As global energy markets grow increasingly volatile, China is looking deeper underground to insulate its economic engine.

The ability to unlock massive, ultra-deep subterranean reserves is no longer just an engineering triumph, but has become a vital geopolitical shield, allowing the world's second-largest economy to steadily replace vulnerable foreign gas imports with a homegrown "ballast stone" of energy security.

At the heart of this strategic shift is the newly certified Ziyang Dongfeng shale gas field in the Sichuan Basin, China's first ultra-deep shale gas field of this scale.

Operated by State-owned energy giant China Petroleum and Chemical Corp, or Sinopec, the field passed the Ministry of Natural Resources' review on May 13 with proven geological reserves totaling 235.69 billion cubic meters.

Tapping into this immense energy reservoir pushed Chinese exploration into uncharted territory. The gas lies trapped within the Earth's oldest commercially discovered shale layer, formed over 540 million years ago. To extract these resources, engineers had to drill to punishing depths ranging from 4,500 to 5,200 meters, said Sinopec.

Operations at this subterranean level present world-class geological challenges, including complex accumulation mechanisms, thick and difficult-to-drill rock formations, and extreme high-temperature and high-pressure conditions, it said.

By integrating artificial intelligence into geophysical imaging and developing fully proprietary ultra-deep drilling and fracturing systems, domestic engineers successfully cracked these global bottlenecks to turn theoretical reserves into commercially viable yields.

Industry experts emphasize that unlocking these staggering reserves substantially elevates China's domestic natural gas self-sufficiency.

In an era marked by severe geopolitical unpredictability and sharp fluctuations in international oil and gas prices, heavy reliance on imported energy can expose a country to imported inflation and supply disruptions, said Lin Boqiang, head of the China Institute for Studies in Energy Policy at Xiamen University.

Tapping into domestic mega-reserves like Ziyang Dongfeng effectively cushions Chinese industrial supply chains and consumer markets from these external shocks. By lowering the nation's overall external dependence, the newly proven reserves act as a crucial stabilizing force, ensuring that energy supply remains uninterrupted despite global market turbulence, Lin added.

This achievement strongly aligns with the broader strategic framework outlined by the National Energy Administration.

For decades, China's fundamental resource endowment has been officially characterized by the NEA as being "rich in coal, poor in oil and short of gas". To bridge the domestic supply gap and enhance self-reliance, the NEA has systematically prioritized the exploration of unconventional oil and gas resources.

According to the NEA's ongoing assessments, as homegrown exploration technologies have matured over the past decade, shale gas has emerged as an indispensable pillar for the country's sustainable reserve growth.

Securing massive, stable domestic outputs is considered vital to accelerating China's broader green energy transition while maintaining economic stability, it said.

The NEA has consistently stressed that in the face of increasingly complex global geopolitical dynamics, national energy security must be anchored by robust, autonomous production capabilities.

Overcoming these ultra-deep hurdles provides a replicable technical pathway to expand China's development frontier. Moving forward, the accelerated capacity growth of the Ziyang Dongfeng field will ensure that China retains firm control over its energy destiny, reinforcing the nation's resilience amidst a complex and shifting global landscape, said Sinopec.

zhengxin@chinadaily.com.cn