Mitigating Environment Impacts of Geothermal Development IEA-GIA ANNEX 1 Workshop Taupo, 15-16th June, 2012 Report to IEA-GIA ExCo

Transcription

1 Mitigating Environment Impacts of Geothermal Development IEA-GIA ANNEX 1 Workshop Taupo, 15-16th June, 2012 Report to IEA-GIA ExCo Chris Bromley Convenor, Wairakei Research Centre Taupo

2 IEA-GIA, Annex 1, 2-day Environmental Mitigation Workshop Targeting : reservoir managers, policy makers, energy planners, geoscientists Sessions: A. Sustainability (long-term models, protocols, roots, tools) B. Surface features (policies, types, monitoring, ranking, categories) C. Reservoir modelling issues and strategies for protected areas D. Induced seismicity E. Subsidence mitigation

3 Summary of Taupo Workshop Friday 15 th to Saturday 16 th of June, 2012 Participants = 30 Countries = New Zealand, Indonesia, Ecuador Organisations = 13 (incl. Chevron, Star Energy, etc) Presentations = 14 (from US, Iceland, Japan, NZ) 5 sessions, + discussion time and a 2-hour fieldtrip PDFs distributed afterwards to participants & IEA-GIA website (members area Annex 1) Cost NZ$9258, Revenue NZ$4304, Difference NZ$4954 = US$ 3963 (@0.8) (includes organisation, venue, bus transport, materials, lunches, & presenters expenses)

4 Discussion time

5 WORKSHOP PROGRAMME: How to mitigate environmental impacts of geothermal development Chris Bromley will co-convene all sessions Location: ; Wairakei Research Centre Participants are welcome to briefly present their relevant experiences during discussion time DAY 1: Friday 15 June 2012 Presenter 9.00 Registration (Tea/Coffee) 9.15 Welcome (Brian Carey) & Introduction Chris Bromley Geothermal Geophysicist, NZ 9.30 Sustainability: Long term reservoir performance Gudni Axelsson Reservoir Modeller, Iceland Geosurvey (ISOR) Iceland enhancement : modelling; protocols; roots; & tools Chris Bromley Geothermal Geophysicist NZ Lunch Surface Features: NZ geothermal management, policies, Mark Chrisp Planner, Environmental Management Services NZ feature types, monitoring, ranking criteria and system Brad Scott Volcanologist, GNS NZ categorisation Chris Bromley Geothermal Geophysicist NZ Afternoon Tea Protected Areas: Japanese re-regulation Sakaguchi & Tosha AIST Japan 16:00 Reservoir modelling : sustainability & renewability Mike O'Sullivan Reservoir Modeller, University of Auckland NZ Close DAY 2: Saturday 16 June 2012 Presenter 9.00 Induced Seismicity: Protocols, review of NZ experience & Ernie Major Seismologist, Lawrence Berkeley National Labor US international state of the art Steve Sherburn Seismologist NZ Chris Bromley Geothermal Geophysicist NZ Morning Tea Subsidence: deformation modelling Mike Bruno President, Terralog Technologies US Nico Fournier Geophysicist, NZ Lunch Subsidence -case study from Wairakei-Tauhara Chris Bromley Geophysicist, NZ Field Trip - Tauhara and Wairakei sites of environmental interest Close

6 Key points from Presenters

7 Sustainability Protocol : goals proposed for geothermal development, covering following items : Resource management/renewability Efficiency Research and innovation Environmental impacts Social aspects Energy security, accessibility, availability and diversity Economic and financial viability / Knowledge sharing Sustainability Indicators Ruth Shorthall PhD topic IEA-GIA June 15,

8 Future utilization of ROOTS of geothermal resources Greater output than from normal-depth wells, if sufficient permeability can be found/enhanced, because of higher temperature and pressure, especially if supercritical Extends resource vertically (in time and space) Less environmental effects expected (a) Because of greater depth (b) Because of smaller horizontal extent Potential for applying reinjection-production doublets or EGS-technology Numerous technical problems to be overcome IEA-GIA June 15,

9 Krafla September 28-29, 2011

10 Recent Advances in Tracers Heat-transfer efficiency of flow-channels between reinjection and production boreholes is the main uncertainty in reinjection and EGS development Depends on flow-channel surface area, information not provided by conservative tracers Emphasis placed on introduction of reactive tracers, in particular in EGS-research Also high-tech tracers such as nano-particles and quantum-dots, designed with different properties Advances in tracer test technology, perhaps adapted from the petroleum industry, can be applied New temperature-tolerant high-sensitivity tracers have been introduced IEA-GIA June 15,

