|Theme||Visible||Selectable||Appearance||Zoom Range (now: 0)|
Chen, Yuan (China University of Petroleum-Beijing) | Sun, Ting (China University of Petroleum-Beijing) | Zhang, Yida (University of Colorado-Boulder) | Qu, Ximo (China University of Petroleum-Beijing) | Shi, Haidong (PetroChina Research Institute of Petroleum Exploration & Development) | Ying, Hao (Arup USA)
In this paper, we conducted simulations of hydrate with different saturation under different confining pressure based on a series of trial compression experiments. M-C and D-P models were applied respectively to calculate hydrate sediment yield stress. After comparing simulation results with experimental results, it was found that Mohr-Coulomb model is suitable for hydrate sediments with high saturation while Drucker-Prager model is suitable for lower saturation.
Natural gas hydrate is a new type of clean energy with huge reserves and wide distribution which is considered as a strategic energy. 1m3 of natural gas hydrate can release 164m3 of natural gas and 0.87m3 of water during the decomposition of hydrate. Natural gas hydrate is an ice-like crystal formed by methane and water under high pressure and low temperature. Currently, there are four main methods for hydrate extraction: depressurization, heat injection, chemical reagent and CO2 injection method. Depressurization is recognized as the method with the lowest cost. Natural gas hydrate will decompose when the phase equilibrium condition is broken during depressurization, which will cause the sediment soil become less dense or unbonded. The decrease of shear resistance and increase of pore space may lead to some geomechanical problems. For example, the hydrate dissociates during the depressurization process, releasing large amounts of methane gas. As a result, the effective stress decreases significantly with the increase in pore pressure and the mechanical properties of hydrate sediments may change, which may cause potential geomechanical disasters, such as subsea landslides, drilling platform failures, casing deformation, and so on (Huang, 2017). Therefore, it is of great significance to study the mechanical properties of natural gas hydrate sediments and determine the collapse of hydrate reservoir to ensure safe and efficient production. Due to the special properties of hydrate sediments, the methods for oil and conventional gas are not suitable for hydrates. Currently, there are four main methods for hydrate extraction: depressurization, heat injection, chemical reagent and CO2 injection method. Depressurization is recognized as the method with the lowest cost.
Lapshin, Victor D. (Far Eastern Federal University) | Slesarenko, Vacheslav V. (Far Eastern Federal University) | Morozov, Alexey A. (Far Eastern Federal University) | Solomennik, Sergey F. (Far Eastern Federal University)
The main reserves of methane on our planet are in the form of gas hydrate and more than 90% of them are at the bottom of the oceans. Scientists in many countries are making active efforts to establish effective technology for the development of gas hydrate deposits and, primarily located in the sedimentary rocks of the ocean floor. However, the first experience indicates that the development costs of gas hydrate deposits are very high. One of the main reasons for the high cost of recovering methane hydrate is the high value of the decomposition’s thermal effect. The heat of methane hydrate decomposition is 410 kJ/kg, that 30% exceeds, even energy intensive process, as the melting water ice. We have proposed and patented the way to develop marine gas hydrate deposits without the cost of thermal energy and using of any environmentally hazardous substances.
The method consists in grinding of sediment filled of methane hydrate and its subsequent lifting platform by the pipeline in the form of a suspension in seawater. When lifting the hydrate-contained suspension crosses the line of phase equilibrium and goes out of his stable thermodynamic state. Decomposition of gas hydrate phase in this case will be provided at the expense of the sea water crystallization energy. In the pipeline the conversion of gas hydrate slurry in the slurry containing of water, ice particles and gas, released from gas hydrate happen. It should be noted that the methane gas released from the hydrate, creates a lifting force in the pipe, thus avoiding the energy costs for transporting hydrate-contained rock on the surface.
Masui, Akira (Natl. Inst. of Advanced Industrial Science and Technology) | Haneda, Hironori (Natl. Inst. of Advanced Industrial Science and Technology) | Ogata, Yuji (Chuden CTI Co., Ltd) | Aoki, Kazuo (Methane Hydrate Research Laboratory, National Institute of Advanced Industrial Science and Technology)