequently, the recently proposed rapid upward migration of brine and HF fluid, predicted to occur as a result of increased HF activity, does not appear to be physically plausible.Unrealistically high estimates of upward flow are the result of invalid assumptions about HF and the hydrogeology of sedimentary basins.

View Article: PubMed Central - PubMed

Affiliation: Gradient, 20 University Road, Cambridge, MA 02138; msharma@gradientcorp.com.

Show MeSH
Related in: MedlinePlus