Crude oil, an unrefined petroleum product, does not “spoil” like perishable food. Its chemical and physical properties can undergo significant changes over time, impacting its quality and commercial value. These alterations are a form of degradation that affects how the oil is processed and used.
Crude Oil’s Stability Profile
Crude oil’s “degradation” refers to the alteration of its inherent properties, not spoilage. It is a complex mixture of hydrocarbons, sulfur, nitrogen, oxygen, and trace metals. Properties like viscosity, density, sulfur content, and acidity are key indicators; a significant shift in these characteristics constitutes degradation. Crude oil maintains stability under optimal conditions, but it is not entirely immutable to environmental factors.
Causes of Property Changes
Several factors can change crude oil’s properties. Oxidation, especially at elevated temperatures, triggers chemical reactions forming heavier molecules like asphaltenes and resins. Microbial degradation, from bacteria and fungi in oil-water interfaces, can metabolize hydrocarbons, increasing acidity or changing density. Temperature fluctuations contribute; extreme heat induces cracking or polymerization, while severe cold increases viscosity or causes wax precipitation. Ultraviolet radiation from light exposure can initiate chemical reactions, and water often promotes microbial activity and corrosion in storage systems.
Consequences of Altered Crude
When crude oil’s properties change, there are significant practical and economic implications. Altered crude reduces refining efficiency, as changes in viscosity, density, or increased sulfur content make refining more difficult and energy-intensive. Degraded crude often leads to lower product yields, meaning less valuable refined products like gasoline or diesel are produced, while less desirable byproducts, such as asphalt, may increase. Elevated acidity can accelerate corrosion in pipelines and refinery equipment, necessitating costly repairs. The accumulation of certain byproducts could pose safety risks during handling and processing, and the overall economic value of the crude oil diminishes considerably due to these issues.
Preserving Crude Oil Quality
Minimizing crude oil degradation during storage and transportation requires several strategic measures. Appropriate storage facilities, such as tanks limiting exposure to oxygen and light, help maintain oil integrity. Temperature control, involving stable, moderate temperatures, prevents chemical or physical changes. Removing water from the oil is crucial, as it inhibits microbial growth and reduces corrosion. Inert gas blanketing, using nitrogen, displaces oxygen in storage tanks, preventing oxidation, and regular monitoring through testing of crude oil samples allows for early detection of property changes.
Crude Versus Refined Products
The stability and “spoilage” characteristics of crude oil differ significantly from refined petroleum products like gasoline, diesel, or kerosene. Refined products are processed and often contain additives to enhance their stability for particular uses. While more stable in their intended applications, refined products can still degrade over time through oxidation, evaporation, or contamination. For crude oil, degradation primarily involves changes in its raw material properties, affecting its suitability for refining. In contrast, refined products can become unusable for their intended purpose when they “go bad,” such as gasoline losing its octane rating or diesel becoming contaminated with water or microbial growth.