Water Technology, March/April 2019

Sweet or sour Forecasting for crude oil environments How operators detect the causes of microbiological oilfi eld souring and accurately forecast whether a reservoir will support souring By Bob Eden Rawwater Engineering Company Limited n the world of oil extraction there is both sweet and sour crude Sweet oil usually contains less than 05 percent sulfur and oil classi ed as sour contains higher levels of sulfur which is typically in the form of foul smelling hydrogen sul de H2S gas Because hydrogen sul de is toxic and highly corrosive sour crude is more expensive to refine and requires the use of corrosion resistant topsides equipment costly sulfate removal plants SRPs and chemical dosing regimes Sul de is often found to occur naturally in oil due to the presence of native geological sul de hence whether as a result of geology or geochemistry sour crude is common across several oil producing regions of the world Yet while sour crude requires expensive treatments it is important to note that sweet crude having a very low H2S content is beneficial to the oil well environment and the processing equipment due to the reduced risk of damage to asset metallurgy and lower chemical treatment costs With the cost of oilfield reservoir souring control rumored to consume as much as one third of typical production budgets it is essential for operators to accurately assess whether souring is likely to take place in their fields and if so to understand the degree of souring in order to treat it effectively and economically Microbiological oilfi eld reservoir souring Successfully extracting oil throughout the life of a reservoir however requires additional downhole pressure And it is the process of pumping water often seawater containing sulfate into COVER SERIES OIL GAS WT I 16 Water Technology MARCH APRIL 2019