Compositions and methods for removing heavy metals from fluids

A method for concurrently transporting and removing a trace amount of volatile mercury in a CO2-containing natural gas stream extracted from a subterranean formation, comprising:

• obtaining a produced fluid containing natural gas and produced water from the subterranean formation and having an initial concentration of volatile mercury;
• transporting the produced fluid in a pipeline;
• and
• injecting a sulfidic complexing agent in an aqueous phase into the pipeline carrying the produced fluid to form a treated produced fluid;
• wherein volatile mercury in the produced fluid transported in the pipeline reacts with the sulfidic complexing agent to form at least one non-volatile mercury-containing complex;
• and
• wherein the treated produced fluid has a final concentration of volatile mercury lower than the initial concentration of volatile mercury.

A method for capturing gas phase elemental mercury from a hydrocarbon fluid in an overhead section of a crude oil distillation unit, comprising:

• contacting a hydrocarbon fluid having an initial concentration of gas phase elemental mercury with a sulfidic complexing agent in an overhead section of a crude oil distillation unit to form a treated hydrocarbon fluid;
• wherein the gas phase elemental mercury reacts with the sulfidic complexing agent to form at least one non-volatile mercury-containing complex;
• and
• wherein the treated hydrocarbon fluid has a final concentration of gas phase elemental mercury lower than the initial concentration of gas phase elemental mercury.