Efficient Survey Tools for an Improved Understanding of Deep Seabed Minerals

Abstract

The proposed paper presents a novel method of sampling potential polymetallic nodule and manganese crust extraction sites that improves the efficiency and effectiveness of the campaign when compared to traditional surveying methods. The new method utilizes a work-class ROV to perform survey sampling and testing tasks at a relatively large number of sites per dive. The ROV platform enables the use of precision measurement devices such as high-resolution sonar, cone penetrometer test (CPT) systems and core drilling machines to take in-situ samples and measurements. An ROV mounted skid with integrated sample storage drawers allows samples to be taken from numerous sites using ROV resources and manipulators. Transiting from sample site to sample site at depth improves the efficiency of sampling campaigns especially at very deep polymetallic nodule fields up to 6000 meters deep. Initial studies have shown that high resolution sonar scans can measure nodule abundance and size with sufficient accuracy over a much greater area in less time when compared to traditional box coring methods. Studies of nodule and manganese crust sampling campaign durations have shown that transiting from site to site with the ROV at depth reduces the total duration of a representative sampling campaign by 50% or more. Incorporation of a high accuracy CPT system onto the ROV skid enables in-situ geotechnical testing at depth that are more accurate than the traditional method of measuring sub-core samples taken from box core samples at surface laboratories. For manganese crust fields, a novel core sampling drill rig is capable of drilling core holes on sea floor slopes from 0 – 90° without the need for the ROV to land. These advantages combined with the adaptable capability of manipulator systems to collect samples and the ability to provide high-definition video footage of seafloor topology will result in significant improvements to the efficiency and quality of polymetallic nodule and manganese crust site evaluation. The expected gains in cost and accuracy of assessing deep-sea mineral resources will accelerate the pace of material extraction projects and allow greater investment in marine mineral extraction projects due to greater confidence of project success.