Design and Experimental Study of an Improved Pressure Core Sampler for Marine Gas Hydrates

A pressure core sampler (PCS) is considered an effective tool to retrieve marine gas hydrate cores from hydrate-bearing sediments. However, according to the sampling application statistics, the success rate of pressure coring changed from 30% to 85% in different drilling wells. Such severe fluctuation will cause huge uncertainty in the practical application of technology and economic benefits. Herein, we present a new PCS designed to improve pressure-retaining reliability. The work principle, design and calculations, and structure composition were described. Through the laboratory tests and drilling experiments, the maximum holding pressure in the pressure chamber was 32.1 MPa, and the pressure loss rates of holding pressure after 2 h changed from 1.96% to 2.46%. The maximum temperature-rising value in the pressure chamber was 0.96 °C under a temperature of 23.5 °C in 2 h. Furthermore, the success rate of the pressure core reached 87.5% and the core recovery was not less than 80%, which were verified by 8 pressure core runs in three different offshore wells. Therefore, we conclude that this new and improved PCS has great application value in gas hydrate exploration that seeks to recover more accurate cores in situ, especially in the silt and sand layers.