Hydrocarbon Transmission
Unconventional Oil Flow Challenges Require a New Approach
As more challenging unconventional oil continues to become increasingly available, advances in production, transportation, and storage are necessary. Unconventional oil typically includes heavy oil, ultra or extra-heavy oil (EHO), bitumen, and oil shale. Pipelines are still considered the most effective way to transfer crude oil from the producing field to the refinery. However, this has proven to be an expensive and inefficient struggle with unconventional oil due to its inherently high viscosity and low density.
Heavy Oil Mobility
Viscosity of bitumen can be greater than 100,000 cP. To optimize pumping capacity, pipeline operators apply strict oil viscosity specifications which vary according to the type of crude oil and the region where it is transported. A common viscosity specification is 350 cSt.
Viscosity is influenced by inherent components of heavy oils, such as long-chain linear alkanes, or paraffin waxes, and highly polar, high-molecular-weight asphaltenes known to exponentially increase heavy oil viscosity with increasing concentration. Density of heavy oil is another major challenge for pipeline transmission and is typically measured as less than 22° API.
Extra-heavy oil and bitumen density can be less than 10° API. Without external aid, viscosity and density of unconventional oils, especially at low ambient temperatures, make pipeline transportation economically impossible.
External aid can include viscosity reduction, application of friction/drag reducers, and in-situ partial upgrading. By reducing viscosity, the pressure drop in pipelines is lowered which allows for increased flow rates. As well, pumping costs are minimized.
For Oilfield Operators
For Midstream Pipeline Operators
- Lower oil viscosity, resulting in:
- Significantly lower amounts of diluent required to achieve pipeline specifications.
- Less heat required to mobilize unconventional crude oils in cold ambient temperatures.
- Increase API gravity of heavy oil, extra-heavy oil and bitumen, in many cases, to lower the density in situ.
- Reduce oil BS&W to help meet pipeline specifications.
- Reduce safety and environmental risks by lowering the amount of diluent used.
Case Study
China Heavy Oil Operator Increased Production Rates and Reduced Costs by Lowering Oil Viscosity 65% Using 40% Less Diluent with PhaseShift Bit-Flow™ Technology
Operator in China unable to produce heavy oil without use of diluent. In-situ heavy oil viscosity was 10,000-20,000 cP; crude oil density was 14° API gravity. Operator desired a reduction in mixing pressure, lower viscosity of the mixed oil/diluent produced fluid, and increased production rates.
PhaseShift Bit-Flow technology was applied downhole at 2,000 ppm continuous injection throughout trial. Two and four days after chemical injection, diluted, produced oil was sampled at the wellhead and tested for viscosity at 20°, 30° and 50°C.
- Heavy oil production increased by 22%
- Diluent amount decreased by 40%
- Viscosity of mixed produced crude reduced by 65% at all tested temperatures
- Injection pumping pressure reduced by 12%
- Increased crude oil quality
- Substantially reduced operating costs
- Increased revenue
- Increased operational efficiency
Pipeline Crude Oil Mobility
A Step-Change Approach to Enhance Pipeline Crude Oil Mobility
Precipitation of crude oil wax, asphaltene, and resin molecules can have serious safety, environmental, and financial consequences for both onshore and offshore oilfield production operations. With respect to flowlines and pipelines, under conditions where atmospheric temperature is less than the crude oil pour point, gelation of oil can occur, causing severe challenges, especially in cold ambient temperatures. This decreases the cross-sectional area for flow which in turn reduces flow rates and increases the pressure drop in the line.
Other problems can occur as asphaltenes can create emulsions in the formation. This can cause problems beyond separation operations through to sludge problems in storage tanks. Additionally, asphaltenes are typically the biggest factor causing high viscosity in heavy oils.
Paraffin content in some crude oils has been shown to be as high as 50% and deposition to occur anywhere in production systems, pipelines, and storage tanks.
PhaseShift Assur-Flow Technology Reduced Pour Point of Souedie Crude in Frigid Operating Temperatures
A Syrian oilfield operated in frigid winter temperatures experienced pipeline wax and asphaltene deposition. The problem was resolved with just 750 ppm Assur-Flow chemistry injected after the wellhead into the gathering lines continuously for three weeks. Wax content was lowered from 22 to 2%, which lowered the crude oil pour point by 53°C.
Hydrocarbon Dynamics created PhaseShift Assur-Flow™ technology for maximum oil flow in pipeline transmission. The step change in flow-assurance performance operators experience with Assur-Flow technology is centered on its unique ability to share its outer-shell electrons with those of hydrocarbon molecules aggregated together as a solid.
This unique electron sharing exhibited by Assur-Flow technology is effective at any stage of the wax-solidification process:
- Prior to wax precipitation
- During wax crystallization
- After wax gelling
Assur-Flow technology also controls asphaltenes through the same electron-sharing mechanism.
With this phase-shifting capability, Assur-Flow technology acts to:
- Liquefy and remove asphaltene and paraffin deposits and inhibits further deposition.
- Lower crude oil pour point.
- Lower crude oil viscosity.
- Reduce system pressure drop.
- Minimize pigging frequency and the risk of stuck pigs.
- Increase crude oil flow rates.
- Mitigate the possibility of under-deposit corrosion.
- Increase pump efficiencies and reduce pump wear and tear.
Assur-Flow chemistry is environmentally safe, non-toxic, non-corrosive to mild steel, and compatible with most elastomers found in oilfield equipment. It is easily applied with a high flash point (65°C) and low freeze point (tested to -50°C).
Case Study
PhaseShift Assur-Flow™ Technology Saved a USD 2 Billion South China Sea Oilfield Asset Where 80 Other Chemicals Failed
- After failed attempts with 80 different chemicals to treat severe paraffin and asphaltene blockage of production tubing and flowlines, a South China Sea offshore operator shut down operations of a USD 2 billion asset for over two years. Production had fallen from 11,000 to approximately 1,000 BOPD
- Operator unable to restart transit lines due to shear-stress challenges
- Crude oil pour point was 41°C and ambient sea floor temperature was 27°C
- High asphaltene content formed tight water-in-oil emulsions, elevating BS&W levels resulting in 15% discount to Brent crude pricing.
- Initial dosing of PhaseShift Assur-Flow technology at 400 ppm
- Subsequent maintenance treatment of 250 ppm was applied for five years
- Initial treatment eliminated wax and asphaltene deposition, restored daily production rates and salvaged the subsea flowline without costly and time-consuming replacement of the blocked section.
- Crude oil pour point was reduced to 32°C
- BS&W levels were dramatically reduced and crude oil was sold at highest market prices
- Flow assurance and dewatering solution secured flowline performance and resulted in improved, stable, reservoir lift
- PhaseShift Assur-Flow chemistry replaced requirements for other chemical treatments: pour-point depressant; demulsifier; anti-foaming additives; and wax solvents
- In all, an approximate 60% reduction in system downtime, flowline pigging, and shut-in treatments were experienced
- Regained an asset otherwise destined for permanent shut in or millions of dollars in pigging and repair costs
- Upgraded crude oil quality which eliminated the 15% discount (approximately USD 7 million/month) from the benchmark price
- Enhanced reservoir management and field economics through improved, stable, reservoir lift
- Increased platform operational efficiency through reduced chemical purchases
- Reduced safety and environmental risks from a lower offshore chemical footprint
- Lowered treatment costs by approximately USD 5/BBL