Superdeep: Why We Drill, Why We Stop GEONAVIGATE INDUSTRY CHATTER Runtime: 12:17 (737.080 seconds) Original narration and archival audio. Editorial cutoff: 3 November 2026 (America/Edmonton). TRANSCRIPT 0:00 — A hole is only useful if you can use it [0:00] Russia's Kola Peninsula, 1992. Geophysicist David Smythe takes a video camera onto the rig floor of the Kola Superdeep Borehole. Workers handle pipe beneath a forest of steel. Smythe identifies the operation as an attempt to retrieve dropped drill pipe. This is a hole that has already gone more than twelve kilometres into the Earth. And the job in front of the crew is getting equipment back. Sources: K8 [0:27] That is where the story of superdeep drilling gets interesting. What did people go down there to find? What did the rock actually do? And what finally made the next metre too difficult, too expensive, or no longer necessary? This is a tour of some of the major holes that tested those limits, from scientific experiments to the search for deep gas. Sources: Editorial explanation and general drilling background. [0:50] First, one distinction. Measured depth follows the hole, including its bends. Vertical depth measures how far down you have gone. A long well can travel mostly sideways. At sea, the water above the seabed is another separate measurement. We'll keep those quantities separate, and use reported drilling depths without turning them into a misleading league table. Sources: M13, M16 1:13 — Mohole: the ambition beneath the ocean [1:14] Before Kola, there was Project Mohole. American researchers wanted to drill through the oceanic crust toward the mantle. The ocean offered a tempting advantage: the crust there is much thinner than beneath the continents. It also put kilometres of moving water between the rig and the rock. Sources: MOHOLE_WHOI [1:33] In 1961, a converted drilling barge worked near Guadalupe Island, off Mexico. The deepest test penetrated about a hundred and eighty-three metres beneath the seabed, below roughly three and a half kilometres of water. It recovered basalt. The achievement was learning to drill from a floating platform in deep water, with the much deeper scientific objective still ahead. Sources: MOHOLE_WHOI [1:58] Holding position, losing equipment and keeping holes open were difficult. Costs and management became problems too. Congress ended funding in 1966. Mohole never reached its intended boundary. Here, the stopping point was set above ground, before the central geological question could be answered. Sources: M17, MOHOLE_WHOI 2:20 — Kola: the rock changes the question [2:20] Kola began in 1970, in the Soviet Union, with an ambitious fifteen-kilometre design. The site put ancient crust within reach of the drill. Researchers wanted physical samples and measurements to test their interpretation of the deep Earth. They also wanted to understand the mineral potential of the nickel-bearing Pechenga region. Sources: K5 [2:43] The hole passed through a thick volcanic and sedimentary sequence, then into older metamorphic basement below about six point eight kilometres. Gneiss, amphibolite and other crystalline rocks complicated the simple picture inferred from seismic waves. A change in wave speed did not necessarily mark the neat granite-to-basalt boundary that researchers had expected. Sources: K2, K4 [3:07] That matters because a seismic section is an interpretation. Drilling gives you a sample to test it against. Rock composition, deformation and fluids in fractures can all affect the signal. Kola helped show how much information was hidden inside what had looked like a straightforward boundary. The deeper crust contained a more complicated combination of rocks and fluid-bearing structures. Sources: K4, K1 [3:32] The engineering assumptions were being tested too. Temperatures rose more than expected. The deeper rock was difficult to keep open, and equipment became stuck or broke. After one major accident in 1984, the researchers' retrospective describes kilometres of drill string left in the hole. Reaching a record once did not mean the crew could simply continue downward from it. Sources: K5, K3 [3:58] When equipment is lost downhole, drillers