Heavy crude oil (or simply heavy oil), including extra heavy crude oil (or simply extra heavy oil) and bitumen, is any crude oil that cannot easily flow to production wells under normal reservoir conditions due to high viscosity. As used herein, heavy oil is any viscous petroleum with an API gravity less than 22.3° (s.g. greater than 0.920), and extra heavy oil has an API gravity less than 10° (s.g. greater than 1.0), including waste oils, extra heavy oil, and bitumen. Extra heavy oil having a viscosity greater than 10 Pa-s (10,000 cP) is often called bitumen, e.g., natural bitumen from oil or tar sands. Heavy oil typically contains a relatively high proportion of high molecular weight (60 carbon atoms or more) non-paraffinic hydrocarbons, which may or may not include high levels of resins and/or asphaltenes. Waste oil includes oil-based drilling fluids and substrates from drilling, crankcase oil, machine oil, basic sediment and water (BS&W), process emulsions, and the like.
Almost 70% of present world oil reserves are comprised of heavy and extra heavy crude oils. Popular, but complex and/or inefficient, heavy oil production at the formation includes cold heavy oil production with sand (CHOPS), steam assisted gravity drainage (SAGD), water steam injection, toe-to-heel air injection (THAI), viscosity modifiers, cyclic solvent injection (CSI), vapor extraction (VAPEX), cyclic production with continuous solvent injection (CPCSI), and others, which achieve only temporary physical changes; as well as open-pit mining where the heavy oil has a high sand content. Some variants include injection of one or more treatment fluids, sometimes with the input of heat, into an injection well located proximate to one or more production wells, with flow from the injection well towards the production wells resulting in the release of hydrocarbons in the subterranean formation. Economic factors generally require such treatment fluids and processes to be efficient, and utilize relatively inexpensive materials. A common problem is that not all crude oil constituents, e.g., asphaltenes, are soluble in the treatment fluid, and they can drop out of the reservoir fluid and reduce the permeability of the producing formation.
The physical nature of heavy oils and waste oils also complicates their use. Properties such as flash point, viscosity, lower pour point, specific gravity, aromatics content and/or functional group content may render recovered oil unsuitable and/or challenging for various end uses. The process or processing equipment utilized to remove and/or upgrade the oil may require excessive amounts of energy, require a long treatment time, require large pieces of equipment not easily transported to a processing site, require excessive capital for non-economical equipment, or entail excessive operational risks or other hazards, all of which present significant challenges. Other issues include the quality of the oil obtained, which may not be suitable for pipeline transport without significant treatment such as upgrading or dilution. Numerous attempts have been tried to recover or remove a useful oil from heavy oils and waste oils with limited success. The industry has had a long-felt need to address the quantity of useful oil recovered, which may be very low relative to the total amount of heavy oil produced and/or processed.
For example, many oil upgrading processes are operated at high pressure, e.g., greater than about 10 or 20 atm (about 150 or 300 psig), may require the use of specialized and/or expensive catalysts that may require recovery and regeneration; and/or may also require a separate process unit to supply hydrogen for the upgrading process.
There exists a need for efficient ways and apparatus to upgrade heavy oil, in an environmentally responsible manner, and that can be operated at low pressure and/or with an inexpensive catalyst and/or without adding hydrogen and/or with a high upgraded oil recovery.