GEOTHERMAL MAPPING

USING TEMPERATURE

MEASUREMENTS

By

Godwin Mwawongo

Reservoir Engineer

Introduction-Geo systems

• Mostly located close to active

tectonic plates

• Tectonic activity results in faulting

• Hot rocks are brought close to the

surface

• Water seeps through deep faults

• Hot rocks heat the water

• Pressure builds up

• Faults provide leakage paths

• Heat loss features are formed in

the leakage areas

• Hot springs, fumeroles, hot

grounds are heat loss features

Heat loss mechanism

• Heat loss features continuously transfer heat

and mass from the geothermal system to the

atmosphere

• Heat transfer is by:

–conduction

–convection

–Radiation

• Estimate amount of heat being lost naturally

• Analyze distribution of heat loss features

• Ranking geothermal prospects for development

• Results obtained can be used as an indicator of the

heat source size

• Give an indication of the magnitude of recharge

• Indicates extent of leakage through the capping.

• Assist in locating hidden fracture zones.

Objectives of heat loss survey

Measurements in boreholes

• Down hole temperature measurement

– Bore holes serve as temperature gradient holes

– Results can be used to estimate temperatures at depth

• Down hole pressure measurements

– Assist in modeling hydrological picture of the prospect

– Give an indication of possible recharge and outflow zones.

•14 geothermal prospects in

Kenya

•Estimated power potential is

over 3000 MWe

•Geothermal Resource

Assessment (GRA) was

formed to fast track

geothermal power

development

•From 2004 to 2007 studies

have been conducted from

Menengai to Paka

•Heat flow measurements

included.

Geothermal Prospects in Kenya

Menengai-Olbanita Prospect

• Associated with a 90 km2

Menengai Caldera

• Heat flow survey covered an area of about 900 km2.

• Heat loss features are mainly hot grounds & fumeroles

Menengai

Olbanita

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L. NAKURU

NAKURU TOWN LANET

R . N j or o

KIA

MU

NYI

ES

TAT

E

NGATA FARM

M E NE N GA I S TAT IO N

KABARAK ESTATE

CALDERAENGOSHURA FARM

KABATINICrater stream

BAHATI

SOLAI

BANITASISAL ESTATE

OLBANITA SWAMP & POND

Olba

nita s

tream

kabaragi

KISANANA

MAJANI MINGI ESTATE

ATHINAI SISAL ESTATE

EL BONWALA

OL' R

ON

GA

I HIL

LS

MENEGAI HILL FARM

KAMPIYA MOTO

MOGOTIO

0 10KMLEGEND

200

0Contours in meters above sea level

Roads

Railway line

Rivers

Lake, Pond

Shoppingcenter

Pyroclastic issuecrates

Lava eruption center

Major (r ift scarp) fault

Rift floorfault

Inferred fault

00

II

Borehole

FumarolesProposed exploration well site

MW-1

MW-3MW-2

MW-3

MENENGAI

40

50

60

70

80

Menengai-Olbanita, cont• Orientation of heat loss

features is NNW-SSE and

NE-SW

• Total conductive heat loss

is 1060 MWt

• Total convective heat loss

is 2476 MWt

• This indicates large heat

source for the prospect

Arus-Bogoria Prospect

Arus &

Lake Bogoria • Not associated with a

central volcano

• Heat loss features are hot

springs, geysers, hot

grounds & steam jets

Arus steam jet

Geyser at

L Bogoria

Arus

Bogoria

Arus and Lake Bogoria, cont

• Total heat loss from

the two prospects is

1666 MWt

• Orientation of the

features is NE-SW

at Arus and NW-SE

at Bogoria

Lake Baringo Prospect

• Lake Baringo covers a

large part of this

prospect thus, reducing

the effective area

substantially

• Thick alluvial deposits

lowers natural heat loss

as it acts as an

insulator

• Has no central volcano

Lake Baringo

Lake Baringo prospect, cont

• Anomalous bore holes

have been drilled in this

prospect

• A 90 m bore hole

discharging boiling water.

