IPCFR Integrated Petrophysics for Carbonate and Fractured Reservoirs – A Roadmap

Day 1

• Introduction & Principles
• Reservoir schematic
• Reminder: Borehole, Invasion & Symbols (Schl. Gen-3)
• Aquifer, Transition Zone & Hydrocarbon Zone
• Data Hierarchy and Upward Calibration:
• Logs Provide a Vehicle for Data Integration
• First Step, The Concept of Data Hierarchy
• Data Hierarchy Criteria
• Calibration projects high value data into larger reservoir volumes using more continuous data
• Adopt a problem solving philosophy
• Course Structure & Evaluation Sequence
• CARBONATES ARE DIFFERENT TO CLASTICS: So don’t treat them like clastics
• Contrasting Geological Origins: Clastics, Carbonates & Fractures
• MICROPRACTICAL – QL Sw & k: invasion profiles
• MICROPRACTICAL – QL Sw & k: Porosity vs Rt
• Dominant Minerals – clastics, carbonates, fractures
• About clay minerals
• Carbonates diagenesis: 1 & 2 Always look for dolomitic zones!
• Diagenesis – carbonates more extreme
• Carbonate Diagenetic Facies
• Carbonate Diagenetic Effects on Permeability

• Clastic-Carbonate differences:
  • Carbonate POROSITY : low, high, variable, extreme
  • Clastics PORE GEOMETRY usually simple
  • Carbonates PORE GEOMETRY extremely diverse
  • Carbonates PORE GEOMETRY range
  • But Carbonate PORE GEOMETRY can also be uniform
  • Heterogeneity, mm-m

• Carbonate porosity type are diverse  (Choquette & Pray 1970)
• Summary – Clastic – Carbonate matrix differences
• Stress, Fracture Types & Petrophysical Features
• Fracture Spacing “S”  and  Width “E”
• Geologic Parameters Controlling  “S”  and  “E”
• Reservoir Character created by differences:
• Fracture-Matrix Interaction, q
• Day 1 AM PRACTICAL: Physical Characteristics Questions
• Reservoir Character created by differences – oil wetness
• Wettability:  Wetting preferences dictate the distribution of oil & water within the pore network
• Saturation Exponent vs. Fraction Oil Wet Surface
• The link between resistivity and Sw becomes problematic with mixed n* 3.4 ? 1.8; EHC+48%
• Wettability: Is your reservoir non-strongly water wet?
• ARE CARBONATE GEOLOGICAL CLASSIFICATION SYSTEMS USEFUL FOR CARBONATE PETROPHYSICS?
• Carbonate Classifications-Dunham: Grain support & petrophysics at last!
• Lucia: rock-fabric classes
• Carbonate Classifications – Lucia’s key concepts
• Lucia – vug classes.  Are vugs connected?
• Lucia’s – “Rock Fabric”
• Non-vuggy limestones & dolostones: Class1, 2 & 3
• Fracture permeability
• Parallel plate single fracture set
• Lucia’s – “Rock Fabric” Separate vug permeability – difficult
• Lucia’s – “Rock Fabric” generic inter particle off-the-shelf answers
• In Defence of Lucia – from Ø to k & Sw without core     Use, adapt, replace

• Fractures – Fractured Reservoir Classification:
  • Aguilera
  • Nelson
  • Fooled by Fractures

• Course Structure & Evaluation Sequence
• HOW DO THE PHYSICAL CHARACTERISTICS OF CARBONATES IMPACT RESERVOIR MEASUREMENTS?  
• Impact of Character on Measurement & Evaluation
• Impact on Measurements – Conventional logs: a Failure Point   
• Clastics vs Carbonates
• Impact on Measurements – Matrix porosity
• Matrix porosity measurements compared
• Day 1 PM PRACTICAL: Classification Systems and Petrophysics, Lucia
• 
  

Day 2

• Impact on Measurements:
  • Fracture porosity
  • Matrix saturation Swrt
  • Matrix saturation Swpc
  • Swpc

