Reservoir Rock Properties COPYRIGHT. Sources and Seals Porosity and Permeability. This section will cover the following learning objectives:

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1 Learning Objectives Reservoir Rock Properties Core Sources and Seals Porosity and Permeability This section will cover the following learning objectives: Explain why petroleum fluids are found in underground reservoirs Describe the storage properties of rocks Describe the transport properties of rocks Describe the different kinds of rocks 1

2 Oil Factories Seal Structural Traps Reservoir Rock Sealing Rock Reservoir Source Anticline 2

3 Stratigraphic Traps Sealing Rock Reservoir Seal Reservoir Reservoir Rock Pinchout Source 3

4 Reservoir Rock Is Not All Solid Porosity Fluid-filled voids Phi ϕ 0 ϕ 1 4

5 Some Voids Are Connected Effective Porosity Some Voids Are Connected Total Porosity 5

6 Some Voids Are Connected Pore Connected Pores Allow Fluid Flow 6

7 Permeability 0 Pores Can Contain Multiple Fluids 7

8 Saturation Oil Saturation ;0 1 Water Saturation Gas Saturation Multiple Fluids Slow Things Down 1 ;0 1 ;0 1 8

9 Permeabilities Independent of Fluid Permeabilities Without Dimensions 9

10 Rocks Come in Three Flavors Rocks Igneous Rocks Come in Three Flavors Rocks Metamorphic Sedimentary These rocks are more likely to have porosity and permeability values large enough to accommodate commercial production Metamorphic Sedimentary Igneous 10

11 Sedimentary Rocks Can Be Mixtures Sandstone Rock fragments from other rocks 11

12 Limestone/Dolomite Remains of plants and animals Shale Dominated by clay minerals 12

13 Coal Dominated by carbon Summary Sources, Reservoir and Seal Porosity Effective Total Permeability Absolute Effective Relative Basic Lithology Types of Rock Sandstones, Limestones and Shale 13

14 Learning Objectives This section has covered the following learning objectives: Explain why petroleum fluids are found in underground reservoirs Describe the storage properties of rocks Describe the transport properties of rocks Describe the different kinds of rocks 14

15 Learning Objectives Reservoir Rock Properties Core Compressibility This section will cover the following learning objectives: Describe how rocks change shape under external stress Describe how rocks change shape under internal pressure Explain how stress and pressure affect rock permeability 15

16 Squeezing Rocks Compressibility Bulk compressibility 1 Bulk volume Change in pressure 16

17 Uniaxial Compressibility Hydrostatic Compressibility 17

18 Shrinkage versus Expansion Poisson s Ratio Shrinkage Expansion 18

19 Uniaxial Compressibility Hydrostatic versus Uniaxial Compressibility Pore Volume Compressibility x 10-6, 1/psi [x 10-4, 1/MPa] [43.5] [36.3] [29.0] [21.8] [14.5] [7.2] Compressibility vs Net Confining Stress (CMS-300) [6.9] [13.8] [20.7] [27.6] [34.5] [41.4] Net Confining Stress, psi [MPa] 19

20 Overburden Overburden Overburden 20

21 Uniaxial Compression Uniaxial versus Hydrostatic Compression?? 21

22 Uniaxial versus Hydrostatic Compression?? Lateral Confining Pressures?? 22

23 Porosity Homogeneous, isotropic material Porosity 23

24 Pore Compressibility Fluid Pressure 24

25 Pore Compressibility Pore Volume Compressibility Pore volume compressibility 1 Pore volume Change in pore pressure 25

26 Bulk Volume Compressibility Bulk compressibility Pressure versus Stress 1 Bulk volume Change in overburden pressure 26

27 Bulk versus Pore Volume Compressibility Pressure versus Stress

28 Net Confining Stress Effective stress Effect on Permeability External stress Biot s constant Pore pressure 28

29 Summary Bulk Volume Compressibility Uniaxial Hydrostatic Poisson s ratio Pore Volume Compressibility Net Effective Stress Effect on Permeability Learning Objectives This section has covered the following learning objectives: Describe how rocks change shape under external stress Describe how rocks change shape under internal pressure Explain how stress and pressure affect rock permeability 29

30 Learning Objectives Reservoir Rock Properties Core Heterogeneity and Anisotropy This section will cover the following learning objectives: Define the terms "heterogeneity" and "anisotropy" Describe how porosity and permeability are upscaled Describe how rock texture affects porosity and permeability Explain the differences between various definitions of reservoir thickness 30

