Micelles. Dynamic Optimisation.
Corrosion Inhibitor Analysis
Micelles as indicators of optimal injectionSurfactant based inhibitors are often at the frontline of internal corrosion protection strategies. The ability to accurately monitor the concentrations of active components of the CI formulation is of key importance in determining the diffusion of chemical throughout a production system.
However, traditional methods of analysis, such as methyl orange residuals, are prone to high levels of error due to interferent species within production systems, ranging from crude oil to competing amine chemistry. Time lapse between sample collection and analysis also leads to changes in water chemistry that can afford inaccurate results when shipping to dedicated analysis labs.
Micelles are aggregate species formed when surfactant components in a solution exceed a concentration known as the Critical Micelle Concentration, or CMC. When micelles are observed, a complete surface coverage has been reached and further surfactant addition has no additional inhibitory effect.
Corrosion Inhibitor Analysis
Micelles as indicators of optimal injectionSurfactant Based Corrosion Inhibitors
Corrosion inhibitors are widely used as a primary control mechanism in the oil and gas industry but need to be applied under optimal dosage regimes. Application of too little inhibitor can lead to increased corrosion risk and possible infrastructure failure, whereas too much chemical can lead to physical separation issues such as emulsions and increased operational expenditure.
These chemicals work predominantly using surfactant molecules to form a protective, reversible physisorption film on the pipeline wall.
Complete filming provides protection to the internal surface of a pipeline but the availability of surfactant is governed by a variety of factors such as chemical partition, the presence of alternative adsorption materials and chemical stability.
Defining Optimal Dose
Chemical corrosion inhibitors are routinely used to protect process equipment and pipeline infrastructure. It is difficult to establish optimum in-field dosage due to rapidly changing conditions. Underdosing leaves critical systems at increased risk of corrosion, while conversely injecting too high a concentration can lead to downstream issues such as emulsification.
Both situations can lead to time and resource-intensive remedial action greatly impacting on production costs.
Optimal dose is the point at which there is a sufficient concentration of CI present to film all surfaces of the production, and where there is some additional concentration in the system flow to replace surface-bound surfactant released by desorption and shear.
Micelles and Optimisation
A micelle is a nanoscale cluster of corrosion inhibitor dispersed in fluid. They form at the Critical Micelle Concentration (CMC).
In production systems, micelles form when every surface in the pipe structure has been coated, and the remaining inhibitor in the fluids starts to group together. At this point complete surface coverage has occurred and small reservoir of material in the fluid is present to replace any desorption of bound surfactant.
The ideal functional dose of corrosion inhibitors is therefore the point where micelles begin to form in a system, but before the population is too large to cause downstream production issues.
CoMic™ is the only readily available technology for accurately measuring corrosion inhibitor micelles in the field.
Surfactant based inhibitors are often at the frontline of internal corrosion protection strategies. The ability to accurately monitor the concentrations of active components of the CI formulation is of key importance in determining the diffusion of chemical throughout a production system.
However, traditional methods of analysis, such as methyl orange residuals, are prone to high levels of error due to interferent species within production systems, ranging from crude oil to competing amine chemistry. Time lapse between sample collection and analysis also leads to changes in water chemistry that can afford inaccurate results when shipping to dedicated analysis labs.
Micelles are aggregate species formed when surfactant components in a solution exceed a concentration known as the Critical Micelle Concentration, or CMC. When micelles are observed, a complete surface coverage has been reached and further surfactant addition has no additional inhibitory effect.
Maximum inhibition should be observed around the CMC since additional surfactant molecules lead to the formation of micelles and do not contribute to inhibition.
Factors Influencing CI Availability
Why Dynamic Monitoring Is ImportantAlthough production systems are constantly in flux, corrosion inhibitors are generally injected at a constant volume over long periods of time. Where changes are made to the injection rate, decisions are often made on the basis of old data or on that generated by high interference techniques that may provide inaccurate assessments of chemical availability.
The following factors have a role on the attrition of CI surfactant and its availability to protect systems. Regular assessment of the available surfactant within a system, by micelle analysis, can provide an excellent indication of the protective health of a system. CoMic™ is the only platform that can provide on-site analysis of micelle presence and optimised dose indicators.
Factors Influencing CI Availability
Why Dynamic Monitoring Is ImportantEquipment Failure
Chemical pumps and injection systems are complicated apparatus that are prone to mechanical fault.
Equipment failures and errors can lead to a complete or partial reduction in CI injection. CoMic™ has identified pump failures and umbilical injection problems in offshore fields, flagging problems to operators who were then able to take remedial action and ensure continued chemical injection.
See our Case Studies for a loss in CI due to pump failure, and how CoMic™ detected it.
Variable Water Cut
Formulated corrosion inhibitors are complex chemical mixtures. Partitioning of CI between the water and hydrocarbon phases is a complex equilibrium, highly dependent on the individual components of the formulation. System water cut will influence the available concentration of filming components able to bind to the pipeline wall.
CMC, the concentration at which micelles form, varies with water cut and is a useful monitor of available chemical in production water samples.
Production Solids
Various solids are routinely found in production water samples ranging from scale, wax and salts formed from corrosion.
Each solid forms a competing binding site for surfactant molecules and may prevent complete adsorption of chemical to the pipeline wall, resulting increased corrosion risk.
Each formulation of CI reacts differently with various solid types. CoMic™ allows the operator to assess the micelle population of systems and determine if increased solid production increases corrosion risk through chemical attrition.
See our Case Studies to see the effect of various production solids on formulated CI.
Chemical Decomposition
Individual components within formulated inhibitors are prone to different reactivity and may decompose over time.
Filming components can degrade to forms which have no binding affinity but which still react in standard residual tests.
CoMic™ only measures components which are available as binding surfactants and can be used to determine if sufficient filming components remain present in production systems to provide protection.
Although production systems are constantly in flux, corrosion inhibitors are generally injected at a constant volume over long periods of time. Where changes are made to the injection rate, decisions are often made on the basis of old data or on that generated by high interference techniques that may provide inaccurate assessments of chemical availability.
The following factors have a role on the attrition of CI surfactant and its availability to protect systems. Regular assessment of the available surfactant within a system, by micelle analysis, can provide an excellent indication of the protective health of a system. CoMic™ is the only platform that can provide on-site analysis of micelle presence and optimised dose indicators.
To find out more about the exciting developments in CoMic™ technology, get in contact.