INTRODUCTION TO GEOTHERMAL ENERGY

Presented in: Geothermal Short Course by Geothermal Department IAGI

STTNAS Yogyakarta September 15th, 2016

Presented by :

Alfiady Geologist and Geochemist

Supreme Energy

Outline Overview of geothermal resource

Stages in geothermal project

Geothermal system vs. Petroleum system

Geology in geothermal exploration

Geology in geothermal development

Geology in resource management

Presentation take-away

Geothermal utilization

Underground resource model (Model showing the origin of geothermal energy) Source: Geothermal Energy, Serial No. 87 (July 1999

Encyclopedia Britannica, Inc., 2011

Thermal energy generated and stored in the earth

Heat ‘mining’ from the earth Heat transfer through circulating fluids

(convective), either naturally or engineered

Used either directly (low enthalpy) or indirectly (high enthalpy)

The presentation will be focused on ‘conventional magmatic high-terrain geothermal system’ for electric generation

Geology setting is a key success factor of Geothermal development

Top green fields in Indonesia

Focus in Java and Sumatera

Geothermal Fields in Indonesia

Supreme Energy

Produksi / wells

Rajabasa

Rantau Dadap

Muaralabuh

Sibayak

Gn Salak Darajat

Wayang Windu

Lahendong

Kamojang

Sarulla

Hululais

Lumut Balai

Geothermal in Indonesia (tectonic setting)

Most of the producing

geothermal field are located in

West Java

Dieng (60

MWe)

Sumatra Quaternary volcanism

along strike-slip SFZ

Lahendong and Tompaso

Geothermal resources in remote area with low

electricity demand

Geothermal in Indonesia (current condition)

Resource potential

29.4 GW Badan Geologi, March 2015

Geothermal concession

69 WKP 19 Existing WKP 50 New WKP

Current capacity

1438.5 MW From 11 power plant

Obstacles • Low power price • Forestry and land

overlapping • Permitting • Social issues

• Resource risk

The highest risk phase

Pre-feasibility Exploration Feasibility

Exploration drilling (resource identification)

Development drilling (resource delineation & quantification)

Feasibility study of power plant, etc

Discharge testing Reservoir assessment Environmental impact

assessment

Environmental report Bid document preparation Contract award (plant &

civil) Pipeline routing &

design Final design

Construction & plan installation

Contract management, supervision of construction, inspection

Field management

Construction Design Commissioning & production

Geology Geochemistry Geophysics

Geotechnical Preliminary

engineering design

How to Develop Geothermal Energy from A to Z

Operation and Maintenance

Stages in geothermal project

Cum. Cost

Good geothermal exploration practice will drive good decision making

Geothermal Development (stages)

Stage by stage activities in developing geothermal field is intended to gradually reduce the risks

The highest risk is related to subsurface activity (upstream), i.e. pre-feasibility and exploration stage

The highest cost is related to surface facility construction

The risk is significantly reduced after exploration drilling

Gehringer and Loksha, 2012.

3G Exploration

Resource Risk : Temperature (Enthalpy) Reservoir Depth Permeability Fluid Chemistry Reservoir Extend and

Sustainability

Economic Risk Power Price Demand Gov. Policies (Regulation and

Subsidies) Social Issue

Geothermal Development Risk

Decreasing The Risk By: Application of best practice 3G

technique Development of appropriate

conceptual models Proper planning and execution of

Test Drilling/Exploration Drilling Proper “Reserve” Assessment

and feasibility study

Geothermal system

• Heat source • Reservoir and fluid pathway • Cap rock (clay cap) • Circulating fluid

Heat flow Porosity and permeability Controlling factor Temperature and chemistry

Cumming, 2009

Geothermal vs. Petroleum system

Geothermal Component Petroleum

Heat source is cooling intrusion or batholith not too old (Quaternary) to provide sufficient heat

Source Source rock is organic rich strata mature enough to generate hydrocarbon

Commonly within volcanic environment Reservoir Commonly sedimentary environment

Commonly clay alteration zone (smectite layer) Protecting hot system from surrounding cold water

Cap Impermeable strata (shale, salt, etc.) Trapping hydrocarbon and prevent further migration

Circulating hydrothermal fluid Fluid Accumulated hydrocarbon (oil or gas)

Commonly under pressured Pressure Commonly over pressured

Geothermal vs. Petroleum system

Geothermal Component Petroleum

Covers local geological/volcanic setting Spatial Regional/basin-wide setting

Quaternary volcanoes overly the older formation

Volcano-stratigraphy Temporal

Wider time frame Basin evolution over various tectonic events Lithostratigraphy, tectono-stratigraphy, sequence-stratigraphy, etc.

