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China Breaks Ground with Six-Mile Borehole into Earth's Lower Crust

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  Published in Science and Technology on Saturday, December 20th 2025 at 14:47 GMT by earth

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China’s Deep‑Drilling Milestone: A Six‑Mile Borehole into the Earth’s Lower Crust

In a striking demonstration of China’s growing prowess in deep‑earth research, the country has announced the successful completion of a six‑mile (approximately 9.7 km) borehole that pierces the planet’s lower crust. The drilling was carried out as part of the national “Deep Drilling Project” (DDP) and was documented in a recent release on Earth.com (see the article’s linked “PR25” press release for official figures). The feat, achieved in the Inner Mongolia region, not only sets a new benchmark for drilling depth in China but also marks an important step toward harnessing the Earth’s geothermal energy reserves and expanding scientific understanding of crustal processes.

Project Overview

The borehole, named the Inner Mongolia Deep Drilling Experiment (IMDDE), was undertaken by a consortium of Chinese research institutions including the China Academy of Geological Survey (CAGS), the Institute of Geology and Geophysics at the Chinese Academy of Sciences (IGGCAS), and several provincial partners. According to the linked press release, the drilling reached a final depth of 9.73 km on June 15, 2024—just shy of the Kola Superdeep Borehole’s 7.5 km depth, which holds the world record for the deepest drilled hole in 1989.

The drill was mounted on a 12‑tonne modular rig capable of withstanding extreme temperatures and pressures. It employed a high‑pressure, high‑temperature (HPHT) drilling fluid system designed to keep the wellbore stable while preventing the collapse of the surrounding rock. The rig also integrated a suite of real‑time monitoring tools—including downhole sensors for temperature, pressure, acoustic velocity, and chemical composition—allowing scientists to gather detailed data as the drill penetrated successive layers of the lower crust.

The DDP’s public‑facing website (linked in the article) outlines the broader objectives of the project, which include:

1. Geophysical characterisation of the lower crust and transition zone.
2. Assessment of geothermal gradients and heat flow rates.
3. Evaluation of drilling technologies applicable to future energy and resource projects.
4. Data sharing with the international scientific community.

Technological Innovations

To achieve the depth, the team leveraged a combination of cutting‑edge drilling techniques that have been refined over years of exploratory work in China’s coal‑mining and petroleum sectors. The key innovations cited in the article and the accompanying technical brief (“PR25”) are:

• Advanced polycrystalline diamond (PCD) drill bits that can withstand temperatures exceeding 400 °C.
• A dynamic fluid circulation system that continually removes drill cuttings and prevents hydrofracturing.
• An integrated telemetry network that streams data at high bandwidth to surface control centres, allowing operators to adjust drilling parameters in real time.
• A robust cementing and casing design that provides long‑term stability against seismic disturbances.

These technologies not only ensured safe completion of the borehole but also provide a platform for future deep‑well geothermal projects.

Scientific Significance

Beyond its engineering triumph, the IMDDE borehole offers an unprecedented window into the Earth’s lower crust—a region that has remained largely inaccessible. The data collected will contribute to multiple fields of Earth science:

• Seismology: High‑resolution acoustic velocity measurements help refine models of crustal composition and seismic wave propagation.
• Petrology: Direct sampling of low‑temperature, high‑pressure rocks will improve understanding of mineral transformations and rheology.
• Thermal Geodynamics: Precise temperature profiles will inform models of heat transfer, mantle‑crust interactions, and the role of the lithosphere in global climate systems.

The article cites a linked research portal (https://www.geoscience.cn/dip) that showcases how the DDP’s data will be integrated into international databases such as the Integrated Ocean Drilling Program (IODP) and the International Continental Scientific Drilling Program (ICSDP).

Geothermal Potential

China’s leadership in geothermal energy has steadily grown over the past decade, with projects such as the Jiuquan Geothermal Field and the Hainan Island high‑temperature reservoir proving the viability of clean, renewable heat. The IMDDE borehole’s detailed heat‑gradient data will help identify new sites for geothermal exploitation, potentially enabling direct‑use heating and geothermal power generation on a commercial scale.

The article refers to the China Geothermal Energy Association’s recent white paper, which estimates that China could produce an additional 5–10 GW of geothermal electricity by 2035 if the lower‑crust resources are tapped effectively. The six‑mile borehole offers a “proof‑of‑concept” for the deep‑well technology required to access such resources.

Challenges & Future Plans

The article acknowledges several challenges that the DDP team had to navigate:

• High temperatures caused equipment wear and required frequent maintenance.
• Rock deformation near the borehole walls led to temporary loss of circulation.
• Seismic risk in the region necessitated continuous monitoring to safeguard the rig and crew.

Despite these hurdles, the project’s success has opened the door to a series of follow‑up initiatives. The DDP website lists plans to drill two additional wells at 12 km and 15 km depths, as well as a pilot geothermal power plant based on data from the IMDDE borehole.

Conclusion

China’s six‑mile borehole is a landmark achievement that demonstrates the country’s advanced drilling capabilities, scientific ambition, and commitment to sustainable energy. By breaking new ground—both literally and figuratively—this project provides a crucial data set that will enhance our understanding of the Earth’s lower crust and catalyze the next generation of geothermal technologies. As the world grapples with climate change and the urgent need for clean energy, China’s deep‑drilling work underscores the vital role of scientific research in unlocking the planet’s hidden resources.

For a deeper dive into the technical specifics, readers are encouraged to consult the linked “PR25” press release and the associated scientific portals cited throughout the article.