Geysers Lessons Learned
and EGS Results
Geothermal Research Society of Japan – EGS Workshop
John Farison – Calpine
November 20th, 2019 – Kumamoto Japan
Calpine Corporation

GEYSERS OVERVIEW

Calpine Corporation

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The Geysers Field
Calpine Geothermal Operations• 45 square miles (187 km2)
• 13 geothermal power plant sites
Calpine Geothermal Wells• 333 steam production wells• 60 water injection wells• Deepest well: 12,900 feet (3,933 m)• Average well depth: 8,500 feet (2,590 m)• Total Calpine Geysers’ wells drilled to date: 585• Today’s average drilling time: 85 days (75 days drilling + 10 days rig up/down)• 2017 average steam production per well: 36,000 pounds per hour
• Average reservoir steam temperature: 374 o F
Calpine Power Generation• 2017 average load: 648 MW net• 2017 generation: 5,673,647 MWh net• 2017 average unit availability: 94%
More info at: www.geysers.com
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Commercial Development Began in mid-1950’s

4Calpine Geysers Admin Center

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Geysers Central Operations

24 x 7 Operations
DCS & Data Historian
11,000+ Points Monitored
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Steam Piping at The Geysers

8Geysers Well Pads

Maintaining Steam Purity
Steam scrubbing
desuperheating

New “Super rotor”

Scrubbing out
HCl with NaOH

10• 60 Injection Wells• Injection pipelines 60miles (110 km)• Converted Steam Well
• Protective Hangdown• Slotted Liner• Injection wells takewater on vacuumGEYSERS INJECTION CHALLENGES

Calpine Corporation

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Water Injection for Reservoir Recharge
Steam wellconverted toinjector

Injection Well
Water Flow

SR-1
Pump
StationTop of Standing
Water Column

SteamWater
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Clean Energy from Recycled Water
Santa Rosa Geysers Recharge
Project (SRGRP) - 2003•

30 miles of 48” pipe•

10 miles of 30” pipe•

~12 million gallons per day•

Avoids discharge into Russian River

Southeastern Geysers Effluent
Project (SEGEP) - 1997•

30 miles of 20” pipe•

~8 million gallons per day(NCPA/CPN)•Avoids discharge into Clear Lake

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Geysers Water BalanceSustaining the Geysers Generation
Steam production

Water injection % mass replacement

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Geysers Geothermal Field and Nearby Communities
Seismic Monitoring Networks
Lawrence Berkeley National Laboratory
2003 installation; continuing upgrades
34 stations

Strong Motion Accelerometers
2018 Q1 Nanometrics installation (2)2019 Q3 Nanometrics installation (2)2003 ETNA installation; unreliable/replace

Productive Steam Reservoir Outline

US Geological Survey Regional Network1970’s installation; several upgrades
7 contributing stations“Major” Roads

If a jackrabbit sneezes in The Geysers, we will know …

Calpine Corporation

The Geysers Technical Services Lunch and Learn

Geophysics

The Santa Rosa Geysers Recharge Project and Induced Seismicity
The Environmental Impact Report for the Santa Rosa Geysers Recharge Project addressed induced
seismicity associated with increased water injection and specified a number of required seismicity
mitigation measures:•Seismic monitoring network maintained by The Geysers’ operators and upgraded as required toprovide coverage for the existing water injection wells.

•

Strong motion instrumentation (accelerometers) to determine relationships between The Geysers
induced seismicity and felt effects in nearby communities.

•Automated seismicity hypocenter and magnitude determination software and database access fordetailed analysis of water injection profiles and resulting induced seismicity.

•Continuing evaluation of injected water for individual water injection wells or well groups
susceptible to induced seismicity.

•Semiannual reporting to the City of Santa Rosa by Geysers operators submitted concerning therelationship between SRGRP water injection and induced seismicity.

