SPWLA KUWAIT 2013

FORMATION SATURATIONS

ERCAN OZER

CORE LABORATORIES INTERNATIONAL B.V.

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INTRODUCTION

INTRODUCTION FLUIDS DISTRIBUTION/DESCRIPTIONS SATURATION CHANGES SATURATION DETERMINATION TECHNIQUES PETROPHYSICAL PARAMETERS/DEFINITIONS CORE-LOG INTEGRATION- CASE STUDIES CONCLUSIONS

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SPWLA KUWAIT 2013

INTRODUCTION

IT IS ESSENTIAL THAT RESERVOIR FORMATION SATURATIONS (OIL,WATER,GAS) DETERMINED ACCURATELY FOR RESERVOIR ECONOMICS.

STARTING WITH EXPLORATION STAGE SATURATIONS SHOULD BE MONITORED CAREFULLY DURING THE LIFE OF THE RESERVOIRS.

INITIAL WATER SATURATION THAT DETERMINES THE OIL IN PLACE AND RESIDUAL OIL SATURATION THAT EOR RECOVERY PLANS ARE BASED ON ARE TWO IMPORTANT VALUES.

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INTRODUCTION

OIL IN PLACE

CAPILLARY PRESSURE

ELECTRICAL PROPERTIES

t

n

o

b

hh

BSwVSTOIP .)1.(. −

=φ

ghr

Pc ow )(cos2 ρρθσ−==

tm

wnw

RaRSφ

=

SPWLA KUWAIT 2013

0 100% Sw

Irred

ucib

le W

ater

Sat

urat

ion

Swir

Well

Top Transition Zone

Transition Zone

Free Water Level (Pc = 0)

HC and Mobile Water

Observed HC-WC (Pc = Pce)

HC, water-free

DEPTH

FLUIDS DISTRIBUTION

OIL IN PLACE

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Res

idua

l Oil

Satu

ratio

n

FLOOD

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FORMATION SATURATIONS

WHAT ARE THE IN-SITU WATER AND HYDROCARBON SATURATIONS OF THE FORMATION?

WHAT IS THE Rw ?

HAS DRILLING MUD FILTRATE INVADED THE FORMATION AND ALTERED THE SATURATIONS? IF SO,WHAT IS THE PERCENT CONTAMINATION?

HAS SURFACE HANDLING OF SAMPLES ALTERED SATURATIONS?

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CONNATE WATER SATURATION (Swi) THIS IS THE WATER SATURATION IN THE RESERVOIR

AT THE TIME OF DISCOVERY AND COULD BE HIGHER THAN IRREDUCABLE WATER SATURATION.

IRREDUCABLE WATER SATURATION (Swir) THIS IS THE LOWEST WATER SATURATION THAT CAN

BE ACHIEVED AT HIGH CAPILLARY PRESSURE – GREAT HEIGHT ABOVE OIL-WATER CONTACT- AT WHICH POINT WATER RELATIVE PERMEABILITY APPROACHES ZERO.

DEFINES OIL IN PLACE

SATURATION DESCRIPTION - WATER

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SATURATION DESCRIPTIONS - OIL

THE TERM “RESIDUAL OIL SATURATION” IS USED IN MANY DIFFERENT CONTEXT IN THE LITERATURE.

THE AMOUNT OF HYDROCARBON REMAINING IN THE FORMATION AT THE END OF A SPECIFIED PRODUCTION PROCESS, I.E. WATER/GAS SWEPT ZONES

THE OIL SATURATION AT WHICH REMAINING OIL BECOMES IMMOBILE OR COMPLETELY TRAPPED.

THE VALUE IS FREQUENTLY USED IN THE EVALUATION OF EOR/IOR.

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SATURATION CHANGE

THE RESERVOIR AQUIFER WATER DRIVE GAS CAP EXTENSION IOR/EOR APPLICATIONS

THE WELLBORE

FILTRATE INVASION

CORES FILTRATE INVASION TRIP UP SURFACE EXPOSURE PROCESSING

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GAS

WATERER

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SATURATION CHANGE – DRILLING/CORING

FILTRATE INVASION DRILLING BIT TECHNOLOGY

DEVELOPMENTS AVOIDS DEEP INVASION-PDC (POLYCRYSTALLINE DIAMOND COMPACT) BITS.

