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Capillary Pressure: Reservoir Seal Capillary Pressure / Saturation Relationship (S w * Model)

Capillary Pressure: Reservoir Seal Capillary Pressure / Saturation Relationship (S w * Model). Reservoir Seal. Seal. Seal. Fault (impermeable). Oil/water contact (OWC). Migration route. Reservoir rock. Hydrocarbon accumulation in the reservoir rock. Top of maturity. Source rock.

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Capillary Pressure: Reservoir Seal Capillary Pressure / Saturation Relationship (S w * Model)

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  1. Capillary Pressure: Reservoir SealCapillary Pressure / Saturation Relationship (Sw* Model)

  2. Reservoir Seal Seal Seal Fault (impermeable) Oil/water contact (OWC) Migration route Reservoir rock Hydrocarbon accumulation in the reservoir rock Top of maturity Source rock

  3. Reservoir Seal • The seal for a reservoir is usually provided by a water wet zone with low (but finite) permeability • Typically a shale • Darcy’s Law would indicate that with a finite permeability, gravity effect alone would cause petroleum to pass upward through the seal due to density difference, over a long (geologic) time period • Darcy’s Law is a “Rate Process” (ENGR 112) • For multiple phases flowing, the Darcy flow potential includes pressure, gravity, and capillary pressure terms • Effect of displacement pressure of seal halts upward migration of petroleum in trap • Displacement pressure of seal can limit total height of reservoir, from free water level to highest elevation in reservoir

  4. Capillary Pressure Required for Migration is Function of Pore Size s used in previous discussion From Levorsen, 1967

  5. Capillary Pressure Required for Migration is Function of Pore Size From Levorsen, 1967

  6. Sw* Power Law Model • Having an equation model for capillary pressure curves is useful • Smoothing of laboratory data • Determination of l • Analytic function for integration (future topic) • The Sw* Power Law Model is an empirical model that has proven to work well • Model parameters: Swi, Pd, l

  7. Sw* Power Law Model • Sw* rescales x-axis Sw*=0 Sw*=1 Sw*, fraction

  8. Sw* Power Law Model • Power Law Equations plot as Log-Log straight line

  9. Sw* Power Law Model • Straight line models are excellent for • Interpolation and data smoothing • Extrapolation • Self Study: review Power Law Equations (y=axb) and how to determine coefficients, a and b given two points on the straight log-log line

  10. Sw* Power Law Model • Pd, l can be determined from Log-Log plot • But, Swi can be difficult to determine from Cartesian plot, if data does not clearly show vertical asymptote

  11. Sw* Power Law Model • Choosing wrong Swi limits accuracy of determining Pd, l

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