GEOTHERMAL EXPLORATION & DEVELOPMENT IN KENYA- KENGEN’S

EXPERIENCE

ROSE K. KUBAI

KENYA ELECTRICITY GENERATING COMPANY LIMITED(KenGen), KENYA

27TH FEBRUARY, 2018.

GEOLOGIST, GEOTHERMAL TRAINING

1

LECTURE III: GEOTHERMAL DEVELOPMENT MILESTONES IN

OLKARIA

LECTURE II: PHASES OF GEOTHERMAL DEVELOPMENT

GEOTHERMAL MANIFESTATIONS

LECTURE I :INTRODUCTION

OUTLINE

2

OBJECTIVES

By the end of the three lectures the trainees

should be able to:

• Describe geothermal resources and their

occurrence

• Identify geothermal manifestations in the

field

• Outline all phases of geothermal

development and associated activities

• Demonstrate basic knowledge of geothemal

exploration techniques

3

GEOTHERMAL ENERGY IS HEAT FROM THE EARTH

A GEOTHERMAL WELL DEPTH OF 950M TO

3.65KM DEEP TO TAP STEAM UNDERNEATH

GEOTHERMAL POWER IS THE CONVERSION OF HEAT ENERGY FROM

STEAM TO ELECTRICITY

INTRODUCTION

WHAT IS GEOTHERMAL ENERGY

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GEOTHERMAL SYSTEM

6

Prerequisite

features:

• Heat source,

• Reservoir,

• Recharge area

• Cap rock

FEATURES OF GEOTHERMAL RESOURCE

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GEOTHERMAL MANIFESTATIONS

FUMAROLES AND STEAM JETS

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HOT/BOILING SPRINGS

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GEYSERS

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GEYSERS AND HOT SPRINGS

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MUD POOLS

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ALTERED GROUND

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HOT GROUNDS

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VOLCANIC CENTRES

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SULFUR DEPOSITS

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SILICA SINTERS

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GEOTHERMAL GRASS (Fimbristylis exilis) Geothermal grass

GEOTHERMAL GRASS

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YOUNG LAVA FLOWS

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Caldera

CALDERA

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VOLCANIC ERUPTION

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PLAN

RESOURCE DEVELOPMENT

•Geo-Science

• Infrastructure

•Environment Health & Safety

DRILL

•Equipment Maintenance

•Planning & Logistics

•Drilling

GENERATION

•Main Plants

•Wellheads

• Technical Services

RESERVOIR & STEAMFIELD

•Steamfield

•Reservoir

PHASES OF GEOTHERMAL DEVELOPMENT

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GEOTHERMAL EXPLORATION

• Geothermal surface exploration is a multi-

disciplinary processes.

• Integrates geoscientific methods; geology,

geochemistry, Geophysics and Heat flow

measurements

• Apparently no single geoscientific method

can unambiguously discover a geothermal

system.

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Many factors influence choice of methods

• Dictated by geological conditions

• Availability of surface manifestations

• Geographical setting – terrain etc

• Cost

• Time factor (time required to produce results)

• Specific needs or requirements (projected

use of the resources)

CHOICE OF EXPLORATION METHODS

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APPROACH

Methods of exploration (Reconnaissance and detailed surface exploration) -:• Collection of all available

information and maps• Geology• Ground water hydrology• Remote sensing • Geophysics including heat flow

measurements• Geochemistry• Environmental baseline survey

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Environmental Baseline Study

• Flora and fauna present in the prospect area

• Water resources, their quality, general drainage

trends; climate, ambient air quality

• Socio-economic issues such as land use

• Baseline data collected: to be used in fully-

fledged (ESIA) study for the subsequent

geothermal energy development and utilization

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• At the onset of a geothermal exploration project it is

uncertain whether or not results will be economically,

technically and environmentally feasible.

• Geothermal exploration therefore invariably necessitate risk

money

• Exploration process is carried out on a step-by-step basis,

and is divided into several phases in order to minimize cost

and maximize information for each phase

GEOSCIENTIFIC EXPLORATION

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• Identify areas with potential geothermal energy

• Estimate reservoir temperatures

• To define the geometry of the resource.

• Rank the prospect areas in order of

development priority

• Develop a conceptual model

• Locate suitable drilling targets.