•Also required are semiannual presentations to the Seismic Monitoring Advisory Committee, which
consists of community representatives, academia, government agencies* and Geysers’ operators.
Presentations since May 2014 available at http://geysers.com/smac* Lawrence Berkeley National Laboratory, United States Geological Survey and the Division of Oil, Gas and Geothermal Resources

Calpine Corporation

The Geysers Technical Services Lunch and Learn

Geophysics

Field-wide Seismicity Analysis
Comparison of Eighteen Semi-annual Reporting Periods

Magnitude ≥ 2.0 Downward Trend
Significant Increase From Previous Period
Deviations From Downward Trend = Some Winter Periods
Magnitude ≥ 2.5 Downward Trend
Similar To Previous Period
Magnitude ≥ 3.0 Downward Trend
Significant Decrease From Previous Period
Magnitude ≥ 3.5 Downward Trend
None This Reporting Period
Magnitude ≥ 4.0 1.1 Events Per Year Average
None This Reporting Period

Current Analysis PeriodM ≥ 2.0
Calpine Corporation

M ≥ 2.5

M ≥ 3.0

The Geysers Technical Services Lunch and Learn

M ≥ 3.5Geophysics

M ≥ 4.0Practical Problems With Water Injection• Distribute water for maximum steam returns• Oversaturation of an area by injection• Tracking reservoir response to injection• Breakthrough btw injector and steam wells• Injection well casing corrosion• Induced seismicity response to injection

Injection Derived Steam ConceptTargeting Geysers Injection Wells• Deep permeability to avoid water breakthrough• Hot reservoir to maximize boiling• High chloride and NCG zones• Minimize cost by converting, deepening or redrillingpoor steam producers.

Evaluating Performance of Injection Wells• Monitor flowrate, pressures and temperatures of nearby producers• Monitor NCG changes in nearby producers• Tracer surveys• Water level surveys
DX47 Monitoring Group Total, Ave WHP and FLOWDX22A, 23, 28, 58,59,60,63,64,69,74 75,77

Aver WhpTotal Flow
DX47 INJ

600

2400

550
2000

450
400

1600

350
300

1200

250
200

800

150
100

400

50
0006/ 07/ 07/ 08/ 09/ 10/ 11/ 12/ 01/ 03/ 04/ 05/ 05/ 07/ 07/ 08/ 09/ 10/ 11/ 12/ 01/ 03/ 04/ 05/ 05/ 07/ 07/ 08/ 09/ 10/ 11/ 12/ 01/01/ 01/ 31/ 31/ 30/ 31/ 30/ 30/ 30/ 01/ 01/ 01/ 31/ 01/ 31/ 31/ 30/ 31/ 30/ 30/ 30/ 01/ 01/ 01/ 31/ 01/ 31/ 31/ 30/ 31/ 30/ 30/ 30/
04 04 04 04 04 04 04 04 05 05 05 05 05 05 05 05 05 05 05 05 06 06 06 06 06 06 06 06 06 06 06 06 07

Date

Injection Rate, gpm

Total Flow (kph)/
Average WHP(psig)

500

41st Annual Stanford Geothermal Workshop
Time-Synchronized
Water Injection Volumes and Induced Seismicity Hypocenters
The SKUA GOCAD 3D Project Database currently includes thefollowing data for 1995-2015:
Monthly Water Volumes For All Historical Injection Wells
Refined Tomographic Double-Difference Seismicity Hypocenters

Images captured at ~yearlyinterval from 1995 to 2015
for this example.

Oblique View from SSWof 1995 to 2007
Seismicity to Enhance
Certain Fracture
Zones.

Monthly Water Injection Volume
Equivalent to Blue Disc RadiusSeismicity Hypocenters
Depth-scaled by Sphere Color
Magnitude-scaled by Sphere Size

Benefits of Supplemental Injection SEGEP: +60 mw benefit
 SRGRP: +85 mw benefit
 Decreases non-condensible gas in steam Increases plant efficiency, decreases

abatement cost
 Prolongs economic life of GeysersGEYSERSEGS RESULTS

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Geothermal Technologies Office 2015 Peer Review

Chloride CMF
P-32 Injection Well

PS-31 Production Well

Prati State 31 and Prati 32 Production-Injection Well Pair
Public Service of Colorado Ponnequin Wind Farm

Demonstration of an Enhanced Geothermal
System at the Northwest Geysers Geothermal
Field, CA
Project Officer: Lauren Boyd

Total DOE Project Funding: $6.25 million

Principal Investigator: Mark Walters
Geysers Power Company, LLC (“Calpine”)

Presenter: Julio Garcia

May 12, 2015

2:00 p.m. – 2:30p.m.

