Calculating Asphaltenes Precipitation Onset Pressure by Using Cardanol as Precipitation Inhibitor: A Strategy to Increment the Oil Well Production

Abstract

Asphaltenes precipitation is considered a formation damage problem, which can reduce the oil recovery factor. It fouls piping and surface installations, as well as cause serious flow assurance complications and decline oil well production. Therefore, researchers have shown an interest in chemical treatments to control this phenomenon. The aim of this paper is to assess the asphaltenes precipitation onset of crude oils in the presence of cardanol, by titrating the crude with n-heptane. Moreover, based on this results obtained at atmosphere pressure, the asphaltenes precipitation onset pressure were calculated to predict asphaltenes precipitation in the reservoir, by using differential liberation and refractive index data of the oils. The influence of cardanol concentration on the asphaltenes stabilization of three Brazilian crude oils samples (with similar API densities) was studied. Therefore, three formulations of cardanol were prepared: The formulations were added to the crude at 5:98, 1.5:98.5, 2:98 and 4:96 ratios. The petroleum samples were characterized by API density, elemental analysis and differential liberation test. The asphaltenes precipitation onset was determined by titrating with n-heptane and monitoring with near-infrared (NIR). The asphaltenes precipitation onset pressures were estimated. The envelope phase of the crude oils were also determined by numerical simulation (pipesim). In addition, supported in the downhole well profile and a screening methodology, the adequate artificial lift systems (ALS) for the oils were selected. Finally, the oil flow rates were modelling by NODAL analysis production system in the SNAP software. The results of this study show the refractive index for each sample, and the predictive pressure to asphaltene instability. The asphaltenes precipitation onset of the crude oils were 2.06, 2.30 and 6.02 mL of n-heptane/g of oil. The cardanol was an effective inhibitor of asphaltenes precipitation, since it displaces the precipitation pressure of the oil to lower values. This indicates that cardanol can increase the oil wells productivity.