SPE Distinguished Lecturer Program - Society of Petroleum Engineers

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SPE Distinguished Lecturer Program - Society of Petroleum Engineers

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

1


Unconventional Frac Jobs for

Unconventional Reservoirs –

What Should You Be Concerned About?

Jennifer L. Miskimins, Ph.D., P.E.

Petroleum Engineering Dept.

Colorado School of Mines

Society of Petroleum Engineers

Distinguished Lecturer Program

www.spe.org/dl

2


Outline of today’s presentation…

• Purpose

• Unconventional reservoirs

• Fluids, proppants, and transport

• Growth complexity

• Hydraulic fracturing for reservoir

management

• Conclusions

3


WHY should you be concerned?

• Unconventional reservoirs (UCR’s) are

just that - unconventional

• UCR’s are increasing forming our

reserve/resource base around the world

• Extrapolation of conventional

techniques to UCR’s is risky

– Combination of considerations

4


Conventional vs. Unconventional

“Unconventional

resources…accumulations

that are pervasive

throughout a large

area…not significantly

affected by hydrodynamic

influences…require

specialized extraction

technology…”

SPE-PRMS, 2007 Holditch, 2001

5


Today’s presentation focuses on…

• Shale gas (is a “shale” a “shale”?)

– Nano-Darcy permeability (10 -9 )

– High quartz or carbonate content

• Tight gas

– What is “tight”?

– Micro-Darcy permeability

• Low perm oil

– Various lithologies

6


• “Slickwater”

Fluid Systems

– Minimal polymer loading

– Polyacrylamide friction reducers

– 1 – 10 cp fluid system

– Carrying capacity reduced

F =

• Must minimize damage due to the initial

low permeability

CD

k

f

kX

w

f

Courtesy of Stimlab

7


Retained Permeability With Gel Residue

Stimlab, 2003

8


Lightweight/Smaller Proppants

• Use of lower viscosity fluids = difficult to

carry high proppant concentrations

• Velocity is the transport mechanism, not

viscosity

• Function of fracture width, Reynolds

numbers, densities of proppants and

fluids, diameters of proppants

• 30/50 and 40/70 sizes common

9


Particle Transport

(From Patankar, 2002 and Kern, Perkins, and Wyant, 1959)

10


Example 1 – Bank Placement

0:08 sec 0:35 sec

0:58 sec 1:26 sec

Courtesy of Stimlab

11


Example 2 – Erosion of Bank

0:01 sec 0:10 sec

0:38 sec 0:50 sec 12

Courtesy of Stimlab


Complexity of Growth

• Remember that fracturing is always the

path of least resistance

• How complex is complex?

• 3D is no longer really 3D

13


Lyons sandstone

Polyurethane base

adhesive bond

15.8 ppg cement

Lyons sandstone

Unbonded interface

16.2 ppg cement

Lyons sandstone

Epoxy

15.8 ppg cement

Laboratory experiments – laminated

block before hydraulic fracturing

(28 cm X 28 cm X 48 cm)

Athavale and Miskimins, 2008

After hydraulic fracturing –

notice the complexity for

this “simple” system

14


Treatmen

t Well

Receivers

Monito

r Well

From the lab to the field –

multiple stimulation stages

in horizontal wells

From SPE 119896

15


Reservoir Management/Development

• Reservoir characterization

16


Reservoir Characterization

• Diagnostic

injection tests

1400

1200

1200

1000

– Presence of

natural fractures

– Reservoir

pressure

Pressure Derivative

1000

800

600

400

800

600

400

Pressure (psi)

– Permeability

200

200

– Process zone

stresses

0

0 1 2 3 4 5

G-Function

dP/dG GdP/dG Pressure

0

G-Function Analysis

17


Young’s Modulus vs. Poisson’s Ratio

2.60E+07

Middle Woodford Upper of Lower Woodford Upper Woodford Lower of Lower Woodford

2.40E+07

2.20E+07

Brittle

2.00E+07

E (psi)

1.80E+07

1.60E+07

1.40E+07

1.20E+07

Ductile

1.00E+07

0.00 0.05 0.10 0.15 0.20 0.25 0.30

v

From Aoudia et al, 2010

18


Reservoir Management/Development

• Reservoir characterization

• Well spacing

– 10-20 acres (4-8 hectares)

• Need to maximize contact area

– Low permeability

– Minimal drainage area

19


10-ac spacing 3D view of

wellbore penetrating fluvial

bodies

Body types penetrated as

a function of well-spacing

densities

Modified from Anderson, 2004


Microseismic Events, Side View

From Mohammad and Miskimins, 2010

Well D1; Stages 1 – 7

21


Well D1, Stage 1

Microseismic side view

with hydraulic fracture

model results (proppant

concentration, lb/ft 2 )

superimposed

Microseismic plan view

From Mohammad and Miskimins, 2010

22


Piceance Basin, Western Colorado, USA

23


“S-Curve” Development

From www.csug.ca, 2010

24


Centralized

fracturing

equipment

location

Multiple well pads

(16 wells per pad)

From Miskimins, 2009

Large diameter,

welded surface

lines

25


Shale Gas Reservoir Drainage

Drainage Areas

Horizontal well

system

Vertical well

system

26


Reservoir Management/Development

• Reservoir characterization

• Well spacing

– 10-20 acres (4-8 hectares)

• Need to maximize contact area

– Low permeability

– Minimal drainage area

• Reorientation

27


Reorientation Theory

Courtesy Devon Energy

28


Conclusions

• Hydraulic fracturing for UCR’s requires

combinations of considerations

• UCR’s represent a wide variety of

reservoir types and designs must address

these differences

– Materials, complexity, reservoir management

• The learning curve can be shortened by

studying other successful applications

29


Thank you for your time!

30


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

31

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