Research on the Gelation Performance of Low Toxic PEI Cross-Linking PHPAM Gel Systems as Water Shutoff Agents in Low Temperature Reservoirs

Abstract

Using gel as the water shutoff agent has been widely reported in the aspect of enhanced oil recovery (EOR) of the development of mature oil fields. Cross-linkers such as chromium(III) acetate and phenol−formaldehyde are commonly used, but they are toxic. Today, use of low toxic polyethyleneimine (PEI) cross-linking a copolymer of acrylamide and tert-butyl acrylate (PAtBA) as the water shutoff gel is reported more but is mainly focused on its theoretical research and applications in high temperature reservoirs. Because of the defects of the chromium(III) acetate and phenol−formaldehyde cross-linkers, the gelation performance of PEI/partially hydrolyzed polyacrylamide (PHPAM) gel systems at low temperature (40 °C) is discussed in this paper. The results show that the gelation time and strength of the PEI/PHPAM gel system can be perfectly controlled by adjusting the PHPAM concentration, the molecular weight, the PEI concentration, and the total dissolved solids. The polymer concentration and molecular weight can affect not only the gelation time and the gel strength but also its stability. Among them the polymer concentration is the most important factor that affects the gel stability. For the low temperature reservoirs, the most common used chromium(III) acetate/PHPAM gel system has only around 5 h of gelation time at 40 °C to get a high gel strength. However, the PEI/PHPAM gel system can achieve a much longer gelation time. Polymer gels formulated with a combination of 1.5 wt % PHPAM and added 0.3−0.8 wt % PEI provide a gelation time between 15 h and 9 days, and the maximum gel strength could reach code I. This study suggests that the low toxic PEI/PHPAM gel system can be used in low temperature reservoirs.

Gelation Study on a Hydrophobically Associating Polymer/Polyethylenimine Gel System for Water Shut-off Treatment

“…The formed gel compresses water molecules contained in the gel network structure and shrinks its volume to exclude water molecules out. 19 Moradi-Araghi et al 10 reported that the gel syneresis could be also caused by the alteration of gel mechanical property due to the reaction between carboxyl groups in polymer molecules and bivalent or trivalent ions. However, due to the application of the deionized water in the screening test, the effect of metallic ions on the gel formation was weak; hence the excessive cross-linking was blamed for the gel syneresis.…”

Flow of a Cross-Linking Polymer in Porous Media

“…The reaction between HPAM and PEI can be explained as imine nitrogen from PEI attacking the carbonyl carbon attached to the amide group of the polymer (Fig. 3) (Jia et al 2010). That creates chemical bonds which are much stronger than ionic bonds.…”

Modeling of Partially Hydrolyzed Polyacrylamide-Hexamine-Hydroquinone Gel System Used for Profile Modification Jobs in the Oil Field

“…e effect of temperature ( in degree kelvin) can also be incorporated in (8) and Arrhenius model [19] can be utilized to connect with which is as follows: where is an apparent activation energy and is the gas constant. erefore, the combination of (10) and (11), then we get…”

“…is crosslinking is believed to rely on coordination covalent bonding. It should be mentioned that Cr (III) based polymer gel system were reported to be stable at temperatures up to 300 ∘ F [8][9][10]. e organically crosslinked gels developed using phenol and formaldehyde crosslinkers are thermally stable under harsh environmental conditions.…”