U.S. Department of Energy - Energy Efficiency and Renewable Energy
Geothermal Technologies Office
AAPG Low-Temperature Webinar: Transcript
This is a transcript of the AAPG Low-Temperature Webinar held on November 18, 2010.
Good day, I am Tim Reinhardt with the Geothermal Technologies Program at the Department of Energy and this is a presentation on Low-Temperature Geothermal Resources. There is a slideshow presentation-PowerPoint that goes along with this briefing and it should be up now and we should be on the cover slide with my name and information. The original presentation date for this was November 18th, 2010 and this will serve largely as a re-recording of the original presentation. I would like to thank AAPG for participating in this and making this event possible. We appreciate their flexibility in enabling this event to come together and this rerecording is in part at their request.
This presentation will provide an introduction to low temperature geothermal resources.
Slide 2: Per the feedback that we received for this webinar, we will attempt to answer some of the key questions posed here, albeit not necessarily in the particular order shown. As we go through this presentation, we will provide an overview of the Geothermal Technologies Program (GTP) as well as the Low Temperature and Coproduced subprogram, and then present some details on the subcategories contained within the umbrella label of Low Temperature and Coproduced, we will also provide some detail on what actually constitutes these resources. That will be followed by a brief discussion on the basic economics, geography and geology of these resources, and then we'll close things out with some case-studies of ongoing projects and a look at current activities in the subprogram.
When presented with the opportunity to host this webinar, I felt that an hour would be more than sufficient time to allow for a full presentation and also leave ample time for Q&A as well, but I think as is always the case, the task tends to expand to fill all the time allotted. So, with that being said, I will make an earnest effort to keep this presentation to 40-45 minutes so that we do have time at the end for at least a few questions. We will see how well I stick to that goal.
Slide 3: The mission of the Geothermal Technologies Program (GTP) is to establish geothermal energy as a significant contributor to America's future electricity generation by partnering with industry, academia and the national laboratories to discover new geothermal resources, develop innovative methods, and demonstrate high-impact technologies.
With this mission in mind, the vision of the program is to enable geothermal capacity to reach 12 GW of domestic base-load power by 2020.
In order to achieve this, Low Temperature and Coproduced resources will need to produce electricity at $0.08/kWh by 2016 and to have added 3 GWe of geothermal capacity by 2020.
Additionally, one GWe of undiscovered hydrothermal resources will need to be confirmed and brought online by 2020. The DOE Strategic Plan goal is 400 MW confirmed by 2014.
Will also need significant advancement in Innovative exploration technologies (IET) such as 3D-seismic and remote sensing to reduce exploration risks and costs. Reservoir stimulation technologies will also be needed to enable the creation of high-performance, sustainable geothermal reservoirs with high flow rates and low thermal drawdown.
Lastly, Advanced working fluids and cooling systems will be required to reduce costs and expand the range of resource temperatures that can be utilized economically. Current working fluids are mixes of water, isobutane, and/or isopentane.
Slide 4: This slide shows the most recent breakout of the research, development and demonstration activity subprograms here at the geothermal technologies program which will be used to pursue our mission, vision and strategic goals.
Of the four, EGS has the highest potential payback, but is the longest term technology in the GTP portfolio.
The Innovative Exploration Technologies or IET subprogram actually feeds into the other three components by attempting to decrease the upfront risk for geothermal developers and to accelerate all geothermal deployment by improving the likelihood of exploration success, and by assisting in resource discovery.
The Permeable Sedimentary subprogram is the newest of the areas, and is also the most closely aligned with today's topic area, Low Temperature and coproduced resources.
As we'll see here in a few slides, the Low Temperature and Coproduced, and Permeable Sedimentary subprograms can be seen as being on a time, technology and resource continuum.
Slide 5: The Low Temperature and Coproduced subprogram is aimed at the exploration, development and deployment of non-traditional geothermal resources including low temperature resources below 150°C. Like EGS, LT resources hold the potential to bring geothermal out of just western states in the near term and has the potential to allow utilization of geothermal resources across the nation. New technologies are enabling economic use of these resources. For example, new binary generation units can use water with temperatures as low as 90°C (195° F), and in Alaska, as low as 165°F.
There are three major technology or resource areas in the subprogram:
- Low Temperature: Using fluids below 150°C
- Geopressured: Using heat, chemical energy and pressure (kinetic energy) from brines
- Coproduced: Using fluid coproduced at oil and gas wells or conceivably other hydrocarbon production wells such as coal bed methane.
Advantages of Low-temperature geothermal facilities are that they:
- Are Low cost.
