Successful 3-stage hydraulic stimulation of injection well 16A(78)-32

The Utah FORGE research team has achieved yet another major milestone in advancing enhanced geothermal system technologies with the successful completion of the first large scale 10-day stimulation trial (April 14-24, 2022) in the deep deviated well 16A(78)-32. Three intervals were tested in sequence at greater than 10,000 ft depth, including the open hole at the toe of the well (Stage I), followed by two shallower 20 ft intervals that were lined with solid casing (Stages 2 and 3). In each stage, between 3000 and 4000 barrels of water were injected under pressure, causing pre-existing fractures in the reservoir to dilate and transfer heat to the injected cold water. After a 4-hour shut in, the hot injected water was produced back to the surface under controlled flow conditions. The stimulation trial ran according to schedule and plan, including the seamless deployment and retrieval of the bridge plugs at high pressures and temperature.

The ability to initiate, propagate and ideally control hydraulic fracture growth is essential for realistically evaluating the potential for commercial EGS applications. Success here is important for promoting technical and hybrid EGS methods that use hydraulic injection to provide a heat exchange network or to achieve more effective connections with potentially productive natural fractures.

In late 2022 or early 2023, a second deep deviated well, the production well, will be drilled to intersect the hydraulic fractures. The connectivity of the fractures between the two wells will be established or improved, and short-term circulation testing will begin to assess the thermal viability geothermal reservoir.

Word of the Week – Epidote

Epidote

Alumino-silicate hydrothermal mineral having a distinctive yellow-green color that is used a mineral geothermometer, forming at temperatures above ~230°C. The first down hole occurrence of epidote commonly coincides with the top of a high-temperature geothermal reservoir where it is hosted by igneous rocks.

Word of the Week – Illite

Illite

A potassium-bearing mica-like clay mineral that is a product of hydrothermal alteration. It commonly replaces feldspars and other alumino-silicate minerals and it forms above ~220°C. It also reflects a weakly acidic pH condition in hydrothermal fluids.

Utah FORGE wraps up a 3-stage hydraulic stimulation of well 16A(78)-32

Utah FORGE is excited to announce the successful completion of the three-stage hydraulic stimulation of its first highly deviated injection well, 16A(78)-32.

Well 16A(78)-32 drilling was completed in January 2021. This is an inclined well (65°to the vertical) that will be the injection arm of the doublet that forms the heart of the Utah FORGE experimental configuration.

Subsequently, two additional monitoring wells – vertical – were drilled so that they, along with existing well 58-32, could serve as monitoring wells for future work at the FORGE site. In particular, wells 58-32, 78B-32 and 56-32 had been instrumented with fiber optics and geophones to triangulate on microseismic events during the recent fracturing in Well 16A(78)-32. These microseismic clouds define the morphology of three hydraulic fractures created at the toe (extremity) of Well 16A(78)-32.

A chronology of the events for the recent three-stage hydraulic fracturing is as follows:

  • Fourteen frac tanks were sited on the location and filled with Milford City culinary water. Each tank holds 500 bbl (21,000 gallons per tank) of water.
  • Frontier Drilling Rig 28 was trucked to the location, assembled, and brought into service.
  • A preliminary run of drill pipe was made into the hole. This drill string had a bit with a casing scraper and a drift sub. The bit was run to near the end of the open-hole section of the wellbore while the casing scraper was positioned to stay within the cased-hole and ensured the absence of debris. The drift sub was run one joint above the casing scraper and guaranteed that there was adequate clearance to run additional tools (in particular, bridge plugs).
  • Extreme Wireline next ran a perforating gun on the end of drill pipe into the openhole section (below 10,787 ft MD). In addition to the perforating gun, a mechanical casing collar locator was run and confirmed the casing tally so that the depth of the gun was more accurately known. This 3-1/8” diameter gun was 2 ft long with 6 shots per foot at 60° phasing. MTS Solutions pumped down the drill pipe to seat a dropped ball and fire the guns. The successful firing served as a check shot for orienting geophones in the three offset wells.
  • MTS Solutions next pumped a Shear Stimulation Test for one hour at an average rate of 0.36 bpm followed by shutdown and monitoring the pressure decline for an hour. A total of 52 bbl of water was pumped for this test.

