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TP00-091 Advanced Wellbore Stability Model (WELLSTAB-PLUS) Dr. William C. Maurer.

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Presentation on theme: "TP00-091 Advanced Wellbore Stability Model (WELLSTAB-PLUS) Dr. William C. Maurer."— Presentation transcript:

1 TP00-091 Advanced Wellbore Stability Model (WELLSTAB-PLUS) Dr. William C. Maurer

2 TP00-092 DEA-139 Phase I DEA Sponsor: Marathon Duration: 2 Years Start Date: May 1, 2000 End Date: April 30, 2002 Participation Fee: $25,000/$35,000

3 TP00-093 Typical Occurrences of Wellbore Instability in Shales soft, swelling shale brittle-plastic shale brittle shale naturally fractured shale strong rock unit

4 TP00-094 Cost of Wellbore Instability Problems $500 million/year, before 1992 G.M. Bol, SPE 24975 1992 SPE European Petroleum Conference $92 million, BP 1997 $38 million, BP 1998 first quarter J. Kijowski, BP-Amoco Downhole Talk, Issue 80

5 TP00-095 Wellbore Stability Problems 8 8High Torque and Drag 8 8Bridging and Fill 8 8Stuck Pipe 8 8Directional Control Problem 8 8Slow Penetration Rates 8 8High Mud Costs 8 8Cementing Failures and High Cost 8 8Difficulty in Running and Interpreting Logs

6 TP00-096 Wellbore Failure Mechanisms MAURY et al., 1987

7 TP00-097 Effect of Borehole Pressures

8 TP00-098 PWPW PWPW  max  min High Support PressureLow Support Pressure Effect of Mud Support Pressure on Rock Yielding

9 TP00-099 Rock Failure

10 TP00-0910 Rock Failure Mechanisms PLASTIC BRITTLE

11 TP00-0911 Rock Yielding around Wellbores Laboratory Tests Rawlings et al, 1993 Isotropic StressesAnisotropic Stresses

12 TP00-0912 Change In Near-Wellbore Stresses Caused by Drilling  V (overburden)  Hmin  Hmax  Hmin  Hmax P w (hydrostatic) Before Drilling In-situ stress state After Drilling Lower stress within wellbore

13 TP00-0913 Stress Concentration around an Open Wellbore PwPw PoPo  Hmin  Hmax zz   rr zz rr  r

14 TP00-0914 Strength vs Stress Identifying the Onset of Rock Yielding Shear Stress Shear Strength r´r´ Effective Compressive Stress Stable Stress State q´q´ r´r´ Shear Stress Shear Strength r´r´ Effective Compressive Stress Unstable Stress State q´q´ r´r´ q´q´ Min Stress Max Stress q´q´

15 TP00-0915 Effect of Pore Fluid Saturation

16 TP00-0916 Effective Stresses Partioning of Total Stress between Mineral Grains and Pore Fluids PoPo    ´ =  -  P o  ´ - effective stress  - total stress P o - pore pressure  - Biot Coefficient (  1 for weak, porous rocks)

17 TP00-0917 Effective Rock Stress  z =  o - p f  o = Overburden Stress  z = Matrix Stress p f = Pore Fluid Pressure

18 TP00-0918 Effect of Near-Wellbore Pore Pressure Change on Effective Stresses Shear Stress No Yield Yield Shear Strength Effective Compressive Stress r´r´ ´´ r´r´ ´´ P o increase

19 TP00-0919

20 TP00-0920 MEI Wellbore Stability Model: (mechanical model, does not include chemical effects) 8Linear elastic model (BP) 8Linear elastic model (Halliburton) 8Elastoplastic Model (Exxon) 8Pressure Dependent Young’s Modulus Model(Elf)

21 TP00-0921 Mathematical Algorithms 8Dr Martin Chenervert(Un. Texas) 8Dr. Fersheed Mody(Baroid) 8Jay Simpson(OGS) 8Dr. Manohar Lal(Amoco) 8Dr. Ching Yew(Un. Texas)

