Hydro-mechanical behaviour of GPK4 during the hydraulic stimulation - PowerPoint PPT Presentation

Hydro-mechanical behaviour of GPK4 during the hydraulic stimulation tests – Influence of the stress field X. Rachez, S. Gentier, A. Blaisonneau BRGM BRGM/Geo-Energy unit June 29 - 30, 2006

Objectives of our modeling work > Understand which physical mechanisms are involved in the hydraulic stimulation of the well in crystalline rocks > Extract the main parameters playing a role in the hydraulic stimulation � Focus hereafter on the influence of the stress field on the HM behavior of GPK4 during the stimulation test ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 2 June 29 - 30, 2006

What it could happen during the hydraulic stimulation of a well (if we exclude thermal effect...) σ V σ V σ H σ h σ H σ h But in general, the granite is already fractured In continuous homogeneous and isotropic medium ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 3 June 29 - 30, 2006

More in details... σ V U n Evolution of the hydraulic aperture is linked to the normal displacement (Un) and the tangential displacement (Us) σ H U s Well initial state Increase of the aperture T o opening : reduction of the normal component σ H T 1 U n release of the shearing U s T 2 σ h T f closure of the fracture ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 4 June 29 - 30, 2006

3DEC code > Based on the Distinct Element Method • allows finite displacements and rotations of discrete bodies, including complete detachment, • recognizes new contacts automatically, • � perfect for modelling discontinuous media, such as fractured rock masses > Fractured rock mass considered as a blocks assembly, cut by joints/discontinuities • blocks are rigid or deformable, • joints behaviour is governed by springs that takes into account the opening/closing of the fractures as well as their shearing. > Flow takes place only in the fractures (blocks are impermeable). Flow is laminar and obeys the cubic law � Hydro-mechanical coupling ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 5 June 29 - 30, 2006

Fractured rock mass > Take into account with 3DEC the selected fractures that cross the well • 9 fractures for GPK4 > Generate them in a parallelepiped volume 1000m > Take into account the well geometry (here, centred and vertical) GPK4 400m 400m GPK4 ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 6 June 29 - 30, 2006

Hydraulic stimulation > Stimulation test • Apply an overpressure in the well. Value taken from the real stimulation test conducted in the GPK4 well. • FISH HM coupling procedure • Calculate the injected flowrate at the well, in each fracture • Stop the run when equilibrium between in and out flowrates is reached well Injection under P = P i + ∆ P ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 7 June 29 - 30, 2006

Boundary and Initial HM conditions > Boundary conditions σ v x=z=0 North σ h > Pressures East • Hydrostatic field σ H > Stress field • From in situ measurements σ x 1) either x = z = 0 Klee and Rummel, 1993, σ z 2) or P i = ρ g y Cornet et al. (to be published) Y (Vertical Upwards) y = 0 Z (North) X (East) ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 8 June 29 - 30, 2006

Stress field > Klee and Rummel, 1993 σ h = 15.8[MPa] + 0.0149[MPa/m] (depth[m]-1458) σ H = 23.7[MPa] + 0.0336[MPa/m] (depth[m]-1458) σ v = 33.8[MPa] + 0.0255[MPa/m] (depth[m]-1377) σ H oriented N170°E ± 15° > Cornet et al. (2006, to be published) σ h = (0.54 +/- 0.02)* sv σ H = (0.95 +/- 0.05)* sv σ v = 1377*0.024[MPa] + 0.0255[MPa/m] (depth[m]-1377) σ H oriented N175°E +/- 6° ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 9 June 29 - 30, 2006

Stress regime ? Stress (MPa) 0 50 100 150 0 1. Klee and Rummel (1993) Sh(1) σ H : N170° SH(1) 500 SV(1) 2. Cornet et al. (2006?) Phyd σ H : N 175° 1000 σ V SV(2) SH(2) 1500 Sh(2) Shmin(2) Shmax(2) 2000 Depth (m) Normal fault 2500 stress regime ? 3000 3500 4000 σ H 4500 Strike slip regime σ h P hyd 5000 ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 10 June 29 - 30, 2006

GPK4 - Influence in terms of flow in well P [MPa] 20 15 Overpressure 10 In-situ 5 Stress Field n°1 Stress Field n°2 0 0 10 20 30 40 50 60 70 Total well flowrate [l/s] > Very little difference ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 11 June 29 - 30, 2006

