Mitigation of corrosion in the production and field treatment of crude oil & natural gas is of major importance to the oil industry to avoid the consequences of pipeline and equipment failure. Apart from the choice of materials of adequate resistance, corrosion inhibitors represent one of the best ways of providing effective protection and thus minimizing operating costs.
Oilfield corrosion inhibitors are designed to adsorb spontaneously on the surface of carbon steel equipment to form water impermeable barrier between the steel surface and the corrosive fluid. This adsorbed layer becomes eroded away from the steel surface due to the produced fluid traveling through the pipe.
To maintain an effective corrosion mitigation program, corrosion samples must be monitored and not allowed to fall below a minimum corrosion inhibitor concentration to maintain system integrity. There are three different method currently being used to determine inhibitor residuals.
ProChem’s utilizes the Wilson Analytical QuatBox Florescence Spectrophotometer to analyze corrosion inhibitor residuals from our customers’ facilities. This instrument provide our customers a highly accurate method for determining corrosion inhibitor residuals.
The QuatBox relies on the ability of the quat molecule to absorb and subsequently re-emit light at a certain wavelength that can be detected by an instrument. Most oilfield chemical have no fluorescence properties and those that do have limited fluorescence do not interfere at the same wavelength used for quat detection.
This method relies on adding a known amount of organic solvent to a known volume of water that contains corrosion inhibitor. The amount of inhibitor is then determined colormetrically with a spectrophotometer.
A High Performance Liquid Chromatography instrument is used to retain quaternized compounds on a column and then a solvent is used to remove the quaternized portion off the column and through a detector that measures the refractive index.
Only detects quaternized compounds with similar molecular weight. Quaternized corrosion inhibitors are usually mixtures of dozens of different carbon chain lengths, which alters the molecular weight and often do contain 30% unquaternized starting material that are not detected