31 Heterogeneity Upscaling Porosity #1 Porosity #2 Porosity #3 31

32 Homogeneity Porosity #1 Averaging Porosity #2 Porosity #3 ϕ 1 h 1 ϕ 1 h 2 ϕ 1 h 3 32

33 Upscaling Upscaling Permeability ϕ average h total k average h total 33

34 Parallel Flow Perpendicular Flow 34

35 Anisotropy Random Flow k h???? k v.. 35

36 Rock Texture Texture 36

37 Grain Size Distribution Cementing 37

38 Rocks Come in Layers Cap Rock Reservoir Thickness 38

39 Top and Base Top and Base Cap Rock Reservoir Top Reservoir Reservoir Base Cap Rock Reservoir Gross thickness 39

40 Gross vs. Net Net = Gross on this side Net < Gross on this side Pay vs. Net Pay Reservoir Reservoir Pay Reservoir Reservoir Non- Reservoir Non- Reservoir Not Pay Oil-Water Contact Also Not Pay 40

41 Dip 45 True Stratigraphic Thickness 41

42 Observed Well Thickness Well Deviation 42

43 True Vertical Thickness Summary Heterogeneity Weighted Averages Upscaling Anisotropy Texture Gross vs. Net vs. Pay True Vertical vs. True Stratigraphic Dip Deviation 43

44 Learning Objectives This section has covered the following learning objectives: Define the terms "heterogeneity" and "anisotropy" Describe how porosity and permeability are upscaled Describe how rock texture affects porosity and permeability Explain the differences between various definitions of reservoir thickness 44

45 Learning Objectives Reservoir Rock Properties Core Maps and Geostatistics This section will cover the following learning objective: Describe several techniques for interpolating rock property data between wells 45

46 Geostatistics Basic Geostatistics Well #1 Well #2 Reservoir 46

47 Nearest Neighbor Step Changes Property Value 47

48 Linear Interpolation Property Value Inverse Distance Property Value ϕ 1 ϕ 2 ϕ a d 1 d

49 Multiple Dimensions Variable Exponent Porosity Value ϕ 1 ϕ Well Cross Section Interpolated values with n = 1 Interpolation of properties between wells Well #1 Well #2 49

50 Variable Exponent Porosity Value ϕ 1 ϕ 2 Generalization Well Cross Section Interpolated values with n = 2 Well #1 Well # Interpolation of properties between wells 50

51 Kriging [ ] Data Holes D, ft [m] 51

52 Data Transforms Permeability - Millidarcies III Crystal Size > 0.06 mm [0.002 in.] II/III Crystal Size mm [ in.] II Crystal Size < 0.02 mm [ in.] Correlations: log Permeability - Millidarcies III Crystal Size > 0.06 mm [0.002 in.] II/III Crystal Size mm [ in.] II Crystal Size < 0.02 mm [ in.] Porosity [%] Porosity [%] 52

53 Classification Co-Kriging 53

54 Digital Maps Earth Models 54

55 Manual Maps 2100 ft [640 m] Contouring 55

56 Contour Maps 2100 ft [640 m] Step 1: Post the Wells North East 56

57 Step 2: Post the Values Decide on Intervals 45 Next you need to decide which values you are going to contour Conventionally, we choose equally spaced values over a range that will cover all the values at the wells shown on the map

58 Step 3: Start at the Top Step 4: Next Contour

59 Step 5: Third Contour Step 6: Fourth Contour

60 Step 7: Last Contour Step 8: Dressing Contours

61 Step 8: Smoothing Algorithms Summary Basic Geostatistics Nearest Neighbor Inverse Distance Kriging Data Transforms Co-Kriging Contouring

62 Learning Objectives This section has covered the following learning objective: Describe several techniques for interpolating rock property data between wells 62

63 Learning Objectives Reservoir Rock Properties Core Log and Core Analysis This section will cover the following learning objectives: Describe how log analysis is used to calculate reservoir engineering rock properties Describe how core analysis is used to measure reservoir engineering rock properties 63

64 Log Analysis Related PetroAcademy Skill Modules Petrophysical Data and Open Hole Logging Operations Core Mud Logging, Coring and Cased Hole Logging Operations Core Gamma Ray and Spontaneous Potential Logging Core Porosity Logging (Density, Neutron and Sonic) Core Formation Testing Core Resistivity Logging Tools and Interpretation Core Petrophysical Evaluation Core Core Analysis Core Knowledge Special Petrophysical Tools: NMR and Image Logs Core 64

