Hydrates are unstable compounds of water and hydrocarbons, which may emerge in oil wells under high pressure and low temperature. Hydrates plug oil well tubing and equipment making the oil production more difficult. Inhibitors or retarders are used to cope with this problem, i.e., substances suppressing or hampering the process of hydrates generation. Usually, methanol and glycols are used for these purposes. It is possible to improve the inhibitors’ performance using the methodology allowing for forecasting generation of hydrates in oil wells.
To develop such methodology the scientists from Perm Polytechnical University selected an oilfield, where every third well was subject to hydrates generation. To forecast the interval of hydrates accumulation they measured temperature and pressure at different points of the bore hole and then defined the dependency of hydrates accumulation on these metrics with account of the composition of the associated petroleum gas and stratum water. Based on their calculations the scientists built the pressure-from-temperature influence curve allowing for identifying the thermobaric conditions for starting the process of hydrates generation. This new methodology allowed for forecasting the depth of hydrates accumulations in 22 wells.
“In the course of our study we identified the parameters influencing the intensity of hydrates generation: high gas-oil ratio, electric submersible pumps suction pressure below the saturation pressure and high oil water cut. The proposed calculation methodology allows for forecasting the depth of hydrates accumulation with up to 90% accuracy”, Perm Polytechnical University is citing Alexander Lekomtsev, the Associate Professor of Oil and Gas Technology Department.
The authors of the study identified that small concentration of nitrogen and low mineralisation of stratum water increase the risk of hydrates generation. This conclusion will allow for minimising the operational expenses when operating oil wells.