- Have a short lead time.
- Have a broader geographic distribution than conventional geothermal.
- Binary units can be modular, easily scalable and available off the shelf. As a resource is proven, the number or size of units can be scaled up. 280 kW units can be deployed in parallel or larger units can be used.
DOE's objectives in this area are to:
Demonstrate production from:
Oil and gas fields, Geopressured fields, and Low temperature resources in a technically feasible and economically viable manner, with the long-term goal of bringing 3 GW online by 2020.
Slide 6: While this slide does not contain the subcategory of low temperature resources that occur outside of sedimentary systems, it is useful in describing the relationship between the Low Temperature and Coproduced subprogram, and the Permeable Sedimentary subprogram.
Initially, Geothermal resource investigation was limited to crystalline rock formations. However, many sedimentary formations, including some that contain oil or gas, may be hot enough to serve as commercial geothermal reservoirs. Unlike conventional geothermal reservoirs which generally occur in those fractured igneous and metamorphic formations, these reservoirs have intergranular porosity, which allows relatively easy estimation of the hydraulic characteristics of a well from cores and well logs.
The implied geology of this slide shouldn't be taken too seriously, rather it serves to demonstrate the evolutionary quality of low temperature coproduced fluids into permeable sedimentary. As we proceed from left to right across the slide we are proceeding both temporally, economically and technologically.
Geopressured resources have been shown to be feasible for decades, while coproduced generation has come on more recently. As we continue across, using the geothermal resource in strata lacking hydrocarbons and eventually combining carbon sequestration with energy production are the most technically and economically challenging, and therefore the most long-term activities. Hence the latter two technologies fall under the Permeable Sedimentary subprogram and not the Low Temperature and coproduced subprogram.
Slide 7: We'll now take a look at low temperature resources, and to avoid as much confusion as possible I should probably restate at this point that when we talk about Low temperature resources, we are speaking of those geo-fluids that have a temperature below 150°C, and not coproduced or geopressured resources. All three fall under the rubric of the Low Temperature and Coproduced subprogram, but as a resource, they are considered separately.
Slide 8: What are low temperature resources? Well, it depends on who you ask. For the USGS, in their previous resource assessments, they have defined low temperature geothermal resources as those geo-fluids with a temperature below 90°C, and moderate as those with a temperature below 150°C. For us at DOE's Geothermal Technologies program, low temperature resources combine the two USGS categories into one, and we say that anything below 150° is low temp. From an industry perspective, Subir Sanyal from Geothermex authored a paper on the subject in which he defined non-electrical grade geothermal resources as those below 100°C and very low temperature resources as those between 100° and 150°.
While this may make it seem that there is some disagreement as to the definition of "low temperature," there is in fact a general consensus. At this time there is agreement that fluids below 150°C must use binary generation technologies if electricity is to be generated, and that this barrier provides the clearest delineation between low temperature and conventional hydrothermal geothermal systems. So with some confidence and for the purposes of this presentation and the subprogram, low temperature resources are defined as those below 150°C, or about 300°F. These resources can be used for either direct use or power generation.
Slide 9: Unlike conventional hydrothermal geothermal resources, low temperature geothermal resources are more widely distributed throughout the US. As can be seen from the map, at a depth of 6km, the resource base spreads out of the western states and expands into the gulf coast region as well as significant swaths of the upper midwest.
Slide 10: The primary uses of low-temperature geothermal resources are currently in district and space heating, greenhouses, and aquaculture facilities, though numerous other uses for geothermally heated water exist. Over 120 operations throughout the U.S. are using geothermal energy for district and space heating. District systems distribute hydrothermal water from one or more geothermal wells through a series of pipes to several houses and buildings, or to blocks of buildings. District heating can save consumers 30% to 50% of the cost of natural gas heating. By contrast, space heating uses one well per structure. In both cases the geothermal production well and distribution piping replace the fossil-fuel-burning heat source of the traditional heating system.
Direct use geothermal energy has also been well received within the agribusiness industry, with the two primary uses being greenhouses and aquaculture (fish farming). Geothermal water with temperatures as low as100°F has been used within greenhouses since the late 1970's, with at least 40 greenhouses in 10 western states (Geo-Heat Center). Many of these facilities cover several acres, raising vegetables, flowers, houseplants and tree seedlings. Most greenhouse operators estimate that using geothermal resources instead of traditional energy resources saves around 80% of fuel costs.
