Oil Muds –Acid Gas

•Hydrogen sulfide (H2S) is a poisonous and dangerous acidic gas encountered in many formations and produced fluids. –It can quickly deaden senses and can be fatal even at low concentrations. –Personal protection and the appropriate safety measures should be taken any time hydrogen sulfide is suspected. •Oil and synthetic muds provide good protection from hydrogen sulfide corrosion and hydrogen embrittlement. –The continuous oil or synthetic phase of the mud is non-conductive and does not provide an electrolyte for the corrosion process. –If the mud has adequate wetting agents, the drill pipe will be preferentially oil-or synthetic-wet. –If the emulsion becomes unstable, and the mud water-wets the drillstring and casing, the corrosion protection provided by oil and synthetic muds will be lost. •Use personal safety protection and the utmost caution if hydrogen sulfide is encountered. –When hydrogen sulfide is expected or encountered, the oil mud alkalinity (POM) should be maintained at >5.0 cm3of 0.1 N H2SO4at the flow line with additions of lime. –Addition of Zinc oxide is also recommended •When hydrogen sulfide is encountered, the mud may require large additions of lime, emulsifier and wetting agents to stabilize its properties. –The mud should be watched for indications of water-wetting. •When Hydrogen Sulfide is encountered –Mud may turn black –The excess lime will drop rapidly –The mud should be tested for H2S with the Garret Gas Train and treated with scavenger and lime as required