1 Overview of the “Meng Xiang” ocean drilling vessel
The “Meng Xiang” ocean drilling vessel represents China’s first independently developed, designed, and constructed scientific ocean drilling vessel (Fig.1). With a length of 179.8 m, a width of 32.8 m, and a gross tonnage of 33,000GT, the vessel boasts impressive capabilities. It features a cruising range of 15,000 nautical miles, an endurance of 120 days, and can accommodate 180 personnel. The vessel is designed for global unrestricted navigation and operations, maintaining normal operational status in sea state 6 and ensuring survivability under super typhoon conditions up to category 16. It meets bridge clearance and port berthing requirements in major sea areas worldwide. Currently, the “Meng Xiang” leads globally in drilling capacity, scientific research functionality, intelligent automation levels, and operational cost efficiency among ocean drilling vessels.
The project began its preliminary evaluation in 2015, received initiation approval in 2017, completed the feasibility study in 2019, finalized the preliminary design in 2020, and commenced construction in 2021. The main hull was launched in 2022, and the vessel was officially named in 2023, with completion and commissioning occurring on November 17, 2024. Over the course of more than a decade of intensive development, the project adopted modular and integrated design concepts to address the complexities of combining multiple functions—scientific ocean drilling, deep-sea oil and gas exploration, and natural gas hydrate exploration and test production—into a single vessel. By achieving multifunctionality and high performance within a relatively small tonnage, the project significantly enhanced the vessel’s capabilities while effectively controlling operational costs. Upon commissioning, the “Meng Xiang” was selected as one of the Top Ten Domestic Science and Technology News Stories of 2024 by China Media Group and Science and Technology Daily. It was also recognized by academicians from the Chinese Academy of Sciences and the Chinese Academy of Engineering as one of China’s Top Ten Scientific and Technological Advances of 2024.
2 Research and design innovations of the “Meng Xiang” ocean drilling vessel
The “Meng Xiang” adheres to the design and construction principles of “small tonnage, multifunctionality, and modularization,” achieving breakthroughs in over 50 core technologies across ten major categories. These innovations include the optimization of hydrodynamic performance for vessels with large moonpool openings, modular integrated layout optimization for multiple operational systems, structural safety assessment and optimization of critical areas, integrated multifunctional onboard laboratory design, environmentally friendly hydraulic drilling and coring system integration, and high-efficiency construction and precision control. The vessel innovatively integrates functions for scientific ocean drilling, deep-sea oil and gas exploration, and natural gas hydrate exploration and test production.
2.1 Developing a specialized vessel platform: achieving “multifunctionality” with “small tonnage”
“Small tonnage” was a central research and development target for the “Meng Xiang,” driven by three main considerations: first, controlling vessel size to reduce construction and operational costs; second, managing draft to improve adaptability for channel navigation and port berthing; and third, controlling vessel height to meet the navigation clearance requirements of the Shenzhen–Zhongshan Bridge. “Multifunctionality” was the core construction objective, requiring the vessel to support not only scientific ocean drilling but also deep-sea oil and gas exploration, as well as natural gas hydrate exploration and test production. The design incorporates the latest technological advances in deep-sea drilling and coring, with the system allowing for future functional expansion to maintain technological leadership.
The gross tonnage of the “Meng Xiang” was controlled at 33,000 GT, more than 40% lower than that of Japan’s “Chikyū” ocean drilling vessel, achieving effective control over construction and operational costs. To ensure navigability under the Shenzhen–Zhongshan Bridge, the vessel’s height above water was restricted to within 76.5 m—a significant challenge, as conventional vessels typically exceed 100 m due to their tall derricks. To address this, specific measures were adopted in the drill floor and derrick design. For the first time globally, a recessed moonpool design was proposed, utilizing the sunken space on the main deck at the aft side of the moonpool to accommodate the movement of the BOP below the drill floor, thereby reducing the drill floor height by more than 20%. The derrick height is determined by the drilling rig type, the height of the gas-liquid separator vent pipe, and the storage requirements for pre-connected drill strings. After a comparative analysis of different rig types, a hydraulic lifting rig was selected, offering advantages in both height control and drilling efficiency.
Additionally, a foldable gas-liquid separator vent pipe design was proposed for the top of the derrick. This vent pipe can be hydraulically folded during navigation under bridges. Optimized matching between the derrick and the setback further enabled efficient storage of triple stands of drill pipes within the derrick, while controlling the overall derrick height to 52.4 m. By achieving greater functionality and higher performance with a smaller tonnage, the “Meng Xiang” established a globally leading, specialized vessel platform for deep-sea drilling operations.