• What is Capillary Pressure?
• WFTs Provide FWL, Mobile Fluid Type
• & Actual Capillary Pressure = Excess Pressure = Saturating Pressure
• Impact on Measurements – Matrix saturation Swmr
• MICROPRACTICAL – Matrix porosity Error in
• “tight” carbonates

• Impact on Measurements:
  • Matrix permeability
  • Fracture permeability
  • Netpay thickness, h
  • FWL

• MICROPRACTICAL – Data Hierarchy drives Data Flow
• CAUTION! MISLEADING DATA IN CARBONATE & FRACTURED RESERVOIRS   

• Misleading Data: 
  • Fracture wells tests
  • Access the matrix
  • Routine core analysis
  • Biased RCA

• Use high sample density fixed spacing RCA

• Misleading Data:
  • Inadequate pore throat size data
  • Missing Clay Bound Water
  • Mercury capillary pressure data correction, for ClayBW
  • Rt
  • Viscourse oil shortens NMR T2

• Carbonate & Fracture Major Petrophysical Difficulties
• Day 2: AM1 PRACTICAL: FWL from single WFT point
• Day 2: AM 2 PRACTICAL: Clasification System & Petropysics, Fractures 
• Course Structure & Evaluation Sequence
• USEFUL DATA – LOG IT, USE IT
• Achieving Optimal Data Acquisition

• Useful data:
  • Drilling, Mudlogs, Chromatograph
  • Rxo
  • Whole core, Miniperm
  • Core
  • Sonic, Density
  • Logged Water Zones
  • A*Rw, m from Deielectric BVW and Rxo
  • Analogs cheap!
  • Analog superimposed RCA for SCAL
  • Analog FZI for SCAL Pxc data
  • Stoneley Permeability

• POWERFUL DATA – NICE IF YOU CAN GET IT!
• Powerful data – Fracture Check & Managed Pressure
• Drilling (MPD) Control swab/surge & detect permeable fracs
• Powerful data – Fracture Test Design & analysis (1 & 2)
• Dual porosity pressure build up vs. time  characteristics

• Powerful data:
  • Image Logs
  • NMR: Principle
  • NMR: Think Sw-Ht
  • NMR: Convert T2 to Ht & BVW
  • NMR bins imply Sw for a given Pc (Ht)
  • NMR: Acquire Fast BFV, BVI

• Day 2 PM PRACTICAL: Impact of Physical Characteristics on Measurements

Day 3

• Powerful data:
  • Array Sonics e.g. SLB Sonic Scanner (MSIP)
  • What we need from Array Acoustics

• Dielectric Tools: SLB: ADT Array Dielectric Tool SPE116130 (Sep-08)
• MICROPRACTICAL  Sw: Calculate Swi_mr from

