Analytical Chemistry of Oil Well Treating Chemicals
Authors: Maddin C.M. , Lopp V.R. 
Published: December 2007

This paper was prepared for the Oilfield Chemistry Symposium of the Society of Petroleum Engineers of AIME, to be held in Denver, Colo., May 24–25, 1973. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor of the appropriate journal, provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
Chemical reactions in an oil reservoir are often an unknown and can only be simulated in the laboratory. One aid in correlating downhole reactions with lab tests is analysis of returned treating fluids from the reservoir. Analytical chemistry provides powerful tools for monitoring oil well treating chemicals. Visible absorption spectrophotometry provides methods for cationic, anionic and nonionic surfactants as well as for acrylate- and phosphorus-based scale inhibitors. It is useful for measuring sequestrant concentrations from their reactions with metal ions, alcohols by chromate reduction, arsenic-based acidizing inhibitors, nitrogen-based downhole inhibitors, polyacryldemide- and carbohydrate-based fracturing and inverting chemicals. Ultraviolet spectrophot metry is well suited to the measurement of cement-setting retarder concentrations and organic acidizing inhibitors. Gas-liquid chromatography measures nonreactive solvent concentrations and acetylenic alcohols used in acidizing inhibitors. Direct titrimetric analysis can be applied to organophosphonate scale inhibitors, iron (III) sequestrants such as NTA, reactive solvents such as the inorganic acids and EDTA. Titration of reaction products permits the measurement of cationic surfactants permits the measurement of cationic surfactants following their reaction with eosin and glycols after their reaction with periodic acid. Specific ion electrodes are particularly useful for the determination of fluoride.

Introduction
Chemical reactions during well treatment are studied in the laboratory under conditions simulating those existing in the well. Further insight is gained by analyzing returned treating fluids. During acidizing, how completely does the acid spend? How much inhibitor is left in the returned fluids? Were fluid loss additives present in designed amounts? Do the returned present in designed amounts? Do the returned fluids contain natural formation fluids also? These are examples of many questions which arise from treating oil or gas wells. It is our purpose here to emphasize the analytical chemistry purpose here to emphasize the analytical chemistry involved in monitoring treating chemicals in returned well fluids. We have not intended to be exhaustive in our treatment of the subject but wish to show the types of treating chemicals which have been monitored by visible and ultraviolet absorption spectrophotometry, gas-liquid chromatography, direct and indirect titrimetry, and specific ion potentiometry.