Design and study of a deep-sea multi-depth in-situ pore water pressure-retaining sampler

A high-standard pore water sampling in deep-sea sediments is essential for scientific and technical studies such as determining geochemical anomalies on the seafloor. This paper designed a multi-depth in-situ pore water pressure-retaining sampler (MIPPS). It can sample deep-sea in situ pore water with multiple depths, high resolution, and low disturbance. We evaluated the indicators and functions of the sampler through simulation calculations, laboratory, offshore and deep-sea experiments. The diffusion between pore water and deionized water was determined using Ansys Fluent simulation to select a suitable tube to reduce contamination. The pressure test shows that the sampler has a pressure-retaining capacity of 30 MPa. The experiments show the laboratory sampling rate in sediment at different temperatures. Furthermore, in the offshore experiment, we analyze the reasons for the decrease in the offshore sampling rate. Finally, the sampler was carried on board the heavy-duty ROV-Jellyfish for a deep-sea experiment in the South China Sea. The deep-sea experiment's success indicates that the MIPPS is accurate and trustworthy in practice. Then the sampler continued to be used for the sea area of methane seepage for in-depth scientific applications.