Water Challenges

at The Geysers

John Farison

Calpine

Geothermal Water Challenges

• Geothermal plant siting and water use

• Geothermal power plant waste heat rejection

• Geysers water balance and reservoir recharge

• Practical problems with water injection

• Current Research Efforts / R&D

Evaporative

Cooling by

Mechanical

Draft CT

Air Cooled

Condenser

Geothermal Energy = Water

• Heat captured in Water and Steam

• Heat Transported to Surface in Geofluids

• Converted to Electricity or for Direct Use

• Evaporative Cooling for Power Cycle

• “Working Fluid” for Heat Transfer

• Reservoir Recharge

Uses of Water at The Geysers

• Evaporative Cooling in Power Cycle

• Auxiliary cooling of plant equipment

• Process makeup water– Stretford & Burner H2S Abatement Systems

– Wash down water

• Domestic & Potable Water

• Reservoir Recharge– Secondary & Tertiary treated Reclaimed Water

Geysers Steam

Wells

Geysers

Injection Well

SEGEP and SRGRP Facilities

0 2000 4000

FEET

SRG RP P IPELIN E

SRG RP IN JEC TIO N W ELLH EAD

C alp ine

N C PA

1,8

08

,00

0 E

391,000 N

1,7

44

,00

0 E

431,000 N

A N D ER SO N

SPR IN G S

W H ISPER IN G

PIN ES

C O B B

FO R EST

LA K ES

H O B ER G S

HIG

HW

AY

17

5

BO

TTLE R

OC

K R

D

SO

CR

ATE

SM IN E RO AD

HE

AL

DS

BU

RG

CLO

VERD

ALE 10 M

ILES

HIG

HW

AY

175

4 MILE

S

TO

AL

EX

AN

DE

R V

AL

LE

Y

SEG EP P IPELIN E

6000 8000

20

MIL

ES

C ALPIN E PO W ER PLAN T

Low-rate injector

Area of increased injection

Area of decreased injection

Ø

Ø

SR-1 Pump

Station

Rejection of “Waste Heat”

• Condensing Turbines– Expansion into Vacuum

– Maximizes Available Heat Energy

– Requires heat rejection equipment

• Evaporative Cooling– Used for Dry Steam and Flash Geothermal Plants

– Mechanical draft cooling towers

– Most efficient and cost effective

– Loss of geothermal “working fluid” over time

– Reservoir Makeup water required to maintain generation output

• Air-cooled condenser– Low temperature and binary geothermal plants

– Increased capital cost and large equipment footprint

– Large parasitic load especially on hottest days

FIGURE 1 --

1,400

Geothermal

Steam plant

1,800Gal / MWh

Thermoelectric Power Plant with Cooling Tower

Geysers Water Balance

Geysers Water Balance

Figure 2: Steam Production and Injection at The Geysers

0

25,000

50,000

75,000

100,000

125,000

150,000

175,000

200,000

225,000

250,000

1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015Year

Pro

du

ctio

n/I

nje

ctio

n (

millio

n lb

m p

er y

ear)

steam water

Data from CA Div. of Oil, Gas & Geothermal Resources

Santa Rosa 2003Lake County 1997

Types of Water

• Geothermal Waters or “Geofluids”

• Geothermal Steam Condensate

• Fresh water

• Groundwater

• Storm water runoff

• Reclaimed Waters

• Sea Water / Brines

Practical Problems With Water Injection

• Distributing water for maximum returns

• Oversaturation of an area by injection

• Tracking reservoir response to injection

• Breakthrough btw injector and steam wells

• Injection well casing corrosion

• Micro-seismic response to injection

2006 thru May 2011 SRGRP Delivery

SR_99_INJ_RTPTNKOUTFR_AA

MGD

Ad-Hoc Trend

1/1/2006 3:00:58.423 PM 5/19/2011 3:00:58.423 PM1963.96 days

5

10

15

20

0

25

I/O Timeout

20

15

10

MGD

2006 2007 2008 2009 2010 2011

5

Western U13 and Eastern U18 Production Flow

(Mod1-4, DV23-25, D&V2-4 and CA956A6)

360

380

400

420

440

460

480

500

5/7/09 8/15/09 11/23/09 3/3/10 6/11/10 9/19/10 12/28/10 4/7/11

Date

Ste

am

Flo

w R

ate

(k

ph

)

0

500

1000

1500

2000

2500

Inje

cti

on

(g

pm

)

Total Flow Total Injection DV2-4

Product\U18east_U13west steamflow

Growth of saturated zone around 87G injector and breakthrough to 36C

Saturation of deep steam entries resulting in loss of steam flow.

Example of Micro-seismicity MEQ Around Injection Wells

SE

GE

P S

tart

up

SR

GR

P S

tart

up

0

500

1000

1500

2000

2500

3000

3500

4000

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

Date

An

nu

al C

ou

nt

M ≥

1.2

0

50

100

150

200

250

An

nu

al

Ste

am

Pro

du

cti

on

, W

ate

r In

jec

tio

n

(10

9 l

bs

) a

nd

An

nu

al

Co

un

t M

≥ 3

.0

Fieldwide Count M≥1.2

Fieldwide Count M≥3.0

Fieldwide M≥4.0 Occurrence

Steam Production

Water Injection

(Fresh) Water Use Terminology

• Water “Withdrawal”

– Water extracted from surface waters including

rivers, streams, lakes or groundwater.

• Water “Consumed”

– Water not returned to surface waters

(primarily evaporative losses)

Water Quality for Geothermal

• Scaling, Corrosion and Fouling

• Water Quality Limits

– Suspended solids

– Scale forming minerals

– Bio-fouling

• Compatibility mixing with Geofluids

• Treated Reclaimed Water

– Filtered & Disinfected to meet required uses

Water Use in Geothermal – Summary

• Siting depends on thermal resource not cooling water

• Once through cooling not used

• Evaporative losses higher than other thermoelectric plants

• Steam condensate for cooling in steam and flashed steam plants

• Dry cooling used for Binary Geothermal Plants

• Impact on fresh water sources very low

Water Use in Geothermal – Summary

• Geothermal operated as “Zero Discharge”

• Reservoir recharge for sustainability

• “Degraded waters” usable for recharge

• Definitions of “withdrawal” & “consumption”

imply Fresh Water generally do not apply.

Calpine

The Geysers Geothermal Field

Thank You