characterising the deep subsurface: what can we understand ... · test analysis 04 more from the...

Characterising the

deep subsurface:

what can we

understand from

single well tests?GARETH DIGGES LA TOUCHE,

MARK COTTRELL & LEE HARTLEY

July 2015

___AGENDA

Context 01

The Single Well 02

Well Testing 03

Test Analysis 04

More from the Well 05

Case Studies 06

Summary & Conclusion 07

2

Context

___Utilising the deep subsurface in the UK

4

C O N T E X T

___Utilising the deep subsurface in the UK

5

C O N T E X T

The Single Well

___Your well should not be alone

7

I T H A S F R I E N D S

Model Validation Loop

Applications

Typical

Data Sources

Conceptual

Fracture Model

Static and

Dynamic

Validation

Derivation of

DFN

parameters

DFN Models

Data Analysis

Reservoir Engineering

Reserves

Development Strategies

Connections and Compartments

Outcrop

Seismic interpretation

Seismic attributes

VSP

Core & Well logs

Image Logs

Production data

Well tests

Micro-seismics

Structural modelling

Analogues

Fracture Orientation

Fracture Intensity

Fracture Size

Fracture KH

Identification of what is

important

Field Wide Drivers

Fracture Rules

Reservoir Geomechanics

Hydraulic Fractures

In Situ Stress

Subsidence

Upscaling

for Flow

Simulators

Workflow valid for fractured

shales, coals, carbonates,

sadnstones, and volcanics

Well tests

Well Testing

___Testing Workflow

9

Test Design

Why?

Where?

Time?

Resources?

Test Execution

Mobilisation

Set up

Execution

Demob

Quick Look

Real time analysis

Analysis

Analytical

Numerical

Transient Behaviour

___Test Design

10

G E T T H I S W R O N G A N D T H E R E S T I S … .

tS

T2r

It is important to design your test in order

to maximise the value of the results

This is relevant as much to rising/falling

head (slug) tests as it is to a long term

pumping test or a drill stem test.

Step 1: What is the Conceptual Model?

What do you want to know? T, K

and or S (and of what?, also gas

perm or water perm?), boundaries,

impact on features etc? Hydraulic,

Gas or Geophysical Testing?

___Test Design

11

G E T T H I S W R O N G A N D T H E R E S T I S … .

tS

T2r

It is important to design your test in order

to maximise the value of the results

This is relevant as much to rising/falling

head (slug) tests as it is to a long term

pumping test or a drill stem test.

Step 2: Based on Step 1, select an

appropriate test or series of tests

(“slug”, injection, open hole,

packer)

Step 3: Design your test. For example

how long does the test need to run

for.

___Why Testing?

12

S I M P L E Q U E S T I O N S

Testing facilitates decisions on the next steps once a borehole is drilled.

Questions asked:

• What is the permeability? Is the permeability sufficient?

• Is further well stimulation needed (acidisation, fracturing)?

• What is the best design and expected outcome of hydraulic fracturing? Direction,

size, fracturing pressure, well pattern…

• Was the well stimulation successful?

• Is the source formation finite? Are there flow boundaries?

• What is the water chemistry? Are there issues concerning precipitation or corrosion?

• Optimization of the production system: pumping, well completion.

Aim is to prove productivity and operate effectively

___Types of Test

13

T H R E E VA R I A N T S

FL

OW

RA

TE

ZEIT

CONSTANT PRESSURE TESTS

Pressure recovery

CONSTANT RATE TESTS SLUG- AND PULSE-TESTS

Pressure recovery

PR

ES

SU

RE

___Multiple Phase Tests

14

W H Y J U S T D O O N E W H E N Y O U C A N D O M A N Y ?

