Asphaltenes: The Cholesterol Of Petroleum

Abstract

#Presently with Saudi Aramco, Dhahran, SAUDI ARABIA Abstract Asphaltene precipitation and deposition has been recognized to be a significant problem in oil production, transmission, and processing facilities. The precipitation of asphaltenes is caused by a number of factors including changes in pressure, temperature, chemical composition of the crude oil, mixing the oil with diluents or other oils, and during acid stimulation. The precipitated asphaltenes reduces the permeability of the reservoir near the wellbore region causing formation damage and can plug-up the well-bores and well tubings. Deposition of asphaltenic organic scales leads to operational problems, safety hazards and an overall decrease in production efficiency, thereby increasing the cost of oil production. This paper presents a review of the important factors which affect asphaltene precipitation in petroleum reservoirs and in processing facilities. The nature and characteristics of asphaltenes in the crude oil and their molecular and colloidal properties are discussed. A description of the asphaltene deposition problem manifestations in the reservoir, well bores and well tubings, processing and transportation equipment is presented. Current research work in this area is also discussed. Introduction Miscible and immiscible flooding of crude oil reservoirs by light hydrocarbon gases, carbon dioxide and other injection gases has the potential for enhanced recovery. The flooding process however causes a number of changes in the flow and phase behavior of the reservoir fluids and can significantly alter rock properties. One such change is the precipitation of asphaltenes which can adversely affect the productivity of the reservoir during the course of oil recovery. Precipitation of asphaltenes can cause formation plugging and wettability reversal which can lead to reduced recovery efficiencies. In many cases, the precipitated asphaltenes can plug up the well tubing or can be carried to the well head and downstream separators causing expensive problems. Presently the asphaltenes are removed either by mechanical cleaning, chemical cleaning or reservoir condition manipulation. P. 169