OIL BASED MUDFILTRATE DISPLACES FLUIDS IN THE LARGE PORES,THEREFOR Sw WILL NOT CHANGED, ESPECIALLY IN THE OIL COLUMN.SIMILAR TO A DRY GAS/OIL PRODUCTION IN A WELL.

WATER BASE MUD FILTRATE INVASION CAN BE MINIMIZED AND LIMITED TO THE OUTER PART OF THE CORES BY LOW INVASION CORING TECHNOLOGY APPLICATION.

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Core

Fluid

channe

l

Courtesy BHI

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SATURATION CHANGE – DRILLING/CORING OIL PRODUCTIVE

In reservoir

At surface

Badly Flushed Water Base Mud

12%

58%

70%

30%

30%

Not Flushed

30%

50%

20%

70%

30% water oil gas

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SATURATION CHANGE – DRILLING/CORING GAS PRODUCTIVE

In reservoir

At surface

Badly Flushed Water Base Mud

1%

50%

70%

30%

49%

Not Flushed

30%

68%

2%

70%

30%

water oil gas

Badly Flushed Oil Base Mud

40%

30%

70%

30%

30%

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SCHEDULE SHOULD BE BASED ON; BUBLE POINT AND GOR VENT DESIGN DEPENDENT ON GOR CARE SHOULD BE TAKEN FOR DE-GASSING

TYPICAL DE-GASSING MODEL

80% SPEED TO BUBLE POINT 3 MIN/STAND FROM BUBLE POINT TO 2000 FT 6 MIN/STAND FROM 2000 FT TO 1000 FT 15 MIN/STAND FROM 1000 FT TO 200 FT 30 MIN/STAND FROM 200 FT TO SURFACE

SCHEDULE SHOULD BE DESIGNED BY DRILLING DEPARTMENT AND

CORING COMPANY AS IT IS RESERVOIR SPECIFIC.

SATURATION CHANGE – CORING/TRIP UP

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FLUID EVAPORATION SHOULD BE KEPT TO MINIMUM ONCE THE CORE REACHES SURFACE. PROPER SURFACE HANDLING

TECHNIQUES ESSENTIAL VARIOUS PRESERVATION AND

STABILIZATION TECHNIQUES CAN BE EMPLOYED.

PROPER SAMPLE MANAGEMENT RAPID ANALYSIS

SATURATION CHANGE – SURFACE

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SALT CRYSTALS

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THERE ARE 3 INDIRECT WAYS OF SATURATION EVALUATION. DOWN HOLE LOGS

CORES

PETROPHYSICAL MEASUREMENTS CAPILLARY PRESSURE TESTS ELECTRICAL PROPERTIES

CHEMICAL TRACER TESTS

SATURATION DETERMINATION TECHNIQUES

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LOGS ARE COMMONLY USED FOR SATURATION CALCULATIONS UTILISING ARCHIE MODEL THAT IS REPRESENTED BY THE FOLLOWING EQUATIONS(CLEAN AND SHALY FORMATIONS) AND THE ACCURACY OF Sw IS CONTROLLED BY INPUT PARAMETERS.

WHERE; a ,coefficient Ro/Rw value at φ=1 m, porosity (cementation) exponentB = n, saturation exponent φ, total porosity Rt, resistivity of reservoir Rw ,resisitivity of reservoir water Sw ,water saturation B,specific counterion activity Qv , quantity of cation exchangeable clay present

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WATER SATURATION

tm

wnw

RaRSφ

=

+

=

w

wt

wnw

SQvBRR

RFS..1.

.**

SPWLA KUWAIT 2013

WATER SATURATION-Rw

DETERMINATION OF FORMATION BRINE RESISTIVITY (Rw) IS ANOTHER VARIABLE THAT IS EXTREMELY IMPORTANT FOR Sw CALCULATION.

