China Achieves Breakthrough with 1900A Subsea Electromagnetic Technology 15km Detection and 3000m Depth Milestones

China’s domestically-developed high-power controlled-source subsea electromagnetic exploration technology has completed industrial demonstration in deepwater areas such as Liwan, Liuhua, and Lingshui—signaling a significant leap forward for marine oil and gas exploration. This achievement paves a new technological path for discovering and developing complex deepwater hydrocarbon reservoirs.

Unlike traditional seismic methods, which have high vertical resolution but are less sensitive to hydrocarbon saturation, subsea electromagnetic (EM) surveying leverages subsurface resistivity to directly identify oil and gas accumulations. With high sensitivity to reservoir saturation, this technology addresses a core challenge in deepwater exploration—accurately predicting high-saturation reserves, which is key for economic viability.

Led by the CNOOC Research Institute, in collaboration with Ocean University of China and China University of Geosciences (Beijing), the team developed an integrated system, including a high-power EM transmitter, subsea acquisition stations, and advanced data processing. For the first time, EM technology was industrially applied in China’s offshore oil and gas sector, enabling complementary synergy with seismic exploration: seismic offers fine reservoir imaging, while EM enhances recognition of high-saturation zones, thus boosting forecast reliability.

This demonstration delivered three industry-firsts:

• Achieved a record-breaking 1900-ampere current excitation, expanding effective detection range from the usual 8–10 km to an unprecedented 15 km, and reaching reservoir depths up to 3000 meters.
• Pioneered multi-frequency D-wave excitation for stable and accurate detection at different burial depths.
• Overcame deepwater, rugged seabed challenges with real-time positioning, keeping the source within 30–40 meters above the complex seafloor at depths of 1500 meters.
• Achieved high-precision receiver deployment in strong ocean currents, limiting drop error to within 5% of water depth, setting a new industry benchmark for data accuracy.

Looking ahead, subsea EM technology is set to further integrate into deepwater oil and gas development, enhancing success rates and bolstering China’s energy security and marine economic growth with technological innovation.