Hydrogen sulfide (H2S) scavengers are used to reduce the total well operation cost of working with H2S by reducing the need for gas sweeting equipment, manpower costs for H2S monitoring, fines due to out of specification production and liability due to H2S release. Commonly used H2S scavengers such as triazine and glyoxal have limitations in different applications. When overspent, triazines can form difficult to remove solid deposits. The prescence of triazines in crude oil can lead to the formation of amine hydrochloride salts that cause corrosion in refinery operations. Glyoxal based H2S scavengers are acidic and can cause corrosion especially in stagnant pipelines containing oil and water. In this paper laboratory and field results are provided on new H2S scavengers that are both non-amine and neutral pH. The applications that are examined are batch tower applications and inline injection.

Acidithobacillus ferrooxidans (A. ferrooxidans) is a gram-negative, acidophilic and chemolithotropic bacterium that utilizes oxidation of ferrous ions, hydrogen and reduced inorganic sulfur compounds, such as H2S, as sources of energy. Sulfur oxidation in A. ferroxidans is catalyzed by the Sulfide Quinone Reductase (SQR) enzyme system. The initial step of the SQR reaction is the oxidation of sulfide to elemental sulfur or to the less-toxic polysulfide. SQR can eliminate the accumulation and persistence of H2S in waters and reservoirs contaminated with sulfur-reducing bacteria (SRB). H2S causes reservoir souring, corrosion problems, and presents a danger to oilfield personnel because of its inherent toxicity. SQR does not destroy the SRBs present in the system, but it does catalytically attack the H2S and H2S precursors produced by SRBs. As an enzyme, SQR is an environmentally compliant, sustainable, and catalytic solution to the growing H2S problem. The Sulfide Quinone Reductase enzyme (Bio-molecular scavenger-BMS) was evaluated for its efficacy as an H2S mitigation strategy. The evaluation showed that the BMS could convert H2S from different sources in liquid and gaseous phases in to nontoxic polysulfide. The studies also showed that the BMS-based H2S mitigation reactions did not cause corrosion, and the formulations are compatible with oilfield metals, plastics and elastomers.

Sour production from offshore and land-based wells causes hydrogen sulfide (H2S) release during downhole and topsides operations. Improper handling of H2S can lead to serious environmental and safety concerns as well as numerous corrosion and compliance issues. Consequently, H2S can add significantly to the total cost of well operations. The application of efficient H2S management technologies can reduce environmental and safety concerns, enable the use of lower-cost materials, and comply with H2S specifications. To remove H2S from mixed production applications, several chemistries are commonly used. The most common are triazines, glyoxal, and metal-based chemistries. Although each can be effective to a certain extent, these technologies have issues with efficiency or they can create serious side issues. The reaction of triazines with H2S in mixed production is highly inefficient and it creates scaling. Glyoxals suffer from poor efficiency, thermal instability, and corrosivity. The metal-based chemistries are the most efficient in mixed production, but in certain application regimes they can create serious solids and emulsion issues. These challenges can increase CAPEX and OPEX as well as lead to significant downtime and lost production. To overcome issues with currently used chemistries in mixed sour production, extensive research was conducted to identify chemistry that would efficiently remove H2S while minimizing negative side effects. Systematic evaluation was performed for a series of chemistries to compare the scavenging efficiency, with a special emphasis on mixed production systems. Focus was also given on studying the associated side effects like emulsification tendency, scaling tendency, etc. to ensure the chemistry had no/minimal side effects seen by the more conventional chemistries. A high-throughput lab technique is presented that was designed to mimic scavenging tendency in sour mixed production environment. A continuous gas flow testing technique that helped study the reaction kinetics is also described. Laboratory and pre-field results proved the efficacy of the new non-MEA, non-triazine chemistry in mitigating H2S in upstream, midstream and downstream applications while being especially efficient in mixed production systems. Laboratory testing proved the chemistry to be highly efficient compared to triazine in mixed production systems. Results also indicated the chemistry is non-emulsion forming and has very little scaling tendency. Testing conducted in the field demonstrated that the new chemistry cost-effectively removes H2S and meets the operator specifications. The novel, non-triazine scavenger technology has significantly better performance than triazine, no emulsion concerns, acceptable HSE, non-corrosive effects, and less downstream concern than MEA triazine or metal-based scavengers. The new and differentiated chemistry reduces CAPEX and OPEX, drives productivity, improves reliability and reduces non-productive time.

Currently used scavengers in mixed production applications can have issues with poor efficiency and thermal stability (triazines, glyoxal), scaling tendency (triazines), corrosivity (glyoxal), and emulsification (metal-based scavengers). Research was conducted which resulted in a new scavenger that avoids negative side effects while maintaining efficient performance over a wide range of applications. The application of this scavenger into mixed production can avoid or reduce the need for H2S removal post-separation, thereby reducing overall cost. The development and field application of a new Hydrogen Sulfide (H2S) Scavenger in oilfield mixed production applications is presented. Several field applications will be discussed comparing the overall performance of this new H2S scavenger with existing technologies. Field application results will show that this novel scavenger avoids issues with currently used scavengers including poor efficiency, corrosivity, scaling, and emulsification. This new H2S scavenger technology is suitable for both surface and downhole injection. It will be demonstrated how removing H2S upstream in mixed production can save overall treatment cost.

Accurate and in-time monitoring of corrosion inhibitor (CI) residual concentration is a key factor in asset integrity management for oil and gas operations. However, the natural variability of CI residual due to field conditions is usually convoluted with the error introduced by sampling and analytical techniques. In traditional analytical techniques, it is typical to encounter error of over 100%. Recently, a novel nanoscale technique (TrueDetect™, TD) was developed to accurately measure CI in the field. This technique is based on a proprietary spectrometry technique and allows quick and accurate analysis of CI residual at the ppm level. The portable instrument allows field samples to be analyzed on-site without the need for shipping them to a centralized laboratory. In the current study, the TD technique was applied to analyze field samples from various fields. Moreover, the TD technique was capable of analyzing CIs at low dosages and could be used as a method to qualify CI products in the lab and in the field.