fresh formation water in tight reservoir rocks creates ... · introduction •in low salinity...

Fresh Formation Water in Tight Reservoir Rocks Creates Contention

Between Petrophysics and Geoscience

Ko Ko Kyi and Abbel Alexius KiobPETRONAS Carigali Sdn. Bhd.

EAGE/FESM Regional Technical Conference17 – 18 February 2014

Kuala Lumpur, MalaysiaOpen

INTRODUCTION

• Positive identification of a water bearing interval is crucial to evaluating hydrocarbon bearing reservoirs in a well.

• Accurate estimation of formation water resistivity iscritical for proper computation of reservoir parametersused in hydrocarbon resource assessment.

• In reservoirs with high formation water salinity, it isrelatively easy to differentiate water bearing zones fromthose bearing hydrocarbon.

Open

INTRODUCTION

• In low salinity environment, close to being fresh water, itbecomes difficult to positively identify a water bearingreservoir, since the formation resistivity is relatively high.

• In some cases, a fresh water bearing interval may be

misinterpreted as a hydrocarbon zone.

• In the Malay basin, there are several reservoirs which

contain relatively fresh formation water, making it

difficult to evaluate the well logs from these reservoirs.

Open

Example of a Stiff diagram for theMalay Basin, with a characteristicpeak of HCO3

- typical of fresh waterenvironments. The low conductivitymultiplier (0.3) for conversion toNaCl equivalent has a large effect atlow TDS.

Map of the Central Malay BasinCentral production fairway withcontours of salinity for the J-Reservoirs. Values as low as1kppm NaCl equivalent have beenanalyzes in the Tapis field.

After Heavysege, SPWLA 43rd Annual Logging Symposium, 2002

INTRODUCTION

Open

INTRODUCTION

• Some of these reservoirs are deep and have low porosity,which in combination with low water salinity, leading torelatively high formation resistivity.

• In certain reservoirs, there may even be some hydrocarbonshows, such as an oil stain on cuttings, which may havebeen due to residual hydrocarbon effects.

• The above often cause confusion and uncertainty ininterpreting the fluid type in these reservoirs.

• This creates a contention between geoscientists andpetrophysicists.

Open

INTRODUCTION

• Logs, such as the Dielectric log and Nuclear MagneticResonance log, may help in resolving this issue, oftentimesthey are not available.

• The simple but useful Spontaneous Potential SP log, whichcan identify fresh formation water, is not available in wellsdrilled with Oil Base Mud or in those where log data isacquired while drilling with LWD tools.

• Formation Tester tools can identify fluid type andacquire samples, but the tight nature of the reservoirrocks poses additional challenges in getting reliablefluid gradients and samples.

• Several attempts to take formation fluid samples usingwireline formation tester either failed or wereinconclusive.

Open

INTRODUCTION

• In some wells, Drill Stem Tests were carried out to acquirefluid samples and determine well deliverability if any.

• Most of these tests resulted in a very small influx offormation water into the well bore with little or no flow atthe surface.

• Consequently, there was a contention about the validity ofthe well tests and the conclusion on the fluid type.

• Bottom-hole samples taken during the tests indicate thatthe produced fluid from tested reservoirs was freshformation water.

• Static Gradient Surveys carried out in these wells alsoconfirmed some influx of fresh formation water.

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Well Logs From Exploration Well: AX-1

Open

Mud Log From Exploration Well: AX-1

Open

Interpretation of Exploration Well: AX-1

Interpretation carried out using water salinity of 5,000 ppmNaClOpen

Wireline Formation Tester Result: Well AX-1

DepthmMDDF

DepthmTVDSS

Gauge Type

HydrostaticPressure

Before (psia)

Formation Pressure

(psia)

Hydrostatic Pressure

After (psia)

Mobility (md/cp)

Remarks

x173.0 x137.14 Quartz 9979.30 - 9987.94 -Super

charged

x177.0 x141.17 Quartz 9999.80 9354.71 10000.40 0.3 Valid

x183.6 x147.77 Quartz 10020.90 - 10021.10 -Super

charged

No.Depth(mMD)

Recovery

LithologyOil Show

(Tr, P, F, G)

Visual Porosity(P. F. G)

Detailed Descriptioncm Cond

1 x173 4.2 Good Silty Sand No Show P

Clear, transparent to translucent, light grey, light brown, occasionally off white, loose quartz grain, hard consolidated core, very fine grain, graded to silty, sub angular to sub rounded, moderately sorted, poor visible porosity. No show.

2 x177 4.7 Good Silty Sand No Show P

Clear, transparent to translucent, light grey, light brown, occasionally off white, loose quartz grain, hard consolidated core, very fine grain, graded to silty, sub angular to sub rounded, moderately sorted, poor visible porosity. No show

3 x179 1.9 Mod. Silty Sand No Show P

Clear, transparent to translucent, light grey, light brown, occasionally off white, loose quartz grain, hard consolidated core, very fine grain, graded to silty, sub angular to sub rounded, moderately sorted, poor visible porosity. No show.

