Institute of Petroleum Engineering

Centre for Gas Hydrate Research Publications

Abstract 069
Application of Quartz Crystal Microbalance to Gas Hydrate Stability Zone Measurements
Burgass, R., Tohidi, B., Danesh, A. and Todd, A.C.
4th International Conference on Gas Hydrates, Yokohama, Japan, 19-23 May (2002).
We present a novel method for the fast, accurate and relatively inexpensive measurement of hydrate dissociation conditions using a technique based on Quartz Crystal Balance (QCM). The QCM is comprised of a thin disc of AT cut quartz sandwiched between 2 electrodes. Application of an electric current across the electrodes causes the crystal to oscillate at a particular resonant frequency. This frequency is determined by crystal density, dimensions and shear modulus, and is therefore intrinsically very stable. If any of these physical parameters change, then the resonant frequency will also change. This means that any mass that attaches to the surface of the crystal disc will cause a change in the resonant frequency. Based on this principle, we describe a simple, yet accurate method for the detection of hydrate dissociation conditions. A small droplet of water is placed in contact with the surface of the QCM mounted within a high pressure cell. The cell is then filled with the appropriate hydrate forming gas or fluid. Upon cooling and hydrate formation, a significant decrease in the QCM's resonant frequency is observed. Following hydrate formation, the temperature of the cell is step-heated, while cell pressure and QCM resonant frequency are recorded. The point of hydrate dissociation is clearly determined from a significant differential rise in the resonant frequency of the QCM. In the work presented here, experimental results using this new method are compared with literature data and data generated using the conventional temperature search method. Agreement in both cases is excellent. The QCM method is advantageous in that it is simple, accurate, yet significantly faster than conventional techniques, requiring only a small volume of test fluids.

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