To Changgui Xu, theoretical innovation, equipment breakthroughs, and on-site validation are different stages of the same process.
The chief scientist and chief geologist at China National Offshore Oil Corporation (CNOOC) Ltd. and this year’s recipient of the Distinguished Achievement Award for Individuals at Offshore Technology Conference Asia, Xu possess both theoretical expertise and major project implementation capabilities. He has achieved breakthroughs in theories including deep oil and gas enrichment in highly active extensional‑strike/slip composite fault zones, deep‑layer exploration in high‑temperature composite continental margin basins, and the accumulation mechanism of ultradeepwater and ultrashallow gas. His work has reshaped exploration frontiers once regarded as high‑risk, low‑confidence, and even inaccessible into interpretable, predictable, verifiable, and developable domains, thereby establishing a new paradigmatic framework for deep‑layer exploration in globally distributed, intensely active, high‑temperature basins. With his guidance, CNOOC has logged world-class discoveries and reserves growth and provided a Chinese solution for the methodological evolution of exploration in analogous geological settings worldwide.
He is advancing R&D efforts in theoretical front-loading, equipment hardening, and data empowerment, while focusing on the potential of Asia’s offshore frontier areas through an approach based on targeted breakthroughs, insight-led exploration, and technology-driven growth.
In the following Q&A, Xu shares his thoughts on overcoming technical obstacles, where Asia’s future frontiers might lie, CNOOC’s R&D efforts, and how to cultivate scientific curiosity in the next generation of industry professionals.
The following conversation has been edited for length and clarity.
JPT: Describe the key theoretical and technological innovations that enabled the discovery of major deep and ultradeep oil and gas fields in China’s offshore basins.
Changgui Xu (CX): The geological conditions of China’s offshore basins are globally unique, characterized by intense tectonic activity and high geothermal gradients, making traditional exploration theories inapplicable. Over nearly 3 decades, our team has ventured step by step into this ‘uncharted territory,’ ultimately developing an exploration theory and technology framework suitable for China’s offshore basins, leading to the discovery of multiple world-class oil and gas fields.
The greatest difficulty lies not in any single technology itself, but in re-answering three fundamental questions: whether deep-layer oil and gas can form, whether they can be preserved, and whether they can be effectively predicted under the unique geological setting of intense tectonic activity and high geothermal gradients in China’s offshore basins. Unlike many worldwide classic passive continental margin basins, China’s offshore basins were formed in a multi-plate convergence zone, with intense tectonic activity, long-term multiphase fault activity, thin crust, and high geothermal temperatures. Traditional theories often cannot be directly applied here.
The first challenge was the long-standing obscurity of deep oil- and gas-enrichment mechanisms in intensely active basins. It was widely believed that deep reservoirs in such regions were prone to destruction, making large-scale preservation difficult. My team and I focused on persistent research of the extensional-strike/slip composite fault zones in the Bohai Bay Basin, systematically revealing the formation mechanisms of high-quality reservoirs and the enrichment and preservation mechanisms of deep oil and gas. In particular, we recognized the controlling factors of strike/slip compression zones and internal sealing systems in buried hills on hydrocarbon accumulation. Based on this theoretical breakthrough, we facilitated the discovery of five large oil fields, including the Bozhong 26-6 oil field, with total proven geological reserves amounting to 8×108 tons of oil equivalent (58.6 billion BOE).
The second challenge was to figure out the reason that high-quality reservoirs were still developed under deep and high-temperature conditions. Traditionally, it is believed that high-quality clastic reservoirs primarily were formed below 120°C, which is lower than in many of China’s offshore basins. In combination with fundamental experiments, diagenetic simulations, and integrated seismic-drilling studies, we proposed a new understanding of deep hydrocarbon enrichment in high-temperature composite marginal basins. This extended the temperature limit for high-quality clastic reservoirs in the Pearl River Mouth Basin from 120°C to over 200°C and pushed the economical exploration depth from 3,300 m to more than 5,100 m. The permeability of the drilled reservoirs increased by 100 to 1,000 times, leading to the discovery of large and medium-sized oil and gas fields, including the Kaiping 11-4, Huizhou 19-6, and Baodao 21-1 oil and gas fields, with newly proven geological reserves of 5×108 tons of oil equivalent (36.5 billion BOE).