This presentation does not contain any proprietary confidential, or otherwise restricted information.

Track 4 - EGS 2

The Geysers Reservoir Boundaries• Abrupt Boundaries toNE and SW (structuralcontrols)• NW Geysers:
Reservoir deepens,
non-condensable gas(NCG) increases,
permeability
decreases,
temperature
increases. Therefore
targeted for EGS
study
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Scientific / Technical Approach
EGS
Demonstration
Area
Injection:
Prati 32

Microfractures WithinHigh Temperature Reservoir(260o C - 400o C)

Production:
Prati State 31

SWNE

260o C / 500o F

400o C / 750o F

10,134’1.05 M yr

11,143’5k – 10k yr

Unit
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Unit 11Unit
7&8Wildhorse
Buckeye

A-Pad,
AidlinAccomplishments, Results and Progress
Seismicity Analysis / 3D Visualization of theDevelopment of the Seismic Volume during First Year of SRGRP
injection in Prati 32
Prati 25

Weeks Since Injection Start: 416
128524844403632
282420Prati State 31
Production Interval
6900’ to 10000’

5000’ Subsea Depth
Seismic Event Magnitude
0.5
1.0
1.5

2.0+
Prati 32
Injection Interval
7800’ to 11143’

Area NW Geysers
Detailed Seismicity Analysis
Easting Range
1759041 – 1762691= 3650’ East-WestNorthing Range
426108 – 430968= 4860’ North-South
Longitude Range-122.8459 to -122.8333 degrees

12000’ Subsea Depth

Latitude Range
38.8336 to 38.8471 degrees
Oblique View From Southeast

GEYSERS 3D STRUCTURAL MODEL
Improved reservoir management and induced seismicity mitigation by understanding fluid
flow paths, fluid boundaries, reservoir heterogeneity and reservoir compartmentalization.
Well Corridor SW01
271 well segments; 216 with lithology logs
Top Serpentinite Slicelight purple

Topographic Surface Slicecolor-scaled by depth

Base Serpentinite Slicedark purple
Top Steam Contours
color-scaled by depthNorthwest

Southeast

Top Hornfelsic
Graywacketranslucent tan surface
Induced seismicity patterns
appear to be indicative of fluid
flow pathways and boundaries
Seismic Event Depth (Feet)

Top Granitic Intrusion (Felsite)color-scaled by depth

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Oblique View From SSE

GEYSERS CORROSION CHALLENGES

Calpine Corporation38

PRATI-5
60 kph steam
100 ppmw
HCl in steam
115 psig
447 deg F
100 deg F
Superheat
Residencetime 0.7 sec
beforeseparator

Manual UT Monitoringof Exposed Casing• UT monitoring to assure piping
integrity & safety– Assure piping > t-min– Monitor corrosion rates• Ultrasonic sensors fail with hightemperature• Time consuming and tedious
manual UT• Remove & replace insulation• Manual data collection, transferto PC and create plots
Exposed casing below master valve

Cal State 92-642

Cal State 92-6 Exposed Casing UT

02-03-200943

Cal State 92-6 Exposed Casing UT

06-03-200944

Cal State 92-6 Exposed Casing UT

02-11-201045

Cal State 92-6 Exposed Casing UT

03-28-201146

Cal State 92-6 Exposed Casing UT

07-13-201147

Volatile HCl in Superheated SteamPrati State-31
Shows Repaired
Wellhead prior toreinstalling the outercasing shells, grouting
the annulus andadding the new casingsealThe Geysers