22 TP00-0922 Stress State on Deviated Wellbore   zz rr zz   zz   

23 TP00-0923

24 TP00-0924 (BP) Linear Elastic Model

25 TP00-0925

26 TP00-0926 (Halliburton) Linear Elastic Model

27 TP00-0927

28 TP00-0928 (Exxon) Elastoplastic Model

29 TP00-0929

30 TP00-0930

31 TP00-0931

32 TP00-0932

33 TP00-0933 (Elf) Pressure Dependent Young’s Modulus

34 TP00-0934

35 TP00-0935 Shale Borehole Stability Tests Darley, 1969 DIESEL DISTILLED WATER

36 TP00-0936 Montmorillonite Swelling Pressure Powers, 1967 80,000 60,000 40,000 20,000 0 4th3rd2nd1st 5000 4000 3000 2000 1000 0 SWELLING PRESSURE, psi kg/cm 2 LAYERS OF CRYSTALLINE WATER

37 TP00-0937 Shale Water Adsorption Chenevert, 1970 0.100.200.300.400.500.600.700.800.901.00 5 4 3 2 1 0 WEIGHT % WATER WATER ACTIVITY - a W DESORPTION ADSORPTION

38 TP00-0938 Shale Swelling Tests Chenevert, 1970 TIME - HOURS LINEAR SWELLING - %.010.11.010 0.4 0.3 0.2 0.1 0 -0.1 1.00 0.91 0.88 0.84 0.75 0.25 Activity of Internal Phase

39 TP00-0939 Effect of K+Ions on Shale Swelling Baroid, 1975 Ca++ K+ Na+ Cs+ Na+ Ca++ Li+ K+ Rb+ Cs+ Na+ Mg++ Na+ 10A° Na+ - - - - - - - - - - - - - - -

40 TP00-0940 Effect of Swelling Strains on Wellbore Stability Soft, Swelling Shale Hole Closure due to Swelling Strains Most Likely Scenario for Soft Reactive Shales in Low Stress Settings

41 TP00-0941 North Sea Speeton Shale Specimen Exposed at Zero DP to Drilling Fluid Drilling Fluid: Ionic Water-Base (CaCl 2 Brine) Activity = 0.78

42 TP00-0942 North Sea Speeton Shale Specimen Exposed at Zero DP to Drilling Fluid Drilling Fluid: Oil-Base Emulsion (Oil with CaCl 2 Brine) Activity = 0.78

43 TP00-0943 North Sea Speeton Shale Specimen Exposed at Zero DP to Drilling Fluid Drilling Fluid: Non-Ionic Water-Base (Methyl Glucoside in Fresh Water) Activity = 0.78

44 TP00-0944 Principle Mechanisms Driving Flow of Water and Solute Into/Out of Shales Force Flow Fluid (water) Solute (ions) Hydraulic Gradient (P w  P o ) Chemical Potential Gradient (A mud  A shale ) Hydraulic Diffusion (Darcy´s Law) Advection Diffusion (Fick´s Law) Chemical Osmosis H2OH2O H2OH2O H2OH2O H2OH2O t1t1 t2t2 t3t3 P r Other Driving Forces: Electrical Potential Gradient Temperature Gradient H2OH2OH2OH2O H2OH2OH2OH2O H2OH2O H2OH2O H2OH2O + - - - + + + -

45 TP00-0945 Osmotic Flow of Water through Ideal Semi-Permeable Membrane Ideal Semipermeable Membrane - permeable to water - impermeable to dissolved molecules or ions Water flow direction High concentration of dissolved molecules or ions ( = Low A w ) Low concentration of dissolved molecules or ions ( = High A w )

46 TP00-0946 Effect of Osmotic Flow on Near-Wellbore Pore Pressure for a Balanced Bottomhole Pressure Condition Osmotic flow from mud to shale Pore Pressure Decrease Osmotic flow from shale to mud r a mud a shale PP r PWPW P fm PWPW P Pore Pressure Increase

47 TP00-0947 Water Acitivity in Salt Solution 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 05101520253035404550 Salt Concentration, % w/w Water Activity CaCl 2 NaCl KCl Water Activity in Brine at Room Temperature