Slide 11: Most geothermal areas contain low-to-moderate-temperature water (below 300°F). For electricity generation, energy is extracted from these fluids in binary-cycle power plants. Hot geothermal fluid and a secondary (hence, "binary") fluid with a much lower boiling point than water pass through a heat exchanger. Heat from the geothermal fluid causes the secondary fluid to flash to vapor, which then drives the turbines. Because this is a closed-loop system, virtually nothing is emitted to the atmosphere. Moderate-temperature water is by far the more common geothermal resource, and it is believed that most geothermal power plants in the future will be binary-cycle plants, until EGS comes online commercially in the US.
The USGS is currently conducting a resource assessment for the entire united states, to include geothermal fluids down to a temperature of 90°C, which should help to give us much more accurate and up-to-date look at much of the low temperature resource potential.
Slide 12: Geopressured resources are the next of the low temperature and coproduced subcategories that we'll take a look at.
Slide 13: Geopressured resources are simply subsurface reservoirs containing hot pressurized brine saturated with dissolved gas, largely methane. Water temperature can range from 90°C to 200°C.
Three forms of energy: thermal, hydraulic from the high pressure which can be used to drive turbines, and chemical from burning the dissolved methane as in a natural gas plant, are potentially obtainable from this resource. The northern Gulf of Mexico is the largest region discovered that contains this type of resource.
Slide 14: As stated, a geopressured resource consists of hot brine saturated with methane and found in large, deep aquifers that are under higher pressure due to water trapped in the burial process due to rapid sedimentation and growth faulting. These resources are found in sedimentary strata at depths of 3km to 6 km.
The U.S. Department of Energy conducted a geopressured-geothermal research program in the northern Gulf Coast to gather reliable geological, engineering, environmental and economic information about this resource to determine its viability for development from 1975 to 1992. Four wells were drilled and tested during this program and another twelve wells donated by the oil and gas industry were tested. The program involved industry, universities, and national laboratories. The program identified geopressured and geothermal fairways in Louisiana and Texas, determined that high brine flow rates (20,000 40,000 barrels per day) are possible for long periods of time, gas/brine ratio averaged 34 Scf/STB and that used brine could be re-injected into sands below fresh-water aquifers without contamination. Inhibitors controlled corrosion and scaling, and a hybrid power system generated electricity using both separated methane and geothermal heat.
Slide 15: The northern Gulf of Mexico geopressured-geothermal resource has been estimated by various researchers to contain from 150 - 5,000 Tcf of recoverable methane and up to 11,000 quads of thermal energy in sandstone pore fluids to a depth of 22,500 feet. This is equivalent to many times more than the presently known conventional methane resources in the United States. This resource contains chemical energy in the form of methane dissolved in pressurized brine, thermal energy consisting of hot brines at high temperature which could be used for secondary hydrocarbon recovery or electricity generation, and mechanical energy generated through high brine flow rates (20,000+ barrels per day) which could be utilized to drive turbines to generate electricity.
As can be seen from the map, there are also other smaller regions of geopressured areas in the US besides the North Gulf Basin, to include areas in Texas, Oklahoma, Mississippi, Utah, Wyoming and California. To the best of my knowledge, none of these other areas have received comparable amounts of research to the gulf coast zone, and therefore the resource potential in these areas is less quantified.
Slide 16: While profitable commercial development of the geopressured project sponsored by DOE was at that time unfavorable, the energy picture today has changed and gas and oil prices are considerably higher, with predicted major world wide shortages in a world dependent on fossil fuels. With improved technology the development of the geopressured-geothermal energy resource with its numerous direct, and relatively environmentally safe uses could potentially be part of the answer to the country's energy problem. It is time to reconsider the commercial viability of this unconventional alternative energy resource.
This slide shows a conceptual rendering of what a geopressured system might look like. Extracting as much thermal energy from the brine as possible through cascading activities can help to improve the economics of the project. Although with lower brine temperatures precipitation and scaling from the geo-fluid may need to be inhibited depending on fluid chemistry.
Slide 17: The last of the Low Temperature resources we'll look at is coproduced.
Slide 18: Under its current definition, coproduced fluids are those that are brought to the surface as a byproduct of harvesting hydrocarbons. While limited to oil and gas wells currently, there is no reason that coproduced fluids can't be utilized in mining and coal-bad methane operations as well.
Slide 19: At the present time the objective in most hydrocarbon fields is to limit water production as much as possible because it is a major expense. Fracturing and completion strategies are designed to accomplish this goal. If we can show an incentive to produce water, such as through the economic benefits of energy savings and prolonging the life of the field, than there is a potential for power production in the 1000's of MWs.
Slide 20: By installing off-the-shelf technology, geothermal power can conceivably quickly and cost-effectively be brought on-line in existing oil and gas fields.
