Laboratory study of hydrogen sulfide removal in slug flows in a high pressure crude oil loop

Hydrogen sulfide (H2S) undergoes decompression during petroleum extraction from oil reservoirs, during which a certain amount of H2S-scavenging liquid compound is added to absorb H2S in the pipelines. All experiments were conducted in a high pressure flow loop with a thousand feet of coiled tubing to simulate the horizontal section of the pipeline that runs along the ocean floor from the reservoir at 20 bar (1 bar=101.3 kpa) and room temperature with a 40 ppm H2S gas concentration in nitrogen (N2). This paper reports experimental results on the role of superficial liquid and gas velocities (0.2–0.5 m/s and 0.4–1.1 m/s) on H2S removal. All experimental tests were conducted in the slug flow regime, thus this paper also reports the effects of pressure and the distance to which this flow regime prolongs, which is correlated to the H2S removal efficiency. Results indicate that an increase in superficial gas velocity at low superficial liquid velocity decreases the scavenger efficiency while the opposite is seen at high superficial liquid velocity. In addition, an increase in pressure shifts the transition zones in the flow regime altering the scavenger efficiency.

► Laboratory study on slug flow in crude oil recovery with H2S was done. ► A maximum H2S removal efficiency of 80–90% was obtained. ► Long intermittent slugs create a higher probability for scavenger–gas interaction. ► As the pressure rises the transition from one flow regime to another shifts.