STAGE 1

  • Liberty Oilfield Services next pumped down the casing and followed the prescribed fracturing plan for stimulation Stage 1, reaching an injection rate of 50 bpm with slickwater (refer to Figure 1). 4,261 bbl were pumped. The well was shut in for four hours and flowed back.
  • After 16 hours of flowback, Interwell US ran a bridge plug to a depth of 10,670 ft MD (middle of the sealing element). MTS Solutions pumped to set the bridge plug. The bridge plug was tested to 5,000 psi using MTS Solutions’ pumping equipment through the drill pipe and later to over 7,000 psi using Liberty Oilfield Services’ pumping equipment, down the casing.
  • After tripping the bridge plug setting tool out of the hole, an Extreme Wireline perforating gun was run into the hole on the end of drill pipe. This was a 20-ft long perforating gun (6 shots per ft, 60° phasing, 21-gram Hero charges). It was run to cover a depth of 10,560 to 10,580 ft MD. MTS Solutions pumped a dropped ball to a seat to fire the guns. The guns were retrieved. All 120 shots had fired, providing an entry from the wellbore to the formation.

STAGE 2

  • Liberty Oilfield Services next pumped 2,777 bbl of slickwater down the casing and followed the prescribed fracturing plan, reaching an injection rate of 35 bpm. This was Stage 2. There was an intentional hard shutdown in the initial 5 bpm stage and also part way through the 35-bpm stage. The well was shut in and pressure decline was monitored for 4 hours. The well was then opened up and flowed back for 12 hours. The treatment data are shown in Figure 2.
  • After flowback, Interwell US ran a second bridge plug to a depth of 10,466 ft MD (center of the sealing element). MTS Solutions pumped to set the bridge plug. The bridge plug was pressure tested to 4,960 psi by MTS Solutions through the drill pipe and later to 6,800 psi using Liberty Oilfield Services pumping equipment, down the casing.
  • An Extreme Wireline perforating gun was next run on the end of drill pipe to cover a depth of 10,120 to 10,140 ft MD. This was a 20-ft long perforating gun (6 shots per ft, 60° phasing, 21-gram Hero charges). MTS Solutions pumped to seat a ball and fire the guns. The guns were retrieved. All 120 shots had fired, providing an entry from the wellbore to the formation.

STAGE 3

  • Liberty Oilfield Services next pumped down the casing for Stage 3 and followed the prescribed fracturing plan, reaching an injection rate of 35 bpm. A slickwater pad was pumped followed by a crosslinked CMHPG fluid with DEEPROP™ microproppant at planned concentrations of 0.5 to 0.75 ppa. The total pumped fluid volume was 3,016 bbl. The well was shut in and flowed back (for more than 15 hr). Refer to Figure 3.
  • During the shut-in time, the Liberty frac crew began to rig-down their equipment and demobilize.
  • The well was re-entered with drill pipe and an Interwell US retrieving tool to release and recover the second bridge plug that was set. The bridge plug was successfully released and recovered to the surface. After disconnecting and laying down the bridge plug the retrieving tool was run back into the well to recover the first bridge plug that was set. This plug was also successfully retrieved and laid down.
Figure 1. This is the treatment record for Stage 1. The green trace indicates, the pumping rate, reaching 50 bpm. The red trace is the surface treating pressure, exceeding 6,000 psi. This stage was pumped into the 200 ft long open hole section of the well.
Figure 2. This is the treatment record for Stage 2. The green trace indicates, the pumping rate, reaching 35 bpm. The red trace is the surface treating pressure, exceeding 7,000 psi. This stage was pumped into a cased and perforated zone (10,560 – 10,580 ft MD) section of the well. Note the hard shutdown (rate intentionally rapidly brought to zero) part way through the treatment.
Figure 3. This is the treatment record for Stage 3. The green trace indicates, the pumping rate, reaching 35 bpm. The red trace is the surface treating pressure, exceeding 7,000 psi. The other traces show microproppant concentration at the surface and at the perforations. This stage was pumped into a cased and perforated zone (10,120 – 10,140 ft MD) section of the well.

