Worldwide Classification & Reporting Requirements for Geothermal Resources

Transcription

1 Requirements for Geothermal Resources (after paper SPE ) Prof. Dr. Gioia Falcone Institute of Petroleum Engineering Department of Geothermal Engineering 03 May 2012

2 Outline Need for Geothermal Reporting Standards. Review of Key Definition Attempts. Analogy with the Oil & Gas Sector. Risk Assessment. Need for an Integrated Subsurface/Surface Approach. Challenges Ahead & Conclusions. Institute of Petroleum Engineering Requirements for Geothermal Resources 2

3 The Goal Standards? Rules? Guidelines? Codes? Flexibility increases uncertainty Greater uncertainty = greater risk to investor Less confidence in geothermal development Institute of Petroleum Engineering Requirements for Geothermal Resources 3

4 What is the Target? Source? Reservoir? Fluids? Stored heat? Recoverable volume? Recoverable heat? Recoverable power?.or simply the net $$$? (SPE et al, 2007) Institute of Petroleum Engineering Requirements for Geothermal Resources 4

5 Example: Geopressured Resources - 1 Highly pressurised hot brine (water trapped during burial process). Often saturated with methane. Found in large, deep aquifers. Wells flow pressurised to the surface. Water temperature is C. (Texas Renewable Energy Resource Assessment, 2009) Institute of Petroleum Engineering Requirements for Geothermal Resources 5

6 Example: Geopressured Resources -2 3 forms of energy can be exploited: 1.Thermal from the high temperatures. 2.Hydraulic from the high fluid flow pressure. 3.Chemical from the dissolved methane. (Texas Renewable Energy Resource Assessment, 2009) Which one is the target resource? Institute of Petroleum Engineering Requirements for Geothermal Resources 6

7 Definition - by Temperature & Use (5 25 o C) (20 75 o C) ( o C) (> 150 o C) (after Texas Renewable Energy Resource Assessment, 2009) Institute of Petroleum Engineering Requirements for Geothermal Resources 7

8 Calculation of Temperature at Depth (MIT, 2006) Institute of Petroleum Engineering Requirements for Geothermal Resources 8

9 By Temperature, Use, Type & Status (after Bromley, 2009) Institute of Petroleum Engineering Requirements for Geothermal Resources 9

10 By Potential Potential (Piot, 2006; Rybach, 2009) Institute of Petroleum Engineering Requirements for Geothermal Resources 10

11 By Heat Heat-in in-place Place Stored Heat S w = water saturation Φ = porosity (AGCC, 2010) Institute of Petroleum Engineering Requirements for Geothermal Resources 11

12 By Heat Heat-in in-place Place Power Potential (AGCC, 2010) R f = Q WH / Q R for liquid-dominated systems Q WH = heat at wellhead Q R = heat in the reservoir (Muffler, 1979) Institute of Petroleum Engineering Requirements for Geothermal Resources 12

13 Key Oil & Gas Reporting Documents Guidelines for the Evaluation of Petroleum Reserves & Resources (SPE/WPC, 2001). Petroleum Resources Management System (PRMS) (SPE, WPC, AAPG, SPEE 2007). SEC Regulation S-K, Regulation S-X under the Securities Act of 1933, Securities Exchange Act of 1934 & Industry Guide 2. Modernization of Oil and Gas Reserves Reporting Requirements (SEC, 2010). Institute of Petroleum Engineering Requirements for Geothermal Resources 13

14 Differences with Oil & Gas Sector - 1 Commodity to be extracted is heat. Commodity (heat) is stored in both rock & fluid. For some hydrothermal systems, a recharge may take place on a human time scale vs. a geological one. Natural geothermal fluids contain dissolved solids and gas that can be regarded as by-products products. Geothermal energy can be used both for electrical generation & direct use. Institute of Petroleum Engineering Requirements for Geothermal Resources 14

15 Differences with Oil & Gas Sector - 2 According to the SEC, proved undeveloped reserves only applies to projects to be developed within 5 years (too restrictive for geothermal electric power generation projects). Geothermal energy markets are site specific and cannot be compared to global hydrocarbons market. Geothermal energy cannot be easily transported from its site of production (or stored), hence it is deemed to stay a local energy, contrary to oil & gas. Institute of Petroleum Engineering Requirements for Geothermal Resources 15

16 Resources & Reserves Oil & Gas (PRMS, 2007) Institute of Petroleum Engineering Requirements for Geothermal Resources 16

17 Resources & Reserves - Geothermal (AGCC, 2010) Institute of Petroleum Engineering Requirements for Geothermal Resources 17

18 Quantifying Total Project Risk Risking the geothermal value starts by identifying the in situ raw resource, and ends with the assessment of current & future market scenarios. 1. Exploration 2. Drilling 3. Well MW capacity 4. Reserves estimate 5. Geopolitical environment 6. Energy markets Institute of Petroleum Engineering Requirements for Geothermal Resources 18

19 Risk on Recovery Factor Representative historic database for conventional (i.e. hydrothermal) available for making estimates for new analogue geothermal occurrences. not true for the new generation of exploitation concepts (e.g. EGS, low T binary/organic Rankine cycle power). Example: the overall risk of an EGS project is strongly related to the success of the formation stimulation measures adopted. Institute of Petroleum Engineering Requirements for Geothermal Resources 19

20 Risk on Overall Plant Efficiency Energy conversion efficiency Power plant capacity factor Power plant downtime & life Example of cycle thermal efficiencies for energy conversion Risk related to technology, fluid chemistry, maintenance plan, etc. (MIT, 2006) Institute of Petroleum Engineering Requirements for Geothermal Resources 20

21 Need for Integrated Subsurface/Surface Approach 1. Identify possible resource. 2. Calculate heat in place. -A, h, depth, T (with corresponding uncertainty) 3. Calculate heat arriving at surface. -K, Q -Dynamic flow models (reservoir & wells) -Geo-mechanical models -Fluid & heat recharge 4. Calculate recoverable energy. -Efficiency of heat use & energy conversion 5. Apply cut-offs as/when appropriate. 5. Institute of Petroleum Engineering Requirements for Geothermal Resources 21

22 Geothermal Exploitation Components Geology & Geophysics Drilling, Completions, Fracturing & Production Ops., Plants Flow in Porous Media (after Enel, 2005) Field Performance Institute of Petroleum Engineering Requirements for Geothermal Resources 22

23 Need for an Integrated Approach Forward cascade of calculations, or simultaneous solution of reservoir, wellbore & plant, or iterative procedure? What cut-offs and where? What models/packages? Deterministic & statistical approach (including Monte Carlo & Experimental Design). Integrated subsurface/surface modelling. Predictions of cum. heat/energy recovery vs. time. Institute of Petroleum Engineering Requirements for Geothermal Resources 23

24 Challenges Posed by Standardisation Different types of resources & plants. Different uses & economics. Technology advancements. Impact of technology & economics on cut-offs. Naturally permeable aquifers vs. EGS. Varying environmental, policy & regulatory constraints. Standardising a workflow! Institute of Petroleum Engineering Requirements for Geothermal Resources 24

25 Conclusions Geothermal reporting standards needed to reduce risk to investor & increase confidence in geothermal development. Difficult to generalise procedures to quantify recoverable heat/power and associated project risk. Lessons learnt from oil & gas sector. Need for systematic subsurface/surface workflows. Institute of Petroleum Engineering Requirements for Geothermal Resources 25

26 Requirements for Geothermal Resources (after paper SPE ) Prof. Dr. Gioia Falcone Institute of Petroleum Engineering Department of Geothermal Engineering 03 May 2012