Research and Analysis of 30-m Gravity Piston Corer for Natural Gas Hydrate

Abstract

AbstractThe use of natural gas hydrate as a strategic alternative energy has increasingly attracted the attention of researchers in related fields. To study the properties of natural gas hydrate, however, obtaining the cores under in-situ pressure is a prerequisite because the cores are under particular combinations of high-pressure and low-temperature storage conditions. This article mainly presents the mechanism of a gravity piston corer in acquiring the pressure core of natural gas hydrate (up to 30 m long). The sampling theoretical model is established, and the corer's motion equation is thereafter derived. Based on the theoretical model, the penetration process of the gravity piston corer into the submarine sediment is analyzed. The weight, inner diameter, outer diameter, and initial speed, which are factors affecting the sampling process, are comprehensively elaborated. Additionally, the sampling process is numerically simulated using ABAQUS finite element software. It is found that the soil and pipe are influenced back by their coupling action, thus affording theoretical and numerical bases for the design and installation of a seabed operation structure. In its verification deployment in the South China Sea, the corer was operated numerous times at different depths; it successfully extracted pressure cores of natural gas hydrate. The theory and sea trails employed in this study are anticipated to support further research on abyssal pressure core corers.