Protocol for Measuring the Thermal Properties of a Supercooled Synthetic Sand-water-gas-methane Hydrate Sample

The overall goal of this procedure is to determine the thermal properties of a sample comprised of sand, water, methane gas, and methane hydrate. This lesson can help answer key questions in the gas production technology field such as gas production simulation natural methane hydrates. To begin, place the high-pressure vessel on the vibrating table.

Pour 1.5 liters of pure water in a water bottle and 4, 000 grams of silica sand in a sand bottle. Accurately weigh the masses of sand and water in their respective bottles. Then pour 1 liter of pure water in the high-pressure vessel with an inner volume of 2, 110 cubic centimeters from a water bottle until the water fills half the inner vessel.

Turn on the vibrating table to vibrate the entire vessel. Set the vibration rate to 50 hertz and the power supply to 220 watts. Remove the residual air in the drain line and centered metallic filter at the bottom of the vessel by vibrating the vessel.

Pour 3, 300 grams of silica sand from a sand bottle into the vessel at a constant rate of approximately one gram per second using a funnel held near the water surface while the entire vessel is vibrated to ensure uniform packing. Stop the vibration when the water reaches the rim of the vessel. Place a ring as a temporary wall on the rim of the vessel to prevent water from spilling.

Vibrate the vessel again as before, and when the sand reaches the rim of the vessel, turn off the vibration. Remove the excess pour water using the drain line and pour it back into the water bottle. Remove the temporary wall.

Pack the sand by vibrating the vessel once or twice at 50 hertz and 300 watts per one second and add more sand if necessary. Weigh the mass of the sand and water in their respective bottles. Next, calculate the sand and water masses in the vessel from the mass differences in the sand and water bottles.

In this experiment, the mass of sand in the vessel was 3, 385 grams, and the mass of water in the vessel was 823.6 grams. The mass of water in the vessel is denoted as w total. Cover the high-pressure vessel with a stainless steel lid and tighten the bolts of diagonally opposite pairs in sequence.

Move the high-pressure vessel from the vibrating table to the table intended for the experiment. Cover the high-pressure vessel with a heat insulator for controlling the temperature. Then connect the high-pressure pipelines and the cooling water flowlines to the high-pressure vessel.

Open the valves of the input and output gas pipelines. Ventilate 10 liters of methane at a rate of 800 milliliters per minute until no excess water discharges into the trap under atmospheric pressure. The sand discharge is prevented by a centered metallic filter fixed on the bottom of the vessel.

The residual water remains on the sand's surface because the hydrophilic silica sand absorbs the water molecules. Weigh the mass of water in the trap w trap to determine the gas volume in the vessel. Determine the mass of residual water, w resi.

In this case w resi is 360.6 grams and w trap is 463 grams. After closing the valve of the output gas line, inject methane to increase the pour pressure of methane in the vessel to approximately 12.1 megapascal at room temperature. Then, close the valve of the input gas line.

Start recording the pressure and temperature in the vessel during the experiment using the data logger. Turn on the chiller for cooling the vessel from room temperature to 2.0 degrees Celsius by circulating the coolant. Let the coolant circulate from the chiller to the bottom of the vessel, from there to the lid of the vessel and finally back to the chiller.

Set up the measurement parameters using transient plane source, or TPS, analyzer software and calculating the degree of supercooling as determined in the text protocol. The most critical step is performing sonar constant measuerment by keeping the temperature increase over the TPS sensor supercoolant. Simultaneously measure the thermal conductivity, thermal diffusivity, and volumetric specific heat using the TPS analyzer after the degree of supercooling is greater than two degrees Celsius.

After each measurement, manually switch the cables between the TPS probes and the analyzer during the experiment. Collect data every three to five minutes. Repeat the measurements until the degree of supercooling reaches two degrees Celsius again.

In this experiment, the degree of supercooling initially increases with time. After the degree of supercooling reaches the maximum value, it gradually decreases to zero degrees Celsius because the pressure decreases with the formation of MH.Shown here is a temperature profile not affected by methane hydrate melting, and a temperature profile affected by melting. Note that this profile cannot be analyzed by the TPS technique because the analysis equations assume stable sample conditions.

The pressure, temperature, and degree of supercooling in the vessel as a function of time are shown. MH nucleates after the system has reached pressure and temperature equilibrium. The saturation of the sediment with MH, water, and methane gas as a function of time are shown here.

The degree of saturation is calculated using the equation of the state of the gas. An example of the thermal constants measurements is shown here. The double headed arrows denote the data range used in the analysis.

Analysis 1 is an example of an inappropriate range, and Analysis 2 is an example of an approriate range. The TPS inversion analysis results from each range are shown here. The deviation of the temperature data from the linear fit curve is shown.

If the appropriate analysis range is selected, the difference temperature becomes small and approximately constant. Finally, thermal conductivity as a function of time, specific heat as a function of time, and thermal diffusivity as a function of time are shown.