Bakken Core

8/16/2019 Bakken Core

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Core Technology for Evaluating the Bakken

Fundamentals for Reservoir Quality

Assessment and Completion Analysis

John Kieschnick and Roberto Suarez-Rivera

TerraTek


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Topics CoveredTopics Covered• Core Technology Changes and Why

– Photos and Petrophysical Data of the Bakken

• Integrated Approach – Geochemical Analysis• Kerogen Maturity

– Geological Analysis

• Geological Profile – Petrological Analysis

• Lithofacies Recognition

• Clay Quantity, Type and Maturity

• Pore Geometry and Texture – Mechanical Properties

• The Bakken Vision


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BackgroundBackground

• Unlike Conventional Core Analysis whose core

analysis techniques are designed to evaluate

conventional high perm reservoirs, Unconventional

Core Analysis (i.e. TRATM analysis) is structured at

solving the complex issues of measuring many of thenecessary parameters to unlock the potential of tight

reservoirs.


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Effects on Tight ReservoirsEffects on Tight Reservoirs

• During Core Retrieval, Gas and Oil which are typically in solution

(unless liquids are bound by capillarity as in shales) are expressedthrough the more permeable intervals (pore pressure is trying to reachequilibrium with the reduced pressure) therefore pore space formerlyfilled with oil and gas is now filled with expanded gas

• If the pore pressure can’t reach equilibrium fast enough it can cause

stress-release induced microfractures which can greatly alter matrix permeabilities and porosities (a very common effect on tight reservoirs)

• Low matrix permeabilities have a profound impact on all petrophysicalmeasurements

• The presence of kerogen (organics) has altered the way we measure

fluid saturations• The impact of clay type, quantity, and especially maturity has alteredthe way all petrophysical properties are measured


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Bakken Dolomitic Mudstone to Dolomite


6/2866


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Matrix PropertiesMatrix Properties

Average Petrophysical Properties of the

Middle Bakken Dolomitic Mudstone to

Dolomite Members

0.0013.780.626.5819.4381.8444.959.282.8442.8132.689High

0.0000210.290.051.507.2044.838.562.302.7482.7252.561Low

Range Data

0.0002541.500.274.1913.9466.1119.956.222.7962.7542.639Varies

Average Data

md% of BV% of BV% of BV% of PV% of PV% of PV% of BVgms/ccgms/ccgms/ccfeet

Water,Saturation,Porosity,Saturation,Saturation,Saturation,Density,Density,Density,

Permeability,ClayHydrocarbonGas FilledMobile OilGasWater Porosity,GrainGrainBulkDepth,

BoundBoundOil Space-DryA-RA-R


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Bakken Silty / Sandy Mudstone to Sandstone


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Matrix PropertiesMatrix Properties

Average Petrophysical Properties of the

Middle Bakken Silty / Sandy Mudstone to

Sandstone Members

1.29172.000.5310.7817.5788.8930.1613.262.7802.7542.638High

0.0001350.290.002.881.2660.752.473.322.6992.6372.387Low

Range Data

0.09961.110.165.4010.7471.5317.747.652.7422.6982.552Varies

Average Data

md% of BV% of BV% of BV% of PV% of PV% of PV% of BVgms/ccgms/ccgms/ccfeet

Water,Saturation,Porosity,Saturation,Saturation,Saturation,Density,Density,Density,

Permeability,ClayHydrocarbonGas FilledMobile OilGasWater Porosity,GrainGrainBulkDepth,

BoundBoundOil Space-DryA-RA-R


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Bakken EvaluationBakken Evaluation

• Unlocking the full potential of the Bakken

play requires an Integrated Approach ofCore Technologies which include:

– Petrophysical

– Geochemical

– Geological

– Petrological

– Mechanical


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Matrix Permeability and Porosity areMatrix Permeability and Porosity are

altered by:altered by:

Coring induced and stress-release microfractures

– Alter matrix permeability measurements by offering a quick path through the matrix

