1. Comparative Analysis of Performance of Horizontal and Hydraulically Fractured Wells in a Tight Gas Reservoir using Numerical Simulations 1 December 9, 2009

3. Haris Ali Soomro (PE-027)

4. M. OwaisNaseem (PE-025)

5. Muneeb Ahmad (PE-006)

6. Zeeshan-ul-Haq (PE-015)02

7. Contents

8. Objective To compare the Performance of Horizontal and Vertical Hydraulically Fractured Wells in a Tight Gas Reservoir 04

10. The question arises “Which is the suitable method to develop a particular Tight Gas Reservoir?”

11. Our project can serve as a prototype which can be scaled up for the real data.05

12. TIGHT GAS RESERVOIRS A Brief Introduction AsifAzhar (PE-033)

13. Introduction to Tight Gas Reservoirs Tight gas is the term commonly used to refer low permeability reservoirs that produce mainly dry natural gas. ‘Tight Gas Sands’ by Stephen A. Holditch, SPE Texas A &M U 07

14. Definition of Tight Gas Reservoir “ . . . The best definition of tight gas reservoir is a reservoir that cannot be produced at economic flow rates nor recover economic volumes of natural gas unless the well is stimulated by a large hydraulic fracture treatment or produced by the use of a horizontal wellbore or multilateral wellbores . . . ” ‘Tight Gas Sands’ by Stephen A. Holditch, SPE Texas A &M U 08

16. The original sedimentary fabric have been subsequently reduced in porosity by post depositional diagenesis to unacceptably low amounts.‘What is considered a Tight Gas Reservoir’ by Ravi Mishra 09

18. Sembar Sands and Siltstones

19. Sui Upper Limestone

20. HabibRahi Limestone

21. Pirkoh Limestone‘Untapping Tight Gas Reservoirs’ by Muhammad AjazSarwar & AbdurRaufMirza, OGDCL 10

22. Possible Candidates for TGR in Pakistan ‘Scope of Tight Gas Reservoir in Pakistan’ by SalahHaikal, Eni Pakistan Ltd 11

23. TGR Completion Techniques Fractured Vertical Wells Multi-lateral Wells Horizontal Wells 12

25. Obtaining Infinite Conductivity Fractures

26. More effective in reservoirs having permeability less than 10md‘Horizontal Well Technology’ by Sada D. Joshi 13

28. Only one pay zone can be drained per horizontal well

29. Costs 1.3-4 times more than a Vertical well

30. In TGR, Horizontal wells can improve drainage area per well and reduce the number of wells

31. In some cases of TGR horizontal fractured wells may work better.‘Horizontal Well Technology’ by Sada D. Joshi 14

32. RESERVOIR SIMULATION A Brief Introduction Haris Ali Soomro (PE-027)

34. Gordon Adamson in his article “Simulation Throughout the Life of a Reservoir” writes:“Simulation is one of the most powerful tools for guiding reservoir management decisions. From planning early production wells and designing surface facilities to diagnosing problems with enhanced recovery techniques, reservoir simulator allow engineers to predict and visualize fluid flow more efficiently than ever before.” www.wikipedia.org 16