One achievement I am particularly pleased to highlight is the development of ultradeepwater and ultrashallow natural gas. In past deepwater drilling operations, ultrashallow gas was often regarded as a hazard gas, or even a disaster gas. With the Lingshui 36-1 gas field, we have established an accumulation model of ultradeepwater and ultrashallow gas, which is characterized by dual-source hydrocarbon charging, relay migration, and ordered ice-gas distribution. We also pioneered an open-path drilling and logging operation mode, as well as a technology for acquiring samples from ultra-unconsolidated formations. Hence, we transformed this hazardous gas into exploitable resources and discovered the world’s first ultradeepwater and ultrashallow large gas field.
These efforts do not represent isolated achievements. Together, they have propelled China's offshore oil and gas exploration from shallow to deep strata, and from catching up to achieving partial leadership. Over the past 5 years, deep-layer reserves have accounted for more than 55% of the newly proven reserves in China's offshore basins. In my view, this marks that China's offshore oil and gas exploration has truly entered a deep-layer era.
JPT: What breakthroughs were necessary for CNOOC to make its deepwater and deep-layer discoveries? What breakthroughs still remain to be made? Where does CNOOC focus its technology know-how next?
CX: In recent years, CNOOC has achieved a series of world-class breakthroughs in deepwater and deep-layer exploration. I believe the critical reasons can be summarized into four aspects.
First, groundbreaking innovation in theoretical understanding. Instead of replicating the experiences of mature exploration basins abroad, we have reconstructed the cognitive framework based on geological realities, based on the intense tectonic activity and high geothermal temperatures characteristics of China’s offshore basins.
Second, breakthroughs in original innovation of key exploration equipment, such as the Hai Jing towed-streamer seismic acquisition system, the Xuan Ji rotary steering and logging-while-drilling system, and the new Xuan Yue wireline logging system. These technologies have enabled us to access the exploration of deepwater and deep-layer complex targets.
Third, we have established the key technological system spanning from seismic imaging and reservoir prediction to drilling, completion, and testing evaluation. We can not only ‘see clearly’ but also drill accurately, measure effectively, evaluate precisely, and achieve production.
Fourth is strategic focus and systematic planning. CNOOC has consistently prioritized deepwater and deep-layer exploration as the main direction for increasing reserves and production, establishing a mechanism for sustained investment and rapid iteration among organization, resources, research, and field operations.
Of course, these current achievements do not mean all challenges have been resolved. In the next phase, our technological needs remain clear. In terms of exploration theory, we need to further address issues including deep hydrocarbon preservation under multiphase tectonic superimposition, the development of high-quality reservoirs under ultrahigh-temperature conditions, and the large-scale development of ultradeepwater and ultrashallow gas. In terms of equipment, operational water depths need to expand from 1,500 to 3,000 m, drilling rig pressure must upgrade from 15,000 to 20,000 psi, and wireline logging temperature resistance should increase from 235 to 260°C. In terms of digitalization, we must truly integrate geological, geophysical, and engineering data to improve the identification of complex targets and drilling success rates.
I believe the next R&D priorities of CNOOC will focus on advancing toward deeper, more complex, and smarter directions, achieving breakthroughs simultaneously on the three aspects of theory, equipment, and digitalization.
JPT: What is the next frontier for offshore exploration in Asia? What strategy is CNOOC pursuing?
CX: As exploration in the shallow waters of mature petroliferous basins across Asia becomes increasingly intensive, moving toward deepwater frontiers, new regions, and new plays is an inevitable choice for achieving sustainable development. CNOOC will focus on three key directions.
First are the post-salt new frontiers in the offshore Caspian Basin of Central Asia. Previous exploration in this region focused primarily on sub-salt Paleozoic carbonates. By shifting the exploration mindset, we have identified that the offshore post-salt Mesozoic section features widely developed, high-quality deltaic sandstones with superior pooling conditions and vast prospects. In June 2025, CNOOC acquired the Zhylyoi Block in Kazakhstan, which is expected to become a new pivot for the company’s global asset portfolio and reserves growth.
