The recovery or production of hydrocarbons (oil and natural gas) or other fluid resources (e.g., water) to the surface from a hydrocarbon- or water-bearing subterranean formation can be accomplished through a wellbore or drilling of an open hole into the earth to access fluids in such formations. Hydrocarbon bearing formations, and therefore the wellbores, vary in depth below ground surface, and may be less than 100 feet to over 10,000 feet deep. Wellbores may be arranged vertically across the thickness of the formation, or drilled vertically to reach the formation and then extend horizontally within the formation for some distance. In general, the temperature profile of the formation increases with depth. Primary recovery is the phase of oil extraction where no water or gas flooding is needed or used to produce oil from a subterranean formation. Secondary recovery is a recovery improvement process that generally involves water-based flooding or gas flooding. Tertiary recovery, also known as Enhanced Oil Recovery (EOR) represents a variety of technologies used to further oil extraction efficiency from an oil field. EOR has been applied in the oil field as generally only 20% to 40% of oil is recoverable using primary and secondary techniques. Certain heavier and more viscous oils may have no primary recovery phase and only secondary or EOR methods will result in recoverable oil from a formation. EOR methods generally fall into thermal, chemical, or miscible methods. Thermal methods involve large energy inputs using steam, hot liquids, or combustion materials. Chemical methods involve injecting acid, alkali, surfactant, or polymer flooding, and combinations thereof. Miscible methods involve injecting large quantities of hydrocarbons, solvents and gases, such as carbon dioxide, or supercritical fluids. As such, thermal and miscible methods can be costly and only applicable for larger production wells. EOR projects have been conducted in sandstone formations using thermal methods followed by chemical processes. An EOR process used in medium and light oil recovery in sandstone formation is CO2 flooding. EOR in carbonate reservoirs has used miscible gas (e.g., CO2 flooding) with chemical methods with polymer flooding.
USPTO Backgrounds
USPTO Backgrounds