call it a fish. They try to catch it with another tool and pull it free. If that fails, they may plug back and steer a new branch around the obstruction. The rig can spend days working without making the well any deeper. A depth record hides all those metres drilled, abandoned and drilled again. Sources: Editorial explanation and general drilling background. [4:19] That brings us back to Smythe's camera in 1992, and the attempt to retrieve dropped pipe. Here is David Smythe recalling the operation for BBC Witness History in 2024. Sources: K8, BBC_SMYTHE_2024 [4:34] David Smythe — original BBC Witness History recording, 2024; recalling Kola in 1992 And before you can do any more drilling, you had to recover that. They were doing what they call a fishing expedition. Sources: BBC_SMYTHE_2024 [4:40] Kola's famous reported depth is about twelve point two six kilometres. It stopped short of the fifteen-kilometre design. The account written by Kola researchers places the end of drilling in 1992, amid a drastic loss of funding. Heat, unstable ground and repeated recovery work had made progress difficult; the financial collapse then removed the ability to keep trying. Sources: K2, K5 [5:06] But the end of deepening was not the end of every investigation. German research records document a Kola hydraulic project funded from 1998 to 2001. The site was later mothballed and its drilling infrastructure dismantled. The end of drilling, the later research and the closure of the working site were separate chapters. Sources: K6, K7 5:29 — Oklahoma: a depth record and a gas well [5:29] Now to Oklahoma's Anadarko Basin, where the objective was commercial hydrocarbons. The Baden well passed thirty thousand feet in 1972. Its deep Hunton test did not establish the hoped-for commercial result. Bertha Rogers followed, with the Hunton dolomite again a major target. These were expensive attempts to find a working reservoir beneath a very thick stack of sedimentary rock. Sources: USGS_DEPTH_TABLE_1990, BERTHA_DRILLING_FLUIDS_1974 [5:56] The drilling fluid had a difficult job. It needed enough pressure to hold back deep gas, while other formations could take that fluid away. Unstable shales could fall into the hole. Heat changed the mud's behaviour. The operational account describes constant testing and adjustment. The challenge was managing the whole open hole, not just cutting the rock at the bottom. Sources: BERTHA_DRILLING_FLUIDS_1974 [6:20] In 1974, Bertha Rogers reached a reported total depth of thirty-one thousand, four hundred and forty-one feet: about nine point five eight kilometres. Near the bottom, high pressure and sulfur-bearing fluids complicated the ending. The United States Geological Survey records sulfur crystals coming to the surface after the overpressured well was brought under control. Sources: BERTHA_USGS_2014, USGS_DEPTH_TABLE_1990 [6:46] The deepest rocks did not become Bertha's producing reservoir. Gas production came from the much shallower Atokan granite wash. Baden also had shallower completion work after reaching total depth. Stopping the downward advance could be followed by another phase of the well's life. A depth record, a successful geological test and a productive completion are three different measures of success. Sources: BERTHA_USGS_2014, BADEN_WORKOVER_1972 7:11 — KTB: keeping the experiment open [7:11] In Bavaria, Germany's Continental Deep Drilling Programme, KTB, returned to the scientific questions. How hot is the crust? How much stress does it carry? Where can fluids move? The site lay in metamorphic rocks shaped by an ancient continental collision. The team drilled a four-kilometre pilot hole before starting the main borehole in 1990. Sources: KTB_GFZ_TECH, KTB_OPERATIONS_1995 [7:36] The pilot supplied core and practical warnings. Steeply tilted rock fabric made a straight hole difficult to maintain. Under stress, parts of the borehole wall broke away. In the main hole, deeper sections also narrowed with time. Researchers identified this convergence as a particularly serious obstacle below about seven and a half kilometres. Sources: KTB_GFZ_TECH, KTB_INSTABILITY_1997 [7:59] Think about the clearance around the