Asphaltenes are heavy molecular substances found in crude oil that primarily consist of carbon, hydrogen, nitrogen, oxygen and sulfur. Operationally, asphaltenes are defined as substances of a carbonaceous material (such as crude oil or bitumen) that are soluble in toluene but insoluble in n-heptane. Asphaltenes are generally homogeneous/ dissolved in crude oil. Asphaltene precipitation only starts when there are disturbances, some of which include:
- A change in pressure and to a lesser extent temperature
- Mixing of incompatible crude oils
- Injection of gas as lift gas or for EOR purposes
- Application of incompatible chemicals (e.g. acids such as HCl or if CO2 is used for EOR purpose)
Precipitated asphaltene can remain suspended in the bulk oil phase. Otherwise, asphaltene deposition can occur in a number of areas, such as:
- Reservoir and near the wellbore area
- Downhole tubing of the production wells
- Any flow restriction in the oil transportation pathway such as SSSV, wellhead chokes, topside chokes and valves, etc.
- Flowlines and pipelines
- Separation vessels, pump strainers, heat exchanger, electrostatic coalescers
- Crude oil storage tank
Asphaltenes tend to be problematic in the oil and gas industry. Common issues encountered due to asphaltene deposition include fouling of heat exchangers, causing a reduced heat transfer efficiency, plugging of production tubing or formations, and blocking of pipelines. Further complications lead to loss in oil production thereby being a huge economic burden.
In order to manage asphaltene deposition, different mitigation techniques can be looked into. These mitigation techniques can be classified as either remediation options or prevention options.
Remediation options involve dealing with the asphaltene deposition. Some remediation options include:
- Mechanical removal methods
- Chemical soaking (using solvents to dissolve deposited asphaltene)
- Pigging of affected lines
On the other hand, prevention options involve dealing with the asphaltenes before asphaltene deposition. Some prevention options include:
- Asphaltene inhibitor/ Dispersant squeeze treatment downhole
- Asphaltene Inhibitor/ Dispersant continuous injection
The different mitigation techniques should be assessed for economic and implementation feasibility before being executed. Also, it is always better to follow a proactive approach to identify the risk of asphaltene deposition in an oil production facility and implement effective mitigation techniques before any problem is faced.
Veracity CCM™ is a powerful corrosion, chemical and flow assurance management tool that enables users to monitor the performance of their production systems and proactively identify any potential issues that may occur. Veracity CCM™ has been effectively used for flow assurance management by multiple clients and provided a platform where different types of data from a flow assurance management program could be stored and analysed holistically.
As for asphaltene management, Veracity CCM™ is used as a platform to store data such as SARA (Saturates, Asphaltenes, Resins, Aromatics) analysis, production rates (GOW), asphaltene inhibitor and dispersant injection rates, productivity indices, pressure drops and temperature levels. Such data is then trended, compared and analysed to identify risks of asphaltene precipitation and deposition in order to take action in a proactive manner and minimize downtime costs.
Flow assurance management through Veracity CCM™ also includes but is not limited to the management of the formation of scales , wax, hydrates and emulsion problems.