Corrosion Mitigation in the Northwest Geysers• The corrosion-induced leak discovered on February 13, 2013 was caused by high concentrations of HCl .
• PS-31 is currently shut-in and nitrogen gas capped pending remedial actions.
• Installation of an alloy casing string in PS-31 is required to halt future wellbore corrosion attack before PS31 is placed back on-line.
• The likely remedial action is to install a high alloy steel or titanium tie-back liner to prevent future corrosion.
• Calpine is testing several kinds of alloy material test spools in the wellhead piping of several north Geysers
wells to identify an appropriate corrosion-resistant alloy for use in PS-31(see photo).
• We will select the best alloy as a hang-down liner in PS-31 based upon cost effective results of the testing.
• At this time, the estimated installation of the protective alloy liner in PS-31 might occur in late Fall 2014 butdepends upon the fabrication schedule at a specialized mill.

The Geysers

Corrosion Mitigation in the Northwest Geysers• Prati State-31 steam well corrosion mitigation– Corrosion leak occurred due to severe HCl acid-dewpoint corrosion justbelow wellhead on 2-13-13 after only 70 days of initial steam production– Well shut-in and nitrogen capped pending evaluation and mitigation design– Material testing conducted for suitable cost effective alloy for hangdown– Duplex stainless 2507 alloy seam-welded casing selected– 4,000 feet of 8-5/8” and 7-5/8” alloy casing ordered ($1.7M for casing alone)– Workover to install alloy hangdown scheduled for late 2016 or early 20172507 duplex stainless alloy casing

2507 “Landing sub”

2507 Receptacle spool52

Prati State-31 – Alloy Hangdown Casing Installation

2507 Super Duplex SS
Flush welded casing

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Prati State-31 – 2507 Duplex Hangdown Casing

PS-31 wellhead completion
Automatic nitrogen bleed
system for PS-31 annulus
protection
Landing sub and 8-5/8” OD
2507 duplex casing
2507 Super Duplex SS
Flush welded casing
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Geothermal Material Testing• Geothermal acidic fluids limit production– Industry wide problem; high costs & many failures– HCl acid-dewpoint corrosion; Geysers et.al.
– Acidic brines; acidization to prevent scaling• Carbon steel inadequate for acidic fluids• High nickel content alloys or Ti required• Searching for cheaper alloy alternatives…

PRATI-25 Steam Well

Collaborative Corrosion ResearchMultiple upper wellbore casing
failures in carbon steel casing due
to HCl acid-dewpoint corrosion

Cost-effective HCl resistant alloys could
reduce costs by $500k per well or more.
We may be able to help speed up the R&D.

4,050’ installed in PS-31
Alloy casing $1.8m
Installed cost $3m
High costs limit wherethis can be applied.

Prati-5 WH Tee, T2 & T12

CMF Injection Spools
PS-31 Alloy 2507 Casing

13 Cr, Better, but
not good enough
A-10, PS-10

CarbonSteel
CMF
pH = 8.4-8.7

Geysers experience – Alloys required versus pH and temperature

$$

$

$

Can lower costalloys with higher
Mo content work?

???
13 Cr

$
$Carbon
Steel

$
CMF
pH = 8.4-8.7

Primary Test Objective – Find cheaper corrosion resistant alloys!

Alloy Pipe samples from Tenaris-NKK

Test alloys• J55 (carbon steel )• TN80 Cr13
• TN95 Cr13M (1%Mo)• TN95 Cr13S (2% Mo)• TN125 Cr13U (3% Mo)• 17CrSuper13 Cr

Orifice Plate Type Coupon Rack

GEYSERS CONCLUSIONSWATER MANAGEMENT• Geothermal sustainability requires water injection• Strategic Water Injection for best results• Water injection induces seismicity• Locations and injection rates influence seismic response
EGS• EGS methods sustain Geysers generation and provide insight• Creation of new permeability. Sustain steam & pressures.
• Micro-seismic monitoring very important tool
• Engaging local communities critical for success
CORROSION• Geofluid chemistry complex and changes over time
• HCl acid-dewpoint corrosion major concern• UT monitoring & Continuous Scrubbing with NaOH
• Alloy casing may be required for acidic fluids
Calpine Corporation62

Thank You!

Calpine
The Geysers Geothermal Field
www.geysers.com
John.Farison@Calpine.com