Second are the new deepwater regions of the Bengal Fan and Indus Fan in South Asia. These two deepwater fans have massive sedimentary scales but remain significantly underexplored. The Bengal Fan is the world's largest submarine fan system, harboring dual potential for both thermogenic and biogenic gas in deep water. Similarly, the Indus Fan features abundant deepwater clastic deposits with strong exploration potential. CNOOC is currently conducting geological research and technical stockpiling to develop exploration solutions tailored to these regions.
Third is the new deepwater strata in the Andaman Sea of Southeast Asia. Beyond the traditional Miocene deltaic sandstones and reef-flat limestones, the discovery of the Timpan gas field in the North Sumatra Basin in 2022 revealed the immense potential of the Oligocene deepwater fan sandstone play. CNOOC is continuously monitoring the prospects in this area to further enrich the company’s asset portfolio in the deepwater exploration of Southeast Asia.
JPT: What are the three main areas of upstream R&D focus at CNOOC? What are you working to develop? Why does that matter to CNOOC and the larger industry? When might CNOOC start deploying this technology?
CX: CNOOC currently focuses on three key areas for upstream R&D. First, continuing to deepen the theoretical research on the exploration geology of intensely active, high-temperature basins in China's offshore areas, particularly the hydrocarbon accumulation patterns in frontier basins, deep to ultradeep layers, complex buried hills, and lithologic traps in active fault zones. Second, persistently advancing original innovation in high-end equipment for deepwater and deep-layer exploration, including technologies and equipment for deeper depths, higher pressures, and more extreme temperatures. Third, systematically promoting digital transformation and intelligent development, focusing on the construction of digital and intelligent basins to establish unified standards, a data foundation, and smart platforms.
These technologies are crucial for CNOOC because they determine whether we can sustainably achieve high-quality reserve and production increase in deeper and more complex offshore areas in the future. They are equally important for the industry because China’s offshore basins are not globally rare. The composite target characteristics of intensely active, high-temperature, deepwater, and deep-layer share similarities with some abroad basins. If we can develop stable and replicable theoretical and technological systems, they will provide valuable analogues for the exploration of worldwide similar basins.
In terms of technological application timelines, some technologies have already been in field application and large-scale promotion stages, such as deep-layer seismic imaging, geology-engineering integrated fracturing for productivity enhancement, and openhole drilling and logging in ultradeepwater and ultrashallow formations.
Some other equipment and approaches involving higher temperatures and pressures, and deeper water depths, in my judgment, are expected to be in broader application around 2030.
JPT: What is your favorite aspect of working in geology and the energy industry, and why?
CX: I most enjoy the process of exploring the unknown and turning it into reality. What fascinates me most about geological work is that it combines the depth of scientific inquiry with the rigor of engineering implementation.
On one hand, theoretical breakthroughs can lead to genuinely new opportunities. For instance, extending the temperature limit for high-quality clastic reservoirs in the Pearl River Mouth Basin from 120 to over 200°C essentially reopened an exploration window that was once considered impossible. Another example is the discovery of the Lingshui 36-1 large gas field, where we redefined the ultrashallow gas that was thought to be hazardous gas as a developable resource. This process of gaining a new understanding of the subsurface keeps me constantly excited.
On the other hand, I also place strong emphasis on equipment and engineering validation. Without high-quality seismic imaging, drilling, and testing equipment, even the most brilliant theories remain confined to paper. For me, the most rewarding moments are not just proposing a new understanding but witnessing it proven through drilling, testing, and discovery.
Ultimately, what I truly enjoy is working with my excellent colleagues to continually push boundaries in extreme geological conditions like the deepwater and deep layers. This industry is so fascinating because it constantly demands that we advance both our cognitive and practical capabilities to the forefront of offshore oil and gas exploration.
JPT: How do you cultivate a culture of scientific curiosity and risk-taking within your engineering teams?
CX: I have always believed that the culture of scientific exploration and risk-taking within engineering teams is not shaped by slogans but forged through the combined forces of problem-driven focus, institutional safeguards, and outcome-based motivation.