drill pipe. It only has to disappear in one troublesome section to trap the assembly. A harder bit cannot solve that. The crew needs a hole that stays open, drilling fluid that works with the formation, and enough room to install protective casing or a liner. Each recovery operation consumes time and money. Sources: KTB_INSTABILITY_1997 [8:22] At about seven and a half kilometres, temperature exceeded the tolerance of the electronics in KTB's automatic vertical-drilling system. The near-vertical path became harder to maintain. Stuck assemblies and unstable sections forced repeated liners and sidetracks. The contemporary operational account describes the remaining funds running low. In October 1994, deepening ended at a reported nine thousand, one hundred and one metres. Sources: KTB_OPERATIONS_1995 [8:51] The well recorded more than two hundred and fifty degrees Celsius near its bottom. But saying that heat alone stopped KTB leaves out the failing hole and the budget. A drilling system has many limits. The first one you meet can make the others more expensive to manage. Sources: KTB_GFZ_TECH [9:09] KTB's afterlife is part of its achievement. The boreholes became a deep laboratory. The cores remained available for new questions, and experiments could examine stresses and fluids in place. Ending the drilling phase preserved a scientific asset. A useful hole can keep producing knowledge long after it stops producing new metres. Sources: KTB_GFZ_2024, KTB_OVERVIEW_1997 9:32 — China: deciding when the next metre is enough [9:32] The story continues in China. In the Tarim Basin, Shendi Taqe One combined scientific exploration, oil and gas questions, and a test of deep-drilling equipment. Drilling finished on January fifth, 2025, at a reported ten thousand, nine hundred and ten metres. Sources: M02, M03 [9:52] The rock was part of the problem. Hard dolomite with chert inclusions damaged the bits. Crews also battled drill-string fatigue, unstable intervals and drilling fluid escaping into the rock. The operator's account says the last nine hundred and ten metres took more than three hundred days. The deepest stretch consumed a disproportionate share of the effort. Sources: M02, M04 [10:16] Why stop there? The drill had reached ancient Cambrian source rocks. The operator said the required scientific information had been gathered and hydrocarbon shows had been found. Going deeper added risk. The decision was to end deepening and move into testing and further research. A hydrocarbon show still needs testing before anyone can call it a commercial discovery. Sources: M01, M04, M03 [10:40] A newer research paper reports Xin'an One, in the Junggar Basin, completed in October 2025 at eleven thousand, one hundred and fifty-six metres total depth. It tested deeply buried clastic rocks. Reservoir quality was generally poor, although the team identified more promising intervals and oil and gas shows. The gas analysis pointed to highly mature, coal-derived gas. Testing was still being planned in 2026. Sources: M09, M10 [11:10] And Shendi Chuanke One, in Sichuan, passed ten thousand metres in October 2025. Its goals include deep petroleum geology and equipment development. By our November 2026 cutoff, that is the latest confirmed milestone in the operator's account. A final depth and outcome have yet to be established in that record. This part of the story remains open. Sources: M05, M06, M07, M08 11:36 — What makes a hole worth drilling? [11:36] These projects did not encounter a single universal depth limit. Mohole lost its funding. Kola combined difficult drilling with the loss of financial support. Oklahoma's wells could seek production higher in the section. KTB stopped amid hole instability and dwindling funds, then continued as a laboratory. Taqe's team judged that the next stage should be testing what the well had already reached. Sources: M17, K5, BERTHA_USGS_2014, KTB_OPERATIONS_1995, KTB_GFZ_2024, M01 [12:03] The useful question is what we need from the next metre, whether we can keep the hole usable, and whether the answer is worth the work. This is GeoNavigate Industry Chatter. Sources: Editorial explanation and general drilling background. SOURCE