Rotary Side Wall Core description for well AX-1Open

Duration ChokePressure and Temperature Production Rate Fluid Properties

Bottomhole Wellhead Cond. Water SG BSW H2S CO2 Hg

hr:min /64” BHP BHT WHP WHT bbl/d bbl/d % ppm % ppb

psia degF psig degF

Clean Up Flow Period on Multiple Choke Size

22:00 16 1689 335 68 89 - - 0.782 - 1 10 -

Main Flow Period on 12/64” Adjustable Choke

12:00 12 1846 336 1908 157 - - 0.778 0 0 10 23.39

First Main Build Up Period

48:00 S/I 5739 338 3173 338 - - - - - - -

Second Clean Up Flow Period on Multiple Choke Size

12:00 12 1400 339 24 82 - - 0.84 0 0 8 -

Second Main Build Up Period

161:15 S/I 8612 341 6035 85 - - - - - - -

Summary of Well Test data for well AX-1

Open

Case History #2

Open

CASE HISTORY #3

• Water sample recovered from bottomhole has Rw of 0.35 ohmm@ 150oC (4,050ppmNaCl equivalent)

Well: BELURU-1-PEX

PETROPHYSICAL EVALUATION

COMPANY

WELL NAME

FIELD

COUNTRY

STATE

RIG NAME

FIELD LOCATION

LONGITUDE

LATITUDE

PERMANENT DATUM

ELEV of KB

ELEV of DF

ELEV of GROUND LEVEL

LOG MEASURED FROM

DRILL MEASURED FROM

SERVICES

SERVICE COMPANY

DATE PLOTTED

PLOTTED BY

GEOLOG SOFTWARE version 6.6.1p2

RUN INFORMATIONRUN NUMBER

LOG DATE

DRILLER DEPTH

LOGGER DEPTH

BOTTOM LOG INTERVAL

TOP LOG INTERVAL

CASING DRILLER

CASING LOGGER

CASING DIAMETER

CASING WEIGHT

BIT SIZE

HOLE FLUID TYPE

FLUID DENSITY

FLUID VISCOSITY

FLUID PH

FLUID LOSS

RM @ SURFACE (DEGF)

RMF @ SURFACE (DEGF)

RMC @ SURFACE (DEGF)

SURFACE HOLE TEMP(DEGF)

BOTTOM HOLE TEMP(DEGF)

MAX HOLE DEVIATION(DEG)

TOTAL DEPTH

Petronas Carigali Sdn. Bhd.

