Triazine

Due to the dangers posed by the release of H₂S gas, quick removal of Hydrogen Sulfide during drilling is critical. The main application of Triazine in the oil and gas industry is to remove Hydrogen Sulfide. It can be added to the fluid immediately before pumping to improve its performance. In addition, Triazine can be used in surface or subsea pipelines, equipment, storage tanks and production water transfer flowlines.

Some of other industries which use Triazine are:

• Water treatment plants
• Lubricant manufacturing industries
• Production of chemicals (such as bactericides and algaecide)
• Pulp and paper production

Introduction to Hydrogen Sulfide gas

The release of hydrogen sulfide gas during drilling of sulfur-containing formations is a common problem in drilling operations. Hydrogen Sulfide, also known as sulfuric acid or sewage gas, is a Sulfhydryl compound that can be created during the drilling of sulfur-containing formations. Hydrogen Sulfide gas has a molecular weight of 34.08 and a specific gravity of 1.18 compared to air. H₂S is the lightest form of sulfur and has an unpleasant odor similar to rotten eggs that can be detected at concentrations below 0.5 ppm by smell.

Effects of H2S on drilling operations

During drilling in different oil and gas fields of the world, including the United States, Canada, Venezuela, Russia, China, and Middle East countries such as Saudi Arabia, Iraq, Oman, Egypt, and Iran, there is a possibility of H₂S gas release whilst drilling. The initial effect of H₂S release is threatening people’s health and safety of downhole and surface equipment. In addition, the release of H₂S might led to sulfur corrosion of the equipment, which is one of the most severe types of corrosion due to increase in the acidity of the mud, creating corrosive iron sulfide. In fact, the formation of iron sulfide, which is highly corrosive, and its adhesion to the steel surfaces of the equipment can increase the corrosion rate drastically and reduce the equipment’s durability. In addition, H₂S can react with steel as a catalyst or accelerator to produce hydrogen ions. In addition to the problems mentioned above, it should be pointed out that when Hydrogen Sulfide enters the drilling fluid, mud properties such as rheological, filtration, and density are affected. Also, regarding to the decrease in pH, the corrosiveness of mud for metal components increases exponentially

It is worth noting that H₂S liquefies at pressures as high as 350-400 psi. Therefore, H₂S usually remains in the liquid phase in the underground layers of the Earth. But when it gets close to the surface, due to the decrease in pressure and temperature, it faces a sudden increase in volume and turns into a gas.

Generally, Hydrogen Sulfide gas may enter the drilling fluid during drilling through the following ways:

• The release of existing H₂S gas trapped in the sublayers of the Earth
• The release of this H₂S gas from underground trapped water and oil which are contaminated with H₂S gas
• Activity of sulfate-reducing bacteria (SRB) that can grow in oilfield conditions (without air or oxygen)
• Thermal decomposition of drilling fluids containing sulfur

Drilling Fluid Treatment

In oil and gas drilling, each additive plays a specific role. Therefore, the appropriate selection of additives and the precise design of drilling mud are some of the main factors which drive the success of drilling operations. One of the main important additives of drilling fluids are H₂S scavengers such as Triazine. The required amount of Triazine in mud systems must be specified based on the injection environment’s condition such as quantity of H₂S content, pH and other properties. Technically, 2-10 ppm of Triazine can eliminate 1 ppm of H2S gas. Running pilot tests for finding optimized dosage of Triazine is highly recommended.