Vertical Exploration Approach for Seafloor Massive Sulfide Deposits

Abstract

The transition towards renewable energy and the electrification of various industry sectors will undoubtedly lead to higher resource demand of our society. Metals like copper, cobalt or rare-earth metals are the basis of these new technologies. However, these elements are not yet available in sufficient quantities in our economic cycle. Hence, more material would be required to be extracted from open pit land mining. A suitable and promising alternative to land deposits are seabed mineral resources. The focus of this work is the development and analysis of a new method to explore seafloor massive sulfides (SMS) with regards to minimizing footprint of the operation in all aspects. SMS reservoirs are mostly found in water depths between 2000m and 4000m. To explore these deposits in the deep sea a concept study based on a vertical trench cutting system has been developed. The extreme environmental conditions require mechanical calculations of the template stability on highly inclined slopes. Furthermore, the cutter tool performance and wear behavior are investigated on a test stand through cutting into rock probes, which have comparable mechanical properties as massive sulfides. The technical feasibility of the separation system was analyzed by computational fluid dynamic models simulating multiple-phase flow and its behavior. For bulk sampling of massive sulfides two potential concepts were examined and compared against each other. The main difference is the conveying method of the sample material to the ocean surface. A discontinuous lifting system with a collector bucket has major advantages in contrast to a riser system. During short exploration campaigns substantial energy and cost savings were estimated for a mechanical intermittent ore transportation. The first results regarding the effectiveness of the separation container could be demonstrated. The separation process takes place in a large scale hydrocyclone in-situ on the seafloor. The ground stability for the landing and leveling of the deep sea sampling unit was verified. Key aspect of the vertical trench cutting approach is the minimal environmental impact during the whole exploration phase. At the same time this system enables to retrieve large amounts of sample material in an economical way.