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The ABCs of H2S and mercaptans

Thursday, April 18, 2019

H2S Removal Technologies in Crude Oil

Once H2S testing has been performed (see blog posts on sampling and testing), it is necessary to mitigate its impacts…

Q2 Technologies Team

Experts in H2S Scavenging Solutions

With decades of combined experience, the Q2 Technologies team specializes in innovative hydrogen sulfide (H2S) scavenging solutions for the oil and gas, wastewater treatment, and industrial sectors.

Hydrogen sulfide (H2S) is typically a minor gaseous constituent found in crude, gas, and water, produced when sulfate-reducing bacteria (SRBs) break down organic sulfur compounds. Some fracking fluids can also react with rock formations under high pressure to generate H2S.

After performing H2S testing, it is crucial to mitigate its impact and bring crude oil to the desired specifications. Various mitigation techniques, such as mechanical/operational, biological, and chemical methods, are chosen based on factors like crude characteristics, H2S concentration, and economic considerations. To learn more about how we can help mitigate H2S in oil and gas reservoirs, check out this article. Hydrogen sulfide is not found in isolation but together with methane, hydrogen and higher hydrocarbons, and traces of nitrogen-, oxygen-, calcium-, and metal- containing species which complicate the selection of the most suitable H2S mitigation technique.

Managing H2S is a challenge at every stage of hydrocarbon production. Whether it is downstream, midstream or upstream, H2S mitigation techniques are implemented in order to preserve the environment, take care of workers, avoid corrosion and bad smells, and protect the value of refined products and physical assets. Even crude that has already been treated, might produce more H2S, as SRBs continue to digest the oil. Testing and treatment needs to be performed across the different stages of the production line. Learn more about effective solutions for handling toxic crude oil here.

Mechanical/operational H2S mitigation techniques

When natural gas is produced as a byproduct of oil extraction, operators will often vent or flare the gas. Flaring is the practice of burning gas that is deemed uneconomical to collect. Flaring is also used to burn gases that would otherwise present a safety problem. It is common to flare natural gas that contains hydrogen sulfide, in order to convert the highly toxic hydrogen sulfide gas into less toxic compounds. Venting is the direct release of methane gas to the atmosphere. During oil development, gas may vent to the atmosphere. The solids and fluids from the well go to the pits, while the gases are allowed to escape to the atmosphere, or they are flared.

Physically, stripping is less common alternative to remove H2S. The oil industry may use a nitrogen stripping system to remove the H2S. Nitrogen is an inert gas that prevents the flammable gases from igniting and thus eliminates the risk of explosion. Once the H2S has been stripped from the crude oil, it is usually flared. This process tends to create 5-10% barrel losses as other light compounds are stripped from the crude. This process is energy intensive and time consuming as it occurs in batches.

Membrane technology could offer a solution for the nitrogen transportation hassle that some sour crude treatment facilities require. In this case, compressed air is pushed through a set of polymer fibers or the membrane. As the compressed air moves through the membrane, the nitrogen molecules are separated from the other molecules.

Biological H2S mitigation techniques

These are used for water in wastewater treatment plants but not for crude oil at the moment.

Chemical H2S mitigation techniques

Additives to treat H2S in crude oil are very diverse and work in different forms. The reduction in concentration of hydrogen sulfide might follow the absorption route, such as alkanolamine, ammonia solution and alkaline salt solutions; and oxidation of H2S using iron oxide, activated carbon or a Claus process.

H2S mitigation technologies are not mutually exclusive and a combination of techniques might be used. On Table 1, we show the different chemical additives that are commonly used for H2S removal in crude oil.

Table 1.- Chemical Additives for H2S Removal in Crude Oil

H2S is present along the hydrocarbon production line. Figure 1 shows where in the upstream operations H2S scavengers are used as well as the places where H2S is found.

Figure 1.- Points where H2S scavengers are used in oil/condensate production operations.

Midstream operations link the upstream and downstream entities, and mostly include resource transportation and storage services for resources, such as pipelines and gathering systems. H2S scavengers are used for cargo treatment, before introducing the oil in pipelines and when it is being removed from storage units. It is key to meet H2S specs in order to transport crude oil and gas via pipeline.

Downstream operations are oil and gas processes that occur after the production phase such as refineries, petrochemical plants and retail outlets. Figure 2 shows the points in the downstream operations where H2S scavengers are used.

Figure 2.- Points where H2S scavengers are used in refinery operations.

Whether your needs to mitigate H2S are upstream, midstream, or downstream, we at Q2 Technologies can help you treat your crude oil and get more bang for your money. We are reliable suppliers of triazine-based scavengers that will bring your oil to specs. Similarly, we offer our high-performance non-triazine Pro3® scavenger and mercaptan scavenger ProM® to provide you with the best solutions for your H2S challenges. For more information, check out our common questions about H2S removal. Contact us today to discuss how we can serve you.

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FAQs

The optimal method for H2S removal depends on factors such as gas composition, H2S concentration, and operational considerations. Common methods include:

– Mechanical/Operational Methods: Flaring (burning H2S-containing gas), venting, nitrogen stripping, and membrane technology.
– Biological Methods: Used for wastewater treatment but not for crude oil.
– Chemical Methods: Using additives such as alkanolamines, ammonia solution, alkaline salt solutions (absorption), iron oxide, activated carbon, or Claus process (oxidation).

Commonly approved detection methods include:

– Electrochemical Sensors: These sensors measure the electrical current generated by the oxidation of H2S on an electrode.

– Colorimetric Detection Tubes: Glass tubes filled with a chemical reagent that changes color upon exposure to H2S, allowing for a visual concentration estimate.

– Infrared (IR) Sensors: Devices that detect H2S by measuring the absorption of infrared light at specific wavelengths characteristic of H2S molecules.

Each method offers varying levels of sensitivity, response time, and suitability for different environments.

Hydrogen sulfide is soluble in various solvents, including:

H2S can dissolve in alkanolamines, ammonia solution, and alkaline salt solutions, which are used in absorption-based H2S removal methods.

Neutralizing H2S gas involves mainly oxidation:

– Iron Oxide: Reacts with H2S to form iron sulfide and water, effectively removing H2S.
– Activated Carbon: Adsorbs H2S, sometimes with chemical treatments for added oxidation.
– Claus Process: Oxidizes H2S to elemental sulfur and water, commonly used in refineries.
These methods prevent H2S’s toxic and corrosive effects, depending on the application.

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