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Chemical EOR polymers are in general anionic, synthetic, acrylamide based co-and ter-polymers. Those polymers provide viscosity to water based system thanks to their high molecular weight (Mw) and the repulsions between the ionic charges. Uncoiling and entanglements are the two mechanisms linked to Mw and ionic repulsion.When a polymer is injected, different mechanisms will act on its chemical structure by chemical, mechanical, thermal, free radical modifications. The understanding of the resulting rheological properties of the modified PAM is very important since it can change the control over the mobility ratio when it propagates downhole in the reservoir. Various lab experiments can be performed to predict those changes over time. In particular, the intrinsic viscosity is a convenient way of reaching the dimension of the macromolecule in a given solvent and at a given temperature but is time consuming.In this publication, a new and efficient capillary rheology technique is presented allowing measuring the bulk solution rheology and intrinsic viscosity of polymers in various brines even at high temperature (140°C) and at a controlled and low shear rate. It is thus possible to access to the rheological properties of dilute polymer solutions under conditions that, to our knowledge, cannot be performed by viscometers commercially available. The new technique involves a specific set up including a capillary and pressure transducers. It allows monitoring the effect of various chemical, mechanical, free radical and thermal modifications on the PAM structure after various ageing times. The performances of the technique were determined in terms of accuracy, and acquisition time. Various PAM compositions and different molar masses (10 4 -10 6 g/mol) were used for calibration purposes.The technique was then applied to investigate the behavior of two industrial PAM (MϾ10 6 g/mol) used in EOR: a sodium acrylamido-tertiary-butyl sulfonate (ATBS) based PAM (SPAM), and a PAM terpolymer with ATBS, and N-vinylpyrrolidone (NVP) (PAM called SAV). Rheological properties and intrinsic viscosities were determined at low shear rates 8 to 800 s -1 , at 25, 85 and 140°C, and for different salinities (20,000 to 240,000 TDS). In addition, the mechanical stability was evaluated by injection of a polymer solution in a capillary with a low internal diameter (125m), and with a shear rate up to 1,500,000s -1 .The results obtained using the new technique provide an efficient and reliable way of selecting the proper PAM chemistry for a given reservoir condition. Ultimately, it defines the salinity, temperature and shear rate domains where the PAM, SPAM or SAV are stable. The technique can be automated, is made of transportable devices, can be used in anaerobic conditions and provides a fast way of following changes in the rheological property of very high Mw industrial PAM over time.

A novel method is described to extract crude oil surface active species. It is based on the formation of balanced three-phase microemulsions (optimum Winsor III systems) with a well-defined temperature-sensitive nonionic surfactant. The crude oil surface-active species are concentrated in the middle-phase microemulsion, which is separated. The interfacial material is then recovered in the surfactant-rich aqueous phase after cooling. This method was applied to five crude oils and the interfacial materials were then analyzed by Fourier transform ion cyclotron resonance mass spectroscopy (FT-ICR MS). This novel extraction method compares well with the established “wet-silica” method, as evidenced by the analysis in the negative electrospray ESI(−) mode of the interfacial materials of the same crude extracted by the two methods. The analytical data have been related to the interfacial activity of the crude oils, namely, their tendency to form stable emulsions with water or viscous phases in surfactant/oil/water systems at equilibrium, and to their equivalent alkane carbon numbers (EACN). The interfacial materials are confirmed to be responsible for the increased stability of water-in-oil emulsions.

For the first time, to our knowledge, anionic and nonionic surfactants were analyzed in oil matrix by Ultra-High-Performance Liquid Chromatography hyphenated to High-Resolution Mass Spectrometry (UHPLC-HRMS). The feasibility of their analysis was studied using synthetic 2 mixtures of surfactants prepared in water (Quality controls), in a binary THF/Toluene 50/50 v/v (Surfactant+THF/Toluene) and in a binary THF/Toluene containing 1 and 10% of crude oil (Crude1% and Crude10%). These compositions were chosen in order to be as close as possible to petroleum related samples to be investigated in the future. Analyses were carried out by UHPLC methods using both reverse phase and anion-exchange mechanisms with a mixed mode column.Despite the complexity of the oil matrix and the presence of organic solvents used for dilution, the retention times of the surfactants were not affected whatever the concentration of crude oil present in the sample. Nevertheless, a significant matrix effect caused a loss of signal when the concentration of oil reached 10% in mass. For the analysis of samples with this crude oil concentration range, it would be advisable to dilute the sample.The present study was a first insight into the behavior of the HRMS hyphenated to LC for the analysis of surfactants in petroleum matrices. It should be of interest to complete this study by an investigation of the long-term impact of crude oil in a routine use.