Oilfield souring control – and the importance of Rawwater’s pressurised bioreactors
With the cost of oilfield reservoir souring control rumoured to consume as much as a third of typical production budgets, it is vital that operators are able to accurately assess whether souring is taking place in their fields – and to understand the level of souring, including how to treat it effectively.
Until only recently, investigations into oilfield microbiology involved simple sand and seawater ‘bottle tests’ or ‘up-flow’ sand packs at atmospheric pressure. Such tests, however, could not be used to draw accurate comparisons with actual downhole field conditions and biological activity, and could lead to inadequate or even unnecessary chemical dosing regimes.
All that changed, however, in 2006 when Rawwater commenced a pressurised bioreactor programme for oil reservoirs. Rawwater’s bioreactors are pressurised, corrosion-resisting columns that simulate the chemical and physical conditions of an oilfield reservoir environment. Operating at pressure and temperature conditions as found in water-flooded oil reservoirs, they are used to investigate microbiological souring, souring control and enhanced oil recovery under a wide range of field operating conditions and water injection chemistries.
Rawwater’s bioreactor columns range from 25cm to 400cm in length – with operating pressures from atmospheric pressure to 12,000psig, and temperatures from five degrees centigrade to just below the boiling point of water. At least 45 bioreactors are in daily operation at the company’s UK-based laboratories and, in October 2018, Rawwater accrued the equivalent of 400 bioreactor years’ worth of oilfield souring data, with information relevant to oil reservoirs across the globe.
Rawwater has built and operates what is widely considered to be the world’s largest and most advanced facility to study and evaluate microbiological souring in simulated reservoir conditions. Rawwater’s souring studies, including large-scale R&D joint industry projects (JIPs) and single client studies, have lasted from a matter of weeks to a number of years, and have tested seawater and oil samples from major fields globally.
The data harvested by Rawwater is truly unique in that it covers the complete range of operating conditions, including accurate chemistries at pressure and temperature. The creation of Rawwater’s pressurised bioreactor programme led to the birth of the ‘Seriatim’ series of work into oilfield souring and in excess of $10 million in funding for Rawwater to create its pressurised bioreactor dataset.