Geothermal exploration (key questions)

Boseley, et al., 2010

How to prove it through lowest cost exploration drilling Pad location Well targeting

If yes, then How big is it? Area Reservoir thickness Recovery factor

Is it there? Reservoir temperature Fluid chemistry Permeability

Geothermal Exploration Geological and Surface Studies

Geochemical Survey

Geophysical Survey

Surface geology mapping (Volcanic Product Thickness + Heat Source)

Thermal features chemical analysis, and physical features

Magnetotellurics and other resistivity survey as subsurface indicator of system extension

Locating and mapping active geothermal surface features (Possible CM and system extension)

Geothermometry and fluid chemistry analysis (water and gasses) as reservoir temperature indicator, brine chemistry, and flow pattern

Gravity and magnetic as subsurface structure indicators

Structural geological interpretation (Possible permeable structure)

Soil sampling , gas flux reservoir as indicator permeability

Heat flow and temperature gradient as indicator of resource size and extension

Passive seismic as indicator of permeable structures

Provide a framework for Conceptual Model(CM)

Provide a hard data for reservoir temp, type , origin , possible flow pattern for developing CM

Provide a description of subsurface structure which related to reservoir geometry and size

Geothermal exploration (Geology) Regional tectonic setting, fault maps,

and stratigraphy provide general framework for conceptual model of geothermal system

Volcano-stratigraphy, alteration zones and detail structural mapping

Identify possible heat source & major structure permeability

Volcano-stratigraphy or migration of eruption-center sometimes related to timing of formation of various geothermal systems

Volcanic facies model can be guidance to estimates matrix primary porosity distribution

Geothermal exploration (Geochemistry) • Geochemistry

represents reservoir fluid conditions such as temperature, fluid phase, acidity, scaling potential, fluid origin, etc.

• Geochemistry also represents convective hydrothermal flow/hydrologic model (upflow and outflow)

Geothermal exploration (Geophysics)

Combination of various methods instead of one single solution (like reflective seismic for oil/gas industry)

Deep resistivity imaging through EM method (i.e., Magnetotelluric/ MT)

Imaging the base of cap instead of reservoir strata

Combined with • Gravity (basement setting,

intrusion) • Geomagnetic (alteration,

demagnetized body) • Micro-EQ (permeability, fluid flow)

Survey design data acquisition and QA/QC data processing modeling interpretation

Geothermal exploration (data integration) Integrating geological setting,

geochemistry information, geophysical model and thermodynamic principles Geologist leads the process Integrated conceptual model guides

further assessments and decisions (resource estimation, exploration drilling strategy, uncertainty management) Alternative models to capture the

range of uncertainty

Exploration drilling strategy (testing the models)

Exploration wells for proving/disapproving various conceptual model, instead of targeting the ‘unexplained’ anomalies

Using conceptual model elements

• Isotherms to define bulk pattern of permeability

• Thermal manifestation chemistry to constrain isotherms and system geometry

• Resistivity to image low permeability alteration boundary

• Structures to illustrate boundaries and permeable paths

• Geology, geophysics etc to provide context

Well objectives as the drilling program driver: Temperature gradient hole Confirmation well/ Exploration well Production well Make up well Step up well

Well prognosis as a representation of well objectives and covers: Location Well objectives Design well track: KOP, AZI, INC Expected geology characteristic ,

pressure, temperature, and chemistry PCS(Size will affect well derivability) Target depth

Drilling team is responsible to the well construction and drilling operation

Exploration Drilling

rig and steam kick on geothermal well

Exploration drilling

ML-A1 ML-B1

Drilling rig

Cutting

Geologic well data

Core samples

Integration between well data and geophysics

To prove the preliminary interpretation based on 3G survey

Wellbore geology (lithology, alteration, structures)

Fluid chemistry (liquid, gas, condensate) Pressure and temperature profile Permeability (connectivity to the

reservoir)

Key Features Well objective Conceptual Model:

To set well location base on temperature target, target depth, and interpreted reservoir extension Top of reservoir:

Can be predicted from MT data (BOC) for production casing set (PCS)

Expected permeability: Fault target and targeted permeable interval

Conceptual model of Silakitang field , Sarula Source : Gunderson et al., 2000

Pre-Drilling CM to drive well emplacement

Updating conceptual model Post-drilling

conceptual model is constrained by P/T profiles, permeability, reservoir connectivity, chemistry, etc. acquired from wells

Either bigger or (commonly) smaller than early prediction

Numerical simulation and reserve confirmation

Updated conceptual model

Geologic modeling

Numerical model

Model matching

Forecasting

Working process Conceptual Model Numerical Model

Predictive Runs of Development Alternatives

Recommended Development Strategy

Size of Development Production Location

Injection Location Amount of production and injectate

in each location

Geology

Geochemistry

Geophysics

Reservoir

Development drilling and power plant construction

Power plant

Pipe-line

Separator

Yard

Turbine

Cooling tower

Control room Pipe-line Separator GRS

Producing geothermal field

After exploration and field development, Geoscientist’s should involves in reservoir management and monitoring Reservoir management is

important to maintain resource sustainability (balance between extracted and injected fluid) Monitoring effort is mandatory to

detect any significant changes in reservoir dynamic process

Reservoir monitoring

Problems during production phase • Reservoir drying out • Excessive pressure decline • Scaling on wells and surface facilities • Corrosion on wells and surface

facilities • Marginal recharge and cold water

influx • Injection breakthrough • Subsidence • Induced seismicity • Landslides and other geo-technical

issues • Others…

Reservoir monitoring

Reservoir engineering, chemistry, and geophysics provide the data

Geology provides the story

Presentation take-away Geothermal in Indonesia (with low power price and

expensive development cost) needs resource risk reduction to improves its economic

Geologist’s as main player in early stages (where the risk is high) should lead

Good geothermal exploration practice will drive good decision making

The Conceptual model should be the driver of exploration drilling program

Good well planning and execution is require for the success of the project

Thank You