Development and Field Tests of Pressure-Temperature Preservation Coring Tools for Gas Hydrate

Natural gas hydrates that exist in the shallow strata of deep sea floor are notoriously unstable and are easily decomposed when disturbed.It is difficult to obtain samples by conventional coring technology.Therefore,the development and field test of pressure-temperature preservation coring tools for gas hydrate have been carried out.3D software was used to design the overall structure of rope-type pressure-temperature preservation coring tools for gas hydrate.The test incorporated the detailed structures and working principles of four types of coring tools,including telescopic insertion type,piston injection type,impact type and motor rotation type.In order to assure that the tools can maintain constant temperature and pressure,and that they also will have the attributes of pressure compensation,rapid fishing,and reduced coring disturbance,we studied the key technologies of pressure-temperature preservation coring tools.We conducted indoor simulation analysis on key parts such as pressure sealing valve,heat insulation tube,pressure compensation device,core tube,and rope fishing and recovery device.The results showed that the pressure sealing valve could withstand pressure 30.0 MPa,they also demonstrated that an insulation barrel filled with heat insulation composite silica aerogel could reduce the influence of ambient temperature on it,and the performances of other components also meet the design requirements.We completed 13 runs of sampling in two wells in the gas hydrate reservoir of LW3 Block in the South China Sea.Our results demonstrate that the rope-type pressure-temperature preservation coring tools can successfully take gas hydrate cores.This new understanding and knowledge will provide technical support for the independent exploration and coring of gas hydrates in China in the future.