Matrix injection experience in a disposal well (NAM-1)

Well NAM-1

• Produced water injection into far flank of reservoir

• Sandstone 1-2 Darcy

• TVD ca. 1800 m, injection interval 110 m

• Cased - perforated (6spf 60 DP)

• OIW 50-250 ppm

• TSS ‘high’ (from settling tank). FeS, wax, sand.

• II ca. 40 m3/d/bar. 1500 m3/d injection @ 60 bar THP.

• No indication of stress anomaly. 0.7 psi/ft 100 bar THP!

• PW negligible cooling

NAM-1

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

Oct

-94

Dec

-94

Jan-

95

Apr

-95

Jun-

95

Aug

-95

Oct

-95

Dec

-95

Feb

-96

Apr

-96

Jun-

96

Aug

-96

Oct

-96

Dec

-96

Feb

-97

Apr

-97

Jun-

97

Aug

-97

Oct

-97

Dec

-97

Feb

-98

Apr

-98

Jun-

98

Aug

-98

Oct

-98

Dec

-98

Feb

-99

Apr

-99

Jun-

99

Aug

-99

Oct

-99

Dec

-99

Feb

-00

Apr

-00

Date

Su

rfac

e In

ject

ion

Rat

e (B

PD

)

3,000

4,000

Inje

ctio

n P

ress

ure

(p

si)

Injection Rate

Pressure "THP"

Pressure "BHP"

Injection Rate & Pressure vs. Time

NAM-1: Injection data

Acid jobNRV removal

NAM-1

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

Oct

-94

Dec

-94

Jan-

95

Apr

-95

Jun-

95

Aug

-95

Oct

-95

Dec

-95

Feb-

96

Apr

-96

Jun-

96

Aug

-96

Oct

-96

Dec

-96

Feb-

97

Apr

-97

Jun-

97

Aug

-97

Oct

-97

Dec

-97

Feb-

98

Apr

-98

Jun-

98

Aug

-98

Oct

-98

Dec

-98

Feb-

99

Apr

-99

Jun-

99

Aug

-99

Oct

-99

Dec

-99

Feb-

00

Apr

-00

Date

Inje

ctiv

ity

Ind

ex (

BP

D/p

si)

3,000

4,000

Bot

tom

hol

e In

ject

ion

Pre

ssu

re (

psi

)

Inj. Index "II"Inj. Pressure "BHP"Acidification Jun/95

Injectivity Index and Pressure vs. Time

Acid treatment

s

NAM-1: Injectivity index

Acid jobNRV removal

Well NAM-1: fractured or not?

• II deterioration very slow: 25% in 2 yrs (600,000 m3 of water)

• Step-rate tests: Constant slope (II) of 40-50 m3/d/bar.

No inflection point.

• ‘Ideal’ (undamaged) matrix II estimated at 90 m3/d/bar.

• SR tests: Intercept p-axis dependent on shut-in time.

‘Leaking box’ reservoir? (nearby faults known).

• Injection pressure far below frac pressure.

• II appears to increase with injection rate.

Well NAM-1: fractured or not?

NAM-1

2,500

3,500

4,500

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000

Surface Injection Rate (BPD)

Bot

tom

hol

e In

ject

ion

Pre

ssu

re (

psi

)

Flow Rate vs. Pressure