11 Geothermal Tracer Testing Possesses predictive power because thermal break-through time (onset of cooling) is usually 2-4 orders of magnitude greater than tracer breakthrough time. Heat-transfer depends on flow path surface area not flow path volume Tracer test duration is site specific and hard to pinpoint beforehand Soultz Krafla IEA-GIA June 15,

12 Suggested Strategies Practical strategies for geothermal field management that optimize long-term sustainability. (Many commercial reservoir simulations only consider depletion over economic lifetimes of ~30 yrs) 1. Cyclic/intermittent utilization, depletion and recovery, relying on enhanced mass and heat recharge. Allocation of standby reserves for future use? 2. Optimize total energy yields: using high extraction rates over short duration cycles, or low extraction rates for long duration cycles. Include economic and risk factors. 3. Use adaptive reinjection to support pressure and replace fluid, while avoiding premature cooling or suppressing natural hot recharge. Also use injection to suppress acid fluid production, and excess enthalpy steam. 4. Drill replacement or make-up wells to retain surplus production/ injection (for optimum flexibility) and to extend reservoir information boundaries. 5. Stage development sizes incrementally to test boundary conditions and recharge parameters, and to reduce risk.

13 Summary of Geothermal Resource Sustainability Strategies Geothermal resources are renewable. Even with drawdown, they can be utilised over a long term (~100 years) then, if necessary, retired. Pressure and temperature recovery will follow; the former occurring more quickly than the later. Utilising a system in this cyclic or intermittent way, without prejudicing its ability to recover, is a sound resource utilisation strategy. Medium term extraction rates are typically more than 10 times greater than natural heat discharge rates. Optimised reservoir management involves countering the adverse effects of early temperature decline with appropriate and flexible production and injection strategies. Flexibility in locating and utilising future injection wells both inside and outside the hydrological edges of a geothermal system, and at different depths, is a key means of achieving a successful outcome. Pressure (bars) at - 500m ON draw-down OFF recovery pressure temperature ON drawdown OFF recovery Years Temperature (degc)

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15 Parameters for several geothermal systems Name Type Area (km 2 ) Natural heat flow (MW) Heat flux (W/m 2 ) Electricity Production (MW) Production heat flow (MW) PR Recovery time (years) East Mesa Hot water Wairakei- Tauhara Liquiddominated 2-phase Darajat Vapourdominated 2-phase Cooper Basin EGS (hot dry rock)

16 Values Associated with Geothermal Systems Source of renewable electricity generation Cultural (traditional and contemporary) Ecological Scientific Education Intrinsic Aesthetic Commercial / tourism Private uses (e.g. hot tubs)

17 NZ Waikato Region Policy Requirements for Significant Geothermal Features (SGFs) in Different Geothermal Systems Development Geothermal Systems Significant adverse effects on SGFs from the take, use or discharges of geothermal energy and water are remedied or mitigated. Small and Limited Development Geothermal Systems Significant adverse effects on SGFs from the take, use or discharges of geothermal energy and water are avoided. Research and Protected Geothermal Systems Adverse effects on SGFs from the take, use or discharges of geothermal energy and water are avoided.

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21 Summary In Japanese Natural Park zones, special protection zones (SP, SP1, SP2 and SP3) have the best geothermal resource potential in quality and quantity. By the ordinance of the Ministry of the Environment on 27 March 2012, drilling, small scale development (<3 MW) and hot spring use is permitted in SP2 and SP3 only (not SP or SP1) Exploration (MT and gravity) Investigations in all Natural Parks, including special zones, are permitted to better understand the geothermal resources.

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23 Conclusions Geothermal features can be ranked for significance according to selected criteria. This helps classify geothermal systems into categories based on gradations of protection versus development status. Geothermal feature types can be classified into three main groups: a. Active features that are predominantly subject to subsurface fluid management; b. Associated thermal habitats (mostly subject to land use management); c. Remnant features that are subject to land use controls. Tables of feature types and subtypes allows application of ranking values of significance, through assessments of criteria such as rarity, resilience, vulnerability to reservoir utilisation, visual appeal, and site specific factors such as naturalness, memorability, accessibility, and cultural, historical, recreational, research or educational value. A proposed ranking scheme for categorisation of geothermal systems takes into account five primary criteria (thermal feature types, habitat rarity, landscape values, natural hazards, and access/size constraints)

24 Wairakei, Craters of the Moon, Steam eruption Lady Knox geyser, Waiotapu White Island, fumarole Kuirau Park, hydrothermal eruption Photos from personal and GNS archives