Wax, Asphaltenes, Pour Points
Wax Precipitation
Wax deposition in pipelines and risers is an ongoing challenge to operators, and can have a significant effect on oil production efficiency. Build-up in pipelines can cause increased pressure drops, resulting in reduced throughput and thus reduced revenue. In more extreme cases, pipelines/processing facilities can plug, halting production and leading to potentially huge losses in earnings.
Pigging to remove wax from a subsea transfer line
As a result of increasing understanding of the problems of wax deposition, there are now successful preventative solutions, including chemical treatments and hot oiling.
For wax, the cloud point temperature - or wax appearance temperature (WAT) - is commonly measured in laboratories, and this traditionally used in developing and/or validating wax models. However, the WAT is not an equilibrium point; wax appearance is a kinetically-controlled nucleation process, and as such can be influenced by many factors, including temperature, temperature gradients (e.g. wall cooling), cooling rates and availability of nucleation sites (e.g. small particles). This means that quite different WATs may be observed for the same oil depending on experimental procedure.
Furthermore, when determining the wax phase boundary at pipeline conditions, the common practice is to measure at atmospheric pressure, and then apply the results to real pipeline conditions. However, this neglects the effect of pressure and associated fluid thermophysical/compositional changes, which can lead to unreliable results.
In addition to standard methods such as visual and ASTM Cloud Point, at Hydrafact we have developed a number of reliable in-house methods for studies of heavy hydrocarbon solids deposition in crude oils, including novel QCM and cold finger techniques.
Wax technical studies we offer include:
- Wax appearance and disappearance temperatures (WAT/WDT)
- Wax formation/dissolution rates
- High pressure studies
- Wax inhibitor performance assessment
Wax appearance and wax disappearance temperature (WAT and WDT) measurements using novel in-house QCM detection methods
Asphaltenes
Asphaltene deposition can present a major flow assurance challenge. Deposition can occur in various parts of the production system including well tubing, surface flow lines and even near the wellbore. The conditions of asphaltene deposition are controlled by factors such as pressure, temperature, composition and flow regime. Asphaltene deposition and fouling of flowlines/facilities can greatly reduce productivity and increase operational costs through the requirement for frequent chemical treatment and removal of deposits.
Hydrafact have previously been active in the modelling of asphaltene deposition in crude oils, and we are currently expanding our asphaltene measurement capabilities. At present, we offer ASTM asphaltene content determination (ASTM D 6560) and visual studies of asphaltene deposition at high pressure conditions.
Pipeline asphaltene fouling
Pour Point
Knowledge and control of the pour point of hydrocarbon fluid - i.e. the temperature at which it ceases to flow - is a vital in designing production systems. High pour points usually occur in crude oils that have significant paraffin content; these paraffins (or waxes) will start to precipitate as temperature decreases until at some point they accumulate to such an extent that the fluid can no longer flow. High pour points are common to heavy oils, but the phenomenon can also occur in light oils.
Pour point studies we offer can include:
- Pour point determination by standard (e.g. ASTM D-97) and novel in-house (high-pressure) methods
- Assessment of pour point depressants