Beyond that, producing electricity from coproduced oil/gas fluids has the potential to turn what was a nuisance waste-stream into a source of additional revenue.
Slide 21: This map provides some sense of the quantity of heated water created in oil/gas production. At an average temperature of 140°C, NREL estimates that coproduced fluids could generate close to 12GW of potential power. NREL is currently re-analyzing their data, and we should have an updated reserve estimate in the coming months.
Slide 22: What we do know for certain right now, and as can be seen from this map, is that there is an extensive resource base of hot co-produced water that already exists in the United States, while not all of it is currently being produced, whether because the well is shut-in, plugged or orphaned, the resource is there.
So, while low Temperature resources have only recently come back to the forefront in DOE's GTP portfolio, the Geothermal Technologies Program has dedicated itself to a much broader portfolio, with Low Temperature resources and technologies among the new areas of focus. While still in its infancy, the Low Temp program is rapidly developing robust technical, demonstration and R&D sections to help capture some of this vast potential energy source.
Slide 23: I was asked to present some of the economics involved with Low temperature resources, and will do so briefly here. What I will be speaking to is largely a summation of different works by Subir Sanyal at Geothermex, and I would encourage those of you interested in further information to read his and other's papers on the topic.
Slide 24: As can be seen from this graph, the levelized cost of power (electricity) in sedimentary systems, is sensitive to reservoir flow capacity (kh) and temperature. An obvious take-away is that the higher the temperature and kh of the reservoir, the lower the levelized cost of producing energy. Not charted here, but also economically sensitive is drilling depth. In general, and this is far from a ground-breaking observation, shallower, hotter wells with high flow rates are more economically viable than deep, cool wells with low flow rates.
A few more general conclusions, and this is again largely based on Sanyal and Butler, that can reached on low temperature, geopressured and coproduced resources are that:
- Whether an existing normal-pressured gas well, if reworked, can be an economic source of geothermal power and gas is a highly site-specific issue
- Drilling new wells to produce geothermal power from a normal-pressured aquifer without any gas saturation is unlikely to be economic for self-flowing wells but may be economic for pumped wells
- Gas-derived component of total power from a geopressured well is larger than the geothermal component; the kinetic energy component is minor
- Economic value of a geopressured well is sensitive to temperature and overpressure, and highly sensitive to gas content
- Geopressured systems are economic sources of geothermal power plus gas, if re-worked existing wells are used
- Geopressured systems can be economic sources of geothermal power and gas even if new wells are drilled
- Selling produced gas from a geopressued well becomes more attractive than making gas-derived power as gas price increases
- Economics of geothermal and gas-derived power from abandoned or new wells is sensitive to resource degradation rate, which cannot be generalized
Slide 25: We'll now take a look at some of the projects that we have partnered on or partially-funded recently.
Slide 26: Recent improvements made in binary-cycle technology will allow for economical production of electricity from low-temperature, co-produced fluids. One notable case in point is the successful commercial Ormat power production unit at RMOTC.
RMOTC is located within the Teapot Dome oil field, also known as the Naval Petroleum Reserve No. 3 (NPR-3). The field is thirty-five (35) miles north of Casper, Wyoming. NPR-3 is operated by the Department of Energy as both a producing oil field and a test site for new and developing oil and gas, and renewable energy related technologies.
To verify the concept of electrical power from oil field produced water, RMOTC developed a program in conjunction with Ormat Nevada to test an air cooled unit. The project operated for over a year and then became part of the present collaborative project with the Geothermal Technologies Program.
In September 2008 at the Naval Petroleum Reserve No. 3 (NPR3), Ormat Technologies and the Rocky Mountain Oilfield Testing Center (RMOTC) achieved the first successful generation of electricity from geothermal technologies integrated with existing oil infrastructure.
Slide 27: The Ormat power generating unit known as the Ormat Energy Converter (OEC) has been producing 150-250 gross kilowatts of power since its inception.
In February 2009, the unit was shut down because of equipment problems caused by operating the unit in excess of the rated capacity of 225 net kW, (phase 1). Changes in the control system and repairs to the generator/turbine system were made. The new control system included the installation of a second hot-water flow control valve, a turbine vibration sensor and temperature probes on both generator bearings. The startup control for the unit was also changed providing for a smoother, startup. The unit was restarted in May 2009 but was shut down to address related field issues with the production wells and electrical system.
