Natural fracture systems, hydraulic fracturing ... · Natural fracture systems, hydraulic fracturing stimulations and fluid flow in shale gas reservoirs Dr Basim Faraj, V. P. International,

Natural fracture systems, hydraulic fracturing stimulations

and fluid flow in shale gas reservoirs

Dr Basim Faraj, V. P. International, Questerre Energy Corp.

Quebec Oil and Gas Association (QOGA) Conference

Hilton Montreal Bonaventure Hotel, Montreal

October 23- 25, 2011

Outline

• Shale is different• Fluids in natural fracture systems• Fluid Loss during fracture stimulation• Interaction of fluids flow with natural fractures• Contamination of underground aquifers• Conclusions

10 cm (100,000 µm)

pores 50,000 to 100,000 µm

200 µm

pores ~50 µmSandstone reservoir Reef reservoir

Conventional Reservoirs: Scale Matters!(pore sizes and shape!)

Shale Gas Reservoirs: Scale Matters!(pore sizes and shape!)

1 µm

(Haynesville Shale)pores < 5 µm

Barnett Shalepores ~ 5 µm

10 µm

Permeability Terminology

Permeability (mD)

0.001 0.01 0.1 1.0 10.0

Extremely Tight

Very Tight Tight Low Moderate High

ConventionalTightTighter than Tight

US DOE Study (modified by B. Faraj, 2009)

Granite

Montney shale

Barnett Sidewalk Cement

0 % porosity Limestone

General oilfield rocks

0.0001

Good Shale

µD100nD

Microseismic Fracture Mapping

Meyerhofer, 2008

L&S C3H Microseismic Mapping Side View

55005600570058005900600061006200630064006500660067006800690070007100720073007400750076007700780079008000

-440

0-4

200

-400

0-3

800

-360

0-3

400

-320

0-3

000

-280

0-2

600

-240

0-2

200

-200

0-1

800

-160

0-1

400

-120

0-1

000

-800

-600

-400

-200 0

200

400

600

Distance Along Wellbore (ft)

Dept

h (ft

)

SE

Barnett Shale

NWlooking NE – perpendicular to well trajectory

Scale 2:1GR

Fracture Height: 290-360 ftDepth: 6800 to 7100 ft

Modified afterClawson, 2007

After the initial flow,fluids will remainin the shale reservoirFractures!

Barnett Shale Hydraulic fracturing height Is far away from aquifers

4,500 ft8,500 ft

Source: The American Oil & Gas Reporter, July 2010

Marcellus Shale Hydraulic fracturing height is far away from aquifers

8,500 ft

Source: The American Oil & Gas Reporter, July 2010

5,000 ft

Stress Tensor and Deformation

The presence and orientation of structural elements such as natural fractures and faults can be related directly to the stress tensor that gave rise to these features.

Source: David Campagna, 2007

If Pb = Pa then there will be no flow!

Darcy’s Flow Equation

If Pb > Pa then there will be flow!

Published 1856!

Q

Natural Hydraulic Fracturing(Doig Fm, Williston Lake, photo taken June, 09)

Calcite veins

Calcite fracture fill in conventional and shale:(evidence of paleofluid flow!)

Calcite fill

Calcite fill

Bowen BasinSandstone

Barnett Shale

Mineralized fractures of Montney Shale at Williston Lake, BC

Faraj and Brown, 2010

Calcite

AnkeriteIllite

2 cm

Mineralization in Permian coals from the Bowen Basin, Australia

Faraj, 1995

Conceptual Triassic water flow in the Bowen Basin, Australia

~ 300 km scale

Severalkm

scaleLarge hydraulic head is necessary

For flow

Faraj, 1995

Faraj, 1995

Regional mineralization event in the Bowen Basin, Australia brought about by regional paelofluid flow over a period of 30 million years!

K/Ar ages of illite cleat-fills from the Bowen Basin, Australia

0

200

400

600

800

1000210220230240250

Dep

th (

m)

K/Ar Age (Ma BP)

~20 MaYear event

~14 MaYear event

Faraj, 1995

• Slickwater fracking of shale is well-established technology. Itis the only way that we are able to extract natural gas andliquids from these ultra tight rocks.

• The bulk of the frac water remaining in the reservoir willstay there for millennia. As such, there is virtually nopossibility of the frac water contaminating fresh wateraquifers. Aquifers are also protected by casing and cement.

• Natural water flow in porous rocks and fractures takes a verylong time geologically (millions of years!) even with thepresence of large hydraulic heads.

Conclusions