Permittivity Sensors for Detection and Characterization of Hydrate Deposits on Pipe Walls
This paper studies the application of permittivity sensors for the detection of hydrate deposition in a vertical pipe experimental system (deadleg). This is a joint conference paper with Colorado School of Mines and Statoil presented at the 9th International Conference on Gas Hydrates.
In oil/gas production systems, some pipe sections, called deadlegs, are in intermittent use for production or special services. These sections are commonly much colder than the main flowlines because of the absence of flow, so it exposes to hydrate risk, consequently, which leads serious issues in terms of safety and productivity. Here, we introduce and discuss the application of permittivity sensors for the detection of hydrate deposition formed on vertical deadleg wall. The applicability of the sensors for the quantification of hydrates (amount/thickness and porosity) is tested from a number experiments considering the changing conditions in the pipe in terms of temperature, pressure, wetness, and hydrate amount. A small (1-inch inner diameter pipe) and versatility system is used for quantification, allowing rapid and controlled hydrate deposition for measurement with the sensor. The applied permittivity sensors are open-ended coaxial probes, mounted flush with the inner pipe wall. It is showed that the sensors are able to detect condensation and hydrate formation/dissociation on the pipe wall. The layer thickness can be estimated for thin layers (below approx. 4 mm for the applied sensors). By applying dielectric mixing formulas, the porosity and free water content of the hydrate deposit can be estimated.