The system was restarted in September, 2009 (Phase 2). Since restart, the unit has averaged 198 kW net power output. The output power fluctuates noted in Phase 1 have decreased with the new control system, compare green line for phase 2 with red line for phase 1 in the Figure. During phase 2, the unit has produced over 896 megawatt hours of power from 4.4 million barrels of hot water. The online percentage for the unit, eliminating downtime caused by field activities, has been a 97%. The power output of the unit over the last 60 days of operational data averaged 212 kW with a control set point of 220 kW.
The initial economic results are also promising, with our NREL analysts coming up with an LCOE of 11 cents for the RMOTC specific data.
Slide 28: We'll now briefly summarize the 10 American Reinvestment and Recovery Act projects that were mentioned earlier. This slide shows the first 6 of 8 Low temperature projects that were selected. The first project Beowawe, will be utilizing a binary cycle power unit to provide additional power to an already existing geothermal plant utilizing the waste-water that is at too low a temperature for a flash plant plants – referred to as bottoming-cycle plants. In fact, all of these projects will be coupled with direct use applications-known as cascading, will be utilizing waste heat from already existing power plants, or will be developing innovative energy conversion technologies, as is the case with the Oasys Water Osmotic Heat Engine.
Slide 29: The last of the low temperature projects are the top two listed on this slide. The two co-produced projects are from Universal Geopower and the University of North Dakota. One award went to Universal Geopower for a demo project in Texas, the other went to the University of North Dakota for a project in the western portion of that state. Highlighted in blue is the sole selectee for a geopressured project, Louisiana tank, which will be building a plant in Cameron Parish, Louisiana that will utilize kinetic, thermal and chemical energy to produce electricity.
All 10 selections bring the total award amount up for negotiation to $18.7 M.
Slide 30: Here is a graphic display of the geographic diversity of the selected projects. While the West enjoyed continued success, Texas and Louisiana along the gulf coast, and North Dakota in the upper-Midwest are the newest states to deploy geothermal power generation. It is one of our goals through the low temperature subprogram to continue eastward expansion of geothermal power production.
Slide 31: Finally, we'll look at some recent and ongoing subprogram activities.
Slide 32: While this is slide covers an internal activity for DOE, I think it bears mentioning for its possible impact on the industry and the level of commitment as it demonstrates DOE's commitment to pursuing geothermal applications in oil & gas fields. So,the Department of Energy's (DOE) Geothermal Technologies Program (GTP), and DOE's Office of Fossil Energy (FE) Rocky Mountain Oilfield Testing Center (RMOTC) have committed to a formalized working agreement that will facilitate responsible development of geothermal power projects at the RMOTC test site. With this MOU, these two programs hope to ensure the continuation of current and future testing and validation of promising, innovative, geothermal technologies - specifically those that are applicable to marrying oil and gas applications with geothermal electrical power generation.
Slide 33: Another activity is the Low Temperature Roadmap, which is currently posted on our website for review and comment. It will be open to review until December 1st.
The Low-Temperature ,Coproduced, Geopressured Geothermal Technology Strategic Action Plan presents an action agenda for the Low-Temperature, Coproduced Geothermal Subprogram to efficiently and effectively leverage its resources in support of the goals and priorities of the geothermal community. Specifically, the action agenda, when implemented, will help provide the geothermal community with the means to achieve the development and widespread deployment of economically viable, innovative, and scalable technologies and ultimately achieve the vision of 3 Gigawatts of installed low-temperature, coproduced and geopressured geothermal capacity in the United States by 2020.
Slide 34: Finally, earlier this year through a FOA, funding was made available in the following topic areas:
A. Low temperature geothermal fluids at temperatures up to 300°Fahrenheit (F) or approximately 150°Celsius (C)
B. Geothermal fluids produced from productive, unproductive, or marginal oil and gas wells, mining operations or other hydrocarbon or mineral extraction processes
C. Highly pressurized or "geopressured" fluid resources that show potential for cost-effective recovery of heat, kinetic energy, and gas
Out of this process, 7 awardees were selected. They are currently finishing negotiations, and should begin work early in the coming calendar year.
||Compliance Review Complete
||Merit review individuals & panels finalized
||Selection completed by HQ
||Conditional awards made by GFO OAFA
||Full awards for Phase I
||Down-Select (??) review for Phase II awards
||Conditional awards for Phase II
||Full awards for Phase II
This concludes the webinar. I would like to thank you, it's been a pleasure. Again, this is Tim Reinhardt and you can reach me at this email address. Please contact me with any questions you may have.
Thanks you very much for listening. I hope you found this useful. I would like to thank the staff here at the DOE, especially Elisabet Metcalfe and Rachel Bilyk. Any questions or comments feel free to contact us. Thank you very much for your time.