RESISITIVITY-SALINITY-TEMPERATURE CHARTS INDICATE DIFFERENCES;

T = 100 F Rw = 0.040…CHART1 T = 100 F Rw = 0.034…CHART2 CHANGE IN Rw = 0.006

T = 220 F Rw = 0.018 T = 220 F Rw = 0.015 CHANGE IN Rw = 0.003

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WATER SATURATION-Rw

IMPACT OF 0.003 ohm-m CHANGE ON Sw HOLDING OTHER PARAMETERS CONSTANT (Φ=25%,m=n=2,a=1) IS 3% AT Sw 20%

SW(Rw=0.0155) vs SW(Rw=0.0185)

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100

SW (%) for Rw=0.0155

SW (%

) at N

ew R

w

Porosity = 0.25M = 2.0N = 2.0A =1

Rw = 0.0155

Rw = 0.0185

20% Sw

23% Sw

Ref;D.Boyd

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Ø SONIC DENSITY NEUTRON NMR

Rw RECOVERED FORMATION WATER Rw CHARTS WIRELINE FORMATION TESTER WATER GRADIENT SP LOGS(SPONTANEOUS POTENTIAL)

Rt RESISTIVITY LOGS

m,n,a CHARTS CROSS PLOTS LITERATURE

n

t

wm

R

RaSw

×

=φ

Key Parameters For Saturation LOG MEASUREMENTS

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Ø MEASEURED ON RECOVERED CORE

Rw MEASURED ON RECOVERED FORMATION WATER

Rt MEASURED ON RECOVERED CORE

m,n,a Rt, Ro, Rw MEASURED ON RECOVERED CORE

n

t

wm

R

RaSw

×

=φ

Key Parameters For Saturation LAB MEASUREMENTS

SPWLA KUWAIT 2013

INCREMENTAL CHANGES IN m (STRESS) and n (ROCK TYPE,WETTABILITY) LEADS TO UNCERTAINTY IN WATER SATURATION

n = 1.6 Sw = 12% n = 2.2 Sw = 21% CHANGE IN Sw = 9%

n = 2.0 Sw = 40% n = 2.3 Sw = 45%% CHANGE IN Sw = 5%

WATER SATURATION - UNCERTAINTIES

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1

10

100

1000

10000

0.01 0.1 1

BRINE SATURATION, fraction Vp

RES

ISTI

VITY

IND

EX

Drainage (at Swi before ageing) 'n' = 2.11

Drainage (after ageing) 'n' = 2.20

Imbibition Cycle (after ageing)

Composite 'n' = 3.03

Drainage Cycle (before ageing)

Composite 'n' = 2.06

SPWLA KUWAIT 2013

LABORATORY CAPILLARY PRESSURE TESTS ARE ANOTHER SOURCE OF OBTAINING RESERVOIR SATURATIONS. POROUS PLATE AND

CENTRIFUGE TECHNIQUES ARE UTILIZED TO MEASURE SATURATION AS A FUNCTION CAPILLARY PRESSURE. UNCERTAINTIES ARE

CONTROLLED BY INTERFACIAL TENSION,CONTACT ANGLE AND FLUID DENSITIES.

WATER SATURATION-CAPILLARY PRESSURE

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0 1

Sw

Cap

illar

y Pr

essu

re o

r Hei

ght A

bove

FW

L

OWC

OWC

OWC FWL

Sedi

men

tary

Seq

uenc

e

A B C Rock Type

0 1 Sw

Sw from Wireline

B

A

C

B

A

B

A

C Sw trace

FLUIDS DISTRIBUTION AND CAPILLARY PROPERTIES

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DIRECT MEASUREMENTS OF WATER SATURATION CAN BE MADE ON THE CORES CUT FROM RESERVOIRS WITH DEAN STARK ANALYSIS.

HOWEVER UNCERTAINTIES IN MOBILIZED FLUIDS DURING CORING, TRIP UP, HANDLING AT THE WELL- SITE, TRANSPORTATION AND LABORATORY ANALYSIS SHOULD BE MINIMIZED BY PRE-PLANNED PROCEEDURES.

