Rheological Study on ATBS‐AM Copolymer‐Surfactant System in High‐Temperature and High‐Salinity Environment

Abstract

Experimental studies were conducted to evaluate the rheological properties of surfactant-polymer (SP) system. This SP system consists of a copolymer of acrylamide (AM) and acrylamido tertiary butyl sulfonate (ATBS) and sodium dodecyl sulphate (SDS) surfactant. Effects of surfactant concentration, temperature, polymer concentration, and salinity on rheological properties of SP system were investigated by means of oscillation and shear measurements. Comparison with classical partially hydrolyzed polyacrylamide (HPAM) was made. For the same temperature range, the viscosity drop for HPAM was about four times higher than the viscosity drop for ATBS-AM copolymer. In deionized water, viscosity of both polymers and SP systems was very high as compared to viscosity in saline water. Viscosity reduction of ATBS-AM copolymer was higher for salts having divalent cations. The SP system showed precipitation in presence of divalent cations. It worked well with monovalent cations even at relatively high salinities. The addition of 0.1% surfactant to the polymer resulted in a 60% decrease in the viscosity. Some interfacial rheological experiments were also carried out to investigate the behaviors on the interface between SP solutions and oil. Addition of 0.1% surfactant showed a 65% decrease inG′at SP solution-oil interface. SP system consisting of ATBS-AM and SDS showed better performance at high temperature compared to HPAM-SDS system. Due to precipitation, the SP system should be restricted to environment having low divalent cations.

Screening of amphoteric and anionic surfactants for cEOR applications using a novel approach

“…NMR analysis was performed to investigate further structural changes. 13 C NMR of surfactant-B before and after aging is shown in Fig. 5.…”

“…5. Several different peaks can be observed from 13 C NMR spectra of surfactant-B before aging. Downfield chemical shifts refer to the hydrocarbon chain and upfield chemical shifts refer to the carbon directly connected with the oxygen of propoxy groups.…”

“…After aging, fewer peaks were observed in the lower and upper range, which indicate possible structural changes in the aliphatic region and propoxy group. 13 C NMR spectra of surfactant-A is shown in Fig. 7.…”

“…Samples for NMR analysis were prepared using 100 mg of surfactant in 5 mm NMR tubes with 600 L D 2 O. JEOL 500 MHz spectrometer was used to obtain NMR spectra of the surfactants before and after aging. 2000 and 32 scans were used for collecting 13 C NMR (carbon NMR) and 1 H NMR (proton NMR) spectra. Thermal aging of the surfactant/SW solution was carried out at 90 • C for 10 days in sealed aging tubes.…”

“…Chemical enhanced oil recovery (cEOR) is one of the techniques employed to oil reservoirs to recover the remaining oil which cannot be recovered by primary recovery. A number of chemical flooding methods were reported in the literature, such as surfactant [2][3][4][5], polymer [6][7][8], alkali [9], surfactant/polymer [10][11][12][13] and alkali/surfactant/polymer [14,15]. Chemical methods are utilized to increase the viscosity of displacing fluid for better mobility control, to increase the sweep efficiency and to reduce the interfacial tension (IFT) between water and crude oil.…”