• Heat loss features are

hot grounds and

fumeroles

Lake Baringo Prospect, cont

Eastings

Tanglubei

Paoyi

Riongo

Loruk

Chesirimion

Chemiril

Kadogoi

Cepkalacha

Komolion

1

2

3

45

6 78

9

10

11

12

13

14

15

16

1718

19

2021

L Baringo

OlKokweisland

°C

Legend

Craters

Contours

Roads

Paka Craters

Lake Tulam

0 42Kilometers

162000 166000 170000 174000 178000 182000 186000 190000 194000 198000

Piezometric Level

CentersBorehole

Temp GradientContour

40

50

60

70

80

Lake Baringo

prospect

• Orientation of heat

loss features is

NW-SE

• Total heat loss

from the prospect

is > 1049 MWt

Korosi and Chepchuk

• Korosi is a central

volcano

• Extends to the North of

Lake Baringo prospect

• Hot grounds and

fumeroles cover about 45

km2

Korosi &

Chepchuk

Eastings

Tanglubei

Paoyi

Riongo

Loruk

Chesirimion

Chemiril

Kadogoi

Cepkalacha

Komolion

1

2

3

45

6 78

9

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19

2021

L Baringo

OlKokweisland

°C

Legend

Craters

Contours

Roads

Paka Craters

Lake Tulam

0 42Kilometers

162000 166000 170000 174000 178000 182000 186000 190000 194000 198000

Piezometric Level

CentersBorehole

Temp GradientContour

40

50

60

70

80

Korosi and Chepchuk, cont

• Heat loss features at

Korosi are controlled

by NE-SW and NW-

SE trending faults.

Conduction

– About 2,135 MWt

Korosi

– About 546 MW at

Chepchuk.

Convection

• 0.4 kWt

Lake Baringo

Chepchuk

Korosi

Paka prospect, cont

• Associated with a central

volcano

• Study covered 500 km2

• Heat loss features are hot

grounds, fumeroles

steaming grounds

• Located in & around the

caldera

Heat loss features cover 32

km2

Max. temperature 93oC

Paka

Paka prospect, cont• Heat loss features

display NE-SW

&NW-SE trend

• Conductive heat

loss is 2,655 MWt

• Convective heat

loss is 10 MWtLake Baringo

Eastings

Tanglubei

Paoyi

Riongo

Loruk

Chesirimion

Chemiril

Kadogoi

Cepkalacha

Komolion

1

2

3

45

6 78

9

10

11

12

13

14

15

16

1718

19

2021

L Baringo

OlKokweisland

40

50

60

70

80

°C

Legend

Craters

Contours

Roads

Paka Craters

Lake Tulam

0 42Kilometers

162000 166000 170000 174000 178000 182000 186000 190000 194000 198000

Temp Gardient Contours

CentersBorehole

Paka

Korosi &

Chepchuk

Temperature & hydraulic

gradient

• Bore holes indicate

230oC/m near the

active zones of the

prospects

• Cold areas indicate

0.02oC/m

• Water flow is from east

& west and from south

to north

Eastings

Tanglubei

Paoyi

Riongo

Loruk

Chesirimion

Chemiril

Kadogoi

Cepkalacha

Komolion

1

2

3

45

6 78

9

10

11

12

13

14

15

16

1718

19

2021

L Baringo

OlKokweisland

40

50

60

70

80

°C

Legend

Craters

Contours

Roads

Paka Craters

Lake Tulam

0 42Kilometers

162000 166000 170000 174000 178000 182000 186000 190000 194000 198000

Piezometric Level

CentersBorehole

Temp GradientContour

Paka

Korosi

Baringo

Chepchuk

Ranking based on heat lossProspect Heat loss Total heat loss

(MWt)Conductive

(MWt)

Convective

(MWt)

Menengai 1095 2440 3536

Paka 2845 10 2855

Korosi 2135 0.4 2135

Bogoria 762 437 1199

Baringo 941 108 1049

Chepchuk 546 Negligible 546

Arus 467 .03 467

Olkaria 400

Domes 187

160 180 200

Eastings (km)

-20

0

20

40

60

80

100

Nort

hin

gs (

km

)

40

50

60

70

80

°C

PakaCaldera

ChepchukKorosi

L Baringo

L Bogoria

Arus

Ol Banita

MenengaiCaldera

KinyachCrater

Equator

Paka Prospect

Menengai Prospect

Menengai to Paka

• Heat loss features display

NW-SE and NE-SW trend

• L. Bogoria and L Baringo

heat loss features are

NW-SE

• Korosi heat loss features

are oriented in NE-SW