Environmentally Preferable Smart Chemicals Improve Production, Performance

Abstract

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper IPTC 20203, “Environmentally Preferable Smart Chemicals for the Oil and Gas Industry,” by Prasad Dhulipala and Melanie Wyatt, Baker Hughes, and Charles Armstrong, SPE, Solvay, prepared for the 2020 International Petroleum Technology Conference, Dhahran, Saudi Arabia, 13-15 January. The paper has not been peer reviewed. Copyright 2020 International Petroleum Technology Conference. Reproduced by permission. The oil and gas industry uses acids and oxidizers as polymer breakers in hydraulic fracturing, and triazene and glyoxal for hydrogen sulfide (H2S) mitigation. In addition to serving their intended purpose, however, these chemicals cause secondary effects such as nonspecific oxidation, acid corrosion, precipitation, and danger to oilfield personnel. This paper describes studies that confirm that enzyme-based, environmentally preferable chemistries can be used to break polymers and mitigate H2S in various systems. The biotechnology-based solutions also offer advantages such as meeting environmental regulations and reducing or eliminating secondary effects and health hazards associated with current chemical treatments. Complexities of Current Chemical Treatments Fluid for hydraulic fracturing operations usually consists of 99% water thickened with guar or derivatized guar polymers. After the highly viscous fracture fluid is placed into the fracture, the fracture fluid needs to be brought back from the proppant pack, leaving the proppant without damaging the conductivity. This is accomplished by thinning the viscous fluid pumped into the fracture into a Newtonian fluid with a very low viscosity. Chemical breakers reduce the molecular weight of guar polymer by cutting the long polymer chain. As the polymer chain is cut, the fluid’s viscosity is reduced. Oxidative breakers react rapidly at elevated temperatures and cause the polymer to break prematurely, leading to loss of viscosity and reduction in proppant transport. Encapsulated oxidative breakers have seen limited use because of rapid degradation that causes premature reduction in fluid viscosity. Additionally, oxidizers react nonspecifically with any oxidizable material, including metals and formations. Oxidizers also pose a significant safety hazard. Reservoir souring is another major problem in oil and gas operations and is estimated to cost $120 billion per year. Reservoir souring occurs as a result of injecting sea water into hydrocarbon reservoirs, causing contamination of fluids with microbial population. Souring decreases production asset value and increases cost. In worst-case scenarios, it necessitates shutting off the wells. H2S scavengers provide a cost-effective alternative for removing H2S when amine treatment is not possible or cost-prohibitive. Triazines are water-soluble H2S scavengers that have been used successfully for many years. They add a minimum amount of nitrogen and reduce H2S instantly. Recent advances include development of greener quaternary amine compounds (quat) and non-quat products, better delineation of a triazine-based scavenger mechanism, formulation of newer combinations, and the invention of newer classes of scavengers such as unsaturated aldehydes, hydroxy alkyl or alkyl oxides, or azodicarbonamides that are resistant to pH and other changes in the reservoir.