Characterization of Partly-Hydrolyzed Polyacrylamide-Chromium(III) Acetate Gels Using Hydrogen Nuclear Magnetic Resonance.

摘要

The continuous decline in the production of conventional light oil and increased demand worldwide is causing liquid fuel price instability. Without opportune mitigation, the economic, environmental, and social cost to meet the demand for oil will be unprecedented. The Canada Energy Board proposes that an aggressive approach to research and technological modernization should be maintained to moderate oil production decline from reservoirs that are past their peak. This approach is only possible with advances in enhanced oil recovery (EOR) techniques. Polymer gel treatment is a chemical method within EOR processes which plays a significant role in the mitigation of conventional oil production decline.;1H NMR transverse relaxation (T2) is related to the mobility of the hydrogen species within the test medium. HPAm/Cr(III) acetate gels are suitable for T2 studies since they are formulated with water concentrations as high as 99.7 wt %. This work was conducted using polymer concentrations from 2,500 to 20,000 mg/L and polymer to crosslinker weight ratios from 5/1 to 60/1. The methods used were 1H NMR T2, Magnetic Resonance Imaging, UV-vis photospectrometry, bottle testing, chromium speciation, and oscillatory rheology.;During the gelation of bulk samples of HPAm/Cr(III) acetate gels, two contributions to T2 were identified: a contribution from the Cr(III) acetate chemistry and a contribution from changes in rheological properties. 1H NMR T2 detects Cr(III) acetate hydrolysis, gelation time, gel syneresis, and hydrogen species distribution of the polymer and gelant solution within model porous media.;The polymer gel most frequently used in the oil and gas industry is formulated using partly hydrolyzed polyacrylamide (HPAm) and Cr(III) acetate. There is no standardized procedure that can be implemented in oil fields to accurately determine the gelation time and gel strength of the HPAm/Cr(III) acetate gels which are critical factors for the proper design of gel treatments. This research provides the basis to develop a new 1H Nuclear Magnetic Resonance (1H NMR) methodology that allows for accurate characterization of gels in oil fields without disrupting the gel network. This methodology aims to relate the rheological properties of the gel with its 1H NMR behavior.