Theory and Measurements of Fates of H2S Scavengers

Abstract

The partitioning of the H2S scavengers/biocides, glutaraldehyde and acrolein, between the oil and the aqueous phases has been determined. The effect of the presence of salt on the partition coefficients has also been studied for salt concentrations from 0 wt% to 10 wt%. Acrolein was found to partition 47% to 66%, and glutaraldehyde 0.2% to 0.3%, to the organic phase, in a heptane/brine system. The effect of aldehyde concentration has been evaluated, from 2-10 wt% for acrolein and 5-50 wt% for glutaraldehyde. Theoretical analysis has been achieved, correlating the acquired experimental data and available literature data using the Elliott, Suresh, Donahue, equation of state 1 (ESD-EOS). INTRODUCTION Hydrogen sulfide can cause signifcant problems in carrying out production operations for, and transport of, oil and gas. These problems include: corrosion, injection well damage, scaling, poor gas quality and environmental and safety concerns. A comprehensive approach is best taken when understanding and remediating H2S in the oil field. This paper addresses an area important to designing H2S remedial treatments: the phase behavior of potential additives for H2S control. The topics of developing a general H2S decision strategy and calculating the mass balance of H2S in a reservoir, combining phase behavior modeling and reservoir simulation, are addressed in separate SPE papers (Kalpakci et. al. 1994, Thrasher et. al. 1994) Two major approaches to remediating H2S problems is through the use of biocides, in those cases where the sulfide is produced by sulfur reducing bacteria (SRB), and chemical reaction of H2S, i.e. scavenging. A class of compounds which can act as biocides and scavengers are the aldehydes. Aldehydes take advantage of the tendency of H2S to ionize and covalently attach to carbon atoms with partial positive charges. Many aldehydes may show an increasing tendency to partition into the hydrocarbon phase as the electrolyte concentration increases.

Identification and Persistence of 5,6-Dihydro-2H-pyran-3-carboxaldehyde in Aged Aqueous Acrolein Media

“…Our earlier analysis of acrolein in aging aqueous media reported on lab data from various titrimetric means, gas chromatography (GC), 2,4-dinitrophenylhydrazine and 4-hexylresorcinol colorimetry, m -aminophenol and J-acid fluorometry, infrared (IR), ultraviolet (UV), 1 H NMR, and differential pulse polarography methods that were used by other researchers. − Transformations of acrolein into soluble byproducts were seen by other researchers using UV spectroscopy. , Additionally, others, using UV and NMR spectra, identified the 5,6-pyran dimer and its UV λ max at 228 nm in aged aqueous media . Interestingly, aqueous acrolein when used as a sulfide scavenger in oilfield operations produces the sulfur analogue 5,6-dihydro-2 H -thiopyran-3-carboxaldehyde. − …”

“…Other than being an industrial raw material, acrolein has a significant history of worldwide use as a registered herbicide in agricultural irrigation systems, serving many kinds of crops. − These applications are generally always batch types into flowing waters, using strict application rates . It is also applied in oilfield waterflood production as a registered biocide for the control of corrosive aerobic, anaerobic, and sulfide-reducing bacteria for both batch and continuous applications in produced waters which undergo subsurface re-injection, as well as for squeeze-batch applications into wellbores. − Under similar conditions, acrolein is used as a hydrogen sulfide scavenger to reduce fouling and corrosion. − The produced treated water containing any byproducts is usually re-injected back into the formation.…”