How Can Petrophysics Support Geothermal Exploration? General - PowerPoint PPT Presentation

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 information of geological relevance Geophysics Interpretation Distribution of Lithologies, Porosities, • Pressure and Temperature Pore Fills, etc. • Composition of the Pore Fill Distribution of • Porosity and Type of Pores Measurable Physical Geological • Texture and Structure Properties in the Subsurface • Mineralogical Composition Model or Reservoir Model Petrophysics Knowledge of the dependencies of physical properties on: Mid-Term Conference 9-12 January 2007 E. Spangenberg, S. Raab, D. Bruhn

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

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

Examples Temperature Dependence Influence of “boiling pore water” Kulenkampff et al., 2005 L.H. Kristinsdóttir et al., 2006 Basalt: Krafla, Nesjavellir Hyaloclastite : Hengill Mid-Term Conference 9-12 January 2007 E. Spangenberg, S. Raab, D. Bruhn

•State of the Art Mid-Term Conference 9-12 January 2007 E. Spangenberg, S. Raab, D. Bruhn

Advantages - Limitations • Reusable internal set up • Shrinkable tubing – FEP, PFA (Fluoropolymers) 250-300°C • Standardized samples • Polymers – PTFE, PEEK and sample preparation 250-300°C • Measurement of different • Seals – Viton, PTFE properties in on experiment 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

Dehydration of Serpentinite Fast Dehydration Slow Dehydration 7 157 °C 10 7 10 200 °C 10 kHz 200 °C 400 °C Resistivity [ m ] 109 Hz 300 °C 6 10 6 Resistivity [ m ] 10 100 mHz ฀ 500 °C ฀ 400 °C 5 10 5 10 500° 600 °C 300° 550° 400° 4 10 560° 4 10 600 °C 3 10 100° 10 kHz 10 kHz 256 °C 413 °C 560° 3 10 20° 500° 109 Hz 2 109 Hz 10 100 mHz 100 mHz 600 °C 400° 2 1 10 10 0 5 5 5 5 5 5 1x10 2x10 3x10 0 2x10 4x10 6x10 Time [ sec ] Time [ sec ] Bruhn et al., 2005 Mid-Term Conference 9-12 January 2007 E. Spangenberg, S. Raab, D. Bruhn

“The Next Generation” Mid-Term Conference 9-12 January 2007 E. Spangenberg, S. Raab, D. Bruhn

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 • 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! Mid-Term Conference 9-12 January 2007 E. Spangenberg, S. Raab, D. Bruhn

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