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SPE Distinguished Lecturer Program. Primary funding is provided by The SPE Foundation through member donations and a contribution from Offshore Europe The Society is grateful to those companies that allow their professionals to serve as lecturers Additional support provided by AIME.

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SPE Distinguished Lecturer Program

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Spe distinguished lecturer program

SPE Distinguished Lecturer Program

Primary funding is provided by

The SPE Foundation through member donations

and a contribution from Offshore Europe

The Society is grateful to those companies that allow their professionals to serve as lecturers

Additional support provided by AIME

Society of Petroleum Engineers Distinguished Lecturer Program

www.spe.org/dl


Spe distinguished lecturer program

Maximizing the Value of an Asset through the Integration of Log and Core data

Tim OSullivan

Cairn India Ltd

  • Colleagues:Hal Warner

    • Dick Woodhouse

    • Dennis Beliveau

    • Ron Zittel

    • Stuart Wheaton

Society of Petroleum Engineers Distinguished Lecturer Program

www.spe.org/dl


Spe distinguished lecturer program

Where is the data area ?

2004

Discovery Well

Mangala, Aishwariya & Bhagyam Fields

( about 2 Billion Barrels STOOIP)

150m - 350m oil columns


Spe distinguished lecturer program

The Reservoir - Excellent Quality Sandstone

Porosity:

26%

33%

17%

Permeability:

20 Darcies

5 D

200md

Clastic Fluvial Reservoirs

Upper Fatehgarh

Lower Fatehgarh


Spe distinguished lecturer program

What’s Interesting? (to Reservoir Teams)

Fatehgarh Sand Reservoirs

Excellent Reservoir Quality Sands

* Porosity 17-33% (average ~26%)

* Permeability up to 20 Darcies (average ~5D)

* Weakly-to-Moderately Oil-Wet

* VERY LOW Water Saturations – Field Avg. 5%

Quite a LOT of Interesting Oil

* Mangala Field – Over 1 Billion Barrels Oil In Place

* An Economic Incentive for Petrophysical ACCURACY

* Very Waxy, Sweet Crude – 27 o API Avg.

An EXCELLENT Dataset

* All Wells with Full “Basic” Logging Suites

* Many Wells with “Specialty” Logs – CMR+, etc.

* 1.7 km of Core in MBA


Spe distinguished lecturer program

100,000

10,000

1,000

100

10

Permeability (OBC), md

1

0%

10%

20%

30%

40%

Porosity (OBC), %

Fatehgarh Sand Reservoirs

Routine Core Analysis – Mangala Field

Coarse

Sand

Silt


Spe distinguished lecturer program

Oil Wet

Intermediate

Water Wet

10

1

5

4

Capillary Pressure (psi)

0

2

3

1

  • Initial Oil Drive

  • Free Imbibition of Brine

  • Brine Drive

  • Free Imbibition of Oil

  • Oil Drive

2

3

4

5

-10

0

Average Sw

100

IAH = WWI - OWI

Fatehgarh Sand Reservoirs

Wettability Index Data – Mangala Field

Combined Amott/USBM Wettability Experiment

No Relationship with Permeability!

WWI= water wetting index

WWI= proportion of the total oil production produced spontaneously

~ -0.35 Weakly oil wet

OWI= oil wetting index

OWI = proportion of the total brine production produced spontaneously


Spe distinguished lecturer program

Wettabilityvs. Various Parameters

No Relationship with K/Phi!

No Relationship with Vol Clay

No Relationship with Grain Size

No Relationship with Depth

Probably Wettability predominantly a function of oil composition, with some natural variation/heterogeneity


Spe distinguished lecturer program

Hydrophobic

(Oil Wet)

Neutral Wetting

0

Hydrophilic

(Water Wet)

0

0

Cos0 < 0

Cos0 = 0

Cos0 > 0

Wettability, Transition Zones and Saturation Ht Functions

Wettability impacts the contact angle in conversions from laboratory to reservoir conditions

PcR = PcL * (TCos0)R/(TCos0)L

T = Interfacial Tension

0 = Contact Angle

At Mangala, OWC & small Transition Zone below FWL due to Weakly Oil Wet Rock !!

OWC

Below FWL

OWC above FWL

OWC ~ FWL

OWC

FWL (FOL !)

FWL

OWC

OWC

FWL


Spe distinguished lecturer program

Fatehgarh Sand Reservoirs

PVT Data – Mangala Field

Variation in oil composition

Mangala-5 oil

Looks VERY interesting

Mangala-5 oil

Looks EXTREMELY interesting

Mangala-5 oil

looks interesting

  • High pour point - solid at ambient temperatures


Spe distinguished lecturer program

600km heated pipeline – world’s longest

SEHMS = Skin Effect Heat Management System

(also known as STS/SECT)

  • SEHMS ensures temperature maintenance above 65 deg


Spe distinguished lecturer program

What’s Interesting? (to Management)

Fatehgarh Sand Reservoirs

Quite a LOT ofOil….But…. EXACTLY How Much?

