A literature review of asphaltene entity, precipitation, and deposition, introducing recently models of deposition in the well column

Abstract

Organic precipitations are highly sticky and hard if some asphaltenes are present. This causes a deposition problem to occur when thermodynamic conditions are suitable for sedimentation in a wide range of production processes. This range may start from the porous media around the oil well and continue to the production pipes. Asphaltene exists in many light and heavy oil reservoirs, which often causes problems in the process of crude oil production. Asphaltenes have up to hundreds of carbon molecules in its structure which will be precipitated as a result of natural pressure drop, temperature changes and oil composition changes. In natural depletion, the main cause of asphaltene precipitation is the reduction of pressure. Due to the process of oil production from the well, which is accompanied by simultaneous reduction of pressure and temperature, this molecule is deposited to the tube wall during three stages of precipitation, growth and deposition, and causes flow obstruction. The precipitated asphaltene generated in the process of oil production from the reservoir closes the well and transmission lines. In the process of exploitation, the chock valves, separators, and other equipment in the way are blocked and broken. In refineries and petrochemicals, the presence of even small amounts of asphaltene results in a significant drop in the efficiency of catalysts and other additives. Therefore, before the reactions are performed, attempts are made to remove as much of these materials as possible from oil. In this paper, scientific literature related to the chemical structure and thermodynamic behavior of the asphaltene molecule has been investigated in order to provide clear overviews of the asphaltene precipitation and deposition, and the processes that lead to its occurrence in the well. Then, the precipitation and deposition of asphaltene in the well column and its effective factors are investigated.