Integrated Petrophysics for Carbonate and Fractured Reservoirs – Details


Logical, Systematic, Complete

Integrated Petrophysics for Carbonate and Fractured Reservoirs – A Roadmap

Detailed Contents





Intro – Course Overview

Intro – Petrophysical Objectives vs. Carbonate & Fracture Log Analysis Failure Points

Intro – The Central Role of Petrophysics is to INTEGRATE !

Course Objectives 1

Course Objectives 2

Intro – Colour codes

Intro – Reservoir schematic

Intro – Reminder: Borehole, Invasion & Symbols

Intro – Aquifer, Transition Zone & Hydrocarbon Zone

Intro – Data Hierarchy and Upward Calibration
Intro – Logs Provide a Vehicle for Data Integration

Intro – Data Hierarchy Concept

Intro – Data Hierarchy Criteria

Intro – Calibration projects high value data into larger reservoir volumes using more continuous data

Intro – Adopt a problem solving philosophy

Course Structure & Evaluation Sequence




Contrasting Geological Origins – Clastics

Contrasting Geological Origins – Carbonates

Contrasting Geological Origins – Carbonates

Contrasting Geological Origins – Carbonates

Contrasting Geological Origins – Fractures

MICROPRACTICAL – QL Sw & k: invasion profiles

Dominant Minerals – clastics, carbonates, fractures

Dominant Minerals – clastics

About clay minerals

Carbonates diagenesis – 1

Carbonates diagenesis – 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

Clastic-Carbonate differences:
Clastics PORE GEOMETRY usually simple

Clastic-Carbonate differences:
Carbonates PORE GEOMETRY is extremely diverse!

Clastic-Carbonate differences:  Carbonates PORE GEOMETRY range


Clastic-Carbonate differences
..but Carbonate PORE GEOMETRY can also be uniform

Clastic-Carbonate differences: heterogeneity, mm-m

Carbonate porosity types are diverse

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

Day1 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 vs 1.8; EHC+48%

Wettability: Is your reservoir non-strongly water wet?

Carbonate Classifications-Dunham: Grain support

Carbonate Classifications – 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

Fractures – Fractured Reservoir Classification – Nelson

Fooled by Fractures

Course Structure & Evaluation Sequence




Impact of Character on Measurement & Evaluation

Impact on Measurements – Conventional logs: A Failure Point

Impact on Measurements – Matrix porosity

Clastics vs Carbonates

Impact on Measurements – Matrix porosity
Matrix porosity measurements compared

Day1 PRACTICAL: Classification Systems and Petrophysics, Lucia





Recap Day1

Impact on Measurements – Fracture porosity
Impact on Measurements – Matrix saturation Swrt
Impact on Measurements – Matrix saturation Swpc
Impact on Measurements – Swpc
What is Capillary Pressure?

Impact on Measurements – Swpc
WFTs Provide FWL, Mobile Fluid Type & Capillary Pressure (= Excess Pressure = Saturating Pressure)

Impact on Measurements – Matrix saturation Swmr
MICROPRACTICAL – Matrix porosity Error in “tight” carbonates

Impact on Measurements – Matrix permeability

Impact on Measurements – Matrix permeability

Impact on Measurements – Fracture permeability

Impact on Measurements – Netpay thickness, h

Impact on Measurements – FWL

MICROPRACTICAL – Data Hierarchy drives Data Flow

Misleading Data Sets – fracture wells tests

Misleading Data Sets.  access the matrix!

Misleading Data Sets – routine core analysis

Misleading data – biased RCA

Misleading Data – wrap
Use high sample density fixed spacing RCA

Misleading Data – inadequate pore throat size data

Misleading Data – missing Clay Bound Water

Misleading Data – mercury capillary pressure data correction, for CBW only

Misleading Data – Rt

Misleading Data – viscous oil shortens NMR T2

Carbonate & Fracture Major Petrophysical Difficulties

Day2 PRACTICAL: Classification Systems & Petrophysics, Fractures

Day2 AM Practical. FWL from single WFT point

Course Structure & Evaluation Sequence




Useful data – Drilling, Mudlogs, Chromatograph

Useful data – Rxo

Useful data – Whole core, Miniperm

Useful data – Core

Useful data – Sonic, Density

Useful data – Logged Water Zones

Useful data – Analogs cheap!

