Experimental investigation into methane hydrate production during three-dimensional thermal huff and puff

In this work, the decomposition behaviors of methane hydrate in the porous media are investigated in the three-dimensional cubic hydrate simulator (CHS) using the huff and puff method with a single well with the different injection temperatures and different injection time. The changes of the system pressure are analyzed by using the biggest increasing degree of the system pressure during injection stage (PII) and the biggest increasing degree of the system pressure during soaking stage (PIS), and the result shows that the injection time has more obvious effect on the system pressure than the injection temperature. The cumulative volume of the produced gas increases with the increases of the injection temperature and injection time. The higher injection temperature results in the smaller volume of the produced water; whereas the higher injection time results in the bigger volume of the produced water. In addition, increasing the injection temperature and injection time may not enhance the thermal efficiency and energy efficiency. The optimum period for the gas production is the first 4–5 cycles. The highest energy efficiency can be obtained at the injection temperature of 130 °C and the injection time of 5 min. Furthermore, the experiment verifies that a moving decomposition boundary occurs in the hydrate decomposition process, and there is a maximum decomposition boundary with the thermal huff and puff cycle. In addition, the injected heat does not diffuse isotropically.