WATER SATURATION

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Condenser

Graduated collection tube

Flask

Core sample

Solvent

Desiccant

SPWLA KUWAIT 2013

0

20

40

60

80

100

0.0 0.2 0.4 0.6 0.8 1.0 Water Saturation, fraction Vp

Hei

ght A

bove

Fre

e W

ater

Lev

el, f

eet

Variation Depending on Factors Controlling Flushing

RESERVOIR VALUE

Core Analysis Value from: OIL-BASE CORE or Tracer-Validated, LOW INVASION WBM CORE

CORE ANALYSIS VALUE FROM WATER-BASE CORE

Mobile Reservoir Water

Immobile Reservoir Water

SATURATIONS – CORE ANALYSIS VS RESERVOIR VALUES

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RRP 14_version 01

INVASION PROFILE AND WATER SATURATION

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

6835 6854 6892 6907 6925 6938 6954 6980 6995DEPTH,ft

Sw,%

PV

MEASURED Sw,%PV CORRECTED Sw,%PV LOG Sw%

LOW INVASION CORE ANALYSIS-EXAMPLE

SPWLA KUWAIT 2013

METHODS FOR DETERMINING RESIDUAL OIL SATURATION

DOWN HOLE SINGLE WELL CHEMICAL TRACER TESTS LOG-INJECT-LOG CARBON-OXYGEN LOGGING RESISTIVITY LOGGING NMR LOGGING

SPECIAL CORING TECHNIQUES PRESSURE CORING SPONGE CORING GEL CORING LIQUID TRAPPER

LABORATORY TECHNIQUES MEASUREMENT OF RESIDUAL FLUID VOLUMES ADVANCED TWO PHASE FLOOD EXPERIMENTS

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RCA 02 WELL LOGS BASICS

High-Resolution 1.2” Sample Rate

2.3 2.8 Bulk Density, g/cm3

Gamma Log 0 150 API

12760

12770

12780

12790

12800

12810

12820

12830

2.3 2.8

Standard 6” Sample Rate Bulk Density, g/cm3

LOG & CORE POROSITY Lower Vicksburg - McAllen Ranch

Authors doing detailed permeability modeling with porosity as input in this gas productive fm

Comparison of core calculated bulk density vs Log revealed some large differences

High-resolution log run showed formation variations not observed at standard log sample rate

Core data correct; log resolution issue

Shows application of core ρb for log-core depth adj.

Grigsby & Langford, AAPG Bulletin 1996 After J.Dacy 5/20/2013 28

RCA 02 WELL LOGS BASICS

0 100 V shale 0 30 POROSITY LOG CORE

3650

3660

3670

3680

3690

3700

3710

0 100 WATER SATURATION Depth, m

LOG CORE (OBM)

North Sea Oil Field; core cut with OBM

Core water saturations reveal log resistivity-based Sw model underestimates reserves Over entire sequence Particularly in more shaley

intervals

Log porosity model validated with core

Resistivity model adjusted to conform with core Sw

CORE & LOG Sw OIL BASED MUD

After Woodhouse; The Log Analyst, May June 1998 After J.Dacy

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SUMMARY

IT IS ESSENTIAL THAT RESERVOIR FORMATION SATURATIONS (OIL,WATER,GAS) DETERMINED ACCURATELY FOR RESERVOIR ECONOMICS.

THIS CAN BE ACHIEVED UTILIZING DATA OBTAINED FROM VARIOUS RELIABLE SOURCES

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SINGLE WELL CHEMICAL TRACER INJECTION IS

ANOTHER INDIRECT METHOD USED IN DETERMINING WATER SATURATION. AN ACETATE TRACER INJECTED,AFTER SOAKING

TAKES PLACE THE PRODUCED FLUIDS ANALIZED. COMPLEX NUMERICAL SIMULATION IS REQUIRED FOR

ANALYSIS. THIS TECHNIQUE IS COSTLY AND REARLY USED.

WATER SATURATION

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OIL SATURATION

ONCE Sw-INITIAL IS DETERMINED ACCURATELY , THEN So-INITIAL OIL SATURATION CAN BE CALCULATED.

HOWEVER,MEASUREMENT OF REMAINING OIL SATURATION(ROS) AT VARIOUS STAGES OF RESERVOIR DEPLETION PLAYS AN IMPORTANT ROLE IN RESERVOIR MANAGEMENT PROGRAMS.

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DEFINITION OF RESIDUAL OIL SATURATION

THE IRREDUCIBLE OIL SATURATION(IOS) IS OFTEN USED AS A DEFINITION OF RESIDUAL OIL SATURATION(ROS).

THIS IS THE OIL SATURATION AT WHICH REMAINING OIL BECOMES IMMOBILE OR COMPLETELY TRAPPED.

