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Title: Capillary pressure – saturation relationships for gas shales measured using a water activity meter

Hydraulic fracturing of gas shale formations involves pumping a large volume of fracking fluid into a hydrocarbon reservoir to fracture the rock and thus increase its permeability. The majority of the fracking fluid introduced is never recovered and the fate of this lost fluid, often called “leak off,” has become the source of much debate. Information on the capillary pressure – saturation relationship for each wetting phase is needed to simulate leak off using numerical reservoir models. The petroleum industry commonly employs air – water capillary pressure – saturation curves to predict these relationships for mixed wet reservoirs. Traditional methods of measuring this curve are unsuitable for gas shales due to high capillary pressures associated with the small pores present. Still, a possible alternative method is the water activity meter which is used widely in the soil sciences for such measurements. However, its application to lithified material has been limited. Here, this study utilized a water activity meter to measure air – water capillary pressures (ranging from 1.3 to 219.6 MPa) at several water saturation levels in both the wetting and drying directions. Water contents were measured gravimetrically. Seven types of gas producing shale with different porosities (2.5–13.6%) and totalmore » organic carbon contents (0.4–13.5%) were investigated. Nonlinear regression was used to fit the resulting capillary pressure – water saturation data pairs for each shale type to the Brooks and Corey equation. Data for six of the seven shale types investigated were successfully fitted (median R 2 = 0.93), indicating this may be a viable method for parameterizing capillary pressure – saturation relationships for inclusion in numerical reservoir models. As expected, the different shale types had statistically different Brooks and Corey parameters. However, there were no significant differences between the Brooks and Corey parameters for the wetting and drying measurements, suggesting that hysteresis may not need to be taken into account in leak off simulations.« less
 [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7]
  1. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Earth and Planetary Sciences
  2. Tennessee Department of Environment and Conservation (TDEC), Knoxville, TN (United States). Division of Geology
  3. Univ. of Tennessee, Knoxville, TN (United States). Bredesen Center for Interdisciplinary Research and Graduate Education; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Energy and Transportation Science Division
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Reactor and Nuclear Systems Division
  7. Univ. of Texas Rio Grande Valley, Edinburg, TX (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of Natural Gas Science and Engineering
Additional Journal Information:
Journal Volume: 33; Journal Issue: C; Journal ID: ISSN 1875-5100
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
54 ENVIRONMENTAL SCIENCES; Water activity meter; Capillary pressure; Volumetric water content; Porosity; Shale; Brooks and Corey
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1406137