John C. Pinkston

Laboratory measurements of compressional and shear wave speeds through methane hydrate

Abstract: Simultaneous measurements of compressional and shear wave speeds through polycrystalline methane hydrate have been made. Methane hydrate, grown directly in a wave speed measurement chamber, was uniaxially compacted to a final porosity below 2%. At 277 K, the compacted material had a compressional wave speed of 3,650 ± 50 m/s. The shear wave speed, measured simultaneously, was 1,890 ± 30 m/s. From these wave speed measurements, we derive Vp/Vs, Poissons ratio, bulk, shear, and Youngs moduli.

Methane Hydrate Dissociation Rates at 0.1 MPa and Temperatures above 272 K

Abstract: We performed rapid depressurization experiments on methane hydrate under isothermal conditions above 272 K to determine the amount and rate of methane evolution. Sample temperatures rapidly drop below 273 K and stabilize near 272.5 K during dissociation. This thermal anomaly and the persistence of methane hydrate are consistent with the reported recovery of partially dissociated methane hydrate from ocean drilling cores.

Measurement of gas yields and flow rates using a custom flowmeter

A simple gas collection apparatus based on the principles of a Torricelli tube has been designed and built to measure gas volume yields and flow rates. This instrument is routinely used to monitor and collect methane gas released during methane hydrate dissociation experiments. It is easily and inexpensively built, operates at ambient pressures and temperatures, and measures gas volumes of up to 7 L to a precision of about 15 ml (about 0.0025 mol). It is capable of measuring gas flow rates varying from more than 103 to less than 10−1 ml/min during gas evolution events that span minutes to several days. We have obtained a highly reproducible hydrate number of n=5.891 with a propagated uncertainty of ±0.020 for synthetic methane hydrate.