Hubei Key Laboratory of Marine Geological Resources, China University of Geosciences, Wuhan 430074, Hubei, China.
Faculty of Engineering, China University of Geosciences, Wuhan 430074, Hubei, China.
Rev Sci Instrum. 2022 Dec 1;93(12):125109. doi: 10.1063/5.0124807.
Gas hydrate is a promising alternative energy resource that undergoes complex phase changes and coupled geological responses during hydrate production. Insufficient knowledge of those coupled behaviors still challenge safe and efficient gas production from hydrate. Here, a novel experimental apparatus was developed to simulate the gas-water-sand production and to evaluate the related multifield and multiphase processes. The experimental apparatus is equipped with displacement, ultrasonic, and electrical resistivity sensors and gas/water flowmeters, and this apparatus can work up to a maximum loading stress of 25 MPa and a maximum pore pressure of 20 MPa over a temperature range from -20 to 50 °C. The hydrate production and sand production case were performed on a synthetic specimen with hydrate saturation of 12.8% by using multi-step depressurization. The pressure-temperature conditions, settlement, ultrasonic propagation, electrical resistivity, and permeability of hydrate reservoirs during production were simultaneously monitored to evaluate the geological characteristics and heat and mass transfer characteristics of the hydrate reservoir. The results indicated that the gas/water production mainly occurred during the first third of each depressurization period, and their production rates were low at the beginning. Flowing water mobilized the sand particles, and the addition of gas exacerbated the sand-particle migration. Interpretation of the coupled behaviors supported that the reservoir could maintain a temporary stable structure even when losing a certain amount of sand particles with no sand control methods; however, necessary sand-prevention approaches are wise to support long-term reservoir production operations. These laboratory insights would contribute to optimizing the field strategies for economical gas production from hydrate.
天然气水合物是一种很有前途的替代能源，在水合物生产过程中经历复杂的相变和耦合的地质响应。由于对这些耦合行为的了解不足，仍然挑战着从水合物中安全高效地生产天然气。为此，开发了一种新的实验装置来模拟气-水-砂生产，并评估相关的多场和多相过程。该实验装置配备了位移、超声波和电阻率传感器以及气体/水流量计，可在-20 至 50°C 的温度范围内工作，最大加载应力为 25 MPa，最大孔隙压力为 20 MPa。在水合物饱和度为 12.8%的合成样本上进行了水合物生产和出砂实验，采用多步降压法。在生产过程中同时监测压力-温度条件、沉降、超声波传播、电阻率和水合物储层的渗透率，以评估水合物储层的地质特征和热质传递特征。结果表明，气体/水的产量主要发生在每个降压期的前三分之一，其产量在开始时较低。流动的水使砂粒移动，而气体的加入加剧了砂粒的迁移。对耦合行为的解释表明，即使在没有防砂措施的情况下失去一定量的砂粒，储层仍能保持暂时稳定的结构；然而，必要的防砂措施对于支持长期储层生产作业是明智的。这些实验室的见解将有助于优化从水合物中经济地生产天然气的现场策略。
