Geothermal Resource Prospecting in the Qualibou Caldera, Saint Lucia

1. Geothermal Resource Prospecting in the Qualibou Caldera, Saint Lucia By Frank Dale Morgan Geo-Caraibes Technical Team & Massachusetts Institute of Technology March 2006

3. Outline • History  Summary • Brief Review of Four MIT Studies • Conclusion • Recommendations

4. History • Serious geothermal resource exploration began in the mid-70s by the British Geological Survey • After dozens of investigations and nine drilled holes, no real geothermal development has resulted to date.

5. Historic Drill Site Recommendations Soufrière Cresslands Soufrière Bay Diamond Ravine Claire Terre Blanche Fond St. Jacques Sulphur Springs Petit Piton Rabot Morne Bonin Anse Des Pitons Belle Plaine Belfond Etangs Gros Piton UNRFNRE USAID – DOE & USGS USAID – LANL Gov’t of St. Lucia GENZL & Aquater British Drilling Programme GENZL Kilometers 0 0.5 1 2 3 4 5 6 • Time Line • British start formal investigation (Willmore) • 1964 Tomblin performs detailed geology survey • Institute of Geological Sciences (IGS) U.K. resistivity survey • 1975-76 Seven wells drilled by IGS (Wells 1-7) • 1976 Aspinall et al. perform seismic monitoring • 1982 Aquater (Italy): Magnetotellurics, gravity, well data evaluation. • 1983-84 Los Alamos (USA): Geology, geochemistry, geophysics • 1987-88 USAID/UN: Drill two deep wells (SL1 & SL2) • 1992 Geothermal Energy New Zealand: Gravity, resistivity, audio magnetotelluric resistivity • 1998-Pesent M.I.T.: Reinterpretation of British resistivity data, self potential geophysics, decision analysis • 2004-Present United Network of the Eastern Caribbean is commissioned to develop geothermal resources.

6. Geology

7. Geothermal Wells & Hot Springs Soufriere Bay Petit Piton Gros Piton

8. GENZL, 1992 USAID (Aquater), 1987

9. Summary • Very complex geology and hydrogeology • The chemistry of the geothermal waters beneath the Sulphur Springs is quite severe. • The geothermal reservoir cap rocks are weak. • Exploration is best optimized by exploring for less hot – but less corrosive – waters away from the Sulphur Springs.

10. Synopsis of Four MIT Studies • Reinterpretation of the British Line 9 resistivity data. • 3D rendering of 2D resistivity inversions. • Self Potential surveying. • Geological/Geophysical data integration using a decision analysis method.

11. Reinterpretation of the British Line 9 Resistivity Data. Data collected in 1974 by Lee and Greenwood, British Geological Survey

12. 9

13. Sulphur Springs (1974) 6 7 1 4 5 SL SL - - 2 2 3 0 40 2 50 100 30 200 500 5 200 Depth (m) 400 15 30 5 600 800 Sulphur Springs (2002) 6 7 1 4 5 SL SL - - 2 2 3 0 200 Depth (m) 400 600 800 4 1 1.5 3 2.5 3.5 0.5 2 Log Resistivity (ohm - m)

14. Sulphur Springs 6 7 2 1 5 SL-1 4 SL-2 3 1000 ohm-m 150oC 30 to 1000 ohm-m 30 ohm-m 250oC

15. 3D Rendering of 2D Resistivity Inversions. All the British resistivity lines were inverted into 2D cross-sections and then rendered into 3D.

16. 3D Resistivity Tomogram Southeast -to- Northwest

17. 3D Resistivity Tomogram Northeast -to- Southwest

18. Self Potential Surveying Small, millivolt electrical potentials were mapped, processed and interpreted throughout the Qualibou Caldera.

19. SP Survey Lines Cressland Diamond. Malgretoute Sulphur Springs 3 Main Belfond Fond St. Jacques

20. 200 100 0 Self Potential -100 Fond St. Jacques Cresslands -200 Diamond Sulphur Springs Rabot Belfond Malgretoute -300 0 2000 4000 6000 8000 10000 12000 Distance Individual SP Lines

21. N Correlation of observed SP anomalies and fault locations.

22. Interpolated SP Data mV Sulphur Springs

23. Geological/Geophysical Data Integration Using a Decision Analysis Method. Eleven disparate data sets were jointly analyzed by a decision analysis methodology to determine possible drilling locations.

24. Re-interpreted British Resistivity 700m BGS 0 km 3 km 6 km Method Morgan et al., (2002) Discretized Caldera Target Region Example Data Map Eleven datasets were used: Seismics, self potentials, fault structure, deep resistivity, shallow resistivity, geology, topography, wells/springs/geochemistry, shallow AMT, deep AMT, and residual gravity.

25. Group Result Cresslands Diamond X4 X3 Malgretoute Sulphur Springs X6 X1 X5 X2 Etangs

26. Conclusion Geothermal resource exploration in Saint Lucia is a very difficult endeavor because of: • Geological complexity • Highly corrosive geothermal waters.

27. Recommendations • Explore for drilling locations away from the Sulphur Springs to balance improved water chemistry with lower temperatures. • The probability of success will increase substantially by doing 3D resistivity/self-potential geophysics to accurately locate drilling positions and to avoid the faux pas of the past.