CASE STUDIES
Upgraded Oil Recovery from Heavy Oil Sands
Ahmed A. M. Algibaly Professor Faculty of Petroleum and Mining Engineering, Suez Canal University Petroleum Engineering Department
Introduction
A case study is simply the study of the particularity and complexity of a single case, coming to understand its activity within important circumstances. Thus, identifying appropriate strategies for the resolution of the ‘case’ while having the ability to weigh pros and cons of the remedial options and strategies, enabling you to recommend and present a rationale for the best resolution. Every engineer must have a tool as powerful as this one among their tool kit as they tackle the problems and challenges that they face, that is why we dedicated a section solely for presenting case studies that might be of great benefit or interest to you.
About nine heavy-oil sand reservoirs exist near Ras Gharib, in the western desert, Egypt. One of them is Assran oil field which is currently under development by Scimitar Oil Company. These oil sand reservoirs are good candidates for thermal recovery methods. In addition, oil spills on land may be another candidate for clean-up by thermal methods. Gulf war in 1991 resulted in the firing of more than 600 oil wells in Kuwait. The crude oil gushed from these wells and accumulated in desert low lands forming over 300 oil lakes of a total area of 49 km2. The amount of oil contaminated soils in the oil lakes and their peripheries was estimated in the range of 40 to 50 Million metric tons. Various oil extraction and soil remediation technologies were evaluated to find the most suitable solution for treatment of the heavily oil-contaminated soil and sludge. It appears that thermal desorption by retorting process is one of the most promising technologies to be suitable for oil lakes soils. The retorting process is based on heating the oil-sand mixture up to 500-600 OC in the vicinity of an inert gas under atmospheric pressure. A great deal of laboratory and field work has been done on oil extraction from oil-shales and tar-sands by this process. The objectives of the present study are: (a) To perform an experimental study that considers the process variables which govern the performance of the retorting
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March 2011
ECHO
process such as heating rates, operating pressures, specific properties of the soil matrix, etc. (b) To develop a mathematical model that can fit the experimental data and characterizes the oil produced during the retorting process. Pyrolysis Mechanisms The quantitative prediction of the thermally recovered oil and its quality by a pyroIysis mechanism is directly related to the economic evaluation of a retorting project. Three successive pyrolysis stages were identified for fuel formation at the combustion front during the in-situ combustion process. These stages were classified as oil volatilization, visbreaking, and coking.
“It appears that thermal desorption by retorting process is one of the most promising technologies to be suitable for oil lakes soils” Experimental program The experimental apparatus used in this study is schematically illustrated in Fig. 1. Experimental runs were carried out on model oil-sands as well as genuine oil-sand samples collected at different depths from bottom beds of the oil lakes.