65 Running Logs on Wireline Displaying Log Data Graphically 65

66 Spontaneous Potential Log Spontaneous Potential Depth Spontaneous Potential Log Shale Shale Depth Spontaneous Potential Wet Sand Oil Sand 66

67 Resistivity Log Resistivity Depth Resistivity Log Shale Depth Resistivity Wet Sand Oil Sand Shale 67

68 Spontaneous Potential Log and Resistivity Log Spontaneous Potential Resistivity Shale Wet Sand Depth Shale Oil Sand Shale Displaying Log Data Graphically Depth 68

69 Calculating Properties from Log Data R o Archie s Law Equation R t 69

70 Archie s Law Assumptions S w = water saturation in lower sand [vol/vol] R o = resistivity in lower sand if S w =1 [Ohm-m] [Ohm-ft] R t = actual resisitivity in lower sand [Ohm-m] [Ohm-ft] Humble Formula R o = resistivity in lower sand if S w =1 [Ohm-m] [Ohm-ft] R w = in-situ water resistivity [Ohm-m] [Ohm-ft] ϕ = porosity [vol/vol] 70

71 Density Log Response 1 ρ b = density log reading [g/cc] [lb/in. 3 ] ρ ma = rock grain density [g/cc] [lb/in. 3 ] ρ fl = in-situ fluid density [g/cc] [lb/in. 3 ] ϕ = porosity [vol/vol] Fluid Density 1 ρ oil = in-situ oil density [g/cc] [lb/in. 3 ] ρ water = in-situ water density [g/cc] [lb/in. 3 ] S w = water saturation in lower sand [vol/vol] 71

72 Simultaneous Solution Archie s Law Humble Formula Density Log Response Fluid Density 1 1 Measured Data Data We Want To Know Auxiliary Data Cased Hole Logs 72

73 Logging While Drilling (LWD) Core Analysis 73

74 Measurement Scale 6 in. [152 mm] Before or After in. [25-38 mm] Wireline Percussion Sidewall Coring Threaded Joint Hard-Formation Coring Bullet Soft-Formation Coring Bullet 6 in. [152 mm] Coring Bit Up to 2 ft [0.6 m] Explosive Coring Bullet After Firing 74

75 Dean-Stark Retort 75

76 Outside Dimensions 4 mm [0.16 in.] Inside Dimensions 100 psi [0.7 MPa] 76

77 Calculating Porosities and Saturations ϕ ϕ porosity [ ] sample bulk volume [cm 3 ] [in. 3 ] sample grain volume [cm 3 ] [in. 3 ] sample water volume [cm 3 ] [in. 3 ] sample water saturation [ ] Permeameters 77

78 Klinkenberg Effects Calculating Permeabilities q = test fluid injection rate [cc/sec] k = observed permeability [D] A = core cross sectional area [cm 2 ] [in. 2 ] perpendicular to flow direction x = core length [cm] [in.] parallel to flow direction p = pressure drop [atm] along core length μ = test fluid viscosity [cp] 78

79 Summary Basic Log Analysis Qualitative Interpretation Quantitative Interpretation Basic Core Analysis Preparing the Core Measuring Porosity Measuring Permeability Learning Objectives This section has covered the following learning objectives: Describe how log analysis is used to calculate reservoir engineering rock properties Describe how core analysis is used to measure reservoir engineering rock properties 79

80 This is Reservoir Engineering Core Reservoir Rock Properties Core Reservoir Rock Properties Fundamentals Reservoir Fluid Core Reservoir Fluid Fundamentals Reservoir Flow Properties Core Reservoir Flow Properties Fundamentals Reservoir Fluid Displacement Core Reservoir Fluid Displacement Fundamentals PetroAcademy TM Applied Reservoir Engineering Skill Modules Properties Analysis Management Reservoir Material Balance Core Reservoir Material Balance Fundamentals Decline Curve Analysis and Empirical Approaches Core Decline Curve Analysis and Empirical Approaches Fundamentals Pressure Transient Analysis Core Rate Transient Analysis Core Enhanced Oil Recovery Core Enhanced Oil Recovery Fundamentals Reservoir Simulation Core Reserves and Resources Core Reservoir Surveillance Core Reservoir Surveillance Fundamentals Reservoir Management Core Reservoir Management Fundamentals 80