Chemical Control of H2S for Unconventional Production: Performance Evaluation of Triazine and Non-Triazine H2S Scavengers in Challenging Environments

Abstract

Abstract Objectives/Scope Production of hydrogen sulfide (H2S) in O&G wells is a major issue for the industry due to concerns about toxicity, corrosion risks, and H2S takeaway limits that can result in well shut-in. One of the primary methods to manage sulfide production is to use H2S scavengers, with triazines being the most common. The scope of this work was to evaluate non-triazine alternative chemistries head-to-head with incumbent products under challenging high H2S and CO2 conditions. Methods, Procedures, Process In this study, monoethanolamine (MEA) triazine was tested head-to-head against five alternative chemical products in challenging lab conditions for accelerated product reaction (25 mol % H2S, 16 mol % CO2, balance CH4). Alternatives included an experimental triazine derivative product, an amine/hemiacetal product, a methyleneamine complex product, and two different methylene bis-oxazolidine (MBO) products. Lab performance testing was done by sour gas bubbling through product liquid at a controlled flow rate and ambient pressure and temperature, with constant H2S monitoring until breakthrough and scavenger exhaustion. Scavenger efficiency, process compatibility, pH of scavengers, and solid byproducts were evaluated. Results, Observations, Conclusions As expected, MEA triazine showed the highest raw efficiency for H2S consumption. However, under full exhaustion conditions, the standard triazine formulation produced high levels of solid byproducts that could not be dissolved or removed by various solvents, and it showed high pH before and after reaction demonstrating likely incompatibility with field water chemistries. Other products showed promising application-specific advantages: an experimental triazine derivative showed significantly less solids with good scavenging efficiency, and the hemiacetal and methyleneamine products showed almost no solid byproducts and lower impact on scaling risk from reduced pH. Surprisingly, both MBO products showed undesirable performance under high CO2 and H2S conditions tested, with extremely high insoluble solids production (> 6 lbs/gal) containing large amounts of carbon, oxygen, and sulfur. These results provide useful performance knowledge and guidance for optimized usage of H2S scavenger products in field applications, especially in challenging high CO2 production environments. Novel/Additive Information This study provided testing methods and novel conditions for triazine and non-triazine H2S scavengers, an area of critical importance for safe and economical management of sour O&G production. Our experiments showed key advantages and limitations of some alternative oilfield chemistries in terms of product efficiency, intractable solids production, and impact on scaling risk. These results underscore the importance of application-specific performance testing to validate chemical solutions for production reliability.