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Comparative Analysis of Performance of Horizontal and Hydraulically Fractured Wells in a Tight Gas Reservoir using Numerical Simulations
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Comparative Analysis of Performance of Horizontal and Hydraulically Fractured Wells in a Tight Gas Reservoir using Numerical Simulations

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Comparative Analysis of Performance of Horizontal and Hydraulically Fractured Wells in a Tight Gas Reservoir using Numerical Simulations Comparative Analysis of Performance of Horizontal and Hydraulically Fractured Wells in a Tight Gas Reservoir using Numerical Simulations Presentation Transcript

  • Comparative Analysis of Performance of Horizontal and Hydraulically Fractured Wells in a Tight Gas Reservoir using Numerical Simulations
    1
    December 9, 2009
  • 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 Members
    • AsifAzhar (PE-033)
    • Haris Ali Soomro (PE-027)
    • M. OwaisNaseem (PE-025)
    • Muneeb Ahmad (PE-006)
    • Zeeshan-ul-Haq (PE-015)
    02
  • Contents
  • Objective
    To compare the Performance of Horizontal and Vertical Hydraulically Fractured Wells in a Tight Gas Reservoir
    04
  • Scope
    • In 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.
    • The question arises “Which is the suitable method to develop a particular Tight Gas Reservoir?”
    • Our project can serve as a prototype which can be scaled up for the real data.
    05
  • TIGHT GAS RESERVOIRS
    A Brief Introduction
    AsifAzhar (PE-033)
  • 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
  • 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
  • What Makes a Reservoir Tight?
    • The original depositional fabric itself was tight.
    • 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
  • Possible Candidates for TGR in Pakistan
    • Lower Goru Tight Sands
    • Sembar Sands and Siltstones
    • Sui Upper Limestone
    • HabibRahi Limestone
    • Pirkoh Limestone
    ‘Untapping Tight Gas Reservoirs’ by Muhammad AjazSarwar & AbdurRaufMirza, OGDCL
    10
  • Possible Candidates for TGR in Pakistan
    ‘Scope of Tight Gas Reservoir in Pakistan’ by SalahHaikal, Eni Pakistan Ltd
    11
  • TGR Completion Techniques
    Fractured Vertical Wells
    Multi-lateral Wells
    Horizontal Wells
    12
  • Fractured Vertical Wells
    Important Issues
    • No significant control over Fracture Height
    • Obtaining Infinite Conductivity Fractures
    • More effective in reservoirs having permeability less than 10md
    ‘Horizontal Well Technology’ by Sada D. Joshi
    13
  • Horizontal Wells
    Important Issues
    • Large Reservoir Contact Area
    • Only one pay zone can be drained per horizontal well
    • Costs 1.3-4 times more than a Vertical well
    • In TGR, Horizontal wells can improve drainage area per well and reduce the number of wells
    • In some cases of TGR horizontal fractured wells may work better.
    ‘Horizontal Well Technology’ by Sada D. Joshi
    14
  • RESERVOIR SIMULATION
    A Brief Introduction
    Haris Ali Soomro (PE-027)
  • 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.
    • 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
  • Simulation Approaches
    • Single Well Simulation
    • Field Scale Simulation
    • Window Study
    17
  • Simulation Approaches
    Single Well Simulation
    Field Scale Simulation
    18
  • Flow Geometries
    • Rectangular Geometry
    • Radial or Cylindrical Geometry
    • Elliptical Geometry
    • Spherical Geometry
    19
  • Flow Geometries and Dimensions
    One-Dimensional Flow
    • A long skinny reservoir
    Two-Dimensional Flow
    • Variety of completion strategies
    • Thin blanket sands
    Three-Dimensional Flow
    • Layered reservoirs
    • Multi layered production schemes
    • Thick reservoirs
    z
    y
    x
    Rectangular Geometry
    20
  • Flow Geometries and Dimensions (contd.)
    One-Dimensional Flow
    • Well test analysis
    • 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.
    z
    z
    r
    r
    θ
    Radial or Cylindrical Geometry
    21
  • Flow Geometries and Dimensions (contd.)
