Logical, Systematic, Complete

**Integrated Petrophysics for Carbonate and Fractured Reservoirs – A Roadmap**

**Detailed Contents**

DAY1

INTRODUCTION

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

PHYSICAL CHARACTER OF CARBONATES & FRACTURES

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

CLICK TO PLAY – NMR

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

CLICK TO PLAY – IMAGE LOGS

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 PHYSICAL CHARACTER ON RESERVOIR MEASUREMENTS

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

END DAY 1

DAY2

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

ACHIEVING OPTIMAL DATA ACQUISITION

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

END DAY 2

DAY3

Recap Day2

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

Powerful data – What we need from Array Acoustics

Powerful data – Dielectric Tools

CLICK TO PLAY – DIELECTRIC

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

FRACTURE ID & QL EVALUATION

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/COMPLEX MATRIX EVALUATION

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

END DAY 3

DAY4

Recap Day3

RESERVOIR ROCK TYPE (RRT) EQUATION SETS – MATRIX SW, K

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 cap.press 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

CLICK TO PLAY – NMR

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

CLICK TO PLAY – WFTS

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

END DAY 4

DAY5

Recap Day4

Course Structure & Evaluation Sequence

FRACTURES & MATRIX INTERACTION

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

CLICK TO PLAY – ARRAY SONICS

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

BUILDING & USING THE GEO-MODEL

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

END

Twice Daily Practical work sessions

Each morning – Your considered questions and debate

100+ Critical Equations in MSExcel format

Abbreviations

Key C&F technical papers

References

Charts

*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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