Identifying the Enhanced Oil Recovery Polymer in Sludge Formed in Water Lines

Sludge formation is extremely undesirable in the petroleum industry. Such sludge formation can be induced by different causes. The deposition of asphaltenes, waxes, inorganic salts, and even corrosion products is among the main causes of sludge formation. Therefore, it is very important to characterize the sludge to identify the causes of its formation and apply procedures to minimize or even avoid it. A protocol to characterize sludge in oil and water lines is already available. However, the role of the polymer used in enhanced oil recovery (EOR) on the sludge formation is already unknown. In this work, a procedure to identify the presence of the EOR polymer in sludge samples was developed. Two techniques to detect polymers were selected: size-exclusion chromatography (SEC) and multiangle light scattering (MALS). These techniques were validated by using polymer solutions at different concentrations. Then, synthetic sludge samples were prepared based on an emulsion of waxes and asphaltenes in toluene and brine, without and with different concentrations of polymers. The synthetic sludge samples were submitted to successive extractions with organic solvents to recover the residue, which was dispersed in water, filtered, and analyzed by SEC and MALS. The procedure was validated with synthetic sludge and applied to eight real sludge samples coming from a Brazilian oil field. The polymer was detected in all of them, and its concentration could be estimated. This kind of characterization makes it possible to identify the causes of sludge formation, preventing it and helping to reduce the environmental impact of the oil industry.