36. Field Scale Simulation

37. Window Study17

38. Simulation Approaches Single Well Simulation Field Scale Simulation 18

40. Radial or Cylindrical Geometry

41. Elliptical Geometry

42. Spherical Geometry19

45. Multi layered production schemes

46. Thick reservoirs z y x Rectangular Geometry 20

49. Flow Geometries and Dimensions (contd.) Ф θ r Elliptical Geometry Spherical Geometry 22

50. Construction of models Data Preparation M. OwaisNaseem (PE-025)

52. Reservoir Rock Properties

53. PVT Data

54. Capillary Pressure Data

55. Relative Permeability Data

56. Well Data24

59. Reason for the substitution of Horizontal Well with Vertical WellRectangular Co-ordinate System 25

61. Isotropic

62. Porosity = 0.02

63. Permeability = 0.1 millidarcy

64. Reservoir Temperature = 300˚F

65. Reservoir Pressure = 5000 psia26

67. Formation Volume Factor

68. Viscosity27

69. Formation Volume Factor ‘Reservoir Engineering Handbook’ by Tarek Ahmed 28

70. Viscosity ‘Reservoir Engineering Handbook’ by Tarek Ahmed 29

71. Carr’s Viscosity Correlation ‘Reservoir Engineering Handbook’ by Tarek Ahmed 30

72. Calculated Formation Volume Factors and Viscosities 31

73. Capillary Pressure Data ‘Empirical Capillary Pressure Relative Permeability Correlation’ By James H. Schneider 32

74. Calculated Capillary Pressures 33

75. Relative Permeability Data ‘Empirical Capillary Pressure Relative Permeability Correlation’ By James H. Schneider 34

76. Determination of λ Brooks and Corey observed that a log-log plot of Sw* against Pc results in a straight line with a slope of -λ 35

77. Calculated Relative Permeabilities 36

79. Constant Flowing Bottomhole Pressure = 1000 psia37

80. Construction of models Reservoir Discretization Muneeb Ahmad (PE-006)

82. Cylindrical Reservoir; r = 225ft & h = 2000ft

83. 12500 Blocks; r:θ:z = 25:25:20

84. Well in the centre; L = 1000ft

85. Quarter of the reservoir is modeled.39

86. Assumed Model 1000 ft 2000 ft 100 ft 200 ft 40

87. Eclipse Generated Model 3-D View Top View 41

89. Rectangular Reservoir with Well in the centre

90. Quarter of the Reservoir is modeled

91. Reservoir dimension (Quarter); 2000 x 200 x 100 ft3.

92. 1680 blocks; x:y:z = 24:07:1042

93. 4000 ft Assumed Model Fracture Width 100 ft Fracture Height 400 ft Fracture Half Length Top view of the quarter of the Reservoir 43

95. Half Fracture Length = 1000 ft

96. Fracture Porosity = 35%

97. Dimensionless Fracture Conductivity = 10

98. Fracture Permeability = 20000 md

99. Equivalent Fracture Width = 2 ft

100. Fracture Porosity = 0.875%

101. Fracture Permeability = 500 md‘Fracture Face Interference Of Finite Conductivity Fractured Wells Using Numerical Simulation’ By SvjetlanaLale 44

102. Flow Geometries and Dimensions (contd.) Equivalent Fracture Width Original Fracture Width 45

103. Eclipse Generated Models 3-D View Top View 46

104. Cases for Comparison Vertical Well Vertical Well Fracture Height Fracture Height Horizontal Well Horizontal Well When the fracture penetrates half of the vertical well length When the fracture penetrates the total vertical well length CASE: 01 CASE: 02 Vertical Well Fracture Height Horizontal Well When the fracture penetrates quarter of the vertical well length CASE: 03 47

105. Classification of Each Case Each Case L = 1000 ft L = 100 ft L = 200 ft L = 400 ft L = 500 ft 48

106. Results Zeeshan-ul-Haq (PE-015)

107. Initial Production Rate Plot 50

108. Decline In Production Rate (Horizontal Well) 51

109. Decline In Production Rate (Vertical Well) 52

110. Cumulative Production (Horizontal Well) 53

111. Cumulative Production (Vertical Well) 54

112. Productivity Index Plot 55

113. Area Open to Flow Plot 56

114. conclusions

116. The production rate is increased,

117. The decline in the production rate is faster due to the closed reservoir system,

118. The cumulative production is more or less same,

119. Economics will dictate the optimum length of the horizontal well or the fracture half length,

120. In case of fractured wells same results can be achieved by either increasing the half length or the height of the fracture.

121. Since the area open to flow for the fractured well is more than that of the horizontal well, its productivity index is also greater. However achieving fracture half lengths similar to the length of the horizontal wells is impossible in practice.

122. The productivity index increases almost linearly for the horizontal well.

123. For vertical fractured wells the increase in productivity index becomes less as the length of the fracture increases.

124. It will therefore be a matter of economics to decide between the fractured wells and the horizontal well.58

125. Recommendations for future work

127. Effect on the performance should also be analyzed by varying other parameters such as Permeability, Location of the Wells, etc.

128. If possible, then it is highly advisable to include economic analysis.60

129. QUESTIONS ??? 61