Useful data – Analog superimposed RCA for SCAL

Useful data – Analog FZI for SCAL Pc data

Powerful data – Fracture Check & Managed Pressure
Drilling (MPD) Control swab/surge & detect permeable fractures

Powerful data – Fracture Test Design & Analysis (1)

Powerful data – Fracture Test Design & Analysis (2)
Dual porosity pressure build up vs. time  characteristics

Powerful data – Image Logs

Powerful data – NMR: Principle

Powerful data – NMR: Think Sw-Ht

Powerful data – NMR: Convert T2 to Ht

Powerful data – NMR bins imply Sw for a given Pc (Ht)

Powerful data – NMR: Acquire Fast BFV, BVI

Day2 PRACTICAL: Impact of Physical Characteristics on Measurements





Recap Day2

Powerful data – Array Sonics e.g. SLB Sonic Scanner

Powerful data – What we need from Array Acoustics

Powerful data – Dielectric Tools

Powerful data – Sigma Logs: BVW

Powerful data – Sigma Logs: BVWe

Powerful data – LWD Sigma log: BVW

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

Carbonate Wireline Logging

Course Structure & Evaluation Sequence




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
This is what we will do..

Carbonate Matrix Evaluation

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, m and..?

Øs: approximate dt matrix

Øs: determine dt_fluid from dtf apparent (dtfa)

Øs: determine vugs & predict m with dtfa

Day3 PRACTICAL: Achieving Cost Effective Data Acquisition & Basic Carbonate Log Analysis

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 – impact on Ro and HC Pore Volume (HPV)

Is Water Zone ‘m’ related to Øvugs?  Use Øvugs to predict HC zone m

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

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

Carbonate matrix evaluation – reality is complex

Carbonate matrix – Determine vugs: Image logs

Carbonate matrix – Determine vugs: NMR logs

Carbonate matrix – summary variable m (mv) determination from Øvug

Day3 PRACTICAL: Basic Carbonate Log Analysis: Platform Carbonate, Gas





Recap Day3




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

Carbonate matrix – Wetting phase (water) desaturation with increasing Pc

Carbonate matrix  – Height positions the Pc-Sw data in the reservoir

Carbonate matrix – Use RCA to project data into the reservoir

Carbonate matrix – Capillary Pressure Measurement techniques

Carbonate matrix  – Core Overburden Electrical Properties combined with porous plate Pc

Carbonate matrix – Capillary Pressure Saturations, 4 controls on Sh

Carbonate matrix – Interfacial Tension IFT

Perched water contacts violate capillary pressure Saturation-height assumptions!

Carbonate matrix – Mercury injection data reveals PTSD

Carbonate matrix – Different Reservoir Qualities yield Different  TZ  thickness

Carbonate matrix  – In Transition Zones Pc is low and Sw>Swi.
Water and oil both mobile

MICROPRACTICAL Cutoff: Relative Perm SCAL data demonstrates the Netpay permeability cutoff

Carbonate matrix – Summary of J Function Sw from Pc data, Swj

Swpc:  J Bundles Ø, k and Ht to correlate with Sw

Some Sw Height Fit Equations..

