Chemistry and resources of heavy oil and natural bitumen deposits

Supplies of conventional crude oil are diminishing; therefore, it is important to understand the reservoir characteristics of unconventional oil deposits. Reservoirs of unconventional deposits contain oils heavier than 20° gravity API and natural bitumens (tar sands and oil sands) are more viscous than 10,000 cp. The resources of these hydrocarbons are very large in the heavy oil of the Orinoco Oil Belt of Venezuela as well as in the natural bitumen of the Western Canada Sedimentary Basin of Alberta, Canada. In addition many small deposits of heavy oil and bitumen occur in the United States. Although the total resources of unconventional oil deposits are impressive, many environmental, economic, and technological factors affect their producibility. A thorough knowledge of the characteristics of reservoir rock includes the mineralogy of the host rock, the amount and type of clay minerals present, and the physical and chemical composition of the hydrocarbons. The presence of trace elements is also important to the utilization of these unconventional oil deposits. The attributes of each individual deposit must be studied and defined before recovery techniques can be modelled and before subsequent steps for upgrading refineries and transportation are taken.