GPK4 - Influence in terms of flow at fractures 50 50 18 (total flow in well) [%] (total flow in well) [%] (total flow in well) [%] SF#1 - F3 16 (flow in fract#1) vs SF#1 - F1 (flow in fract#2) vs (flow in fract#3) vs SF#1 - F2 40 40 14 SF#2 - F3 SF#2 - F1 SF#2 - F2 12 30 30 10 8 20 20 6 4 10 10 2 0 0 0 3.00 6.00 9.00 13.75 15.50 18.30 3.00 6.00 9.00 13.75 15.50 18.30 3.00 6.00 9.00 13.75 15.50 18.30 Overpressure stages [MPa] Overpressure stages [MPa] Overpressure stages [MPa] SF#1 - F4 SF#2 - F4 18 18 18 (total flow in well) [%] (total flow in well) [%] (total flow in well) [%] 16 16 16 (flow in fract#4) vs (flow in fract#5) vs SF#1 - F5 (flow in fract#6) vs SF#1 - F6 14 14 14 SF#2 - F5 SF#2 - F6 12 12 12 10 10 10 8 8 8 6 6 6 4 4 4 2 2 2 0 0 0 3.00 6.00 9.00 13.75 15.50 18.30 3.00 6.00 9.00 13.75 15.50 18.30 3.00 6.00 9.00 13.75 15.50 18.30 Overpressure stages [MPa] Overpressure stages [MPa] Overpressure stages [MPa] 18 18 18 (total flow in well) [%] (total flow in well) [%] (total flow in well) [%] (flow in fract#7) vs 16 (flow in fract#8) vs 16 SF#1 - F8 (flow in fract#9) vs 16 SF#1 - F9 SF#1 - F7 14 14 14 SF#2 - F8 SF#2 - F9 SF#2 - F7 12 12 12 10 10 10 8 8 8 6 6 6 4 4 4 2 2 2 0 0 0 3.00 6.00 9.00 13.75 15.50 18.30 3.00 6.00 9.00 13.75 15.50 18.30 3.00 6.00 9.00 13.75 15.50 18.30 Overpressure stages [MPa] Overpressure stages [MPa] Overpressure stages [MPa] > Very little difference ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 12 June 29 - 30, 2006

GPK4 - Influence in terms of shear disp. ∆ P = 18,3 MPa Tangential Normal fault stress displacements Tangential regime more spread displacements more concentrated in some fractures Strike slip regime Us max ∼ 6 cm x 2 Us max ∼ 13 cm ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 13 June 29 - 30, 2006

GPK4 – Influence in terms of F1 shear disp. F4 F4 well well ∆ P = 18.3 MPa Us max = 7-9 cm Us max = 3-5 cm > Max shear along intersection with F4, not close to the well, greater with strike slip regime ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 14 June 29 - 30, 2006

GPK4 – Influence in terms of F2 shear disp. F3 F4 F3 F4 well well ∆ P = 18.3 MPa Us max = 9-11 cm Us max = 5-7 cm > Max shear along intersections with F3 & F4, greater with strike slip regime ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 15 June 29 - 30, 2006

GPK4 – Influence in terms of F4 shear disp. F1 F2 F3 F2 F3 F1 well well ∆ P = 18.3 MPa Us max = 13 cm Us max = 5-7 cm > Max shear along intersections with F1 & F3, greater with strike slip regime ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 16 June 29 - 30, 2006

GPK4 – Influence in terms of block disp. ∆ P = 18.3 MPa > Blocks instability with strike slip regime ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 17 June 29 - 30, 2006

GPK4 – best fit of ∆ P-Q stimulation curve Initial Resid. Max. Friction Fracture aperture aperture aperture angle ϕ N ° a 0 a res a max ( ° ) [mm] [mm] [mm] Previous F1 to F9 5.0 2.5 150 45 runs F1 0.5 0.25 15 45 F2 5.0 2.50 150 45 F3 5.0 2.50 150 40 F4 2.5 1.25 75 40 Best fit F5 5.0 2.50 150 45 F6 5.0 2.50 150 40 F7 5.0 2.50 150 40 F8 5.0 2.50 150 40 F9 0.5 0.25 15 45 ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 18 June 29 - 30, 2006

GPK4 – best fit – influence in terms of flow 20 Overpressure ∆ P [MPa] 18 16 14 12 10 8 6 In-situ 4 Stress Field n°1 2 Stress Field n°2 0 0 10 20 30 40 50 Total well flowrate [l/s] > Very little difference ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 19 June 29 - 30, 2006

GPK4 – Best Fit – F1 shear disp. well well ∆ P = 18.3 MPa Us max = 1-3 cm Us max = 1-3 cm > Limited and comparable F1 max shear, around the well ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 20 June 29 - 30, 2006

GPK4 – Best fit – F2 shear disp. F3 F4 F3 F4 well well ∆ P = 18.3 MPa Us max = 7-9 cm Us max = 5-7 cm > F2 max shear around the well, and along intersections with F3 & F4 ENGINE Meeting, “Stimulation of reservoir and induced microseismicity” > 21 June 29 - 30, 2006