NOTES This is a selected tour of eight projects: Mohole, Kola SG-3, Baden, Bertha Rogers, KTB, Shendi Taqe 1, Xin’an 1 and Shendi Chuanke 1. It is not a worldwide census or a vertical-depth ranking. Measured depth follows the borehole. True vertical depth, water depth and penetration below the seafloor are different measurements. Reported total or driller depths retain their source definitions. Kola’s deepening ended before all follow-up research ended. The 1998–2001 hydraulic research record and later mothballing belong to different phases. KTB also continued as a scientific laboratory after deepening stopped. Bertha Rogers later produced gas from shallower Atokan granite wash. Its deepest interval and its producing completion are different parts of the well’s history. Taqe’s physical drilling completion on 5 January 2025 is separate from its February announcement. The Xin’an testing-plan meeting was held on 30 March 2026. Chuanke passed 10,000 m on 15 October 2025; a final depth and outcome remain unestablished in the records checked through 3 November 2026. David Smythe filmed the Kola operations in 1992. His original BBC Witness History interview is from 2024 and is identified as a later recollection. It is the only participant recording heard in the episode. CCTV’s Taqe programme was broadcast on 14 April 2025; its footage capture dates are unverified. Source-film soundtracks are muted beneath the narrator. Original project photographs and factual schematics retain their credits and date qualifications. SOURCES [K8] The Kola Superdeep Borehole SG-3 https://www.davidsmythe.org/kola/kola.htm David Smythe’s participant archive identifies his original 1992 Kola film, including seismic fieldwork and rig-floor work to retrieve dropped pipe. The later interview is dated separately. [M13] Chikyu ends IODP Expedition 358 https://www.jamstec.go.jp/e/about/press_release/20190329/ JAMSTEC expedition record illustrating the distinction between penetration below the seabed and the water above it. Chikyu is background context, not a ninth project in this tour. [M16] Sakhalin-1 project drills world’s longest extended-reach well https://investor.exxonmobil.com/company-information/press-releases/detail/786/sakhalin-1-project-drills-worlds-longest-extended-reach ExxonMobil’s dated extended-reach well record illustrates measured length, rather than a greater vertical penetration than Kola. [MOHOLE_WHOI] The Quest for the Moho https://www.whoi.edu/oceanus/feature/the-quest-for-the-moho/ Woods Hole Oceanographic Institution history. Water depth and penetration beneath the seabed are separate measurements; Project Mohole did not reach the mantle. [M17] Records of the National Science Foundation, section 307.9 https://www.archives.gov/research/guide-fed-records/groups/307.html U.S. National Archives finding aid for Project Mohole and its 1966 termination after funding was not appropriated. [K5] The 50th Anniversary of the Start of Drilling the Kola Superdeep Well https://sciup.org/the-50th-anniversary-of-the-start-of-drilling-the-kola-superdeep-well-148322054?lang=en Kola researchers’ retrospective, read alongside later research records. [K2] KSDB — Kola Superdeep Borehole https://dfg-spp-icdp.de/en/icdp/icdp-projects/53 DFG / ICDP project record. The episode uses approximately 12.26 km and retains the distinction between reported drilling depth and independently established vertical depth. [K4] The Kola Superdeep Drillhole and the nature of seismic boundaries https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-3121.1992.tb00456.x Primary research on seismic boundaries and rock properties. The result does not mean that basalt was absent throughout the drilled sequence. [K1] The Kola, USSR, superdeep drill hole https://pubs.usgs.gov/publication/ofr86517 U.S. Geological Survey translation of Soviet research published before Kola reached its final reported depth. [K3] New geothermal data from the Kola superdeep well SG-3 https://www.sciencedirect.com/science/article/pii/S0040195199000657 Primary geothermal research. Measurements affected by drilling and later equilibrated temperatures are different observations. [BBC_SMYTHE_2024] Witness