BELURU-1-PEX

PM 315

Malaysia

Terengganu

5* 02" 58.380' N

104* 51" 06.53' E

04-Jul-2012

hazlina_hashim

10-Feb-2012

-

-

-

-

-

-

-

-

-

- @ -

- @ -

- @ -

-

-

-

-

-

-

-

-

-

-

-

-

- @ -

- @ -

- @ -

-

-

-

-

-

-

-

-

-

-

-

-

- @ -

- @ -

- @ -

-

-

-

VLIME

VCLB

VCLD

VSILT

VSAND

SWT

PHIE

PHIT

NPHI

RHOB

RT

RM

RS

RXO

CALI

GR

VOIL

VGAS

VWATER

VDOLO

GAMMA RAY

CALIPER

FLUSHED ZONE RESISTIVITY

SHALLOW RESISTIVITY

MEDIUM RESISTIVITY

DEEP RESISTIVITY

BULK DENSITY

NEUTRON POROSITY

TOTAL POROSITY

EFFECTIVE POROSITY

TOTAL WATER SATURATION

VOLUME FRACTION OF SAND

VOLUME FRACTION OF SILT

VOLUME FRACTION OF DRY CLAY

CLAY BOUND WATER

VOLUME FRACTION OF LIMESTONE

VOLUME FRACTION OF DOLOMITE

VOLUME FRACTION OF WATER

VOLUME FRACTION OF GAS

VOLUME FRACTION OF OIL

LOG DESCRIPTION

Gas

Oil

Clay

Sand

Silt

Limestone

Anhydrite

Sylvite

Halite Coal

Clay bound water

LITHOLOGIES

Dolomite

-

-

-

-

-

-

-

-

-

- @ -

- @ -

- @ -

-

-

-

-

-

-

-

-

-

-

-

-

- @ -

- @ -

- @ -

-

-

-

SCALE 1:500

PCSB SAND SILT CLAY PETROPHYSICAL MODEL

Well: BELURU-1-PEX


RESERVOIR SUMMARY

2890

2910

2920

2930

2940

2960

2970

2980

2990

3010

3020

3030

3040

2900

2950

3000

DEPTHMETRES

GRGAPI0 200

HCALIN4 24

bsIN4 24

RSOHMM0.2 200

RTOHMM0.2 200

RHOBG/C31.85 2.85

NPHIV/V0.45 -0.15

pe0 20

HDRAG/C3-0.25 0.75

PHITV/V0 0.5

PHIEV/V0 0.5

PERMOHMM0.2 200

SWTFV/V0 1

SWSKELTV/V0 1

VCLDV/V0 1

VCLBV/V0 1

VDOLO0 1

VLIMEV/V0 1

VSILTV/V0 1

VSANDV/V0 1

VOILV/V0 1

VGASV/V0 1

VWATER0 1

COAL0 1

BADHOLE-1 0

ANHYDRITE0 1

• The target sand has high resistivity readings and small possible gas crossover

• Log interpretation using Rw of 0.16 ohmm @ 150oC indicates some possible hydrocarbon

Open

mailto:0.35@150oC

CASE HISTORY #4

• Interpreted logs with watersaturation SWTF computed withRw of 0.2 ohmm @ 145oC

• An oil sample was recoveredwith WFT in the upper Sand-Gwith similar log character

• High resistivity readings in Sand-H (up to 50 ohmm) indicatespossible oil bearing zone

Well: SPAOH-1


COMPANY

WELL NAME

FIELD

COUNTRY

STATE

RIG NAME

FIELD LOCATION

LONGITUDE

LATITUDE

PERMANENT DATUM

ELEV of KB

ELEV of DF


LOG MEASURED FROM

DRILL MEASURED FROM

SERVICES

SERVICE COMPANY

DATE PLOTTED

PLOTTED BY



LOG DATE

DRILLER DEPTH

LOGGER DEPTH

BOTTOM LOG INTERVAL

TOP LOG INTERVAL

CASING DRILLER

CASING LOGGER

CASING DIAMETER

CASING WEIGHT

BIT SIZE

HOLE FLUID TYPE

FLUID DENSITY

FLUID VISCOSITY

FLUID PH

FLUID LOSS

RM @ SURFACE (DEGF)






TOTAL DEPTH

PETROLIAM NASIONAL BERHAD

SPAOH-1

SK306

Malaysia

Sarawak

3° 44' 18.25000" N

112° 27' 7.81000" E

-999.25

21.3

04-Jul-2012

hazlina_hashim

12/19/2010

-

-

-

-

-

-

-

-

-

- @ -

- @ -

- @ -

-

-

-

-

-

-

-

-

-

-

-

-

- @ -

- @ -

- @ -

-

-

-

-

-

-

-

-

-

-

-

-

- @ -

- @ -

- @ -

-

-

-

VLIME

VCLB

VCLD

VSILT

VSAND

SWT

PHIE

PHIT

NPHI

RHOB

RT

RM

RS

RXO

CALI

GR

VOIL

VGAS

VWATER

VDOLO

GAMMA RAY

CALIPER


SHALLOW RESISTIVITY

MEDIUM RESISTIVITY

DEEP RESISTIVITY

BULK DENSITY

NEUTRON POROSITY

TOTAL POROSITY

EFFECTIVE POROSITY





CLAY BOUND WATER






LOG DESCRIPTION

Gas

Oil

Clay

Sand

Silt

Limestone

Anhydrite

Sylvite

Halite Coal

Clay bound water

LITHOLOGIES

Dolomite

-

-

-

-

-

-

-

-

-

- @ -

- @ -

- @ -

-

-

-

-

-

-

-

-

-

-

-

-

- @ -

- @ -

- @ -

-

-

-

SCALE 1:500


Well: SPAOH-1


RESERVOIR SUMMARY

3060

3070

3080

3090

3110

3120

3130

3140

3160

3170

3180

3190

3210

3220

3230

3240

3260

3270

3280

3290

3100

3150

3200

3250

DEPTHMETRES

GRGAPI0 200

CALIIN4 24

bsIN4 24

RSOHMM0.2 200

RTOHMM0.2 200

RHOBG/C31.85 2.85

NPHIV/V0.45 -0.15

pe0 20

drhoG/C3-0.25 0.75

PHITV/V0 0.5

PHIEV/V0 0.5

PERMOHMM0.2 20000

SWTFV/V0 1

SWSKELTV/V0 1

VCLDV/V0 1

VCLBV/V0 1

VDOLO0 1

VLIMEV/V0 1

VSILTV/V0 1

VSANDV/V0 1

VOILV/V0 1

VGASV/V0 1

VWATER0 1

COAL0 1

BADHOLE-1 0

ANHYDRITE0 1

SAMPLING

SA

MP

LIN

G

DST

DS

T

Sand_F BottomSand_G

Sand_G Bottom

Sand_H

Open

CASE HISTORY #4

• Log interpretation with watersaturation computed using Rwof 0.66 ohmm @ 145oC

• Interval (3157-3184mMD) wastested and produced 1,600bbl/day of water with salinity of1,800 ppmNaCl equivalent