First, teams must consistently confront truly significant challenges. The geological conditions of China’s offshore basins are characterized by intense tectonic activity and high geothermal temperatures, which are a vast uncharted territory. We encourage teams to challenge the traditional consensus, such as ‘deep-layer oil and gas in highly active regions are unlikely to accumulate in large scale’ and ‘high-quality clastic reservoirs were primarily formed below 120°C.’ Only when faced with such complex problems can the team’s genuine exploratory drive emerge.
Second, an error-tolerant mechanism oriented toward innovation must be established. Original research and technological breakthroughs cannot achieve 100% success. If every failure is equated with a mistake, no one will dare to venture into technological frontiers. We have been distinguishing exploratory missteps from accountability failures, which relieve team members of undue concerns when they take bold initiatives. Often, the real risk is not in making attempts, but in not daring to attempt at all.
Third, young professionals need to see the value of exploration. When a new theory ultimately guides the discovery of the oil and gas field with proven geological reserves of more than 1×108 tons of oil equivalent (7.3 billion BOE), or when a new equipment effectively solves on-site challenges, these accomplishments foster an intrinsic appreciation for scientific inquiry within the team.
JPT: What skills are needed in the next generation of geoscientists? What advice would you give to young energy professionals?
CX: For the next generation of geological scientists, I think that at least four key capabilities are necessary. First, the ability to construct original geological theories. Second, interdisciplinary skills to understand and engage in the development of high-tech equipment. Third, systems thinking that integrates geology and engineering. And fourth, proficiency in applying digital and intelligent tools. The most outstanding geological scientists in the future will undoubtedly understand the subsurface, engineering, and data alike.
As for advice to young energy professionals, I would say: settle down, embrace patience and solitude, and approach the complexity and uncertainty of the subsurface with both passion and curiosity. The most rewarding careers in this industry often belong to those who dare to challenge established consensus. Always stay rooted in the field yet never lose the imagination to envision what lies beyond the next well. The energy transition and the pursuit of new resources demand precisely this blend of scientific rigor and creative thinking—and for geoscientists, there has never been a more exciting time than now.
Changgui Xu is currently the chief scientist and chief geologist of China National Offshore Oil Corporation (CNOOC) Ltd. He is an expert in offshore oil and gas exploration and has been leading the pioneer work in offshore oil and gas exploration research over the past 3 decades. He is the principal investigator of many national major research projects including the National Key Oil & Gas Special Program of China and the Integrated Project of the National Natural Science Foundation of China. Xu innovatively proposed the theory of hydrocarbon enrichment mechanisms in high heat-flow and strongly active basins and led development of key technologies including the production-capacity enhancement from low-permeability reservoirs in offshore confined spaces. He led his team to achieve major breakthroughs in deep offshore exploration, including the Bozhong 26-6 oil field, the world's largest metamorphic-reservoir oil field; the Kaiping 11-4 oil field, recognized as one of the top 10 global oilfield discoveries in 2023; and the Baodao 21-1 gas field, China's first ultradeepwater and deep-formation gas field. The proven geological reserves of these fields amount to 1.55 billion tons of oil equivalent. His innovative theory and key technology of ultradeepwater and ultra-shallow gas exploration have filled the international technological gap. From 2021 to 2025, he led his team to discover six oil fields with proven geological oil reserves exceeding 100 million tons, accounting for half of total discoveries in China in the same period. This achievement has enabled CNOOC to achieve a world-leading position in deepwater and deep-formation oil and gas exploration. Xu’s personal contribution has significantly enhanced the exploration performance of CNOOC. As recognized by Wood Mackenzie, a global energy research institute, CNOOC has achieved a world-leading position in both exploration economics and exploration success rate of deep-formation over the past few years. Therefore, the exploration team in CNOOC was awarded "Best Explorer in Global National Oil Companies" Award in 2025.
He is known for his rigorous scholarship and has been awarded three National Science and Technology Progress Awards of China (first and second prizes), the Scientific and Technological Innovation Prize of the Ho Leung Ho Lee Foundation, Scientific Research Award of the Li Siguang Geological Science Prize, and the OTC Asia Distinguished Achievement Award. He has cultivated a large number of technical experts in offshore exploration and development, making outstanding contributions to offshore oil and gas exploration.