Carbonate matrix – Converting Laboratory Pc  to reservoir Height

Carbonate matrix – Swj (predicted) vs core plug measured Sw

Carbonate matrix – QuickLook Swpc: arrange your Pc data like this..
Rocktype, Facies, HFU, FZI etc

Carbonate matrix  – Redisplay lab Pc results as a simple Sw-Ht grid

Carbonate matrix – Bulk Volume Water > Cap.Press BVWi Indicates Fluid Zone = Transition Zone; Residuals or Water

Carbonate matrix – Oil and Water mud core Sw compared to reservoir true Sw

Swobm:  Partial Invasion of an Oil Mud Core leaving an un-invaded centre

Carbonate matrix – Dean Stark apparatus used in the determination of oil mud Swcore

Carbonate matrix – Check OBM specs 3days before coring

Day4 PRACTICAL: Achieving Fit For Purpose QL Results 1/2

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)

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Carbonate matrix  – Magnetic Resonance Swi for ‘n’

Carbonate matrix  – A better way to display NMR data, you decide

Carbonate matrix – Four calibrations ensure correct matrix HPV  ..this is what we have done

Course Structure & Evaluation Sequence

k matrix QL: Adapt Chart K-4


Carbonate matrix  –  SDR permeability equation, T2 cutoff not used

Carbonate matrix – Coates permeability

Carbonate matrix – determine vug connectivity p = f.(Øvug)

Carbonate matrix  – Bound Fluid Volumes and logs

Carbonate matrix – Why the Coates Equation is so powerful

Carbonate matrix – Coates equation vs Core

Carbonate matrix – What is an Acoustic Stoneley Wave?

Carbonate matrix – Stoneley waves: Attenuation, Slowness & Mobility

Carbonate matrix –  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, especially in complex reservoirs

Carbonate Matrix – Key Points

Day4 PRACTICAL: Achieving Fit For Purpose QL Results 2/2





Recap Day4

Course Structure & Evaluation Sequence




Fractured Reservoir Evaluation process

Fractures – Basement High & Porosity Distribution, TypeC

Fractures – Fracture POROSITY is small!

Fractures – Limited storage: HPV per GRV << Intergranular

Fractures – Porosity: Outcrop studies

Fractures – Porosity: Core + Image logs

Fractures – Porosity: Well Tests TypeC  and TypeB if  kf>>km

Fractures – Fracture PERMEABILITY is large!

Fractures – Useful calculators
Frac Ø & HPV, from DST kh and Deterministic.  Type C and B if kf>>km

Fractures – Finding & Evaluating Fracs Data, Ranked

Fractures – Acoustic Stoneley Wave Reflection Coefficient

Fractures – Acoustic Stoneley Wave response

Fractures – Stoneley Attenuation and Fracture Aperture

Fractures – What is Acoustic Shear Wave Splitting?

Fractures – Acoustic Wave Shear Anisotropy

Fractures – Conjugate fractures & Smax

QL – Fracture ID: special logs 1

QL – Fracture ID: special logs 2

Fractures – Orientation: Acoustic & Image


Fractures – Circumfrential Acoustic Scanner Tool (CAST) amplitude displayed as dipping planes (fracs) with known orientation

Fractures – Comparison of Fracture Imaging Logs

Fractures – Production Logging Techniques

Fractures – S, E, Orientation and Length?
Fractures – Any other data? Drilling data is best

Fractures – Lithology may influence fracture spacing, S

Determine Fracture-Matrix Interaction

Fractures – Plan view: vertical fractures & horizontal well Fractures – Size, Density & Orientation

Fracture Orientation + Stress Orientation = Drill

Fracture Indicator Scores – exhaustive and definitive but slow

Fractures – Surprising Fluid Distributions after Production

Fractures – Some Key Points

Course Structure & Evaluation Sequence




A Consistent Geological Model

Imagine your reservoir as a road cutting..

Geo-model Checksums
Geo-model – EHC & kh must be equal at all scales of reservoir description!

Course Structure & Evaluation Sequence

Geo-model – 10 Systematic errors which will ruin your carbonate/fracture geo.model (chronological)

Day5  How to Use Capillary Pressure Data  – Questions




Twice Daily Practical work sessions

Each morning – Your considered questions and debate

100+ Critical Equations in MSExcel format


Key C&F technical papers



Recognize, understand and treat all the critical issues which threaten the Carbonate & Fracture petrophysicist.  The structured process detailed in this course will arm you with fresh confidence, knowledge and enthusiasm for your work as a Carbonate geoscientist.

If you love petrophysics you will love this course !

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