Detection of solid asphaltene phase separation via viscosity monitoring at high pressure high temperature conditions

In this study, the viscosimetry method is used for detection of onset of asphaltene precipitation at HPHT conditions. The results are compared to other common methods (HPHT filtration, high pressure microscopy and light refraction). Five different live field oil samples are examined over a pressure and temperature range of 34.72 MPa to 65.90 MPa and 368.4 K to 408.4 K, respectively. A modified version of the Krieger (1972) equation is proposed and used for calculating the amount of precipitation based on viscosity measurements. The results show that the viscosimetry method is an accurate method for determining asphaltene content of crude oils with a gravity range of 18 to 40 American Petroleum Institute (API) degrees in a vast pressure and temperature range from reservoir to atmospheric conditions. The measured phase separation pressure at constant reservoir temperature for light to heavy oil samples ranged from 42.74 to 24.13 MPa, respectively.