Comparative Analysis of Performance of Horizontal and Hydraulically Fractured Wells in a Tight Gas Reservoir using Numerical Simulations
- 1. Comparative Analysis of Performance of Horizontal and Hydraulically Fractured Wells in a Tight Gas Reservoir using Numerical Simulations1December 9, 2009
- 2. Project Team External Advisor: Dr. SuhailQadeer(Senior Manager Production Engineering, Pakistan Petroleum Limited)Internal Advisor: Mr. Adnan-ul-Haq(Lecturer, NED University of Engineering and Technology)Group MembersAsifAzhar (PE-033)
- 3. Haris Ali Soomro (PE-027)
- 7. Contents
- 8. ObjectiveTo compare the Performance of Horizontal and Vertical Hydraulically Fractured Wells in a Tight Gas Reservoir04
- 9. ScopeIn years to come, when conventional resources of Oil and Gas will be depleted, the world will have to look towards Unconventional Resources among which Tight Gas Reservoirs are one of the options.
- 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 RESERVOIRSA Brief IntroductionAsifAzhar (PE-033)
- 13. Introduction to Tight Gas ReservoirsTight 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 U07
- 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 U08
- 15. What Makes a Reservoir Tight? The original depositional fabric itself was tight.
- 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 Mishra09
- 17. Possible Candidates for TGR in Pakistan Lower Goru Tight Sands
- 18. Sembar Sands and Siltstones
- 19. Sui Upper Limestone
- 21. Pirkoh Limestone‘Untapping Tight Gas Reservoirs’ by Muhammad AjazSarwar & AbdurRaufMirza, OGDCL10
- 22. Possible Candidates for TGR in Pakistan‘Scope of Tight Gas Reservoir in Pakistan’ by SalahHaikal, Eni Pakistan Ltd11
- 24. Fractured Vertical WellsImportant IssuesNo significant control over Fracture Height
- 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 SIMULATIONA Brief IntroductionHaris Ali Soomro (PE-027)
- 33. Reservoir Simulation Reservoir simulation is an area of reservoir engineering in which computer models are used to predict the flow of fluids (typically, oil, water, and gas) through porous media.
- 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
- 35. Simulation ApproachesSingle Well Simulation
- 37. Window Study17
- 38. Simulation ApproachesSingle Well SimulationField Scale Simulation18
- 40. Radial or Cylindrical Geometry
- 43. Flow Geometries and DimensionsOne-Dimensional Flow A long skinny reservoir Two-Dimensional Flow Variety of completion strategies
- 44. Thin blanket sandsThree-Dimensional Flow Layered reservoirs
- 45. Multi layered production schemes
- 46. Thick reservoirs zyxRectangular Geometry20
- 47. Flow Geometries and Dimensions (contd.)One-Dimensional Flow Well test analysis
- 48. Flow is constrained to the r-direction Two-Dimensional Flow Single well problems where gravity and/ or layering effects are significant. Three-Dimensional Flow Property variation in all three directions.zzrrθRadial or Cylindrical Geometry21
- 49. Flow Geometries and Dimensions (contd.)ФθrElliptical GeometrySpherical Geometry22
- 50. Construction of modelsData PreparationM. OwaisNaseem (PE-025)
- 53. PVT Data
- 55. Relative Permeability Data
- 56. Well Data24
- 57. Reservoir GeometryHorizontal Well Model
- 58. Fractured Vertical Well ModelRadial Co-ordinate SystemEclipse Limitation
- 59. Reason for the substitution of Horizontal Well with Vertical WellRectangular Co-ordinate System25
- 61. Isotropic
- 62. Porosity = 0.02
- 63. Permeability = 0.1 millidarcy
- 64. Reservoir Temperature = 300˚F
- 65. Reservoir Pressure = 5000 psia26
- 66. PVT DataSpecific Gravity = 0.7
- 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 Viscosities31
- 73. Capillary Pressure Data‘Empirical Capillary Pressure Relative Permeability Correlation’ By James H. Schneider32
- 75. Relative Permeability Data‘Empirical Capillary Pressure Relative Permeability Correlation’ By James H. Schneider34
- 76. Determination of λBrooks and Corey observed that a log-log plot of Sw* against Pc results in a straight line with a slope of -λ35
- 78. Well DataWellbore diameter = 0.6 ft
- 79. Constant Flowing Bottomhole Pressure = 1000 psia37
- 80. Construction of modelsReservoir DiscretizationMuneeb Ahmad (PE-006)
- 81. Horizontal Well Model Radial Geometry
- 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 Model1000 ft2000 ft100 ft200 ft40
- 87. Eclipse Generated Model3-D ViewTop View41
- 88. Vertical Well Model Rectangular Geometry
- 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 ftAssumed ModelFracture Width100 ftFracture Height400 ftFracture Half LengthTop view of the quarter of the Reservoir43
- 94. Fracture Properties Fracture Width = 0.6 inch
- 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 SvjetlanaLale44
- 102. Flow Geometries and Dimensions (contd.)Equivalent Fracture WidthOriginal Fracture Width45
- 103. Eclipse Generated Models3-D ViewTop View46
- 104. Cases for ComparisonVertical WellVertical WellFracture HeightFracture HeightHorizontal WellHorizontal WellWhen the fracture penetrates half of the vertical well lengthWhen the fracture penetrates the total vertical well lengthCASE: 01CASE: 02Vertical WellFracture HeightHorizontal WellWhen the fracture penetrates quarter of the vertical well lengthCASE: 0347
- 105. Classification of Each CaseEach CaseL = 1000 ftL = 100 ftL = 200 ftL = 400 ftL = 500 ft48
- 107. Initial Production Rate Plot50
- 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
- 113. Area Open to Flow Plot56
- 114. conclusions
- 115. ConclusionsAs the length of the fracture or the horizontal well is increased:
- 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
- 126. Recommendations For Future Work The comparison should be done for the realistic values of Half Fracture Length.
- 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