Most oilfield production systems need to tackle one or more problems of organic scales, waxes, asphaltenes, soaps, emulsions and hydrates, all of which can affect the performance of process separation equipment, either by fouling and or the production of off-specification oil, gas and water.
Where such problems exist, it is essential to perform on-site fluids characterization surveys across the entire system. This approach will help to identify and understand the root causes of why a production system generates various flow assurance problems.
For any new field development, it is recommended that on-site fluids and gas characterization work be carried out during appraisal well tests. This work will define the physical and compositional characteristics of oils that will identify the oil type and its propensity for the formation of organic scales and/or gels, providing vital data for the input into a full front-end engineering design (FEED) study.
Scale prediction and mitigation
It is considered that scale-related problems are responsible for a significant portion of the total production chemistry costs for individual operators. These are generally in the form of mitigation costs. In addition, though difficult to quantify, many well losses are attributable to scale-related problems that effect the overall cost of a barrel of oil.
The likelihood of scale formation can be predicted by geochemical computer modelling. We have adopted a step-wise approach to scale management with a view to minimizing the impact of scale at the lowest cost. Typical studies will look at avoidance, prevention and removal.
Soaps and emulsions testing and mitigation
To promote emulsion breaking and oil-water separation, efficient processing is essential from an environmental standpoint and also in the production of "on-spec" export quality crude oil, in a cost-effective manner. Incorrect treatment can lead to the creation of emulsions, interface sludges, wet oils, and poor quality produced waters.
The John Crane team can diagnose such problems, set up monitoring programs, and determine the most effective operational and chemical treatment solutions, for control and mitigation of problems caused by such emulsion separation, naphthenate sludges, and schmoo.
Wax, asphaltene and naphthenate testing and mitigation
Depending on the individual crude oil chemistry and operating conditions within the process stream there is a risk of organic scale deposition. Such organic scales manifest themselves as waxes, asphaltenes, schmoo, or even soaps (often referred to as calcium naphthenates and sodium carboxylate emulsions). The formation of these products can cause the under-performance of a production by:
- Asphaltene or wax-stabilized emulsions and interface sludges, with off-spec produced water qualities
- Fouling of process equipment, thereby reducing efficiency
- Solids deposition in flowlines and pipelines, leading to flow restrictions and even line plugging
- Subsea and surface lines fluid ‘pumpability’ and restart problems due to gel formation
- Storage tanks bottom sludges and 'bad oil' causing reduced export oil storage capacity
- Formation of hard-to-remove composite scales in pipelines
For new or existing fields, our laboratory-based simulation test apparatus can be used on live or stabilized oils to measure parameters such as their propensities to form naphthenic acids (CaN), total acid number, wax deposition tendency, pipeline restart pressure and asphaltene flocculation points.
Hydrate prediction, testing and mitigation
Under the right conditions, gas hydrates can form in a matter of hours, potentially blocking pipelines and causing significant flow assurance difficulties and severe HSE concerns. Deepwater developments are particularly prone to entering the hydrate formation conditions where significant sub-cooling is experienced during shut-in conditions.
Without correct mitigation strategies such as temperature maintenance or chemical inhibition, hydrate slurries can completely block pipelines, potentially costing the industry millions of dollars each year in lost production and even injuries to personnel as high pressure blockages are freed. In general, our hydrate prevention strategies include:
- Maintaining the temperature above the hydrate formation temperature through pipeline insulation and external heating
- Suppression of the hydrate freezing point with thermodynamic inhibitors such as methanol and glycol
- Inhibition of hydrate crystal growth with kinetic inhibitors or anti-agglomerate inhibitors
- Hydrate prediction is accurately achieved through thermodynamic modelling and laboratory testing, both of which are well established within the industry
Pipeline integrity monitoring programs
Microbiologically influenced corrosion (MIC) is often a cause of pipeline failure and known to have a significant impact on safe and efficient operations by corrosion of steel, disintegration of concrete or the production of toxic and corrosive hydrogen sulphide (H2S) gas, resulting in costly production shutdowns.
Our team has experience in corrosion control, fouling and mitigation, particularly when it comes to MIC issues and uses customized equipment to monitor microbiological activity within the system. The resulting microbiological data, physico-chemical properties, pigging solids and biocide residual analysis provide an overall status of the system which is essential before an appropriate mitigation or remediation strategy can be applied.