IOS DEPENDS ON WETTABILITY,WATER THROUGHPUT AND GRAVITY SEGREGATION OF OIL DURING THE WATER FLOOD.

IN A WATER WET RESERVOIR ROS CAN FREQUENTLY BE APPROACHED BY SMALL PORE VOLUME OF WATER.

IN THE MIXED WETTABILITY SYSTEM THE PRODUCING WATER-OIL RATIO BECOMES VERY HIGH LONG BEFORE IOS APROACHES.

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DEFINITION OF RESIDUAL OIL SATURATION

AN AVERAGE(MATERIAL BALANCE) OIL SATURATION (AOS) REMAINING IN THE RESERVOIR AT THE CONCLUSION OF WATERFLOOD IS FREQUENTLY USED FOR ROS.

THIS ESTIMATE CAN BE MISLEADING AS REMAINING OIL IS NOT UNIFORMLY DISTRIBUTED BECAUSE OF; PERMEABILITY STRATIFICATION AREAL HETEROGENEITY GRAVITY SEGREGATION VARIABLE WATER THROUGHPUT

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DEFINITION OF RESIDUAL OIL SATURATION

THE OIL SATURATION REMAINING IN THE WATER-SWEPT ZONES; FROM A PRACTICAL POINT OF VIEW THE ROS IS THE VALUE OF

THE OIL SATURATION REMAINING IN THE MORE PERMEABLE WATER-SWEPT ZONES WHEN THE PRODUCING WATER-OIL RATIO REACHES THE ECONOMIC LEVEL.THIS VALUE IS FREQUENTLY USED IN THE EVALUATION OF EOR.

THE AMOUNT OF HYDROCARBON REMAINING IN THE FORMATION AT THE END OF A SPECIFIED PRODUCTION PROCESS.

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METHODS FOR DETERMINING RESIDUAL OIL SATURATION

SINGLE WELL CHEMICAL TRACER TESTS LOG-INJECT-LOG CARBON-OXYGEN LOGGING RESISTIVITY LOGGING NMR LOGGING

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INCREMENTAL CHANGES IN m (STRESS) and n (ROCK TYPE,WETTABILITY) LEADS TO UNCERTAINTY IN WATER SATURATION

φ = 20% Rt = 15 m = 1.8 Sw = 34.8% m = 2.0 Sw = 40.8% CHANGE IN Sw = 6%

φ = 10% Rt = 15 m = 1.8 Sw = 64.9% m = 2.0 Sw = 81.6% CHANGE IN Sw = 17%

WATER SATURATION-UNCERTAINTIES

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1

10

100

1000

10000

0.01

RES

ISTI

VITY

IND

EX

Drainage ageing

Drainage

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Ø SONIC DENSITY NEUTRON NMR

Rw RECOVERED FORMATION WATER Rw CHARTS WIRELINE FORMATION TESTER WATER GRADIENT SP LOGS(SPONTANEOUS POTENTIAL)

Rt RESISTIVITY LOGS

m,n,a CHARTS CROSS PLOTS LITERATURE

Ø MEASEURED ON RECOVERED CORE

Rw MEASURED ON RECOVERED FORMATION WATER

Rt MEASURED ON RECOVERED CORE

m,n,a Rt, Ro, Rw MEASURED ON RECOVERED CORE

n

t

wm

R

RaSw

×

=φ

Key Parameters For Saturation LOGS VS LAB MEASUREMENTS

SPWLA KUWAIT 2013

a – COEFFICIENT Ro/Rw VALUE AT φ = 1 m - POROSITY (CEMENTATION) EXPONENT

SHOULD BE DIRECTLY MEASURED ON CORE SAMPLES n – SATURATION EXPONENT

SHOULD BE DIRECTLY MEASURED ON CORE SAMPLES

φ - TOTAL POROSITY LOG CALIBRATED AGAINST CORE DATA

Rt – RESISITIVITY OF THE RESERVOIR CORRECTED FOR WELL BORE CONDITIONS,INVASION

Rw – RESISITIVITY OF THE RESERVOIR WATER SHOULD BE MEASURED ON PRODUCED WATER

WATER SATURATION

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SATURATIONS

FLUID SATURATION DETERMINED WITH DEAN STARK ANALYSIS.

Condenser

Graduated collection tube

Flask

Core sample

Solvent

Desiccant

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