Geothermal Innovations in Action: Real-World Insights from Mazama and Halliburton: AAPG Academy: Webinar Summary & Review

Magnetic Ranging Technology for Precision Targeting in Geothermal Wells

     The first presentation was by Pete Schiermeier of Haliburton. It was focused on magnetic ranging technology for precision targeting. High-precision targeting is needed for advanced geothermal systems (AGS) where the configuration is for two horizontal wells to be looped together into one closed-loop system. Magnetic ranging can be utilized for traditional geothermal, AGS, enhanced geothermal systems (EGS), and in supercritical geothermal projects. I have been interested in this technology since I have extensively used less accurate oil & gas magnetometer-based survey tools in my work in geosteering wells. This works well for staying in the desired target zone, but is not precise enough to join two wells together.

     Why use magnetic ranging technologies? Survey tools (gyros, magnetometers, etc.) have limitations. An error of ellipse occurs, which gets larger with depth, inclination, and azimuth change. Ranging tech removes that uncertainty. It gives spatial separation and alignment in relation to the target well.

     What is magnetic ranging? It involves generating and detecting a magnetic field to get the distance and direction to the target.

     There are four ways to generate a magnetic field: 3 active and 1 passive. Active methods generate a magnetic field. The passive method detects an existing magnetic field. Each of the four can be optimized for geothermal applications. 

     The two main methods of detecting a magnetic field are: 1) magnetometers, which are used in oil & gas drilling, and 2) gradiometers – pre and post signals.

     Applications for ranging technologies include relief wells, other kinds of wellbore intersections such as AGS closed-loops, and wellbore avoidance (anticollision).

     Access Dependent Ranging (ADR) means you have access to a well that you are drilling toward. A magnet is conveyed into a target well. MGT = magnetic guidance tool. RMRS uses rare earth magnets conveyed in the target well via wireline. The Magnet is placed in a sub and rotated to generate a magnetic field, which is then detected and utilized. Another way to do ADR is single wire guidance (SWG). In this version, a line is put in the target well. 

     There are also Access Independent Ranging technologies. Halliburton has two tools that do this. WellSpot is Haliburton’s well intersection tool used when there is nothing in the target well. It detects with gradiometers using well tubing, creating a downhole induced field. Another Haliburton ADR method is Aurora Sub, which uses a surface-induced magnetic field.

     Haliburton’s newest geothermal ranging tool is used for well intersections. Eaverloops use them to connect two horizontal wells that intersect at the toes. It can also connect parallel wells or other combinations.

     Geothermal Ranging Overview. The MGT tool is the most efficient way to generate a magnetic field. The new tool is similar but powered by a downhole generator, then powered off when not needed. Thus, there is no need for tripping. This tool is used in AGS.  The MGT detection range is about 30m. The detection range of the new tool is greater than 100m, so this is a big improvement. It takes 10 minutes or less to get data with the new tool. The rotating systems within boreholes to generate magnetic fields can create problems. The new tool eliminates these wireline problems and unnecessary trips. This big distance of direction above 100m opens the door for its use in EGS. Maintaining separation distance from other wells is important. Studies have been done to guide wells without surveys, but only using ranging.  

 

Update on Newberry Volcano Project in Oregon: Hottest EGS Project in the World

     The second presentation was by Gabriel Grubac of Mazama Energy. He notes that a new drilling and completion geothermal heat milestone was reached this year, with a temperature of 331 deg C at the Newberry Volcano Project in Oregon. High-temperature geothermal wells are usually considered to be 150-200 °C, so this is quite hot. Water changes into a supercritical phase at about 374 deg C. 331 deg C = 629°F. It is the hottest EGS project in the world in Newberry, Oregon. Mazama Energy recompleted an injection well, stimulated it, then precisely drilled a production well to within 6 ft of where they wanted. They even retrieved a 12ft core of the 331 °C rock, which is basalt and granodiorite. Completion will become more important. EGS in superhot rock should be more competitive than traditional geothermal. A key finding is that these temperatures can be drilled. One important parameter is engineered reservoir volume (he does not prefer the term stimulated reservoir volume for some reason).

     ROP, a measure of drilling speed, was 72 ft/hour on average, which is great for this kind of well. There were no trips due to drilling motor or MWD failures. 

     Reservoir creation was created in this EGS project via the Thermal Lattice method of hydraulic fracturing. Some breakdown data is shown below.

     The Newberry Volcano has weather challenges due to elevation, cold temperatures, and is in a remote area. Newberry has higher temperatures at shallower depths, which makes it an ideal place to test superhot rock. They utilized induced seismicity detection and a traffic light system to mitigate as needed = safer EGS. It was an engineering challenge to re-enter the injector well to run coiled tubing to perform wireline-based perforation and to frac it. They first made a sleeve to go in and stimulate from it. They utilized what they learned from the injector well for the producing well. Basalt and granodiorite are different lithologically. Creation of a durable reservoir with limited loss of conductivity over time is challenging. What enables longevity? Proppant application is important. The next phase of the project is a 15MW commercial pilot. They think they can transport proppant and drill at 400 deg C, which they plan to test and validate. Two wells are planned for 2026.

 

Q&A for Both Speakers

     Do casing materials affect ranging tools, and if so, how? Yes. Thus, understanding casing is important. Pre-planning scenarios include it, but only when casing is used in the ranging.

     Ranging tech and temperature – 160 deg C is the limit now. There are 200+ °C tools too.

     Can geology impact ranging? Not really, with the latest tools. You can, however, calibrate for formation. They saw little to no difference between surface and downhole tools in trials, so no formation effects were detected.

     How long will Newberry produce heat? This project is a proof-of-concept project, so this is not determinable yet. 20-30-year viability is hoped for.

Are there heat losses through fractures? Higher temperature EGS needs less water to create an economical induced fracture system due to the heat.

     How are Regional subsurface temperature and pressure (T&P) characterized in the Newberry Volcano region? Data has been available for a while on T&P, and more data is now available with the new project.

 

 

 

References:

 

Geothermal Innovations in Action: Real-World Insights from Mazama and Halliburton: AAPG Academy. Webinar. November 13, 2025.