ExxonMobils Electrofrac Process for In Situ Oil Shale Conversion - - PowerPoint PPT Presentation

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ExxonMobils Electrofrac Process for In Situ Oil Shale Conversion - - PowerPoint PPT Presentation

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Upstream Research ExxonMobils Electrofrac Process for In Situ Oil Shale Conversion William A. Symington, David L. Olgaard, Glenn A. Otten, Tom C. Phillips, Michele M. Thomas, Jesse D. Yeakel 26 th Oil Shale Symposium Colorado School of

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SLIDE 1

Upstream Research

ExxonMobil’s Electrofrac™ Process for In Situ Oil Shale Conversion

William A. Symington, David L. Olgaard, Glenn A. Otten, Tom C. Phillips, Michele M. Thomas, Jesse D. Yeakel

26th Oil Shale Symposium Colorado School of Mines October 17, 2006

Colorado Energy Research Institute 26th Oil Shale Symposium October 16-18, 2006

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SLIDE 2

Electrofrac

Oil Shale Conversion via Electrically Conductive Fractures

Upstream Research

+ +

  • V

Hydraulic fractures containing electrical conductant Conductive heating and

  • il shale conversion

Production wells

  • Early screening research indicated:

In situ methods preferred. Heat conduction is the best way to “reach into” oil shale. Linear conduction from a planar heat source is more effective than radial conduction from a wellbore.

  • Electrofrac concept is applicable with

either vertical or horizontal fractures.

  • Conductant electrical resistivity:

high enough for resistive heating. low enough to conduct sufficient current.

  • Electrofrac research has focused on

critical technical issues:

Identification of conductant. Maintaining electrical continuity. Expulsion under in situ stress. Completion strategy for effective heating.

Colorado Energy Research Institute 26th Oil Shale Symposium October 16-18, 2006

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SLIDE 3

#170 Cast steel shot

Core-plug-scale experiments demonstrate:

  • Calcined coke is a candidate conductant.
  • Electrical continuity is not disrupted by

kerogen conversion.

  • Hydrocarbon expulsion under in situ stress.

Modeling indicates:

  • Volume expansion is a large potential drive

mechanism.

  • Fractures will generally be vertical.
  • Longitudinal fractures heat effectively.

5 years 10 years

20/40 Mesh Proppant Calcined Coke Hydrocarbons Expelled under Stress Effective Heating from Longitudinal Fractures Electrical Continuity Undisrupted by Kerogen Conversion Colorado Energy Research Institute 26th Oil Shale Symposium October 16-18, 2006

Electrofrac Laboratory Research has Focused on Critical Technical Issues

Upstream Research

Temp, ºF

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SLIDE 4

Coke Resistivity is Temperature Insensitive

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 100 200 300 400 500 600 700 800

Temperature, degC Normalized Resistivity

EF135 EF136

  • Physical properties (density, particle size)

similar to fracture proppants.

  • Electrical resistivity in desired range and

temperature-insensitive. Resisitivity should be controllable by calcining process.

  • Chemical stability up to calcining

temperature.

  • Readily available. Current uses are -

– Carbon anodes for aluminum smelting. – Anode beds for cathodic protection. – Packing for industrial electrical grounding.

Calcining Temperature Controls Resistivity

Identification of Conductant

Calcined Coke 20/40 Mesh Frac Proppant Data from Hardin, et al, 1992

Colorado Energy Research Institute 26th Oil Shale Symposium October 16-18, 2006

Calcined Petroleum Coke is a Candidate Electrofrac Conductant

Upstream Research

0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 1150 1200 1250 1300 1350 1400 1450 1500 1550

Calcining Temperature, degC Resistivity, ohm-cm

TE-315 TE-315 TE-316 TE-317 TE-431

Normalized Resistivity (ρ/ρ25ºC)

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SLIDE 5
  • Stress applied with hose

clamps to achieve electrical continuity.

  • Sample heated externally to

360ºC for 24 hours – 90% uniform conversion achieved.

  • Although embedment
  • ccurred to a minor degree,

electrical continuity was not disrupted.

Particle Embedment Does Not Disrupt Continuity in Core-Scale Experiments

Maintaining Electrical Continuity Upstream Research

Colorado Energy Research Institute 26th Oil Shale Symposium October 16-18, 2006

1 i n c h 1/16 inch

Calcined petroleum coke or #170 cast steel shot (0.02 inch) packed in 1/16 inch deep tray

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SLIDE 6
  • Heated with 20 amps for 5 hours

(~60 W). Circuit not disrupted by rock alteration.

  • Internal measured temperature

reached 268ºC. Estimated fracture temperature of 350-400ºC.

  • Thermal expansion caused

fractures in the sample.

  • Recovered 0.15 mL of oil.