• Free Fluid and Øt, what assumptions?
• Powerful data – FLEX, LithoScanner, ECS (Elemental Capture Spectroscopy)
• Powerful data – TypeC Fracture Well Tests
• Well test + Image Log ? E ? Øf ? HCIIP !
• Powerful Core + Image Log + NMR + FWL
• Powerful Relative Contribution to Formation Evaluation of different data types. 
• Key Questions for the Data Acquisition program
• Guide – Carbonate Wireline Logging (SLB mnemonics) 
• Course Structure & Evaluation Sequence
• CARBONATES QUICK LOOK – DIFFERENT TO CLASTICS
• QL – Fracture ID, conventional logs
• QL – Fracture Porosity indicated by Conventional Logs
• QL Fracture ID – Key Points
• Course Structure & Evaluation Sequence
• General – Four calibrations ensure correct matrix HPV
• Carbonate Matrix Evaluation: Key Elements
• QL – Achieving Fit-For-Purpose Quick Look Results
• QL – unseen rhog changes in low Ø rock will ruin Ød QL – Porosity density neutron, Ødn
• QL – Porosity sonic (Wyllie Time Average), Øs
• QL – Why sonic porosity?  For vugs!
• QL – (Ødn-Øs) indicates vugs, and m
• Øs: approximate dt matrix
• Øs: determine dt_fluid from dtf apparent (dtfa)
• Øs: determine vugs & predict m with dtfa
• Day 3 PRACTICAL: Achieving Cost Effective Data Acquisition & Basic Carbonate Log Analysis – Questions
• Course Structure & Evaluation Sequence
• QL – Ro prediction  a*Rw, m   Archie:  Sw^n = a*Rw / (Rt * Ø^m)
• Impact of ‘m’ on Ro.    Archie: Ø-m=Ro/Rw
• Actual lab SCAL m variations caused by vuggy porosity – m impacts Ro and HPV
• Is Water Zone ‘m’ related to Øvugs?  If yes use Øvugs to predict m in HC zone
• Ro prediction variable m
• Saturation Archie, Swar
• What is ‘n’?   Archie: Sw-n = Rt/Ro
• QL – HC detection, qualitative
• QL – Saturation.  Resistivity ratio: Swrr
• QL – Saturation: Swrr problems
• QL – Sw resistivity ratio: Swrr
• QL – Reconcile  Swar, Swrr
• FULL CARBONATE MATRIX EVALUATION
• Define the Matrix / Fracture split
• Average m’s:  Interparticle 1.99;  Vuggy/moldic 2.28
• Average m’s: Non vuggy Lucia Classes
• Whole rock m: vugs increase, fracs decrease

• Carbonate matrix evaluation:
  • Vugs increase m
  • Reality is complex

• Carbonate matrix:
  • Determine vugs: Image logs
  • Determine vugs: NMR logs
  • Summary variable m (mv) determination from Øvug
  • Vugs and HPV

• Day 3 PRACTICAL: Basic Carbonate Log Analysis: Platform Carbonate, Gas – Questions

Day 4

• Carbonate matrix evaluation – Rock Fabric Identification
• MICROPRACTICAL Ro: Compute m apparent in Sw100 zone

• Carbonate matrix:
  • Porous plate apparatus used for air-brine capillary pressure data, Sw - Pc
  • Wetting phase (water) desaturation with increasing Pc
  • Height positions the Pc-Sw data in the reservoir
  • Use RCA to project cap.press data into the reservoir
  • Capillary Pressure Measurement techniques
  • Core Overburden Electrical Properties combined with porous plate Pc
  • Capillary Pressure Saturations, 4 controls on Sh
  • Interfacial Tension IFT

• Do Perched Water contacts violate capillary pressure Saturation-height assumptions?
  • Mercury injection data reveals PTSD
  • Different Reservoir Qualities yield Different TZ thickness
  • In Transition Zones Pc is low and Sw>Swi water and oil are both mobile
  • Use RCA to project cap.press data into the reservoir
  • Capillary Pressure Measurement techniques

• MICROPRACTICAL Cutoff: Relative Perm SCAL data demonstrates the Netpay permeability cutoff
  • Summary of J Function Sw from Pc data, Swj
  • Swpc: J Bundles Ø, k and Ht to correlate with Sw
  • Fitting Pc data: FOIL, Lambda, Modified J, Johnson, Skelt
  • Converting Laboratory Pc to reservoir Height
  • Swj (predicted) vs core plug measure Sw
  • QuickLook Swpc: arrange your PC data like this, per rocktype, facies
  • Redisplay lab Pc results as a simple Sw-Ht grid
  • Bulk Volume Water > Cap.Press BVWi Indicates
  • Fluid Zone = Transition Zone; Residuals or Water
  • Oil and Water mud core Sw compared to reservoir true Sw
  • Swobm: Partial Invasion of an oil Mud Core leaving an un-invaded center
  • Dean Stark apparatus used in the determination of oil mud Swcore
  • Check OBM 3days before coring