– Create added porosity that is not present at “in situ” conditions

Specialized techniques are required to correct for both of these

effects


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PorosityPorosity

• Solving the Issues in measuring Tight Reservoir

Porosities- Gas, Oil, Water and Effective

– Reduced permeability effects all saturation

and porosity measurements – Separate measurements are required for

Gas, Oil and Water to determine Effective

Porosities and saturations


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PermeabilityPermeability

• Solving the Issues in measuring Tight ReservoirPermeabilities

– Coring Effects to Permeability Measurements• induced microfractures - mechanical and stress-release

• bedding fractures

• desiccation cracks

• coring fluid damage

– Clay Effects on Tight Reservoir Permeability (Presence ofClay Minerals of varying type, maturity, and location withinthe matrix and pore systems)

– Fluid Effects (including the effect of oil and condensates) onTight Reservoir Permeability measurements

– Stress Effects on Tight Reservoir Permeability


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SaturationsSaturations

• Solving the Issues in measuring Fluid Saturations

– Kerogen/Vapor Pressure/and Low Permeability effects on

Dean Stark Analysis

• Free Hydrogen- Nitrogen/Argon Blankets

• Vapor Pressure Equilibrium (accounting for volume)

• Low Permeability effects on cleaning (it takes energy) – Development of Gravimetric Method

• Humidity drying (associated errors)

– Development of Tight Rock saturation Methods


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Confirming Petrophysical PropertiesConfirming Petrophysical Properties

MeasurementsMeasurements

• Grain Densities should approximate calculated Grain

Densities from XRD• Porosities should match porosities measured on

cleaned and dried samples (where clays are < 3%)

• Fluid saturations should match production results• Permeabilities should match interval K tests on non-fractured intervals with field flow tests

• Petrophysical data should be predictable with wirelinelog data


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Increasing

pore pressure

Increasing

pore pressure

Impact of Kerogen

MaturityType 1: Lacustrine - oil prone source

paraffinic

Type 2: Marine - oil prone source

planktonic

Type 2S: Marine - oil prone sourceheavy sulfur (example Monterey)

Type 3: Marine - gas prone source

higher plant & woody fiber

Type 4: Residual - dry gas prone source


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Impact of

Clay Maturity

Biogenic

Biogenic and

Thermogenic


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Geological AnalysisGeological Analysis• Lithofacies Identification

• Depositional Environments

• Mineralogy

• Diagenetic / Detrital Minerals

• Other Ingredients including fossils• Photomicrographs of Enlarged Thin Sections

• Natural Fractures and Fracture Fills

• Log Responses to Geology / Minerals


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Example Geological ProfileExample Geological Profile


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Petrological AnalysisPetrological Analysis

• Lithofacies Recognition

– Thin Section Descriptions• Clay Quantity, Type, and Maturity

– XRD Analysis

– Bound Clay Water

• Pore Geometry and Texture

– SEM imaging


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Mechanical PropertiesMechanical Properties

• Measuring Heterogeneity

• Fracture Analysis• Tri-axial Testing

• Predicting Stress Profiles• Modeling Fracture Containment

Th Eff t f H t itTh Eff t f H t it


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The Effect of Heterogeneity onThe Effect of Heterogeneity on

InIn--Situ Stress PredictionsSitu Stress Predictions

10340

10350

10360

10370

10380

10390

10400

10410

10420

10430

10440

4000 5000 6000 7000 8000 9000 10000 11000 12000 13000

Stress (psi)

D e p t h

( f t )

Lower limit = 0.72 psi/ft

Low Risk

sig_h sig_vpp

Based on Logs

Based on Lab. Measurements

C t th B kk


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Capture the Bakken

Vision


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Bakken VisionBakken Vision

• The Bakken example may be visionary for Unconventional OilPlays – Near conventional (fracturable/brittle) lithofacies within high TOC

shales having the right thermal maturity (mid-late-post oilgeneration) within an interval where the fracture can be contained.

– Lateral Completions (often multiple oriented laterals required)

– Thermal Maturity, Lithofacies, and fracture containment are and willbe critical issues to these plays.

• New Plays underway – Barnett – Ft. Worth Basin (3 wells currently producing)

– Dolomitic Mudstone in Canada (untested)

– Barnett – West Texas (untested)

• Potential Plays – many (i.e. Lewis, Wolfcamp, the Green River, Antrium, New Albany, Ohio, Devonian…

• Old Fractured Oil Shale Plays needing to be revisited –Monterey and Mancos

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Bakken Core