Well: SPAOH-1


COMPANY

WELL NAME

FIELD

COUNTRY

STATE

RIG NAME

FIELD LOCATION

LONGITUDE

LATITUDE

PERMANENT DATUM

ELEV of KB

ELEV of DF


LOG MEASURED FROM

DRILL MEASURED FROM

SERVICES

SERVICE COMPANY

DATE PLOTTED

PLOTTED BY



LOG DATE

DRILLER DEPTH

LOGGER DEPTH

BOTTOM LOG INTERVAL

TOP LOG INTERVAL

CASING DRILLER

CASING LOGGER

CASING DIAMETER

CASING WEIGHT

BIT SIZE

HOLE FLUID TYPE

FLUID DENSITY

FLUID VISCOSITY

FLUID PH

FLUID LOSS

RM @ SURFACE (DEGF)






TOTAL DEPTH

PETROLIAM NASIONAL BERHAD

SPAOH-1

SK306

Malaysia

Sarawak

3° 44' 18.25000" N

112° 27' 7.81000" E

-999.25

21.3

04-Jul-2012

hazlina_hashim

12/19/2010

-

-

-

-

-

-

-

-

-

- @ -

- @ -

- @ -

-

-

-

-

-

-

-

-

-

-

-

-

- @ -

- @ -

- @ -

-

-

-

-

-

-

-

-

-

-

-

-

- @ -

- @ -

- @ -

-

-

-

VLIME

VCLB

VCLD

VSILT

VSAND

SWT

PHIE

PHIT

NPHI

RHOB

RT

RM

RS

RXO

CALI

GR

VOIL

VGAS

VWATER

VDOLO

GAMMA RAY

CALIPER


SHALLOW RESISTIVITY

MEDIUM RESISTIVITY

DEEP RESISTIVITY

BULK DENSITY

NEUTRON POROSITY

TOTAL POROSITY

EFFECTIVE POROSITY





CLAY BOUND WATER






LOG DESCRIPTION

Gas

Oil

Clay

Sand

Silt

Limestone

Anhydrite

Sylvite

Halite Coal

Clay bound water

LITHOLOGIES

Dolomite

-

-

-

-

-

-

-

-

-

- @ -

- @ -

- @ -

-

-

-

-

-

-

-

-

-

-

-

-

- @ -

- @ -

- @ -

-

-

-

SCALE 1:500


Well: SPAOH-1


RESERVOIR SUMMARY

3060

3070

3080

3090

3110

3120

3130

3140

3160

3170

3180

3190

3210

3220

3230

3240

3260

3270

3280

3290

3100

3150

3200

3250

DEPTHMETRES

GRGAPI0 200

CALIIN4 24

bsIN4 24

RSOHMM0.2 200

RTOHMM0.2 200

RHOBG/C31.85 2.85

NPHIV/V0.45 -0.15

pe0 20

drhoG/C3-0.25 0.75

PHITV/V0 0.5

PHIEV/V0 0.5

PERMOHMM0.2 20000

SWTFV/V0 1

VCLDV/V0 1

VCLBV/V0 1

VDOLO0 1

VLIMEV/V0 1

VSILTV/V0 1

VSANDV/V0 1

VOILV/V0 1

VGASV/V0 1

VWATER0 1

COAL0 1

BADHOLE-1 0

ANHYDRITE0 1

SAMPLING

SA

MP

LIN

G

DST

DS

T

Sand_F BottomSand_G

Sand_G Bottom

Sand_H

Open

CASE HISTORY #5

• Mud log indicates oil show and high gas reading in the tested interval of J25/30 sands.

• The well was drilled to test thetarget sand J25/30.

• The target interval was tested• Well did not flow even after

lifting with nitrogen.

Open

• Several case histories highlight the challenges encountered inevaluating fresh water bearing formations.

• Oil shows or high gas readings on the mud log cansometimes be misleading and should be treated with cautionto avoid unnecessary fluid sampling and well testingoperations.

• The occurrence of fresh water in the aquifer can have asignificant implication on the estimation of water saturationin the hydrocarbon bearing zones.

• The presence of fresh formation water in low porosity (tight)reservoirs can create contention between petrophysicistsand geoscientists with regards to fluid typing.

CONCLUSIONS

Open

The authors would like to acknowledge their gratitude toPETRONAS and PETRONAS Carigali management for theirpermission to present his paper.

ACKNOWLEDGEMENTS

Open

fresh formation water in tight reservoir rocks creates ... · introduction •in low salinity...

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