The Stability Of Fault Systems In The South Shore Of The. St. Lawrence Lowlands Of Québec Implications For Shale Gas Development

Transcription

1 The Stability Of Fault Systems In The South Shore Of The St. Lawrence Lowlands Of Québec Implications For Shale Gas Development John Brodylo, Jean-Yves Chatellier,Guillaume Matton & Michel Rheault Copyright 2011, Society of Petroleum Engineers 1

2 Outline Majority of Québec Utica shale gas exploration in south shore area of St. Lawrence Lowlands Natural and man-made earthquakes in south shore Tectonic domains, in-situ stress and fault styles Fracture stimulation containment within shale gas target Hydrofracturing Utica very unlikely to damage surface structures or shallow aquifers 2

3 Study Area Québec St. Lawrence Graben Québec City Ottawa-Bonnechere Graben Montréal St. Lawrence Lowlands Study Area 3

4 Earthquake A sudden release of energy in the earth's crust or upper mantle as a result of fault slip Destructive at magnitudes of 5 and above Minor earthquakes magnitude 2 to 5 Micro-earthquake is a very low intensity earthquake generally magnitude 2 or less 4

5 Earthquake Magnitude Comparison Perspective Limit of measurement Micro-earthquakes Imperceptible by man Minor-earthquakes rarely felt felt Light shaking Moderate damage Utica Shale Gas Frac Microseismic event 2 X Hiroshima Atomic Bomb 30 tons TNT Average Québec Earthquake Small Firecracker Impact of Brick Falling from 1 meter 1 kg TNT Stick of Dynamite Earthquake (Nuttli) Magnitude 5

6 Southern Québec Earthquakes Southern Québec Earthquakes Major Basement Faults Charlevoix Impact Crator Most Active Earthquake Regions of Southern Québec Québec City South Shore Shale Gas Exploration Areas Montréal US Border 6

7 Magnitude Comparison of Induced Seismic Events Waste Water inj., TX Manic 3 Dam, Qc Dams Various Global Microseismic event Utica Shale Fracs. Québec, Barnett Shale Fracs. TX. Mine Collapse, NY US Army. Co. Fluid Inj., 1962 Geothermal Various countries Event 7

8 Induced Seismic in Québec SM3 Reservoir Impoundment Induced - unspecified Blasting St. Lawrence Lowlands 8

9 Risk? The Earth Sciences Division of the U.S. Department of Energy s Lawrence Berkeley National Laboratory has studied induced seismicity relating to oil and gas activity and to date hydraulic fracturing has resulted in no known surface earthquakes felt by man Update: Blackpool U.K. 2.3 M earthquake attributed to fluid injection following hydraulic fracturing. Felt at surface because of shallow focal depth, very unusual circumstances, no damage to building or aquifers 9

10 Stratigraphy Queenston/Lorraine Sandstone, siltstone and shale Utica Shale Gas target Quartz/carbonate organic shale Potsdam Regional seismic reflector 10

11 3 Major Tectonic Domains South Shore Utica Shale Gas Fairway Disturbed Domain Convergent margin Sediments U Ordovician Lorraine and Queenstown Autochthonous Domain Passive margin Sediments Cambro-Ordovician Shale gas target Grenville Basement Granite & Metasediments Image Modified from: TRIANGLE ZONES IN ACCRETIONARY WEDGES: EXAMPLES FROM THE QUÉBEC APPALACHIANS AND PHYSICAL MODELING Konstantinovskaya et al, AAPG Poster,

12 Borehole Breakouts, Fractures and In-situ Stresses Borehole Breakouts, Fractures and In-situ Stresses Azimuth of Borehole breakouts N s HMAX Bore hole break outs in the direction of Shmin = 315 degrees Drilling induced fractures in direction of SHmax = 45 degrees Present day in-situ Stress borehole Breakout SHmax s hmin Azimuth of Natural, Drilling Induced, and Hydraulic Fractures principal stresses, s 1 > s 3 Drill Induced Fracture Shmin 12

13 Autochthonous Domain Tensional passive margin Normal faulting Result of opening of the Iapetus Sea Hydraulic fractures propagate vertically million years old Fractures in direction of SHmax = 38 degrees Old Healed Fractures From Rift Phase Strike Direction of Fractures s v = s 1 s1 = s v s2 = shmax In Situ Stresses s3 = shmin sv>shmax>shmin s HMAX = s 2 s hmin = s 3 13

14 s3 In Situ = s v Stresses s1 = shmax Disturbed Domain Compressional thrusting Hydraulic fractures in direction of SHmax = 325 degrees Open Fractures From Compressional Phase s2 = shmin s v = s 3 Strike Direction of Fractures shmax>shmin>sv s HMAX = s 1 s hmin = s 2 14

15 Wrenching Bore hole break outs in direction of Shmin = 315 degrees Drilling induced fractures in direction of SHmax = 53 degrees In Situ Stresses s2 = s v Present day in-situ Stress Breakout Drill Induced Fracture s v = s 2 SHmax Shmin s3 = shmin s1 = shmax shmax>sv>shmin s HMAX = s 1 s hmin = s 3 15

16 Fault Slip sn sn Coulomb Stress = tb + m(sn + P) tb = shear stress m = coefficient of friction P = pore pressure sn = normal stress 16

17 Stress Affects on Completions Utica Thrust Wrench Regime Hydraulic Pre-completion fracturing stress state More More horizontal vertical fracturing shmax > > sv shmin > shmin > sv Pore Pressure sv shmax shmin MPa 17

18 Hydraulic Fracture Height Containment GR Hi Y Low Contrasts in fracture toughness form barriers Lorraine High Young s modulus (Y)=Brittle=low toughness Schematic Thrust Low Young s modulus=ductile=high toughness Utica Shale Gas Target Ductile Brittle Ductile Brittle Frac target a brittle zone with low toughness between ductile zones High toughness ductile zones are barriers Trenton Thrust fault are barriers 18

19 Aquifer Micro-seismic Horizontal Shale Gas Well with Micro-seismic Events Utica Microseismic events confined to +/- 50 m of wellbore Minimal vertical height growth Formations above and below zone likely acting as barriers No communication or propagation to shallow aquifers. 19

20 Surface Lineament Analysis South Shore Shale Gas Exploration Area (Study Area) Matton and Rheault 2011 There are a total of 14 minor > M2.5 earthquakes recorded in the South Shore Shale Gas exploration Area 20

21 Inset Map Québec City Cap-Rouge Earthquake Neuville Fault Trace at Potsdam Level Seismic Line St. Lawrence Lowlands Shale Gas Fairway Focal Depth kilometers Earthquake magnitude Earthquake < M2.5 21

22 22 Summary South shore shale gas exploration region is in stress relaxed state and less prone to fault reactivation No correspondance between natural and man-made earthquakes and shallow faults in study area In- situ stress, rock toughness, and thrust faults all act as barriers to vertical propagation of fractures and faults Fracture stimulations are contained within shale gas target Hydrofracturing is very unlikely to cause damage to shallow aquifers or surface structures

23 Acknowledgements Michael Binnion Questerre Energy Corporation Marianne Molgat Talisman Energy Inc Geoff Rait, - IEX Structural Geologist, Talisman Energy Scott McLellan, - IEX Geophysicist, Talisman Energy Heather Davey Exploration Specialist Geology

24 Questions? 23