With huge reserves, marine natural gas hydrate is one of the most potential unconventional alternative energy sources after shale gas, coalbed methane and tight gas. The research and pilot engineering of natural gas hydrate exploitation technology mainly adopts the depressurization method at home and abroad, all of which refer to the exploitation technology of conventional oil and gas. However, if the depressurization method is used to exploit the weak cementing and unstable non-diagenetic marine natural gas hydrate, the hydrate will be decomposed disorderly and uncontrollably, and 6 great risks will be faced. Therefore, the project team led by Academician Zhou of the Chinese Academy of Engineering divided the hydrate into the kind of diagenetic and non-diagenetic, proposed the technological strategy of 6 “utilize”, firstly created the technological principle of solid fluidization exploitation of non-diagenetic natural gas hydrate and the technological process of hydrate mining, crushing, ejection and fluidization of seawater, separation and backfill of sand, slurry lift and deep separation and re-backfill in the platform, and achieved the safe and green exploitation which let nature take its course, turned the harm into a benefit, and turned the uncontrollable into controllable. Based on this principle, Southwest Petroleum University invented the experimental simulation method and technology, cooperating with China National Offshore Oil Corporation and Sichuan Honghua Petroleum Equipment Co. Ltd. The overall process simulation of solid fluidization exploitation with water depth of 1500 m and pipeline length of 4500 m is achieved. The world’s first large physical experimental simulation system of solid fluidization exploitation of marine natural gas hydrate is researched and developed, which has full independent intellectual property rights and includes 3 modules and 12 subsystems of sample preparation of hydrate, crushing and slurry modulation, high-efficient pipeline transportation and separation of slurry, image capture in real-time, data collection and automation of security control and so on. Moreover, the experiment of solid fluidization exploitation is carried out systematically for the first time, which provided an important basis for the formulation of the test scheme, the optimization design of the process and the research and development of downhole tools, supported the world’s first successful test exploitation of solid fluidization method, and proved the scientific feasibility of the principle and the technology of solid fluidization exploitation. The experimental simulation technology and system, as well as the first testing results, were reported in the Journal Science. The successful research and development and the further upgrading of the system are expected to promote the technology of solid fluidization exploitation of marine nondiagenetic natural gas hydrate to become a disruptive technology leading the world’s frontiers, and are expected to accelerate the commercial development of natural gas hydrate in China and even the whole world.
Keywords marine non-diagenetic natural gas hydrate; solid fluidization; exploitation; physical simulation; experimental system; test scheme