Cement-sheath integrity Towards efficient geomechanical simulation

Transcription

1 Cement-sheath integrity Towards efficient geomechanical simulation By: Axel-Pierre Bois, CurisTec North American Wellbore Integrity Workshop Denver, Co, USA 16 October 2013 SARL CurisTec 1bis allée de la Combe LISSIEU apbois@curistec.com

2 Cement-sheath life cycle Liquid Porous solid Start up Time 50 years+ When Mixing Placement Hydration Short term Long term Avoid Pumpability & stability issues Loss of integrity Mud displacement Losses/gains Loss of integrity Gas migration Loss of integrity Mechanical damage Loss of integrity Mechanical damage Chemical degradation Adjust Cement design Density/Rheology Compatibility Hydraulics TCHM properties Initial stresses THM properties TCHM properties Check Lab testing QA/QC Simulation Monitoring Simulation Logging Monitoring Simulation Logging Monitoring Simulation Logging Monitoring Constraints THM: Thermo-hydro-mechanics Geology, Regulation, Wellbore, & Operations TCHM: Thermo-chemo-hydro-mechanics

3 The problematic of cement-sheath modeling Many applications Artic Mature CO2 injector Steam injection Shallow gas Sweet gas Deep water HP / HT Many cement systems Etc Self-healing Foam Gastight Stiff Resilient Class G + S Class G Many software Etc Software 07 Software 06 Software 05 Software 04 Software 03 Software 02 Software 01 3

4 Cement-sheath mechanical integrity: Concepts Compressive damage + 30 MPa + 20 MPa + 10 MPa 0 MPa - 3 MPa Tensile damage 4

5 Cement-sheath mechanical integrity: Concepts Compressive damage + 30 MPa + 20 MPa + 10 MPa 0 MPa - 3 MPa Tensile damage 5

6 Cement-sheath mechanical integrity: Concepts Compressive damage + 30 MPa + 20 MPa + 10 MPa 0 MPa - 3 MPa Tensile damage 6

7 Experimental facts: Elasto-plastic behavior Plastic Elastic 7

8 Axial stress (MPa) Axial stress (MPa) Experimental fact: Pore collapse at young age Uniaxial-strain stress paths Stress-strain curves isoth5 isoth isoth5 isoth Time (h) Axial strain (µm/m) 8

9 Confining Pressure variation (MPa) Experimental fact: Pore collapse at older age 60 Pore collapse threshold D-2 D Volumetric strain (µm/m) 9

10 Experimental fact: Failure envelop 10

11 Loss of cement integrity: Cement shear-damage Heating Increase in mud pressure Stiff formation τ Shear failure Tensile failure σ' r r Decrease in hoop stress Increase in radial stress 11

12 Loss of cement integrity: Cement tensile-damage Heating Increase in mud pressure Soft formation τ Shear failure Tensile failure σ' r r Decrease in hoop stress Increase in radial stress 12

13 Loss of cement integrity: Debonding Shrinkage Cooling Decrease in mud pressure 13

14 Loss of cement integrity: Pore collapse 5 Inner casing Cement sheath 7 Outer casing Flanges 1. Cure cement under T = 120 F Pi = 1,000 psi & Pa = 1,000 psi Jackson & Murphey, 1993 Lab experiment to simulate the creation of micro-annuli under compressive loadings 2. Decrease Pa to 0 psi & measure k, ε 3. Increase Pi to 2,000 psi & record k, ε 4. Decrease Pi to 1,000 psi & record k, ε 5. Repeat 3 & 4, increasing Pi by step till 12,000 psi 14

15 Tubing internal pressure [psi] Loss of cement integrity: Pore collapse Gas leak as a function of time and pressure Flow detected Flow stopped Time from beginning of experiment [min] No increase in permeability at the maximum tubing pressure All cement systems withstood the 6,000 psi pressure cycle Gas started to flow as the tubing pressure was decreased from 8,000 psi (10,000 psi) to 1,000 psi, and continued until tubing is repressurized to 1,900 psi (2,800 psi) 15

16 Loss of cement integrity: Pore collapse CEMENT INNER CASING OUTER CASING 16

17 Inner casing Cement Outer casing Loss of cement integrity: Pore collapse Start of Micro-annuli Micro-annuli = 29 µm P in = 0 psi P in = 10,000 psi P in = 3,7000 psi P in = 1,000 psi 17

18 Cement hydration: Initial state of stress 5 Inner casing Cement sheath 7 Outer casing Flanges 1. Cure cement under T = 120 F Pi = 10,000 psi & Pa = 1,000 psi Jackson & Murphey, 1993 Lab experiment to simulate the creation of micro-annuli under a decrease of tubular pressure 2. Decrease Pa to 0 psi & measure k, ε 3. Decrease Pi by steps of 2,000 psi to 0 psi & record k, ε 4. If flow, increase Pi till flow stops 18

19 Tubing internal pressure [psi] Cement hydration: Initial state of stress Gas leak as a function of time and pressure Flow detected Flow stopped Time from beginning of experiment [min] Little flow untill the tubing pressure was decreased below 3,000 psi Gas started to flow as the tubing pressure was decreased to 3,000 psi, and continued until tubing is repressurized to 4,000 psi (1st cycle) Gas started to flow as the tubing pressure was decreased to 4,000 psi, and continued until tubing is repressurized to 4,000 psi (2nd cycle) 19

20 Cement hydration: Initial state of stress Pi 0 MPa Pi 7 MPa Pi 0 MPa Pi 7 MPa CEMENT GAS DEBOND LIQUID 20

21 Hydration degree Cement hydration: Simulation Measured Computed Time [h] Step 1. Compute hydration degree vs. time 21 C T t = div( k gradt ) + q dx dx dt = A(x) exp æ -E ö a ç è RT ø dt

22 UCS [MPa] Modolus [MPa] Cement hydration: Simulation at 40 C at 20 C Ku Kd measured Kd Time [h] Time [h] Step 2. Compute cement properties vs. time Measurement Homogenization 22

23 Shrinkage [%] Cement hydration: Mechanical effects Increase in grain volume Decrease in water volume psi Decrease in pore pressure psi 1000 psi Decrease in bulk volume psi 100 psi psi Need for a chemothermoporomechanical model Computed Time [h] 23

24 Heat transfer: Simulation Fluid flow Heat conduction Heat convection Heat radiation A least three cases must be distinguished 1. Temperature is known at the casing 2. Temperature is known in the circulating mud 3. Temperature is known in a production/injection tubing 24

25 Heat transfer: Simulation Temperature is known in a production/injection tubing 25

26 Functionalities Loadings 1. Cement hydration 2. Mud pressure 3. Temperature 4. Pore-pressure 5. Formation stress/strain 6. Well shift 7. Dynamic loading Mechanisms 1. Elasticity 2. Shear failure 3. Tensile failure 4. Pore collapse 5. Creep 6. Chemical reaction: CO 2, H 2 S 7. Corrosion 26 What is forgotten?

27 Thank you for your attention 27