Oil= V * Porosity* (1 –Sw)

Sw

)


Spe distinguished lecturer program

An Exercise in Classical Petrophysics

Or… “How to Get to Sw”

Conventional

“Archie” Log Analysis

NMR

Logging

Capillary PressureSaturation-HeightFunctions

Direct

Measurement

Calculation

And

Assumptions

Swn = Rw/Rt *a/phitm

With only log data, and using a value of n of 2.3 (oil wet reservoir) – Sw of 15%

Dean-Stark

Core Analysis

Sw!!

Sw

?

Swn = Rw/Rt *a/phitm

Are low Sw’s 5% and less possible ?


Spe distinguished lecturer program

Mangala, Aishwariya and Bhagyam FieldsAn EXCELLENT Dataset

Summary - Available Core Analysis Data

  • SIXTEEN Cored Wells

    • Routine Core Analysis

    • Mostly Drilled with WBM

  • Mangala 1ST

    • First Core – Early 2004

    • Water-Based Mud

    • Initial SCAL Data

  • Dean-Stark Cores

    • Bhagyam 5

    • Mangala 7ST

Company Culture of taking CORES!


Spe distinguished lecturer program

Mercury Injection Capillary Pressure DataMangala Field

Low Sw !

Sw < 10%

Oil Column


Spe distinguished lecturer program

Validity of MICP data?

Probably reasonable in high quality clean reservoirs

(Honarpour - 2004 )

Main issues : Hg may not replicate reservoir fluid displacement

: destructive – normally conducted on small chips

: remove the effects of quartz compression

Quartz compression can account for 3 to 4 Sw units, as modern MICP machines can reach up to 60,000 psi.

Straight line Tails

Quartz compression


Spe distinguished lecturer program

Dean-Stark Fluid Saturations

Plugs cut at wellsite

SCAL Plug

Dean Stark Extraction

Horizontal

Plug

Vertical

Plug

Oil based mud cores

Plugs cut at wellsite

Minimize fluid loss

Minimize surfactants

Minimize core exposure to air

and to sun

1 inch

Minimize invasion of mud

Maximize retaining of fluids in plugs

Uninvaded core centre


Spe distinguished lecturer program

Dean-Stark Fluid Saturations Contamination Plot –Bhagyam 5

Horizontal

Plug

30%

X80m

25%

X15m

X78m

20%

X32m

15%

OBM Filtrate Contamination

in Oil%

10%

5%

0%

A

B

C

D

E

F

G

H

I

Plug Location

A BC D E F G H I


Spe distinguished lecturer program

Dean-Stark Water SaturationsMangala Field

Laboratory Apparatus

Dean Stark Extraction

Avoid any water

loss in laboratory

Toluene

110°C

Collect all water

even droplets


Spe distinguished lecturer program

xx50

xx00

Lab A

Lab B

xx50

<-- Depth

xx00

xx50

0%

2%

4%

6%

8%

10%

Dean-Stark Water Saturation, %

Dean-Stark Water SaturationsMangala Field

Plugs sent to 2 independent laboratories

One lab had consistently lower Sw’s by about 1 unit (Lab A)


Spe distinguished lecturer program

Oil-Brine Capillary Pressure Data (porous plate)Mangala 1ST

Laboratory Apparatus

Oil-Brine Capillary Pressure and Resistivity Index

N2 Pressure

Crude oil

Core

Plug

Ultra fine

Fritted glass

disk

Brine


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300

250

200

150

100

50

0

0

10

20

Oil-Brine Capillary Pressure DataMangala 1ST

Sw < 10%

2A

18A

28A

38A

45A

60A

65A

74A

 Oil Column 

Height Above FWL, m

89A

96A

110A

114A

124A

131A

143A

148A

30

40

50

Water Saturation, pct.


Spe distinguished lecturer program

Cementation Exponent “m” Mangala 1ST

“m” ~ 1.75

Archie’s original paper 1942

Swn = Rw/Rt *a/phitm


Spe distinguished lecturer program

Saturation Exponent “n”Mangala 1ST

1000

Conducted on aged, restored samples

100

Even though rocks are intermediate-wet to oil-wet, “n” is less than 2 !!

High perms and low salinity water

Resistivity index, RI

“n” ~ 1.8

10

1

Swn = Rw/Rt *a/phitm

0.01

0.10

1.00

Water Saturation, v/v


Spe distinguished lecturer program

Water Saturation CalculationsMangala 7ST

Note scale from 0 to 0.2

Good agreement with Archie, Dean Stark core data & Saturation Ht Sw’s


Spe distinguished lecturer program

Saturation Ht Function

Divide the capillary pressure data into permeability bins

Model the capillary pressure curves according to the Skelt equation (Harrison 2002)

SWcap_press = 1-A*exp(-((B/(HAFWL+D))^C))

Establish relationships as to how A,B,C,D vary with permeability

Actual Data

Modeled

Pressure vs Saturation

Pressure vs Saturation

Mercury Pressure (psia)