History: The deepest man-made hole in the world — interview with David Smythe https://www.davidsmythe.org/kola/kola.htm Original David Smythe interview for BBC World Service Witness History in 2024, recalling Kola operations in 1992. The episode uses one short excerpt; it is a later recollection, not 1992 location sound. [K6] Hydraulische Eigenschaften der supertiefen Kola-Bohrung, Rußland https://dfg-spp-icdp.de/en/research/dfg-projects/369 DFG record of hydraulic research funded in 1998–2001. Funding and project objectives do not establish that every planned measurement succeeded. [K7] Кольская сверхглубокая буровая скважина (СГ-3) https://ke-culture.gov-murman.ru/slovnik/?ELEMENT_ID=95946 Murmansk regional institutional history. Mothballing is a later event than cessation of deep drilling. [USGS_DEPTH_TABLE_1990] Summary of Deep Oil and Gas Wells and Reservoirs in the U.S. https://pubs.usgs.gov/of/1990/0305/report.pdf U.S. Geological Survey total-depth and completion table. Completion dates do not necessarily identify the day a depth was first reached. [BERTHA_DRILLING_FLUIDS_1974] A Resume of the Drilling Fluids Used on the World's Deepest Well https://ngds.egi.utah.edu/files/GL03846/GL03846.pdf Original operational paper describing the deep Hunton objective, overpressure, unstable shales and drilling-fluid problems. [BERTHA_USGS_2014] Thermal Maturation of Petroleum Source Rocks in the Anadarko Basin Province, Colorado, Kansas, Oklahoma, and Texas https://pubs.usgs.gov/dds/dds-069/dds-069-ee/pdf/dds69ee_Chapter3.pdf U.S. Geological Survey account supports the sulfur crystals, well-control event and shallower Atokan production. It does not establish a molten-sulfur lake or a specific pipe-failure mechanism. [BADEN_WORKOVER_1972] Baden To Remove Bridge https://gateway.okhistory.org/ark:/67531/metadc2370071/m1/2/ Contemporary Elk City Daily News report supports shallower completion work after total depth, rather than a complete production history. [KTB_GFZ_TECH] KTB Deep Crustal Lab https://www.gfz.de/en/section/geomechanics-and-scientific-drilling/infrastructure/ktb-deep-crustal-lab GFZ technical description of the main and pilot holes, temperature observations and the deep laboratory. [KTB_OPERATIONS_1995] The KTB Borehole—Germany's Superdeep Telescope into the Earth's Crust https://earthscrust.org.au/build/pdf/dekorp4_ftb-85_ktb-bore-hole.pdf Contemporary Oilfield Review operational account. Instability, tool recovery and diminishing funds accompany the temperature limit on steering electronics. [KTB_INSTABILITY_1997] Borehole instabilities in the KTB main borehole https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/96JB03669 Primary analysis of borehole-wall failure and narrowing in stressed, foliated crystalline rock. A proposed convergence mechanism is not evidence of liquid or melted rock. [KTB_GFZ_2024] Germany's deepest point celebrates 30th anniversary https://www.gfz.de/en/press/news/details/der-tiefpunkt-in-deutschland-feierte-jubilaeum GFZ anniversary history and photographs. The 2024 bit display and core archive are later views; the displayed bit is not identified as the final-depth drilling bit. [KTB_OVERVIEW_1997] The German Continental Deep Drilling Program KTB: Overview and major results https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945 Primary overview of the scientific programme and its results. Research continued after the main drilling phase. [M02] How Shendi Taqe 1 climbed beyond ten thousand metres https://news.cnpc.com.cn/2025kpzp/17sdtk.pdf CNPC illustrated operational account and actual Taqe photographs. Unverified photograph capture dates are not inferred from the report date. [M03] China’s first scientific exploration well beyond 10,000 m completes drilling https://zrzyt.xinjiang.gov.cn/xjgtzy/mtxc/202502/21fd5cee464d4e19a62e9e435160bee9.shtml Xinjiang Natural Resources Department account of Taqe’s drilling completion on 5 January 2025, before its February announcement. [M04] Drilling ten thousand metres underground to explore oil and gas https://finance.people.com.cn/n1/2026/0113/c1004-40643875.html First-person field account by the Taqe implementation leader, published by People’s