ENHANCED OIL RECOVERY (EOR) IN

UNCONVENTIONALS

Williston Basin Petroleum Conference

Regina, Saskatchewan

May 3, 2017

Jim Sorensen

Principal Geologist

© 2017 University of North Dakota Energy & Environmental Research Center.

PRESENTATION OUTLINE

• Overview of U.S. Oil Production

• Tight Oil Size of the Prize

• Challenges to EOR in Tight Oil

• Addressing the Challenges

• Williston Basin ROZ Activities

• Future Outlook

3

TIGHT OIL

PRODUCTION 2016

U.S. Total = 4.2 Mbpd

Bakken = 1.0 Mbpd

Eagle Ford = 1.1 Mbpd

Permian Basin = 1.6 Mbpd

Rapidly increasing production

and development of new

plays

OOIP Estimates

300 Bbbl (Flannery and Kraus, 2006)

900 Bbbl (Continental Resources, 2011)

7.4 Bbbl (USGS, 2013)

24 Bbbl (Continental Resource, 2011)

Technically Recoverable Reserve

Estimates

• Currently, only a 3%–10% recovery

factor.

• Small improvements in recovery

could yield over a billion barrels of oil.

• Can CO2 and/or rich gas work in the

Bakken?

BAKKEN PETROLEUM SYSTEM SIZE OF THE PRIZE

ESTIMATION OF BAKKEN CO2 EOR POTENTIAL

The DOE methodology for estimating CO2 EOR and storage

capacity (2007) was applied to the Bakken in North Dakota:

Potential Incremental Oil

from CO2-Based EOR

CO2 Needed to

Realize Bakken EOR

Cumulative

Production

Method

648 Mbbl

187 Mt

Reservoir Properties Method

7000 Mbbl

3200 Mt

Reality ?

4000 Mbbl

2000 Mt

CHALLENGES OF EOR IN THE BAKKEN

• Fractures act as fast-flow pathways, limit fluid

interactions with the matrix.

• High heterogeneity of the lithofacies

complicates the understanding of flow regimes.

• Multiphase fluid flow behavior varies

substantially depending on the size of the pore

throats.

– Fluid viscosity and density are much different

in nanoscale pores than in macroscale pores.

• Sorptive capacity of organic carbon materials

affects CO2 mobility, EOR, and storage?

Source: Alharthy, Nguyen, Teklu, Kazemi, and Graves, 2013, SPE 166306

Colorado School of Mines and Computer Modelling Group

EFFORTS TO ADDRESS BAKKEN EOR CHALLENGES

CO2, ethane,

methane…

EERC’S BAKKEN CO2 STORAGE AND EOR

RESEARCH PARTNERS

8

MINIMUM MISCIBILITY PRESSURE (MMP) STUDIES

MMP by vanishing

interfacial tension/

capillary rise

0

50

100

150

200

250

0 5 10 15 20

He

igh

t o

f O

il in

Eac

h C

apill

ary,

Pix

els

Pressure, MPa

small capillarymedium capillarylarge capillary

MMP17.4 ± 0.4

DOES THE CAPILLARY RISE–VANISHING INTERFACIAL

TENSION METHOD WORK?

MMP (psi) Values for Bakken Live Oils

Cap. Rise EOS Slim tube

Live oil A 129 C CO2 3180 ±114 3220 3161

Live oil B 126 C CO2 3196 ±139 3150

We now have a less expensive and faster “tool” to study the

effects of reservoir conditions and fluid composition on MMP.

MMP STUDIES – CO2, METHANE, ETHANE, MIXTURES

Ethane is very effective

at achieving lower

MMPs; methane is not !

API 41.5 Crude

(Bakken), 110°C

EOR STUDIES ON

BAKKEN ROCKS

Rock Core Sample Well Locations

• Cores come from six well locations.

• Samples represent:

– Middle Bakken and Three Forks

reservoir lithofacies.

– Upper and Lower Bakken shale

source rocks.

– Reservoir‒shale interface.

• Samples provided by Marathon and

North Dakota Geological Survey.