2.2 Modular integrated design enabling four drilling operation modes
By applying a “modularization” design concept and adopting the principles of “fixed drilling rig, switchable drill pipe racks, and shared transportation facilities,” the “Meng Xiang” achieves four drilling operation modes on a single vessel: conventional riserless drilling, conventional riser drilling, open water intervention riser system drilling, and riserless mud return drilling. The drilling rig serves as the key equipment of the ocean drilling vessel. The project team developed the world’s first hydraulic lifting rig capable of both coring and oil and gas exploration (Fig.2), with the lifting capacity of 907 tons, sufficient to operate a drill string of up to 11,000 m. The hydraulic system integrates lifting and heave compensation functions into a single system. Compared with conventional electrically driven rigs, the hydraulic lifting rig offers advantages such as higher drilling efficiency, reduced weight, and lower derrick height. These features significantly reduce the vessel’s overall weight and height without compromising operational performance. The pipe rack areas for risers, drill pipes, and casings at the stern of the vessel employ switchable modular designs, allowing flexible configuration according to operational requirements. Additionally, the transportation facilities for risers, drill pipes, and casings were optimized from traditional dedicated systems into a generalized system, effectively reducing deck space occupation. A large-capacity setback within the derrick can accommodate 11,000 m of drill strings and associated auxiliary tools, enabling efficient transfer of drill strings from the pipe rack area to the working area under the derrick.
Furthermore, the vessel incorporates a novel integrated dual-moonpool design, proposed for the first time globally (Fig.3). By combining a large and a small interconnected moonpool, the design supports all four drilling modes, optimizes vessel dimensions, enables shared use of moonpool operational facilities, enhances operational efficiency, and substantially reduces additional hydrodynamic resistance during navigation, achieving significant energy savings. Through iterative optimization of hull dimensions, hydrodynamic performance, and general arrangement, the “Meng Xiang” became the first vessel internationally to support four drilling operation modes and three coring methods on a single platform.
These innovations enable the “Meng Xiang” to reach a maximum drilling depth of 11,000 m, increasing comprehensive drilling and coring efficiency by more than 40%. The vessel now holds the strongest drilling capacity and the highest operational efficiency among international ocean drilling vessels, offering greater flexibility in site selection for scientific ocean drilling.
2.3 Applying human factors engineering to improve operational efficiency
The “Meng Xiang” adopts human factors engineering principles throughout its design, balancing the efficient execution of operational tasks in working areas with the comfort of personnel living areas. In the layout of the working area, the drilling system is concentrated around the moonpool, located in the midship section where vessel motion is minimal, ensuring maximum operational stability during drilling and coring. Above the moonpool, the drill floor is equipped with a derrick, within which a large-capacity setback is arranged. This storage system accommodates up to 11,000 m of drill strings and associated auxiliary tools in a triple-stand vertical storage mode, enhancing continuous drilling efficiency. At the aft deck area behind the moonpool, pipe racks for drill pipes, casings, and risers are sequentially arranged from aft to forward. These storage areas utilize a modular, removable stanchion design. An innovative catwalk system, connecting the forward and aft pipe racks, was developed, enabling the efficient transfer of drilling materials from the storage area to the working area beneath the derrick.
Adjacent to the forward side of the drill floor, the onboard laboratories are arranged to facilitate the prompt and convenient transfer of core samples from the drill floor to laboratory facilities for immediate experimental analysis. The “Meng Xiang” features comprehensive onboard laboratories covering nine major disciplines, including core, paleomagnetism, inorganic geochemistry, organic geochemistry, microbiology, marine science, natural gas hydrate, geophysics, and drilling technology. With a total area exceeding 3,000 m2, it establishes the world’s largest and most functionally comprehensive “mobile offshore laboratory.” For example, in the onboard paleomagnetism laboratory, magnetic shielding was optimized through simulation analysis, leading to the development of a shielding system combining permalloy and peripheral steel structures. This design effectively isolates the geomagnetic field and shipborne electromagnetic fields, ensuring precise natural remanent magnetization measurements of core samples and supporting research in magnetostratigraphy. Additionally, to create a highly clean experimental environment, a specialized clean ventilation and air-conditioning system was designed. The indoor environment achieves ISO Class 7 cleanroom standards under negative pressure ventilation, with the work table achieving ISO Class 5 cleanroom standards. This setup meets the requirements for contamination-free sampling and experimental analysis of microbiological and other sensitive samples.
2.4 Advancing intelligent applications to enhance vessel smart operation
The “Meng Xiang” is equipped with the world’s most advanced “vessel intelligent brain,” which integrates the intelligent ship system, drilling system, and onboard laboratory system. This system aggregates and analyzes data from over 20,000 monitoring points in real-time, with live visualization at the Project Control Center (Fig.4). The system enables intelligent operational monitoring, smart laboratory collaboration, intelligent health management, vessel-to-shore smart integration, and intelligent decision support.
