Characterization of ethoxylated alcohols in friction reducers using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Abstract

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) provides detailed information for the analysis of ethoxylated alcohols and polymers. In this study, five friction reducers used in commercial hydraulic fracturing processes were analyzed in their as-received form to identify their ethoxylated alcohol content. The friction reducers were then subjected to lab-simulated downhole conditions. Characterization of friction reducers before and after being subjected to reactive conditions can provide fingerprints associated with produced oilfield waste for source apportionment and information on the stability of these key hydraulic fracturing additives. Five different industrially used friction reducers were analyzed for their ethoxylated alcohol content using MALDI-TOF-MS. Three different matrices were assessed for optimal response: α-cyano-4-hydroxycinnamic acid, 2,5-dihydroxybenzoic acid, and 2,5-dihydroxybenzoic acid with 2,2,2-trifluoroethanol (2,5-DHB + E). Reaction times, temperatures, and sample matrices (deionized water, produced water inorganic, produced water, and produced water + shale core) were varied to assess changes in molecular weight distribution and polydispersity of the ethoxylated alcohols relative to their as-received content. A preference for the 2,5-DHB + E matrix was observed. The friction reducers were found to contain ethoxylated alcohols with carbon chain lengths of 12 and 14 with degrees of ethoxylation ranging from 6 to 18. Upon being subjected to 100°C for 24 hours, the ethoxylated alcohols tended to polymerize further, returning higher average molecular weights. Less polymerization was seen in more complex matrices, as supported by dispersity calculations. Ethoxylated alcohol content was effectively determined in friction reducers using MALDI-TOF-MS. Although this is not a new technique to characterize ethoxylated alcohols, it has proven to be a quick and effective way to determine ethoxylated alcohol content in friction reducers in complex oilfield matrices. This technique can be used as a rapid and straightforward way to determine ethoxylated alcohol content in friction reducers and hydraulic fracturing wastewater for fingerprinting.