The conceptual design of a novel offshore borehole mining technology and study on granularization principle

• Proposes cavity creation mining through the design of serpentine flexible borehole mining equipment that operates via boreholes, enabling mining operations without the need for roadways and underground personnel, thereby making marine mining feasible. • Proposes a mining method utilizes a complex wellbore network, drilled from a marine platform into the underlying mineral deposits mineral resources beneath the seabed. • The flexible borehole mining equipment proposed in this study, which operates through boreholes, employs a stage-wise fragmentation method to gradually break down rock mass into granules, with the objective of enabling transportation in the form of granular flow. • Based on rock mechanics theory, this paper derives a fragmentation energy consumption model required for geological bodies to transition from hard solids to granular flow. • This research is not only applicable to the development of mineral resources beneath the seabed. The flexible mining system can create cavities for mining in a fluid-filled environment through the well bore channels. It is expected to replace the traditional vertical shaft mining technology in deep underground strata with high burial depth, prone to collapse or water seepage, and has opened up new ideas for the development of deep-earth mineral resources. Currently, subsea mining is primarily limited to sea sand extraction and deep-sea mining that focus mainly on mining activities at the seabed surface. These conventional methods not only pose significant environmental risks but are also struggles to exploit sub-seabed mineral deposits. It is necessary to explore new methods, new technologies and new equipment for the safe and efficient development of resources within the strata beneath the ocean floor without damaging the seabed and the marine environment. In this study, a novel offshore borehole mining technical concept is proposed for extracting mineral resources from subsurface marine strata. In addition, This study further investigated the granulation law of rocks under energy injection conditions based on the proposed concept of offshore borehole mining technology, and providing robust theoretical support for the offshore borehole mining technical concept. Furthermore, this study presents the offshore borehole mining technology and equipment.The offshore borehole mining process utilizes a complex wellbore network, drilled from a offshore platform into the underlying mineral deposits. The wellbore system enables three-dimensional, controlled mining centered around the well axis. A serpentine, flexible borehole mining equipment is deployed into the well to facilitate ore extraction and transport. Solid minerals are mined in a controlled manner via a network of slurry-filled chambers. Upon completion of mining, tailings or aggregates are used for in-situ backfilling, thereby enabling efficient extraction of mineral resources beneath the seabed without the need for personnel to enter the shafts or construct tunnels.