48 TP00-0948 A Critical Issue: How Efficient Are Shale ²Membranes² ? Laboratory Measurements, Chenevert, 1998 Membrane Efficiency of Speeton Shale when Exposed to Various Water-based Fluids 00.10.20.30.40.50.60.70.80.91 de-ionized water 0.78 a w CaCl 2 0.4 a w CaCl 2 0.4 a w KCOOH 0.78 a w Glycerol Osmotic Membrane Efficiency

49 TP00-0949

50 TP00-0950 Limitations of Existing Models 8Do not handle shale hydration 8Very complex 8Input data not available 8Limited field verification 8Cannot field calibrate

51 TP00-0951 Mathematical Algorithms 8Dr Martin Chenervert(Un. Texas) 8Dr. Fersheed Mody(Baroid) 8Jay Simpson(OGS) 8Dr. Manohar Lal(Amoco) 8Dr. Ching Yew(Un. Texas)

52 TP00-0952 Mechanical/Chemical Property Input

53 TP00-0953 Help Information as Clicking Question Mark

54 TP00-0954 Pore Pressure Input/Predict

55 TP00-0955 Pore Pressure Prediction via Interval Transit Time Log Data

56 TP00-0956 In-Situ Stresses Input/Predict

57 TP00-0957 Correlation to Determine Horizontal Stresses

58 TP00-0958 Output Windows

59 TP00-0959 Safe Mud Weight vs Well Inclination

60 TP00-0960 Wellbore Stability Design (through Mud Weight-Inclination diagram)

61 TP00-0961 Safe Mud Weight Distribution by Azimuth

62 TP00-0962 Near-Wellbore Stresses Distribution

63 TP00-0963 Mohr Diagram

64 TP00-0964 Wellbore Stress Distribution

65 TP00-0965 Propagation of Swelling Pressure

66 TP00-0966 Effect of Concentration of Salt in Mud

67 TP00-0967 Effect of Membrane Efficiency

68 TP00-0968 Too large inclination Wellbore Stability Design (continued)

69 TP00-0969 Wellbore Stability Design (continued) Decrease inclination

70 TP00-0970 Wellbore Stability Design (continued) Too high mud weight

71 TP00-0971 Wellbore Stability Design (continued) Decrease mud weight

72 TP00-0972 Not enough salinity Wellbore Stability Design (continued)

73 TP00-0973 Increase salinity Wellbore Stability Design (continued)

74 TP00-0974 Wellbore Stability Design (through Mud Weight-Salinity diagram) Too low mud weight

75 TP00-0975 Wellbore Stability Design (continued) Increase mud weight

76 TP00-0976 Wellbore Stability Design (continued) Not enough salinity

77 TP00-0977 Increase salinity Wellbore Stability Design (continued)

78 TP00-0978 Wellbore Stability Design (continued) Low Value Membrane Efficiency

79 TP00-0979 Wellbore Stability Design (continued) High Value Membrane Efficiency

80 TP00-0980 Field Calibration

81 TP00-0981 Field Calibration (continued)

82 TP00-0982 Effect of Concentration of Salt in Mud

83 TP00-0983 Multi-Depth Data/Calculation Display

84 TP00-0984 Microsoft Word Report

85 TP00-0985 Microsoft PowerPoint Presentation

86 TP00-0986 Project Tasks 8Distribute Wellbore Stability Model (WELLSTAB) 8Develop Enhanced Model (WELLSTAB-PLUS) 8Add time dependent feature to model 8Hold workshops 8Conduct field verification tests 8Write technical reports

87 TP00-0987 Field Verification Goals 8Determine model accuracy 8Improve mathematical algorithms 8Field calibrate model 8Make models more user-friendly 8Convert wellbore stability from an art into a science

88 TP00-0988Benefits  Accelerate Technology Implementation  Affordable Software  Compound R & D Funds  Technical Interchange  Unbiased Information  Schools and Forums

89 TP00-0989

90 TP00-0990


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