Mercury Pressure (psia)

Saturation

Saturation


Spe distinguished lecturer program

Nuclear Magnetic ResonanceNative State Plug - Mangala 1ST

Note T2 distributions of native state plug and oil almost identical

0.12

Crude, DST 2, 70 Degrees C

0.10

Crude, DST 2, Ambient

Plug, Ambient

Plug, 70 Degrees C

0.08

Conclusion:

0.06

T2 dist almost entirely due to bulk oil response

Normalised Amplitude

0.04

0.02

0.00

Applying cut-off for bound fluid as defined in lab, will give Sw

0.1

1

10

100

1000

10000

T2 (ms)

Relaxation Time


Spe distinguished lecturer program

Defining the T2 cut-off for Bound Water

Cumulative T2 distribution for Saturated Sample

Swi (5%) from Capillary

Pressure

Bound fluid cut-off

1.9

Relaxation Time


Spe distinguished lecturer program

Wireline NMR Sw and Dean-Stark SwMangalaField

All Data support low Sw’s

Data from very different sources

Sw’s 5% or less !!!!

Such low Sw’s are possible …..

Further confirmation of low Sw

NMR

Archie

Dean Stark Saturation Ht

Bound water cut-off of 1.9ms


Spe distinguished lecturer program

Current STOIIP Estimate

+

~350 million barrels

=

Economic ImplicationsMangala, Aishwariya, and Bhagyam

Initial STOIIP Estimate


Spe distinguished lecturer program

120 wells drilled to date

Multi well pad concept

Rapid rig design

Purpose built wheel mounted rigs capable of moving easily between slots on a pad without rigging down

ST-80 Iron Roughneck


Spe distinguished lecturer program

Large Savings $$


Spe distinguished lecturer program

Start of Chemical Injection

Coreflood recovery nearly 95% of STOIIP

Additional oil from ASP

EOR

Pilot Stage

MANGALA COREFLOOD RESULT

(Post waterflood result displayed)

PHASE BEHAVIOR EVALUATION

% Sodium Carbonate

0.0 0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25 2.5 2.75 3.0 3.5 4.0

Type-I

Type-II

Type-III

0.2% Surfactant; 0.6% NaCl; 30% Oil


Spe distinguished lecturer program

Conclusions

  • Archie “n” in Oil-Wet Reservoir

    • Contrary to “conventional wisdom”, moderately oil-wet reservoirs can exhibit Archie “n” values NOT significantly above 2.0.

  • Very Low Water Saturations

    • As evidenced here, very low water saturations (avg. 5%) exist in Mangala, Aishwariya and Bhagyam Fields

  • Model “Case Study” of the VALUE Of PETROPHYSICS

    • This is a case-study illustrating the economic worth of “Doing it Right” in initial petrophysics studies of high-value fields.

  • VALUE Of Taking Cores & Technology Culture


Spe distinguished lecturer program

CONTACT DETAILS

Petrophysics – Tim OSullivan - [email protected]

http://in.linkedin.com/pub/timothy-osullivan/12/a39/193

Provide a “free” 5 day petrophysics course to NOC’s

Drilling – AbhishekUpadhyay- [email protected]

Pipeline – Marty Hamill - [email protected]

EOR – AmitabhPandey- [email protected]


Spe distinguished lecturer program

10

1

5

4

Capillary Pressure (psi)

0

2

3

1

  • Initial Oil Drive

  • Free Imbibition of Brine

  • Brine Drive

  • Free Imbibition of Oil

  • Oil Drive

2

3

4

5

-10

0

Average Sw

100

IAH = WWI - OWI

Wettability Index

Principle -the wetting phase will tend to spontaneously imbibe into a pore system, while an applied pressure is necessary to push the non-wetting phase into the pores.

Combined Amott/USBM Wettability Experiment

Capillary Pressure” (Pc) is defined as the pressure of the non-wetting phase minus the pressure of the wetting phase, and thus is always a positive number.

In petroleum engineering typically define Pc as the pressure in the oil phase minus the pressure in the water phase (Pc = Po – Pw); so Pc would be positive for a water-wet system and negative for an oil-wet system.

The experiment starts with a core at initial oil saturation and looks at how much water will spontaneously imbibe (“spontaneous production”), as shown on step 2 of Figure 2. This is followed by a measurement of how much water enters the core under an applied pressure gradient as the core is flooded to the residual oil saturation (Sorw). This is the “forced production” shown in step 3 of Figure 2.

Note that the production measured is actually oil, since for each unit of water that enters the core an equivalent amount of oil is produced into a collection device. Obviously if the core was strongly water-wet, most of the oil production would happen spontaneously, with little need to apply an external pressure. The water-wetting index (WWI) is defined as the proportion of the total oil production that is produced spontaneously, and would be 1.0 for a strongly water-wet system and 0.0 for an oil-wet system.

WWI= proportion of the total oil production produced spontaneously

OWI = proportion of the total brine production produced spontaneously


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