Capillary Pressure Properties of Hydrocarbon Reservoir Sequences

1
Title
Capillary Pressure Properties of Hydrocarbon
Reservoir Sequences Combining Core Data with
Petrophysics
Digital Formation, Inc. November 2003
2
Contents

• Benefits
• Overview
• How to Run the Model
• Examples
• Pro-Forma Modeling
• Tight Gas Sand
• Oil Reservoir with Stacked Accumulations
• Conclusions

This technique is protected under US Patent
6,484,102Additional patent application pending
3
Benefits Petrophysics I

• Integrates capillary pressure information with
  petrophysics.
• Allows for realistic choices of free water level,
  even if it is below the total depth of the well.
• Quantifies changing rock quality as defined by
  porosity/permeability relations, and hence a
  method to estimate permeability profiles.

4
Benefits Petrophysics II

• In combination with relative permeability
  analysis, allows for estimates of effective
  permeability to each fluid component.
• Better understanding of vertical changes in
  reservoir quality.
• Direct comparison with NMR results, and
  categorization of mobile vs. immobile water.

5
Benefits Reservoir Engineering

• Definition of flow units and barriers within
  hydraulic units.
• Direct comparison with well test results fluids
  produced, flow capacity.
• Identifies which intervals to complete, and which
  intervals should be isolated from one another.
• After calibration in a specific reservoir
  sequence, permits estimates of I.P. before the
  well is completed.
• Allows for recognition of any depth level with
  respect to location of top transition zone (above
  or below), and hence likely productive
  capabilities.

6
Benefits Exploration

• For stacked accumulations, free water levels of
  each hydraulic unit can be estimated from a
  single wellbore. When data from multiple wells
  are combined allows for detailed mapping of
  hydrocarbon/water contacts.
• For an area with sparse well control with
  uncommercial hydrocarbon shows, is a method to
  predict optimum structural position to penetrate
  reservoirs above top hydrocarbon/water transition
  zone.

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Overview Part 1
8
Overview Part 2
9
Overview Part 3

• For any one sample, record Pce, H1, H2, Swmc, Swi
  (single number for each)
• For a group of samples, relate these to porosity
  and permeability
• Relations change from one reservoir to the next

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How to run the Model Part 1

• Generate petrophysical profiles of effective
  porosity and water saturation
• Estimate depth of zero capillarity
  (hydrocarbon/water contact)
• Run the model, which will calculate ranges of
  theoretical Sw at each level
• Compare with petrophysical model and choose
  closest match, level-by-level (rock category)

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How to run the Model Part 2

• From rock category and porosity, calculate
  permeability
• Using normalized relative permeabilities
  (reservoir-specific) calculate fluid effective
  permeabilities
• Calculate components
• Capillary-bound water
• Immobile water in very low permeability rocks
• Mobile water
• Hydrocarbons

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How to run the Model Part 3

• Choose a series of levels of particular interest
• Knowing rock quality and porosity, determine for
  each level
• Permeability
• Specific reconstructed capillary pressure curve
• Location of sample on the capillary pressure curve

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Example 1

• Pro-Forma
• Moxa Arch Wyoming, Frontier Sands

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Example Pro-Forma
Best matches indicated by arrows
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Example Pro-Forma
A permeability change of 3 orders of magnitude,
even though porosity is the same
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Example 2

• LaBarge Area Wyoming, Frontier Sands
• Taking a more detailed look at the fluid
  components
• Comparing the results to core data

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Example LaBarge Area Wyoming, Frontier Sands
Petrophysics only
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Example Tight Gas Sand
Example LaBarge Area Wyoming, Frontier Sands
Petrophysics and Core Data
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Example 3

• Rocky Mountain Cretaceous Gas Sands
• Comparing the results to NMR data

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Example Rocky Mountain Cretaceous Gas Sands
Petrophysics only
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Example Rocky Mountain Cretaceous Gas Sands
Petrophysics and NMR
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Example 4

• Oil Reservoir

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Example Oil Reservoir
Specific capillary pressure modeling points
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Example Oil Reservoir
1
2
3
Specific capillary pressure modeling points
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Conclusions

• Technique is reservoir specific and yields
  detailed categorization of changing rock quality
• Allows detailed assessment of reservoir quality
  before the well is completed
• Gives fluid categorization comparable to NMR
  output
• Allows estimates to be made of effective
  permeability profiles of the separate reservoir
  fluids, which can then be compared with test and
  production data
• Allows detailed analysis of the reservoir
  level-by-level
• Within or above transition zone
• How far above/below the top of the transition
  zone
• Down dip limits of water-free production
• Structural elevation gain required for water-free
  production