Daily. Used for the dolomite/chert, bit damage and recovery-work descriptions. [M01] Taqe 1 completion press-conference Q&A https://news.cnpc.com.cn/system/2025/02/21/030155715.shtml CNPC completion press-conference account. The announcement followed the end of drilling; hydrocarbon shows are not proof of commercial production. [M09] Evaluating the natural gas exploration potential of the Carboniferous reservoirs in the Junggar Basin from the perspective of 10 000-m oil and gas exploration practices https://opaj.napstic.cn/periodicalArticle/0120261002264943 Primary Natural Gas Industry research, September 2026. Xin’an’s figure is reported total depth; no separate surveyed vertical depth is supplied in the retrieved abstract. [M10] Xin’an 1 testing-plan technical meeting https://www.hrl.ac.cn/xjri/84.html Huairou Laboratory Xinjiang Research Institute record of the 30 March 2026 testing-plan meeting. Planning a test does not establish commercial production. [M05] 2025 Annual Report https://www.cnpc.com.cn/cnpc/ndbg/202605/9bd863d39e164b148f12da864d852587/files/93a5b5189bef42a2a9499dd70e766167.pdf CNPC annual report confirms reported milestones; it does not provide a final outcome for Chuanke 1. [M06] CNPC October 2026 retrospective https://mp.cnpc.com.cn/web/dingyue/resources/html/80001254/2026102110405564639.html?item_id=994395123&time=1792564278578 CNPC’s 21 October 2026 retrospective repeats the Chuanke 10,000 m milestone. That statement does not establish whether drilling was continuing on publication day. [M07] A key step in deep energy exploration: exceeding 10,000 m https://www1.xinhuanet.com/politics/20251015/392ea93e5701482b87bdef15615441bb/c.html Xinhua’s 15 October 2025 report; project image and operational information supplied by China Petroleum Southwest Oil and Gas. The milestone is separate from a final depth. [M08] Why drill Shendi Chuanke 1? https://news.cnpc.com.cn/system/2023/07/24/030107539.shtml CNPC account of the Chuanke research objectives. Its 10,520 m design is not presented as achieved final depth. [M11] Innovation in Progress: Ten Thousand Metres Underground https://tv.cctv.com/2025/04/14/VIDExS5J3NzzZAsIFyWbsQr7250414.shtml Original Taqe footage from CCTV’s Innovation in Progress programme broadcast on 14 April 2025. The broadcast date does not identify the filming dates; the programme soundtrack is not used. [BADEN_USGS_PHOTO] Geologic Controls of Deep Natural Gas Resources in the United States https://pubs.usgs.gov/bul/2146/report.pdf The USGS Bulletin 2146 cover identifies GHK Company’s photograph as the Earnest Baden rig. It is not a Bertha Rogers photograph. [MOHOLE_SCRIPPS_PHOTO] Scientists aboard CUSS I during Project Mohole, 1961 https://www.flickr.com/photos/scrippsocean/32121154277/ Scripps Institution of Oceanography archive photograph. It shows scientists aboard CUSS I, not a drilling-floor or ship-exterior scene. The publisher marks the photograph All rights reserved. ORIGINAL FILM AND RECORDING LINKS Kola SG-3 and Kola-92 fieldwork Original film: 1992 https://www.davidsmythe.org/kola/kola.htm David Smythe’s participant archive identifies his original 1992 Kola film, including seismic fieldwork and rig-floor work to retrieve dropped pipe. The later interview is dated separately. Original film and photographs: David Smythe. Witness History: The deepest man-made hole in the world Audio interview: 2024; recalled event: 1992 https://www.davidsmythe.org/kola/WitnessHistory-20241128-TheDeepestManmadeHoleInTheWorld.mp3 Original David Smythe interview for BBC World Service Witness History in 2024, recalling Kola operations in 1992. The episode uses one short excerpt; it is a later recollection, not 1992 location sound. BBC World Service, Witness History, 2024. Recording hosted in David Smythe’s archive. Innovation in Progress: Ten Thousand Metres Underground Broadcast: 14 April 2025 https://tv.cctv.com/2025/04/14/VIDExS5J3NzzZAsIFyWbsQr7250414.shtml Original Taqe footage from CCTV’s Innovation in Progress programme broadcast on 14 April 2025. The broadcast date does not identify the filming dates; the programme soundtrack is not used. CCTV Science and Education. Original logos and captions retained.