Experimental study on the influences of pressure and flow rates in the deposition of asphaltenes in a sandstone core sample

Abstract

Hydrocarbon production leads to the disturbance of several thermodynamic equilibriums including the destabilization of crude oil. Asphaltenes precipitation, aggregation and deposition inside the hydrocarbon reservoirs remains challenging issue due to the multiple factors controlling these processes. The influences of pressures and flow rates changes on the formation damage are assessed in a sandstone core sample during a set of experiments in this study.For this study, we have designed and assembled an experimental apparatus that can be used to study the asphaltene accumulation in porous media during oil and gas flow. We have used this apparatus to investigate the impact of pressure and flow rate on the asphaltene deposition process in a Berea sandstone core plug. The impacts of pressure were evaluated by injecting simultaneously crude oil and a mixture of 72% of methane and 28% of ethane at pressures of 4,500 psi, 3,570 psi and 3,150 psi, at a constant flow rate of 0.025 ml/min and temperature of 170 °F. This co-injection of crude oil and the gas mixture was also conducted at flow rate of 0.25 ml/min to evaluate the influence of flow rate on asphaltenes deposition in the core sample.The experimental results show that the permeability loss due to asphaltenes accumulation is more severe as the injection pressure approaches the minimum miscibility pressure (MMP) value. At pressures lower than the MMP, a process of asphaltenes accumulation and re-solubilization is observed. We also observed that an increase of flowrate from 0.025 ml/min to 0.25 ml/min prevents the deposition of asphaltenes, indicating that formation damage by asphaltenes is a slow process which can be prevented by increasing injection or production rates.