natural fracture systems, hydraulic fracturing ... · natural fracture systems, hydraulic...
TRANSCRIPT
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