Following the recovery of the bridge plugs from the well, on April 23, 2022 the rig started rig-down operations and laying down drill pipe.

Word of the Week – Propylitic Alteration

Propylitic Alteration

A term borrowed from studies of hydrothermal ore deposits that refers to an assemblage of secondary hydrothermal minerals which forms in igneous rocks. This assemblage is made up of chlorite, illite, feldspar (both Na and K-rich varieties), epidote, calcite and pyrite, imparting a dark green tint to the appearance of altered rocks. It is commonly developed in volcanic-plutonic sequences that host high-temperature geothermal reservoirs.

Word of the Week – Mineral Geothermometer

Mineral Geothermometer

A secondary mineral phase whose stability is defined by a lower and sometimes an upper temperature threshold. Common mineral geothermometers comprise clays, zeolites and epidote, with crystal structures that contain a hydroxyl (OH-) or water (H2O) molecule. The temperature ranges of mineral geothermometers are calibrated from investigations of a large number of drilled geothermal resources where mineral zonations and temperature gradients have been determined.

Did you know… 20% of the Island of Hawai’i’s power comes from geothermal energy?

Did you know... 20% of the Island of Hawai'i's power comes from geothermal energy?

Located in Puna (Kilauea East Rift Zone), is Hawai’i’s geothermal power plant, Puna Geothermal Venture (PGV). PGV has two air-cooled power plants, a binary system, and a combined cycle system. The plants together generate up to 38 megawatts of electricity. The first plant reached commercial operation in 1993, and the second followed in 2012. PVG is one of Ormat Technologies’ many global geothermal projects.

From 1997-2001, PGV replaced the burning of about 475,000 barrels of fuel oil a year. In that time period, the cost of one barrel was around $27.37, meaning PGV saved Hawaiian Electric about $13 million a year on fuel costs. The PVG plant reduces the amount of fuel oil that needs to be shipped from the refineries on O’ahu, which also then reduces the risk of oil spills.

The Puna Geothermal Venture originally generated electricity from 1993-2018, and comprised 31% of the electricity demand on the Island of Hawai’i (more than half of the island’s renewable energy production). However, in May of 2018, the Kilauea volcano erupted and the production field was partly buried beneath a lava flow causing the PVG power plant to shut down.

After two and a half years of work between Ormat Technologies and Hawaiian Electric, PVG resumed operations on November 5, 2020. Currently, the plant generates 24 megawatts of the original 38 MW. However, it still supplies around 20% of the power needs of the island.

The reappearance of geothermal energy on the island puts Hawai’i back on track to meet the goals established in the 2008 Hawai’i Clean Energy Initiative (HCEI). The HCEI is a partnership between the state of Hawai’i and the Federal U.S. Department of Energy and is an attempt to reduce Hawai’i’s use of petroleum and other fossil fuels for its energy needs. The initial goal was to have a 70% clean energy economy by 2030. Hawai’i’s renewable portfolio standard was amended to make Hawai’i the first state to have a legally required deadline of having 100% of its electricity come from renewable sources.

While geothermal energy currently only provides 5% of Hawai’i’s renewable electricity supplies, the reopening of PGV allows for even further development of the resource. The Hawai’i State Energy Office found in 2016 that the Island of Hawai’i may have more than 1,000 megawatts of geothermal reserves – enough to power Maui, the Big Island, and a quarter of O’ahu collectively.

https://www.khon2.com/empowered/puna-geothermal-venture-helps-community-with-natural-energy/

https://www.higp.hawaii.edu/hggrc/projects/geothermal-digital-collection/geothermal-collections/geothermal-topic-guides/puna-geothermal-venture/

https://www.ormat.com/en/company/news/view/?ContentId=8820

https://www.bizjournals.com/pacific/news/2020/11/12/puna-geothermal-resumes-production.html

https://climate-xchange.org/2020/10/29/what-the-reopening-of-the-puna-geothermal-plant-means-for-hawaii/

https://www.higp.hawaii.edu/hggrc/geothermal-energy-a-no-brainer-for-hawaii/