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How Can Petrophysics Support Geothermal Exploration? General Remarks Specifics for Geothermal Applications Recommendations Mid-Term Conference 9-12 January 2007 E. Spangenberg, S. Raab, D. Bruhn Exploration allows to extract

SLIDE 1

How Can Petrophysics Support Geothermal Exploration?

General Remarks
Specifics for Geothermal Applications
Recommendations

Mid-Term Conference 9-12 January 2007

E. Spangenberg, S. Raab, D. Bruhn

SLIDE 2

Exploration

Geophysics

Distribution of Measurable Physical Properties in the Subsurface

Mineralogical Composition
Texture and Structure
Porosity and Type of Pores
Composition of the Pore Fill
Pressure and Temperature

Interpretation Geological Model or Reservoir Model

Knowledge of the dependencies of physical properties on: Distribution of Lithologies, Porosities, Pore Fills, etc. allows to extract information of geological relevance

Petrophysics

Mid-Term Conference 9-12 January 2007

E. Spangenberg, S. Raab, D. Bruhn

SLIDE 3

Petrophysics for Geothermal Application – A Challenge for Experimentalists

Simulation of in situ conditions in the laboratory is characterized by confining and pore pressure controlled experiments under high temperatures. Requirements and Problems

Special materials
Special design of internal set up
Longer experimental time
Higher failure probability
Higher costs

Mid-Term Conference 9-12 January 2007

E. Spangenberg, S. Raab, D. Bruhn

SLIDE 4

Possible Subjects of Investigation

Dependence of physical rock properties on temperature
Production stimulated fluid rock interactions under high temperature

Assessment of long term behaviour of the reservoir

Phase transitions in the reservoir
Mid-Term Conference 9-12 January 2007
E. Spangenberg, S. Raab, D. Bruhn

SLIDE 5

Examples

Temperature Dependence Influence of “boiling pore water”

Kulenkampff et al., 2005 Basalt: Krafla, Nesjavellir L.H. Kristinsdóttir et al., 2006 Hyaloclastite: Hengill

Mid-Term Conference 9-12 January 2007

E. Spangenberg, S. Raab, D. Bruhn

SLIDE 6

State of the Art

Mid-Term Conference 9-12 January 2007

E. Spangenberg, S. Raab, D. Bruhn

SLIDE 7

Advantages - Limitations

Reusable internal set up
Shrinkable tubing – FEP, PFA

(Fluoropolymers) 250-300°C

Standardized samples

and sample preparation

Polymers – PTFE, PEEK

250-300°C

Measurement of different

properties in on experiment

Seals – Viton, PTFE

250-300°C

Piezoceramics – sonic transducers

Curie temperature up to 300°C Mid-Term Conference 9-12 January 2007

E. Spangenberg, S. Raab, D. Bruhn

SLIDE 8

Dehydration of Serpentinite

Fast Dehydration Slow Dehydration

Resistivity [ m ] ฀ 10 10 10 10 10 10

7 6 5 4 3 2

20° 100°

2x10 4x10 6x10

5 5 5

Time [ sec ]

10 kHz 109 Hz 100 mHz

500° 560° 560° 550° 500° 400° 300° 400°

Resistivity [ m ] ฀ 10 10 10 10 10 10 10 0 1x10 2x10 3x10

7 6 5 4 3 2 1 5 5 5

600 °C 600 °C 600 °C 500 °C 400 °C 157 °C 400 °C 300 °C 200 °C 200 °C

Time [ sec ]

256 °C 413 °C 10 kHz 109 Hz 100 mHz

Bruhn et al., 2005

Mid-Term Conference 9-12 January 2007

E. Spangenberg, S. Raab, D. Bruhn

SLIDE 9

“The Next Generation”

Mid-Term Conference 9-12 January 2007

E. Spangenberg, S. Raab, D. Bruhn

SLIDE 10

Higher temperatures require:

sample protection against confining pressure medium by a metal jacket
to avoid chemical reactions between the pore fluid and the jacket is has

to be chemically inert (gold, platinum)

high temperature gradients within the pressure vessel
high temperature in the centre where the sample is placed
low temperature at the closers to protect seals and some

temperature sensible parts (piezoceramic transducers)

special design of the internal set up

Mid-Term Conference 9-12 January 2007

E. Spangenberg, S. Raab, D. Bruhn
special preparation techniques
the parts in the hot zone of the set up are “one way components”
Do not underestimate the effort, time, and costs for

experiments under high temperature!

SLIDE 11

Recommendation

If a problem is identified that requires petrophysical experiments within a geothermal Project it is important to:

define the objective of the investigation clearly
design an experimental set up for exact this objective
budget sufficient
lead time for the construction and test of the experimental set up,
men power for the design, set up, test, preparation,

and measurement

money

Mid-Term Conference 9-12 January 2007

E. Spangenberg, S. Raab, D. Bruhn