An intelligent integrated control system was developed, incorporating automated functional modules such as one-click ballast water management, automatic emergency shutdown of the safety system, top drive torque control, and automatic mud circulation system. These functions significantly reduce crew workload and minimize the risk of human operational errors. An intelligent driller control system was installed, capable of real-time control over more than 30 subsystems and 200 devices within the drilling operation system. Additionally, an intelligent anti-collision system was developed to continuously monitor the relative movements of multiple devices in the drilling operational area. If potential interference is detected, the system issues alarms and initiates response actions to prevent collisions during equipment operation. A surveillance network and remote diagnostic system are integrated into the driller control system, enabling shore-based technical support in the event of onsite operational issues that cannot be resolved locally.
The vessel is also equipped with the world’s first onboard core automatic transport and storage system (Fig.5), which covers three areas: the onboard laboratories, the core store, and the open deck. These areas are seamlessly connected via vertical elevators. Within the core store, an onboard core automatic storage system was installed for the first time globally, utilizing a Rail Guided Vehicle (RGV) combined with automated stackers to achieve fully automated storage and retrieval of core trays. On the open deck, the world’s first onboard core container automatic loading system was developed, allowing the automated transfer of core trays between the elevator and storage containers. Through this automatic core transport and storage system, the “Meng Xiang” achieves complete automation of core handling, from laboratory entry into the core store, core store to the open deck, and container loading. This eliminates the need for manual handling traditionally required on ocean drilling vessels. The backend management system enables real-time tracking of core location and store capacity, achieving intelligent, efficient management, storage, and transfer of core samples. The time required to deliver a fully loaded core container from the vessel to shore is reduced to less than two hours, representing a several-fold improvement compared with traditional manual handling methods.
2.5 Comprehensive performance enhancement: achieving “larger capacity,” “higher speed,” and “stable positioning”
The “Meng Xiang” ocean drilling vessel supports a variable load exceeding 15,000 tons, enabling the carriage of more living and operational supplies. It achieves an endurance of up to 120 days, with a minimum cruising range of 15,000 nautical miles and a maximum cruising range exceeding 27,000 nautical miles, sufficient to circumnavigate the Earth’s equator. To meet these advanced variable load requirements, a full-process precision control mechanism for lightship weight and center of gravity management was implemented throughout the vessel’s development and design, equipment procurement, and construction phases. Measures included lightship weight design optimization, tracking and evaluation of equipment weight specifications, three-dimensional routing optimization for piping and cabling, multiple-stage critical-phase weight and center of gravity measurements, and the formulation of weight reduction plans. Based on the results of periodic weight and center of gravity measurements from inclining test, further structural optimizations were conducted, including redesigning the drill floor structure, catwalk platform structure, height adjustment of stanchions in pipe racks, and substitution of lightweight materials. Therefore, the vessel achieved a 1% reduction in real lightship weight, a 2% reduction in center of gravity height, and maintained deviations in longitudinal and transverse center of gravity within 2‰. These measures fully achieved the weight and center of gravity control targets, providing a solid foundation for realizing variable load and comprehensive performance specifications.
The “Meng Xiang” achieves a maximum design speed of 13 knots, which is 30% higher than that of the US vessel “JOIDES Resolution” and more than 8% higher than that of Japan’s “Chikyū.” Increasing speed for an ocean drilling vessel is particularly challenging, as the midship moonpool—connecting the vessel to the sea—generates significant additional resistance at higher speeds. By employing the novel integrated dual-moonpool design, the “Meng Xiang” effectively reduces hydrodynamic resistance during navigation, achieving higher speeds with lower fuel consumption.
The “Meng Xiang” is equipped with an “integrated air–sea” position reference system, combining satellite positioning through the BeiDou and GPS systems with an underwater ultra-short baseline acoustic positioning system. This enables precise real-time determination of the vessel’s coordinates. It is also outfitted with the most advanced DP-3 class dynamic positioning control system, which automatically adjusts the thrust magnitude and direction of the vessel’s thrusters to counteract external environmental forces such as wind, waves, and currents, thereby maintaining drilling stability comparable to a “pillar anchoring the sea.” Sea trials of the “Meng Xiang” dynamic positioning system demonstrated that the vessel can maintain position across 360 degrees under Beaufort scale 9 wind conditions and maintain favorable heading control under typhoon conditions up to scale 12, significantly extending the vessel’s operational weather window for offshore drilling activities.
3 Conclusions
The “Meng Xiang” ocean drilling vessel serves as a crucial platform for deep-sea resource exploration, the development of critical technological equipment, and scientific ocean drilling research conducted by scientists worldwide. It plays a significant role in advancing the construction of a shared future for humanity. Moving forward, the “Meng Xiang” will continue its planned operations, undertaking tasks such as deep-sea energy resource exploration and scientific ocean drilling. It will also expand international marine cooperation and support global scientists in uncovering the mysteries of the Earth. Through these efforts, the vessel will contribute to advancing human understanding, fostering sustainable development, and safeguarding the planet.
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