Detection and Assessment of Asphaltene Precipitation/Deposition at Reservoir Conditions and Gas Hydrate Formation in the Presence of Thermodynamic Hydrate Inhibitors

Abstract

Abstract The occurrence of asphaltenes and gas hydrates represents a serious flow assurance problem faced by engineers at different stages of oil production. Early detection and evaluation of the impact of these solids on the hydrocarbon flowability is key in reducing the OPEX for remediation treatments. The access to reliable experimental data on asphaltene and gas hydrate formation and mitigation at reservoir/field conditions represents a valuable tool to improve the accuracy of existing prediction models / software packages and make them applicable for new scenarios faced by the industry. In this work, asphaltene precipitation/deposition and redissolution in a core was detected by using in-situ acoustic measurements at ambient and high CO2 pressures. Acoustic velocity increased during asphaltene deposition, indicating a cementing effect in the sample pores. In contrast, asphaltene redissolution with toluene induced a reduction in velocity of the acoustic wave travelling through the sample. Rheological properties, such as viscosity and yield stress, were measured for hydrate slurries in crude oil for under-inhibited systems with two different thermodynamic hydrate inhibitors (THI): methanol (10 vol.%) and monoethylene glycol (10 vol.%). The addition of these thermodynamic hydrate inhibitors reduced the amount of formed hydrates with respect to the untreated system, and thus the viscosity and yield stress were also reduced.