Monitoring the Movement of CO2 at the Upper Spraberry Reservoir Using Well Logs

Gokul LakshmanTexas A&M University

Pioneer Natural Resources

Outline Pilot Information

Location Pilot Design Pilot Highlights Upper Spraberry Makeup

CO2 Flood Mechanism Log Monitoring

Objectives and Tools Used Looking Inside CNL tool What the logs have to say?

Decision Analysis Production Outlook Conclusions and Future Scope

Glasscock Co

Reagan CoUpton Co

Midland Co

Martin Co

Cany

on R

eef

Carr

iers

CO2 S

uppl

y

Cany

on R

eef

Carr

iers

CO2 S

uppl

y

O’Daniel

Shackelford

Driver

MerchantNorth

Pembrook

Benedum

Pembrook

Aldwell

Sherrod

Preston

MidkiffTippett

Location

Pilot Design

Producers

CO2 Injectors

Observationwells

Water Injectors

N

Pilot Goal

To evaluate the technical and economical feasibility of using CO2 as a tertiary recovery agent in the low permeability, fractured sandstone of the Spraberry Trend

Pilot Objectives

Collection and Analysis of pilot performance data To understand vertical and horizontal heterogeneities To determine optimal usage of CO2

Comparison of waterflood and CO2 flood performance Work within the limitations of allocated budget

Spraberry Reservoir : Looks Complicated??

CO2 Flood Mechanism

CO2+OIL OILHEAVIER FRACTIONS

1550 PSI

CO2

1U

3U

4U

2U

5U

7045

7230

PAY ZONES

CO2

Key Operating Targets

• CO2 Injection Rate= 91MSCF/D• Average Reservoir Pressure= 2300PSI• Target Water Injection Rate= 250BPD

Log Monitoring of CO2 flood – A Forensic science

Objectives

Monitoring the movement of CO2 in the formation

Calculation of the saturation of fluids

Logging Tools Used

Compensated Neutron Log Array Induction Log

Enter Tool Physics

CNL TOOL

H+Formation

Gamma Rays

Thermalized neutrons

SSD

SOURCE

SSLS

LSD

Logging Runs Conducted

Total HCPV to be injected : 22HCPV(128MMCF)How much has been injected until now:76MMSCF

RUNS MONTHS

1 Jan

2 Feb

3 Mar

4 Apr

5 Jun

6 Aug

7 Dec

Feb 22nd Start of CO2 Injection

Successive Neutron porosity decrease observed-Jan to Dec Well 49

1u

2u

3u

4u

5u

Gas entry

What the logs have to say ?

1u Frequency Distributions in Well #49Jan-Mar Distribution 1u

0

5

10

15

20

25

0.02

5-0.

038

0.03

8-0.

050

0.05

0-0.

063

0.06

3-0.

075

0.07

5-0.

088

0.08

8-0.

100

0.10

0-0.

113

0.11

3-0.

125

0.12

5-0.

138

0.13

8-0.

150

0.15

0-0.

163

0.16

3-0.

175

0.17

5-0.

188

0.18

8-0.

200

0.20

0-0.

213

0.21

3-0.

225

Neutron Porosity Distribution

Rel

ativ

e fr

equ

ency

0102030405060708090100

Cu

mu

lati

ve

freq

uen

cy

Jan rel freq Mar rel freq jan cum freq mar cum freq

1

2

Jan-Apr Distribution 1u

0

5

10

15

20

25

Neutron Porosity Distribution

Rel

ativ

e F

req

uen

cy

0102030405060708090100

Cu

mu

lati

v F

req

uen

cy

Jan rel.freq Apr Rel.freq Jan Cum freq Apr Rel.freq

1

2

Jan June Distribution 1u

0

5

10

15

20

25

0.02

5-0.

038

0.03

8-0.

050

0.05

0-0.

063

0.06

3-0.

075

0.07

5-0.

088

0.08

8-0.

100

0.10

0-0.

113

0.11

3-0.

125

0.12

5-0.

138

0.13

8-0.

150

0.15

0-0.

163

0.16

3-0.