OIL EXTRACTION FROM BAKKEN ROCKS IN THE LAB

• 46 core samples from six wells have been extracted using CO2.

• 24-hour oil extraction was conducted for the rock samples using different gases.

• All experiments were carried out under reservoir conditions (5000 psi, 230°F).

ca. 11-mm-dia. rod

• Rock is “bathed” in gases, not

swept with gases as would be the

case in confined flow-through tests.

OIL EXTRACTION FROM BAKKEN ROCKS IN THE LAB

24-hour oil recovery

using CO2

McKenzie County well

• 24-hour oil recovery comparing methane, ethane, CO2, nitrogen, and rich gas–CO2 mixtures.

• C2H6 has the best performance, while N2 has the lowest oil recovery.

OIL EXTRACTION FROM BAKKEN ROCKS IN THE LAB

0

20

40

60

80

100

0 4 8 12 16 20 24

Oil

re

co

ve

ry,

%

Time, hr

C2H6

CO2

85/15 CH4/C2H6

CH4

N2

Middle

Bakken

0

10

20

30

40

0 4 8 12 16 20 24O

il r

eco

very

, %

Time, hr

CO2

85/15 CH4/C2H6

CH4

N2

Lower

Bakken

Green = organics

Red = unconnected Φ

Blue = connected Φ

Shales are dominated by intergranular

distribution of organics, likely kerogen.

The amount of connected and unconnected

pore space is roughly equal.

FIB-SEM of

Upper Bakken Shale

Sample

FIB–SEM OF UPPER

BAKKEN SHALE SAMPLE

Very little

organic

material

is

present.

Although the

aperture of the

pore network is

at the

nanoscale,

much of the

porosity is

connected.

Green = Organics

Red = Unconnected Φ

Blue = Connected Φ

MIDDLE BAKKEN LAMINATED FACIES

FIB–SEM (SAME SAMPLE, DIFFERENT ANGLES)

EERC BAKKEN COMPUTER SIMULATION RESULTS

18

DFNFrom NW McGregor (Mission

Canyon)

From NW McGregor (Mission

Canyon)

• Simulated a variety of Bakken injection‒production schemes.

• Best cases showed significant improvement in total recovery

factor (some over 100%).

• Production response is delayed compared to CO2 EOR in a

conventional reservoir, but appears to improve with time.

Lab work and modeling are great…

But what happens in the real world?

www.bakkendispatch.com

• Lessons learned– Injectivity has been demonstrated.

– Production responses have been observed, so fluid

movement can be influenced.

– But the improvements that have been predicted by

models have NOT been observed in the field tests.

These can lead us to design the next set of field tests.

EVALUATION OF PAST BAKKEN FIELD INJECTION TESTS

2017 BAKKEN EOR PILOT TESTING

Photo - EERC

EERC is involved in a Bakken CO2 pilot injection test with XTO Energy.

• Small scale test into a vertical well.

• How do the things we see in the lab translate into behavior in the real-

world reservoir?

IDENTIFICATION OF RESIDUAL OIL ZONES (ROZS)

IN THE WILLISTON AND POWDER RIVER BASINS

• Identify and characterize the presence

and extent of potential ROZs in the

Williston and Powder River Basins.

• Translate geologic history of basins

into an input for modeling.

• Estimate residual oil in place and CO2

storage potential.

• Determine potential for CO2 EOR in

identified ROZs.

NORTH DAKOTA BAKKEN–THREE FORKS EOR

POTENTIALRich gas EOR

deployment may be

imminent.

But rich gas supply has

limitations, so it may be a

niche solution.

Widespread deployment

of CO2 EOR is a longer

game, largely due to a

currently limited market

of commercially available

CO2.

23

Jim Sorensen

Principal Geologist

Energy & Environmental Research Center

(701) 777-5287

jsorensen@undeerc.org

Thanks!

ACKNOWLEDGMENT

This material is based upon work supported by the U.S. Department of Energy

National Energy Technology Laboratory under Award No. DE-FE0024454.

Disclaimer

This presentation was prepared as an account of work sponsored by an agency of the

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