## 1 Introduction
However, the core diameter of the PCS was limited, and the core could not be removed from the system without releasing the pressure from the sample [21]. Hence, two developments of a new wireline pressure coring tool were initiated in response to the perceived limitations of the PCS on Leg 164. The PTCS was invented in 1998 and was upgraded in 2004 by Aumann & Associates Inc. and the Japan National Oil Corporation, which was designed to retrieve longer, larger cores than the PCS and to provide a temperature control system. And two types of wireline pressure coring tools, the FPC and HRC (HYACE rotary core), with the former also known as FRPC (Fugro rotary pressure core), were developed in the European-funded Hydrate Autoclave Coring Equipment project (HYACE) in late 1997. These wireline pressure core tools were designed to recover hydrate cores in liners that were to be subsequently transferred into a Pressure Core Analysis and Transfer System (PCATS) [22; 23]. Later, the Hybrid PCS was developed from PTCS, designed mainly by a combined design of PCS and PTCS for the drilling vessel Chikyu, and fitted to PCATS, which included core handling and an analysis system [24; 25]. In 2012, the Hybrid PCS was successfully used in the Nankai Trough offshore Japan expedition 802 and obtained 18 pressure cores [26; 27; 20], as shown in Table 1.  
Based on the Hybrid PCS and the PCATS, Geotek has further developed the PCTB. The PCTB has been widely used in China, India, Japan, and the United States to recover a large number of pressure-holding core samples, while the PCATS has been instrumental in processing and analyzing the cores [28; 29; 30]. Pressure coring that maintains the in situ hydrostatic pressure is a critically important technical issue. As shown in Table 1, it could be found that it was very difficult to make the cores conserve their original formation pressure after coring. Specifically, more than half of the cores failed to conserve their original pressure. To achieve this goal, the pressure chamber must seal the core and be able to withstand the hydrostatic pressure at the coring depth using a sealing mechanism (flapper or ball valve) when lifting to the surface. As shown in Table 2, the ball valve and flapper valve were the main types for sealing, and the Hybrid PCS was the most active pressure coring tool. The presence of the gas hydrates can be inferred through the utilization of geophysical tools, yet the sole direct method for ascertaining the in situ concentration of the natural gas embedded in this gas hydrate is to core the formation while meticulously maintaining the constant in situ pressure [5]. To obtain a more comprehensive and minimally perturbed sample of seafloor gas hydrate in situ pressure, a novel wireline pressure coring system (WPCS), which is rooted in the ball valve sealing mechanism, was successfully devised and deployed during the Guangzhou Marine Geological Survey (GMGS) expedition conducted in the South China Sea in 2023. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \begin{tabular}{c} **Drill Pipe** \\ **Diameter** \\ **(in)** \\ \end{tabular} & \begin{tabular}{c} **Core OD** \\ **(in)** \\ \end{tabular} & \begin{tabular}{c} **Max Core** \\ **Length (m)** \\ \end{tabular} & \
\begin{tabular}{c} **Max** \\ **Pressure** \\ **(MPa)** \\ \end{tabular} &
\begin{tabular}{c} **Sealing** \\ **Mechanism** \\ \end{tabular} & **Active** \\ \hline PCS & & 1.575 & 1 & 69 & ball valve & No \\ \hline FPC & 5 or 51/2 & 2.125 & 1 & 25 & flapper valve & No \\ \hline HRC & & 2 & 1 & 21 & flapper valve & No \\ \hline PTCS & 65/8 & 2.625 & 3.5 & 24 & ball valve & No \\ \hline Hybrid PCS/PCTB & 5 or 51/2 & 2 & 3.5 & 35 & ball valve & Yes \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of available pressure coring techniques [13].