Enhancing Mercury Prediction

May 18, 2020   Written by Alessandro Speranza, Product Champion, PVT Technology

Just over a year ago KBC started a Research and Development (R&D) collaboration with INPEX Corporation and Heriot-Watt University, along with co-funding from the Oil & Gas Innovation Centre (OGIC). The objective of the collaboration was to generate new data for enhanced prediction of mercury solubility in oil and gas processing activities. The project lasted one year and I’m excited to provide a brief update on our progress as our results go for peer-reviewed publication.

Mercury contaminates crude oil and approximately five per cent of the total cost of oil and gas production facilities are attributable to mercury removal. In order to make our products safer industry mitigation measures typically involve incorporating costly design margins and mercury removal units. However, even with these measures in place there is still some uncertainty about whether the mercury reaches the right places to be removed safely or if it spreads across the entire plant, contaminating products and threatening the integrity of the facilities.

Mercury has a tendency to drop out of solution and accumulate in pipes, heat exchangers or separators. Being highly corrosive, it can cause leaks with associated fires and other damage. Not knowing how much mercury and where it is, adds a lot of expense. Identifying key areas to protect has historically been through experience, testing and rudimentary modeling. These historical solutions have meant that sometimes the whole economic basis of the project is at risk. Enhanced prediction of mercury accumulation across facilities would enable more effective selection and right sizing of equipment within safety margins, as well as more efficient operation and maintenance without compromising the wellbeing of personnel and the environment.

To this end, KBC has been actively researching experimental techniques, equipment and thermodynamic modelling for investigating the phase behavior of systems in the presence of mercury. If analytics can improve accuracy – which we believe it can – then engineers will be able to more effectively assess the risks associated with mercury contamination, thereby optimizing capital and operational expenditure. This, in turn, enhances engineers’ capability to operate the plant within actual productive limits, without compromising the safety of personnel and the environment.

The Multiflash® mercury model was originally developed in 1995 and has been routinely updated to incorporate new experimental measurements. Research like this continuously increases our understanding and further improves the scope of our predictive capabilities by providing data on new systems. This work shows that our model correctly calculates mercury partitioning over a wide range of conditions (temperature, pressure and systems). At intermediate pressure (P<7 MPa) and in the vapor region, we find that the solubility of mercury decreases with pressure. Mercury solubility then increases with carbon number for n-alkanes and is higher in liquid hydrocarbons than in carbon dioxide.

We know that the oil and gas industry is pushing the limits of operating envelopes. We are matching these new conditions by providing robust and accurate thermodynamic modelling to lower project costs and provide inside-pipe analysis of potential mercury corrosion hotspots.

Our focus on mercury modelling is not stopping here. Being able to confidently predict the amount and speed of mercury adsorption by pipes and processing facilities is fundamental for managing asset integrity risks. At a time when capital projects need to be designed more efficiently and operated leaner, these enhanced mercury prediction and control capabilities will be a key enabler for moving toward more autonomous systems.

Find out more about Multiflash advanced thermodynamics software.