• Day 4 PRACTICAL: How to Use Capillary Pressure Data  – Questions
• RESERVOIR ROCK TYPES (RRTs)
• Carbonate matrix – Characterise EACH RRT: NMR T2 distribution may indicate Pore Throat Size distribution
• Carbonate matrix  – Characterise EACH RRT: will the pore system unload it’s oil?
• Summary – Reservoir Rock Typing (RRT)
• World’s Largest Tanker: JahreViking 4.1mm bbls crude
• Ultra Large Crude Carrier (ULCC).  Planet Earth consumes 20 of these per day
• Carbonate matrix:
  • Magnetic Resonance Swi for 'n'
  • A better way to display NMR data
  • Four calibrations ensure correct matrix HPV

• Course Structure & Evaluation Sequence
• CARBONATE MATRIX PERMEABILITY EVALUATION
• k matrix QL: Adapt Chart K-4
• Carbonate matrix:
  • SDR permeability equation, T2 cutoff not used
  • Coates permeability
  • Determine vug connectivity p = f.(Øvug)
  • Bound Fluid Volumes and logs
  • Why the Coates Equation is so powerful
  • Coates equation vs Core
  • What is an Acoustic Stoneley Wave?
  • Stoneley waves: Attemuation, Slowness & Mobility
  • Stoneley waves Slowed & Attenuated by Mobility

• FWL – Supercharging: WFT measured pressures may be above formation if permeability is low
• FWL Excess Pressure plots clarify FWLs and show actual reservoir capillary pressure
• Carb matrix – Diverse data with the same result creates confidence in the result, specially in complex reservoirs
• Carbonate Matrix – Key Points
• Day 4 PRACTICAL: How to use Capillary Pressure Data contd.

Day 5

• Course Structure & Evaluation Sequence
• FRACTURES

• Fractured Reservoir Evaluation process
• Fractures: 
  • Basement High & Porosity Distribution, TypeC
  • Fracture POROSITY is SMALL!
  • Limited storage: HPV per GRV <<Intergranular
  • Porosity: Outcrop studies
  • Porosity: Core + Image logs
  • Porosity: Well Tests TypeC and TypeB if kf>>km
  • Fracture PERMEABILITY is BIG!
  • Useful calculators Frac Ø & HPV, from DST kh and Deterministic.  Type C and B if kf>>km
  • Finding & Evaluating Fracs Data, Ranked
  • Acoustic Stoneley Wave Reflection Coefficient
  • Acoustic Stoneley Wave response
  • Stoneley Attenuation and Fracture Aperture
  • What is Acourstic Shear Wave Splitting?
  • Acoustic Wave Shear Anisotrophy
  • Conjugate fractures & Smax

• QL – Fracture ID: special logs 1 & 2
• Orientation: Acoustic & Image
• Circumfrential Acoustic Scanner Tool (CAST) amplitude displayed as dipping planes (fracs) with known orientation
• Comparison of Fracture Imaging Logs
• Mechanical Properties Log
• S,E, Orientation and Length? Any other data?
• Lithology may influence fracture spacing, S
• Determine Fracture-Matrix Interaction
• Plan view: vertical fractures & horizontal well
• Size, Density & Orientation
• Fracture Orientation + Stress Orientation? Drill
• Fracture Indicator Scores - exhaustive and definitive but slow
• Surprising Fluid Distributions after Production
• Some Key Points

• Course Structure & Evaluation Sequence
• CARBONATE GEO-MODEL INPUT
• What are the Matrix and Fracture Grids in  simulation?
• A Consistent Geological Model
• Imagine your reservoir as a road cutting
• Geo-model Checksums
• EHC & kh must be equal at all scales of reservoir description!
• Course Structure & Evaluation Sequence
• 10 Systematic errors which will ruin your carbonate/fracture geo.model (chronological)
• Day 5  PRACTICAL Achieving Fit For Purpose QL Results 
• THE END

• To understand why carbonate & fracture petrophysics is problematic 
• To help you pinpoint the problems specific to your reservoir
• To design and execute an optimal evaluation routine which enables optimal operational decisions and optimal static and dynamic geo-models as well as highlighting critical data acquisition needs.