Two months after the stimulation and the well being shut in for the winter, we are pleased to have had the opportunity to present our results to the geothermal community at the 38th Stanford Geothermal Workshop. During the Wednesday morning session of talks on EGS, Susan Petty and Trenton Cladouhos of AltaRock presented our stimulation results to a crowd eager to hear of our progress.
Presentation by Susan Petty
Susan’s presentation focused on our efforts to gather information and data to develop our comprehensive operation plan before engaging in the permitting process and various public outreach campaigns (including this blog!).
She also addressed the timescale of field work at the project site, confirming that the highly anticipated Newberry EGS Demonstration has finally become reality. Susan also addressed the effectiveness of the diverers usedduring stimulation, showing marked improvements in well permeability and evidence of stimulation/diversion locations from continuous temperature monitoring within the well.
Overall, the stimulation results presented by Susan were well received at Stanford, and the geothermal community posed many questions about our diversion practices and the implications it has on performing future EGS stimulations in a cost-effective way.
Presentation by Trenton Cladouhos
Trenton presented further evidence of our success at Newberry, discussing the details of our seismic monitoring during the stimulation. Trenton laid out how monitoring can enhance geosciences and engineering techniques, and he described other procedures essential to the expansion of EGS.
Trenton showed that our improvements to the local seismic network made it possible to detect micro-events. This allowed us to monitor the progress of the stimulation, detecting micro-events previously invisible to existing seismic detection equipment. The locations of over 100 events detected by the network showed that over the course of the stimulation, the diverter caused a shift in the location of the local micro-seismicity. This was further indication of our diversion’s effectiveness.
Finally, Trenton shared some of the lessons we learned regarding EGS seismic monitoring, including how crucial the borehole monitoring stations we installed were to the stimulation. The crowd at Stanford was pleased and amused to learn that even our largest events were barely noticeable on surface stations, which seemed to be more effective at detecting cars and trains than seismicity from EGS.
-Kyla Grasso, Geologist, AltaRock Energy, Inc.
Although the stimulation phase of the Newberry EGS Demonstration has come to a close, field work continues throughout the winter months on the volcano (brrr!). We’re currently collecting and analyzing groundwater samples in order to monitor any changes in the local groundwater system. This work is intended to make sure thestimulation hasn’t affected the quality of the groundwater high on the flanks of the volcano. Water samples are collected by AltaRock’s staff monthly and sent to independent laboratories where they’re analyzed for 30 different elements. Characterization of the local groundwater chemistry means we’re able to show that EGS can be developed safely and without negative impact on the surrounding aquifers and hydrologic features.
We will continue to collect and analyzing water samples from several sites surrounding the stimulation well for six months following the stimulation. Sample sites are located both up-gradient and down-gradient from the stimulation well. In the winter we sample the hot springs at East Lake and Paulina Lake in Newberry Caldera, two wells located on the volcano, and a residential well in the valley. Once spring weather comes around (we’ll hedge our bets on mid-July, since last year it snowed June 26th!), we’ll be able to access several other wells which are shut in for winter to protect them from freezing. So what does groundwater quality sampling look like in the field? Check out these photos!
Field work in the winter months is always tricky. Newberry Volcano often hosts 5-6 feet of snow, making a tracked vehicle and snowshoes must-haves for winter field
work. Collecting just two samples can take an entire 10-12 hour field day if all goes well. We’ve all heard the phrase, “an ounce of prevention is worth a pound of cure”, and when it comes to working in an environment where temperatures can range from -15 °F 100 °F, that couldn’t be more true. While we’re out sampling groundwater, we often make time to check on seismic equipment, perform any needed maintenance and make a stop at the stimulation well to check on things.
Each sample collected is first analyzed in the field. We record pH, water temperature, electrical conductivity and a number of other measurements as soon as we take the sample. Once these are recorded, the water is filtered, bottled and sealed to prevent contamination before being sent for analysis. Three laboratories perform more than 30 different tests on each sample. Our staff compiles the data, compares it with previous results, and looks for any significant changes.
