Environmentally Preferable Smart Chemicals for the Oil and Gas Industry

Abstract

The oil and gas industry uses chemicals like acids and oxidizers as polymer breakers in hydraulic fracturing and triazene and glyoxal for H2S mitigation. In addition to serving the intended purpose, the chemicals cause secondary effects like non-specific oxidation, acid corrosion, precipitation and danger to oil field personal. We present novel, environmentally preferable chemistries to address various issues in the oil and gas industry. The studies using -Mannanase HT enzyme as polymer breaker showed breaking of cross-linked guar polymers at elevated pH (7-12) and temperature ( 175°F) ranges. Chlorophyll-treated cross-linked fluids showed more than 90% viscosity reduction. The chlorophyll worked efficiently up to 250°F, but the optimum temperatures are at 175 to 200°F. The chlorophyll treatment also showed a reduction of molecular weights of a linear polymer from 1,472,000 to 6,000. Further, H2S mitigation was addressed using a novel recombinant Sulfide Quinone Reductase enzyme (SQR). Functional studies conducted by treatment of soured brine and oil revealed 72% and 90% reduction in H2S concentration, respectively. The scavenger showed 75% reduction of sulfide in simulated mixed production samples containing a 30:70 ratio of brine to oil. Field testing of SQR showed a reduction of headspace sulfide from 400 ppm to 2 ppm and BS&W values less than 0.5%. These studies confirm that this novel biotechnology based environmentally preferable tools can be successfully used to break polymers and mitigate H2S in various systems. Further, the biotechnology solutions have several advantages such as meeting environmental regulations, reducing, or eliminating secondary effects and health hazards that are associated with current chemical treatments.

Scavenging Alkyl Mercaptans: Elucidation of Reaction Mechanisms and Byproduct Characterization

“…In the oil and gas industry, numerous sulfur containing species occur in produced fluids and gases. These species are derived from geological and biological processes and include H 2 S, alkyl mercaptans, carbon disulfide, carbon oxysulfide, alkyl sulfides, and alkyl disulfides. − Many of these species can present challenges for producers as they are required to be removed. − H 2 S is the most commonly encountered and troublesome contaminant and is responsible for corrosion in the oil and gas industry as well as the well-known health and safety concerns of this very toxic gas. , Often overlooked and overshadowed by H 2 S are the alkyl mercaptans, which also need to be removed to reduce the overall undesirable volatile sulfur content of the produced fluids and gases. Concentrations of mercaptans encountered in the produced oil and gas wells can vary; however, it is most typical for total mercaptan concentration to range from 0 to 150 ppm although most cases will be on the lower end of this range (<20 ppm).…”