175

0.17

5-0.

188

0.18

8-0.

200

0.20

0-0.

213

0.21

3-0.

225

Neutron Porosity Distribution

Rel

ativ

e F

req

uen

cy

0102030405060708090100

Cu

mu

lati

ve

freq

uen

cy

Jan rel.freq Jun rel.freq jan cum.freq jun cum.freq

Jan-Aug distribution 1u

0

5

10

15

20

25

Neutron Porosity distribution

Rel

ativ

e Fr

eque

ncy

0102030405060708090100

Cum

ulat

ive

Freq

uenc

y

Jan rel.freq Aug.rel.freq Jan cum.freq aug rel.freq

1

2

Frequency Distribution-Well 49 5u(Jan-Mar)

0

5

10

15

20

25

30

0.02

5-0.0

38

0.03

8-0.0

50

0.05

0-0.0

63

0.06

3-0.0

75

0.07

5-0.0

88

0.08

8-0.1

00

0.10

0-0.1

13

0.11

3-0.1

25

0.12

5-0.1

38

0.13

8-0.1

50

0.15

0-0.1

63

0.16

3-0.1

75

0.17

5-0.1

88

0.18

8-0.2

00

0.20

0-0.2

13

0102030405060708090100

jan rel freq mar rel freq jan cum freq mar cum freq

Frequency Distribution-Well 49 5u(Jan-Apr)

0

5

10

15

20

25

30

0102030405060708090100

jan rel freq apr rel freq jan cum freq apr cum freq

Frequency Distribution-Well 49 5u(Jan-Jun)

0

5

10

15

20

25

30

0.02

5-0.0

38

0.03

8-0.0

50

0.05

0-0.0

63

0.06

3-0.0

75

0.07

5-0.0

88

0.08

8-0.1

00

0.10

0-0.1

13

0.11

3-0.1

25

0.12

5-0.1

38

0.13

8-0.1

50

0.15

0-0.1

63

0.16

3-0.1

75

0.17

5-0.1

88

0.18

8-0.2

00

0.20

0-0.2

13

0

20

40

60

80

100

jan rel freq jun rel freq jan cum freq jun cum freq

Frequency Distribution-Well 49 5u(Jan-Aug)

0

5

10

15

20

25

30

0

20

40

60

80

100

120

jan rel freq aug rel freq jan cum freq aug cum freq

5u Frequency Distributions in Well #49

Decision Analysis--Lets be practical?

Oil in tank-Is it significant??

Whether a nominal PV of CO2 has been injected ?

Have Log So Responses Been Stabilized

Cease CO2 Injection

Production Outlook -Cumulative CO2 Injection

0

10000

20000

30000

40000

50000

60000

70000

80000

09-Jan-01 28-Feb-01 19-Apr-01 08-Jun-01 28-Jul-01 16-Sep-01 05-Nov-01 25-Dec-01 13-Feb-02

Time (Days)

Cu

mu

lativ

e o

f CO

2 In

j/Pro

d (M

cf)

Cumulative of CO2 Injection Cumulative of CO2 Production Cumulative of CO2 at A#1

0

10

20

30

40

50

60

01/09/2001 02/28/2001 04/19/2001 06/08/2001 07/28/2001 09/16/2001 11/05/2001 12/25/2001 02/13/2002

Time (Date)

Oil

Pro

du

ctio

n R

ate

(BB

LS

/D)

A#1 #38, 39 and 40 Series3 Series4

Series5 Series6 Series7 Series8

Series9 Series10

CO2 Injection Started

(2/26/2001) 7/20/2001 8/21/2001 10/2/2001 11/6/2001 12/8/2001 1/3/2001

Are we still getting enough oil in the tank??

Conclusions• From neutron porosity logs there is indication of gas movement in all layers• More Logging runs required to get a clear picture of CO2 movement

My present status of research

Trying to calculate Sg using count rates Awaiting more data from field

What I plan to achieve? Calculate Sg for all layers Compute extent of vertical displacement of CO2 using log

analysis Predict the horizontal movement of CO2 using tracers and gas

compositions at different wells