So far we’ve collected and analyzed 21 samples from nine different sites surrounding the stimulation well, and we’ll head out again next week to collect another set. Our sampling program can detect changes as small as 0.2 parts per million for some elements. As expected,
to date no significant changes to water quality have been found at any of the sampling sites.
GigaOM.com, a website dedicated to the intersection of technology and business, recently featured AltaRock’s work at the Newberry EGS Demonstration. The article was written by GigaOM editor Katie Fehrenbacher, a seasoned reporter in the energy and investment space, who interviewed AltaRock’s Susan Petty for the piece. Fehrenbacher’s writeup offers a nice overview of the technology behind our work at the demonstration, but even moreso explains EGS’s role within the larger geothermal/renewable energy landscape.
Welcome Back! With serious winter weather at the site, demobilization of equipment that took months to mobilize, and the holidays, we fell behind on the blog entries. Now that we have recovered, we want to give a quick overview of how things turned out.
1. On November 26th we finally got all the problems with the stimulation pumps ironed out and returned to full operating capacity. Shortly after, we injected TZIM (thermo-degradable zonal isolation material) and witnessed about a 50% reduction in flow into the formation, as the TZIM plugged up flow zones in the well. Then as we increased the pressure, flow and microseismicity increased again as new fractures in the wellbore were enhanced.
2. We injected more TZIM on December 3rd, and again watched flow decrease due to blocking previously enhanced zones. Again flow increased as the third stimulation zone was created. We stimulated zone 3 until December 7th when we turned off the pumps.
3. The final EGS reservoir as defined by the microseismicity (yellow dots on map) eventually reached a dimension of about 2 x 1 km (6600×3300 ft). We injected about 11 million gallons or 34 acre-ft, half the water that we expected to use.
We are now analyzing all the data that we collected and planning for the next field season. We will also be getting back into the swing of blogging. We will soon provide more details of what we experienced (besides the cold and snow) and what we are learning over the winter and spring.
Our EGS reservoir continues to grow! Check out the satellite image below which shows the twenty seismic events (red, orange, and yellow dots) that the Pacific Northwest Seismic Network (PNSN) has located below our well (located on the tan square). In addition to pushing cold water over 500 m from the well as indicated by these tiny earthquakes, we have improved the injectivity of the well about 1o-fold, meaning that at a given pressure we can inject 10 times as any gallons per minute as when we started.
We are preparing to inject diverter soon and start on our second stimulation zone. We anticipate that will go fast once we get all the pieces in place. For all of you locals wishing for skiing on Thanksgiving, please wish that Mount Bachelor hogs all the snow and leaves none for Newberry!
Cold water has been flowing out the bottom of the hole for a week now, producing 15 microseismic events. The map above shows the locations of the events (orange dots) as located by the Pacific Northwest Seismic Network (PNSN). The main cloud of microseismicity (the two events to the south are likely mis-located) is about 1 km long. A lot more analysis is going to be needed to make sure those locations are as precise as they can be.
For now, the flow rate into the well and an approximately 1 km long zone, indicate that we have reached our goal for the first zone. We are now preparing to inject the first round of diverter to temporarily plug this zone where it intersects the well, and force the water to find another depth to exit the well.
We have exciting news to share this morning. Yesterday, we got both pumps running at full capability and brought the well head pressure up to 1800 psi. Shortly afterwards, two microseismic events with magnitudes close to zero occurred near the bottom of the bore hole. In addition, the permeability increased slightly. This means that hydroshearing and creation of an EGS reservoir has begun! As we continue to slowly increase the rpm’s of the pumps, we anticipate many more microseismic events over the next week.
The map above shows the locations (red dots) of the events in relation to the geothermal well’s surface location and five of our closest monitoring stations.