OBJECTIVES OF GEOSCIENTIFIC EXPLORATION

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Geological Exploration

Geological Exploration include basic geological mapping

to unravel and understand:

Geological history,

Structural mapping to understand the tectonic history,

Volcanic mapping to unravel and understand the volcanic

history,

Hydrothermal mapping to understand paleothermal history.

Geological Exploration results in the siting of exploration

wells.

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Geologists carrying out Exploration studies

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Geophysical Exploration

Deals with measurements on the physical properties of the

earth

Emphasis on parameters sensitive to temperature and

fluid content of the rocks

Aim is to:

Delineate geothermal resources,

Locate, site & depth of heat source

Outline drilling fields,

Locate aquifers and site wells

Estimate properties of the system

31

Methods used in Geophysical Exploration

Direct Methods Structural and Indirect methodsThermal Methods Magnetics

Electrical Methods Gravity

Self Potential Method Seismic Methods

Seismicity

32

Geophysical MT&TEM data Acquisition

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Geochemical Exploration

Geochemical Exploration main objective is to

understand relationship between fluids at surface and

parent rock.

Aim is to:

Study type fluids in the system

Classify the geothermal reservoir

Determine fluid flow in the system

Determine paleothermal temperature

Determine heat source and its depth

34

Methods used in Geochemical Exploration

Geochemical studies covered:

Fluid sampling and analysis

Fumarole steam gas and condensate

Sampling of springs

Soil gas survey measurements

Mainly CO2

Radon

Interpretation of chemical analysis results

Fluid chemistry

Soil gas data; contours and Probability plots

35

Geochemists carrying out gas measurement

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Reservoir: Heat Flow Measurements

• Heat loss is related to temp gradients

• Heat lost through conduction-mainly in contact

with the system rock bodies

• Through convection: Mainly through

discharging fluids eg.fumaroles,steaming

ground, hot springs etc.

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Conceptual Model

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Exploratory & Appraisal Drilling

Include Exploratory and Appraisal drilling

Exploratory drilling is aimed at: 3 wells

Determining whether the resource exists in the area

demarcated by the geoscientific reports.

Appraisal drilling is aimed at: 6 wells

Proving the size/span of the reservoir

Demarcating areas of continuity and diversity in a

reservoir

Evaluate the production rate from the reservoir

39

Used to determine viability of the project.

Review of geoscientific & drilling data

Environmental Issues

Legal & Regulatory matters

Project Organization and Management

Project Financial Requirements

Project Economics

Feasibility Study

40

Production Drilling

Done to:

Gather steam for power generation plant construction

Understanding reservoir characteristics

Continuous monitoring of the reservoir response

during production

41

GEOTHERMAL WELL DRILLING

Vertical well ProfileCurrent Programme

• Deep drilling to

3000m–Production casing shoe 700

-1200m

–Average depth Olkaria I =

1200

–Average Depth Olkaria II =

2200m

–Average Depth 3000m

–Reservoir bottom not yet

reached

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GEOTHERMAL DRILLING RIG

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Power plant construction

Designed according to steam quality & quantity for

optimization

Utilize steam to generate electricity

Alleviation of possible harmful environmental hazards

is key in design

Various practices carried out to safeguard the power

plant: chemical monitoring of steam quality & pressure

and condensate.

44

Reservoir monitoring

Begins after commissioning of power plant

Monitors sustainability of the reservoir

Check for wells interference

Identification of potential re-injection sites

Monitors chemistry of geothermal fluids, pressure changes

in reservoir

Possibility of drilling makeup wells

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COMMISSIONED IN 1981-

1985

INSTALLED CAPACITY :45MW

11Olkaria Geothermal Development Milestones

OLKARIA I POWER PLANT(45MW)

46

OLKARIA II POWER PLANT

UNIT 1 & 2 COMMISSIONED IN 2003

UNIT 3 COMMISSIONED IN 2010

INSTALLED CAPACITY : 105MW

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NO. OF UNITS: 15

INSTALLED CAPACITY: 81.1MW

WELLHEAD PLANTS

48

OLKARIA IV POWER PLANT

COMMISSIONED IN 2014

INSTALLED CAPACITY : 140MW

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OLKARIA I AU (Units IV&V) POWER PLANT

COMMISSIONED IN 2015

INSTALLED CAPACITY : 140MW

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1st lagoon

91◦C receives brine from reinjection line

2nd lagoon

86◦C receives brine from 1st lagoon

3rd lagoon 30-35◦C

Children’s lagoon

Administration block