0 5 10 15 20 25 30 35 40 45 50 55

2000

2100

2200

2300

2400

2500

2600

2700

Pre

ssu

re [

kPa]

Time [h]

INFCOM PSR

SWSWS RW RWS

PIDEF

Test-Initialisation Diagnostic Phase Main Phase Final Phase

___Mini-Frac

15

J U S T A L I T T L E T I N Y F R A C

Test Analysis

___The Bourdet Derivative

17

P U B L I S H E D 1 9 8 3

___Derivative Analysis

18

T H E H I D D E N S T O R Y

Decrease in T

across boundary

Skin

Recharge

boundary

___Derivative Analysis

19

T H E H I D D E N S T O R Y0.11 10

100

1.E-11

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-02 1.E+00 1.E+02 1.E+04 1.E+06

No

rmalized

Deri

vati

ve

[m2/s

]

Elapsed Time [s]

___Analysis

20

C U R V E S A N D M O D E L S

30hrs

100hrs 300hrs

HydroBench

• well bore simulator

• radial variation in K

• assessment of skin

• flow boundaries

FracMan

• 3D numerical simulation of

fracture networks

Test analysis allows:

• k anisotropy to be characterised

• boundaries to be identified

• refinement of well field design

___Well Bore Simulator - HydroBench

21

D E F I N E T E S T S E Q U E N C E S


22

L O G - L O G D I A G N O S T I C


23

M AT C H I N G – P R E S S U R E / R AT E S

More from the Well

___Stress Measurement

25

H O W W I L L T H E R O C K B E H AV E ?

Isolation of interval with

packer

• Pore pressure is raised

through injection

• Fracturing occurs when pore

pressure drops

• Effective stress can be

quantified

Stress Orientation & Magnitude

• Acoustic televiewer

___Wireline Geophysical Logs

26

P O R O S I T Y – P E R M E A B I L I T Y - S T R E S S

Not just for lithology (but…)

• Gamma log

• Clay = high

• Sand = low

• Coal = very low

• Density

• Clay 2.2-2.6g/cm3

• Sandstone 2.65 g/cm3

• Sonic

• Shale 100 ms/ft

• Sandstone 53 ms/ft

• Resistivity

• Coal = high

• Sand = lower

Formation Factor Equationk =PermeabilityConstant/((Tortuosity/(Porosity^CementationExponent))^PorosityExponent)

Wylie Rose Equationk =10^(PorosityExponent*Porosity+PermeabilityConstant)

___Pore Pressure

27

S I M P L E N U M E R I C A L A P P R O A C H

Simple pore pressure

vs depth relationships

work

Can correct based on

other logs – e.g. less

dense than expected =

higher pore pressure

Brief Case Studies

___Injection Constraints – Avoiding Fracking

29

U S E O F W E L L T E S T A N A LY S I S T O O L S

Formation Pore

Pressures

• Measured or predicted

World Stress Map

Well In-Situ Stress

Measurements

Critically Stressed

Faults

Confidential Image

Deleted

___

Wireline logs used to estimate in situ

stress profile with depth

Bulk density log derived vertical in situ

stress profile

Injection Constraints – Avoiding Fracking

30


Horizontal stress from testing or models

Sh provides estimated maximum

permissible pore fluid pressure – i.e. to

avoid hydraulic fracturing

Confidential Images

Deleted


31


Permeability from well tests core and wireline

Two units identified as potentials injection horizons

Confidential Image

Deleted


32


Limits on permeability/transmissivity calculated by reverse

modelling injection conditions within the identified pressure

constraints

Confidential Image

Deleted

___Maximising Value

33

U N D E R S TA N D I N G K , F L O W R E G I M E A N D B O U N D A R I E S

Confidential Images

Deleted

___Maximising Value

34

U N D E R S TA N D I N G K , F L O W R E G I M E A N D B O U N D A R I E S

Confidential Images

Deleted

Summary & Conclusions

___

36

Summary and Conclusions

Single well tests are valuable for

characterising the hydraulic properties

of deep aquifers, reservoirs and fluid

bearing strata.

Conventional testing should be

supplemented with data derived from

wireline geophysics

Consider the well test within part of a

larger workflow rather than in isolation

to maximise the benefit of testing.

Do not ignore analogues.

S I N G L E W E L L S H AV E VA L U E

Characterising the

deep subsurface:

what can we

understand from

single well tests?GARETH DIGGES LA TOUCHE

& MARK COTTRELL

Email: [email protected]

characterising the deep subsurface: what can we understand ... · test analysis 04 more from the...

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