Heavy Oil Production Enhancement by Viscosity Reduction
- Patrick J. Shuler (ChemEOR) | Yongchun Tang (California Inst. of Technology) | Hongxin Tang
- Document ID
- Society of Petroleum Engineers
- SPE Western Regional Meeting, 27-29 May, Anaheim, California, USA
- Publication Date
- Document Type
- Conference Paper
- 2010. Society of Petroleum Engineers
- 4.1.2 Separation and Treating, 4.2 Pipelines, Flowlines and Risers, 2.2.2 Perforating, 5.4.10 Microbial Methods, 5.4.6 Thermal Methods, 2.5.2 Fracturing Materials (Fluids, Proppant), 4.3.4 Scale, 1.8 Formation Damage, 4.1.5 Processing Equipment, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex)
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This paper presents an evaluation of different chemical agents that can reduce dramatically the apparent viscosity of a heavy crude oil or a thick emulsion. The focus of this study is on methods to improve the production of heavy oils and very viscous emulsions such as are found in California, Canada, and Venezuela. This study identified several surfactant-demulsifier formulations that can reduce the viscosity of such heavy fluids by as much as 3 orders of magnitude.
If efficient chemical solutions are applied downhole to reduce produced fluids viscosity this offers an economical means to reduce the energy required to move the oil between the well to the surface facilities, thereby improving well productivity and reducing lifting costs. It is especially suited for wells that are producing fluids at colder temperatures (less than 150 °F) that have extreme fluid viscosities (from 10,000 to 100,000 cp); these may be reduced to 100 - 500 cp by gentle mixing with aqueous-based chemical treatment solutions. Wells with high hydraulic pressures, poor pump efficiencies, or excessive pressure losses in the facility gathering systems are good candidates for these treatments. Reducing these extreme viscosities will have benefits such as lowering the power consumption to lift the produced fluids and reduce system pressures. Chemical costs for such chemical treatments are less than a dollar a barrel of oil, and can be even less than $0.50 per barrel of heavy oil.
These same or similar chemical systems also may be beneficial for longer distance transportation of heavy oils, as pre-treatments for cyclic steam treatments, or as additives in the stimulation fluids applied in heavy oil wells. .
This laboratory investigation employed a unique novel viscometer that will measure accurately the effective dynamic viscosity of multi-phase liquids (emulsions) from several centiposes to thousands of centipoise. This instrument was developed to overcome the limitations of conventional laboratory viscometers to measure unstable emulsions that may separate during the measurement process.
The well production, lifting, and transportation of heavy oil and their viscous emulsions are a significant challenge for this more difficult hydrocarbon resource. Simply put, the viscous nature of these fluids restricts the practical rates of producing and moving heavy oil fluids, increases the energy costs required to accomplish this, thereby increasing the overall cost of producing this hydrocarbon.
Some of the major options available for decreasing the viscosity of such heavy oil and their produced emulsions include:
• Increasing the fluid temperature -- for example, steam injection, heated flowlines and pipelines
• Adding a hydrocarbon diluents of low viscosity
• Adding a treatment chemical
The focus of this paper is on the third option; to identify practical chemical treatment systems and application strategies to decrease heavy fluid viscosity. Practical systems means chemical treatment solutions that may be applied in a routine manner and also that can be performed at a reasonable cost. One study objective is to identify such candidate chemical systems that may be mixed into these very viscous fluids and accomplish the viscosity reduction effect at a chemical cost of approximately $0.50 or less per barrel of oil. The general technical objective is to create a final fluid viscosity that is in the range of 50 - 500 cp, which can represent 100 times lower or even more than the viscosity at initial conditions.
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