Mercury in the offshore industry

06 October 2009

Almost all oil and gas is found within the tiny spaces in sedimentary rocks, mainly sandstone and coarse-grained limestone. Bedrock limestone and sandstone, even though hard, also contain lots of pores that can contain water or oil or gas and other elements. Along with the gas and oil is a mixture of sand, silt & mud.

Heavy deposits

This sludgy silt mud is rich in heavier metal elements including Uranium and Mercury. Even the heavy Uranium can be suspended in the product as it is drawn from the well. However because mercury exists naturally in vapour form it is readily drawn along with the gas product.
Where these contaminants end up in the plant depends on many factors. Mercury as suspended vapour in the product will act in the same way as many other oil and gas products. During fractional distillation temperature and pressure changes allow vapours to condense into selected by-products.
In the same way, certain vessels on the rig or in the refinery may lend the right conditions for vaporised Mercury to condense back into liquid. Here it will form as either small globules or in small puddles when collected in the base of pipes and vessels.
In the case of the heavier elements suspended in the product, over time these form scale that can be egg shell like or brown or grey to whitish slate like layers or even layered variations like tree rings. This can develop to heavier deposits such as in the pipe cross section shown below. Here deep layers of tree ring type deposits are clearly seen. These deposits are formed of various elements that may contain heavy metals from Uranium ores to Mercury.
It is expected that the heavier elements from the sludge will be drawn up increasingly along with the product from older wells. These contaminants will be heavier metals like Uranium and Mercury. Recently on offshore installations when breaking containment in vessels, engineers have found deposits and small puddles of liquid mercury.
Mercury will evaporate and produce harmful vapours at relatively low temperatures. When a pressurised vessel that contains mercury droplets is depressurised, these vapours will start to be released.
When breaking confinement, even though a thorough gas test has proved there is no flammable gas present the vessel could still present a hazardous health risk from invisible mercury vapours.
ABLE Instruments offer the Jerome 405 portable Mercury analysers to determine the amount of Mercury vapour at any given location. The Jerome 405 is redefining the portable mercury vapour analyser market by way of significant performance enhancements and modern communication capabilities combined to create a new option for mercury spill detection and clean up analysis. It is considered the instrument of choice within the UK Oil and Gas industry, with many major oil companies and operators already taking advantage of its impressive capabilities.
With emphasis on health and safety at the forefront, reliable, fast and accurate mercury monitoring is vital when breaking containment of pressurised vessels containing hydrocarbons. Like its predecessor, the 431-X, the Jerome 405 utilises the industry proven, inherently stable and reliable gold film sensor technology and simple one button operation. The ergonomically designed handle, lighter exterior case and significantly lower detection capability (0.5 µg/m3) have reset the bar for portable and simple to use, low-level mercury detection instrumentation.
The Jerome 405’s sensor is highly specific for mercury, eliminating interferences common to ultraviolet analysers such as water vapour & hydrocarbons. It has a detection range of 0.5 – 999 µg/m3 with an accuracy of +/-10% at 1 µg/m3. Its response time is 12 seconds in sample mode and 2 seconds in survey mode. Its light-weight design (2.5kg) facilitates portability.
Additional applications and industries utilising the Jerome include mercury spill response and clean up, mercury exclusion testing, facility monitoring, source surveys, hazardous waste sites, fluorescent lamps disposal and recycling, worker safety, landfill monitoring, exhaust duct monitoring, plant environmental monitoring.
For further information, please contact Senior Product Manager, Dave Quelch on 0118 916 9407 or dquelch@able.co.uk.