    Ф
    θ
    r
    Elliptical Geometry
    Spherical Geometry
    22
  • Construction of models
    Data Preparation
    M. OwaisNaseem (PE-025)
  • Data Preparation
    • Reservoir Geometry
    • Reservoir Rock Properties
    • PVT Data
    • Capillary Pressure Data
    • Relative Permeability Data
    • Well Data
    24
  • Reservoir Geometry
    • Horizontal Well Model
    • Fractured Vertical Well Model
    Radial Co-ordinate System
    • Eclipse Limitation
    • Reason for the substitution of Horizontal Well with Vertical Well
    Rectangular Co-ordinate System
    25
  • Reservoir Properties
    • Homogenous
    • Isotropic
    • Porosity = 0.02
    • Permeability = 0.1 millidarcy
    • Reservoir Temperature = 300˚F
    • Reservoir Pressure = 5000 psia
    26
  • PVT Data
    • Specific Gravity = 0.7
    • Formation Volume Factor
    • Viscosity
    27
  • Formation Volume Factor
    ‘Reservoir Engineering Handbook’ by Tarek Ahmed
    28
  • Viscosity
    ‘Reservoir Engineering Handbook’ by Tarek Ahmed
    29
  • Carr’s Viscosity Correlation
    ‘Reservoir Engineering Handbook’ by Tarek Ahmed
    30
  • Calculated Formation Volume Factors and Viscosities
    31
  • Capillary Pressure Data
    ‘Empirical Capillary Pressure Relative Permeability Correlation’ By James H. Schneider
    32
  • Calculated Capillary Pressures
    33
  • Relative Permeability Data
    ‘Empirical Capillary Pressure Relative Permeability Correlation’ By James H. Schneider
    34
  • 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
  • Calculated Relative Permeabilities
    36
  • Well Data
    • Wellbore diameter = 0.6 ft
    • Constant Flowing Bottomhole Pressure = 1000 psia
    37
  • Construction of models
    Reservoir Discretization
    Muneeb Ahmad (PE-006)
  • Horizontal Well Model
    • Radial Geometry
    • Cylindrical Reservoir; r = 225ft & h = 2000ft
    • 12500 Blocks; r:θ:z = 25:25:20
    • Well in the centre; L = 1000ft
    • Quarter of the reservoir is modeled.
    39
  • Assumed Model
    1000 ft
    2000 ft
    100 ft
    200 ft
    40
  • Eclipse Generated Model
    3-D View
    Top View
    41
  • Vertical Well Model
    • Rectangular Geometry
    • Rectangular Reservoir with Well in the centre
    • Quarter of the Reservoir is modeled
    • Reservoir dimension (Quarter); 2000 x 200 x 100 ft3.
    • 1680 blocks; x:y:z = 24:07:10
    42
  • 4000 ft
    Assumed Model
    Fracture Width
    100 ft
    Fracture Height
    400 ft
    Fracture Half Length
    Top view of the quarter of the Reservoir
    43
  • Fracture Properties
    • Fracture Width = 0.6 inch
    • Half Fracture Length = 1000 ft
    • Fracture Porosity = 35%
    • Dimensionless Fracture Conductivity = 10
    • Fracture Permeability = 20000 md
    • Equivalent Fracture Width = 2 ft
    • Fracture Porosity = 0.875%
    • Fracture Permeability = 500 md
    ‘Fracture Face Interference Of Finite Conductivity Fractured Wells Using Numerical Simulation’ By SvjetlanaLale
    44
  • Flow Geometries and Dimensions (contd.)
    Equivalent Fracture Width
    Original Fracture Width
    45
  • Eclipse Generated Models
    3-D View
    Top View
    46
  • 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
  • Classification of Each Case
    Each Case
    L = 1000 ft
    L = 100 ft
    L = 200 ft
    L = 400 ft
    L = 500 ft
    48
  • Results
    Zeeshan-ul-Haq (PE-015)
  • Initial Production Rate Plot
    50
  • Decline In Production Rate (Horizontal Well)
    51
  • Decline In Production Rate (Vertical Well)
    52
  • Cumulative Production (Horizontal Well)
    53
  • Cumulative Production (Vertical Well)
    54
  • Productivity Index Plot
    55
  • Area Open to Flow Plot
    56
  • conclusions
  • Conclusions
    • As the length of the fracture or the horizontal well is increased:
    • The production rate is increased,
    • The decline in the production rate is faster due to the closed reservoir system,
    • The cumulative production is more or less same,
    • Economics will dictate the optimum length of the horizontal well or the fracture half length,
    • In case of fractured wells same results can be achieved by either increasing the half length or the height of the fracture.
    • 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.
    • The productivity index increases almost linearly for the horizontal well.
    • For vertical fractured wells the increase in productivity index becomes less as the length of the fracture increases.
    • It will therefore be a matter of economics to decide between the fractured wells and the horizontal well.
    58
  • Recommendations for future work
  • Recommendations For Future Work
    • The comparison should be done for the realistic values of Half Fracture Length.
    • Effect on the performance should also be analyzed by varying other parameters such as Permeability, Location of the Wells, etc.
    • If possible, then it is highly advisable to include economic analysis.
    60
  • QUESTIONS ???
    61