(403b) Characterization of Hydrate Slurry Transportability: Comparison of High Pressure Rheometer Measurements with Industrial Scale Flowloop Data

Ahmad AA Majid^1,2, Carolyn A Koh^1*

1. Center for Hydrate Research, Colorado School of Mines, Golden CO 80401, USA
2. Faculty of Chemical & Natural Resources Engineering, Universiti Malaysia Pahang, Malaysia

ABSTRACT

Gas hydrates are solid inclusion compounds that contain small gas molecules trapped inside a lattice of water cages, and typically form at high pressure and low temperature. In the oil and gas industry, the formation of gas hydrates in flowlines is a major concern as it can cause plugging of the flowlines. This is a major concern as it poses both safety and environmental risks. The transportability of a gas hydrate slurry was evaluated using two different apparatuses; both large and lab-scale measurements. For the large-scale measurements, an industrial-scale flowloop was used and the transportability of the hydrate slurry was evaluated from pressure drop data (see (Grasso et al. 2014; Majid et al. 2016)). In lab-scale measurements, in-situ viscosity measurements of hydrate slurries were conducted using a high-pressure rheometer. Both apparatuses have advantages and disadvantages. In order to compare the results across both apparatuses, experimental parameters were specifically chosen to ensure both systems have relatively similar conditions. Two different parameters were investigated in this work; water cut and shear rate. Specifically, three different water cuts (30, 50 and 90 vol.% water cut) and five different shear rates were investigated for a crude oil system. In this investigation, there is qualitative agreement between results from the rheometer with the flowloop. From the analysis of the gas consumption data at similar experimental conditions (water cut and pressure), similar amounts of hydrate formed in both the rheometer and flowloop. Furthermore, in order to qualitatively compare the results from the rheometer with the results obtained from the flowloop, relative calculations (relative pressure drop and relative viscosity) were used. Results from the relative calculations show that the relative viscosity and relative pressure drop are on a similar order of magnitude. However, relative viscosity is higher than the relative pressure drop. Finally, in this work, the relationship between relative viscosity and relative pressure drop was developed investigated. This relationship can ultimately help flow assurance engineers in evaluating the transportability of hydrate slurries in flowlines.

References:

Grasso GA, Lafond PG, Aman ZM, et al. 2014. Hydrate Formation Flowloop Experiments. In: The 8th International Conference of Gas Hydrates.

Majid AA, Lee W, Srivastava V, et al. 2016. The Study of Gas Hydrate Formation and Particle Transportability Using a High Pressure Flowloop. In: Offshore Technology Conference.