Pressure-retaining sampler for sediment including overlying water based on heavy duty ROV-Jellyfish

Abstract

Methane leakage at the interface between sediment and overlying seawater is an important basis for gas hydrate exploration. Therefore, a low disturbance in-situ encapsulation and pressure-retaining sampler for this interface with a working depth of 3000 m is developed recently, which can separate and transfer sediment and overlying water under pressure-retaining conditions. The tube-soil interaction during sampling process is investigated by the coupled Eulerian-Lagrangian (CEL) approach in the ABAQUS (a finite element analysis software), and the penetration resistance of the sampling tube is 599 N at a penetration depth of 150 mm without damage. The pressure-retaining transfer process of overlying water is investigated by the dynamic mesh technology in the Fluent (a computational fluid dynamics software), and the transfer scheme can ensure that the pressure fluctuation of the sample does not exceed 0.03%. Moreover, the laboratory pressure test verifies the strength and sealing performance (the pressure decreased from 30.77 MPa to 29.57 MPa) of the sampler. Furthermore, the pressure-retaining samples of more than 700 ml were obtained from sea trial, which verifies feasibility of the device application.