Deformation-assisted fluid percolation in rock salt

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Science  27 Nov 2015:
Vol. 350, Issue 6264, pp. 1069-1072
DOI: 10.1126/science.aac8747
  • Fig. 1 Brine percolation in rock salt.

    PT trajectories of multiple subsalt petroleum wells are shown together with experimentally measured dihedral angles θ for the salt-brine system (8). The static theory predicts that fluid must overcome a percolation threshold in the gray area, whereas fluids are predicted to percolate at any porosity in the white area. The light gray area highlights the transition zone, 60° < θ < 65°, between percolating and disconnected pore space (8). The segment of each well that is located within the salt has a lower geothermal gradient due to the high conductivity of salt and is shown as a dashed line. The depth axis is only for illustration and assumes an overburden with constant density, ρ = 2300 kg/m3.

  • Fig. 2 Pore networks in rock salt.

    Hydrostatic experiments on synthetic rock salt have been performed at P = 20 MPa and T = 100°C (Exp-I) and P = 100 MPa and T = 275°C (Exp-II). (A and B) 3D reconstruction of the pore network at textural equilibrium; all edges of the 3D volumes correspond to 660 μm. (C and D) The skeletonized pore network extracted from the reconstructed 3D volume; colored according to local pore-space-inscribed radius, with warmer colors indicating larger radius. (E) Distribution of apparent dihedral angles in the experiments. (F) Exp-I and Exp-II in the θϕ space regime diagram with the percolation threshold obtained from the static pore-scale theory (10, 12). Inserted images show the details of automated dihedral angle extraction from 2D images (13). We report the median value of dihedral angles and the estimated errors based on the 95% confidence interval. (G) Porosity of natural rock salt inferred from resistivity logs (Fig. 3B).

  • Fig. 3 Petrophysical observations.

    Wireline well logs and mud logs data constraining the fluid distribution and connectivity in the well GC8 from the deep water Gulf of Mexico (13). (A) Gamma-ray log, (B) electrical resistivity, (C) total hydrocarbons gas, (D) gas chromatography, (E) hydrocarbon signs (FL, fluorescence; OS, oil stain; DO, dead oil; and OC, oil cut) in mud logs, and (F) the dihedral angle inferred from experimental data (Fig. 1). Shading around each curve shows the measurement error and average fluctuations in data. The gray background corresponds to shaded areas in the experimental data (Fig. 1).

  • Fig. 4 Fluid distributions in salt wells.

    Hydrocarbons signs from mud logs of all 48 wells covering 150,000 m of salt are shown as a function of dihedral angle (13). Wells are divided into 14 groups based on spatial proximity. Salt extent is shown by an arrow in each region. Theoretical fluid connectivity is indicated by gray scale (Fig. 1). Abbreviations denote the following protraction areas in the Gulf of Mexico: AT, Atwater Valley; GC, Green Canyon; KC, Keathley Canyon; MC, Mississippi Canyon; and WR, Walker Ridge.

Supplementary Materials

  • Deformation-assisted fluid percolation in rock salt

    Soheil Ghanbarzadeh, Marc A. Hesse, Maša Prodanović, James E. Gardner

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods
    • Figs. S1 to S7
    • References
    Database S1
    Pressure, temperature, hydrocarbon signal, and well information.

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