Steel Balls Fracture Face Spent Oil Shale Epoxy-Filled Fractures Conversion Zone Initial Conversion Zone Unaltered Oil Shale

Spent Oil Shale Thin Section Showing Porosity (blue)

3 mm

Experiment Summary

Photomicrograph under Fluorescent Light

#170 Cast steel shot

Simulated Electrofrac Heating Circuit Undisturbed by Kerogen Conversion

Maintaining Electrical Continuity Upstream Research

Photomicrograph section

Colorado Energy Research Institute 26th Oil Shale Symposium October 16-18, 2006

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SLIDE 7

Expulsion Under In Situ Stress Upstream Research

Experiments Demonstrate Expulsion

  • f Hydrocarbons Under Stress
  • Stress is applied in axial direction,

strain is inhibited in lateral directions.

  • Experiments under stress recovered

21 to 34 gal/ton from 42 gal/ton samples.

Oil shale inside Berea cylinder - jacketed and clamped High temperature (Inconel) springs provide axial load. Gold foil records maximum spring deflection.

Colorado Energy Research Institute 26th Oil Shale Symposium October 16-18, 2006

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SLIDE 8
  • Product compositions derived from MSSV (micro-sealed spherical vessel)

pyrolysis experiments.

  • Equation-of-state model used to calculate expected density and phases at

typical Electrofrac conditions.

8.1 ft3 kerogen 7.2 ft3 mineral 7.2 ft3 mineral 2.9 ft3 coke 9.4 ft3 HC vapor 6.6 ft3 HC liquid 15.3 ft3 total 26.1 ft3 total Before Conversion After Conversion @ 2400 psi, 750ºF (without liquid cracking to gas) 1 Ton of Green River Oil Shale (22% TOC, 42 gal/ton)

Volume Expansion Provides a Large Potential Drive Mechanism

Upstream Research Expulsion Under In Situ Stress

Temperature, ºF

200 400 600 800 1000 4000 3000 2000 1000

Pressure, psi

Electrofrac P/T

B u b b l e p

  • i

n t Dew point 25% vapor 5 % v a p

  • r

75% vapor

Phase Diagram

Colorado Energy Research Institute 26th Oil Shale Symposium October 16-18, 2006

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SLIDE 9

Higher Lower

Present day surface Oil shale Wasatch Mesa Verde

N

  • r

t h

Oil shale

  • utcrop

5 miles

In Piceance Basin, Electrofrac Heating Fractures will be Dominantly Vertical

Upstream Research Completion Strategy for Effective Heating

Colorado Energy Research Institute 26th Oil Shale Symposium October 16-18, 2006

Fracture Orientation Transition Elevation

Humble tests (1964) constrain horizontal/vertical transition Borehole ellipticity/breakouts constrain stress difference

Stress → Elevation →

Fracture jobs constrain minimum principle stress

σvertical σeast-west σnorth-south

Geomechanical Model Calibration Location A

Stratigraphic Markers Symington, W. A. and Yale, D. P, 2006, ARMA GoldenRocks Conference

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SLIDE 10

+ +

  • V

Hydraulic fractures containing electrical conductant Conductive heating and

  • il shale conversion

Production wells

  • Heating wells drilled horizontally,

perpendicular to direction of least principle in situ stress.

  • Vertical longitudinal fractures filled

with electrically conducting material.

  • Electrical conduction from the heel to

the toe of heating wells.

  • For reasonably spaced fractures,

induced stresses should not alter the least principle in situ stress direction.

  • Multiple layers of heating wells may

be stacked for increased heating efficiency.

Preferred Process Geometry Relies on Vertical Electrofrac Heating Fractures

Completion Strategy for Effective Heating Upstream Research

Colorado Energy Research Institute 26th Oil Shale Symposium October 16-18, 2006

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SLIDE 11

Process Schematic

Modeling Optimizes Heating Efficiency

Simulation Case Selected as “Typical” – 150 foot fracture height, 5-year heating sufficient to convert 325 feet of oil shale, 120-ft frac spacing, 74% heating efficiency

Completion Strategy for Effective Heating

Thermal model view direction

Upstream Research

2.5 years 5 years 7.5 years 10 years

Temp, ºF

Colorado Energy Research Institute 26th Oil Shale Symposium October 16-18, 2006

300 ft

100 ft 100 ft

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SLIDE 12

Electrofrac

Oil Shale Conversion via Electrically Conductive Fractures

Upstream Research

ExxonMobil’s Electrofrac research has focused on critical technical issues. Research highlights include:

  • Laboratory experiments demonstrating –

Calcined petroleum coke is a suitable Electrofrac conductant. Electrical continuity is unaffected by kerogen conversion. Hydrocarbons will be expelled from heated oil shale even under in situ stress.

  • Modeling including the following –

A phase behavior model showing volume expansion is a large potential drive mechanism for expulsion. In situ oil shale can expand by 70% upon kerogen conversion. A Piceance Basin geomechanical model showing the stress state of the Green River oil shale favors vertical fractures. Heat conduction models showing that several fracture designs can deliver heat effectively. A “typical” case requires one Electrofrac heating well every 1.5 acres.

Colorado Energy Research Institute 26th Oil Shale Symposium October 16-18, 2006