Ultra-high temperature resistant preformed particle gels for enhanced oil recovery

Abstract

Gel treatment is one of the most efficient enhanced oil recovery techniques used for conformance control. In recent years, preformed particle gels (PPG) have gained attention for conformance control and to reduce water production. However, there are no current products available to withstand reservoir conditions with high temperature, high pressure, and high salinity. In this paper, we describe the development, characterization and detailed evaluation of a unique hydrogel composition with ultrahigh temperature resistance (HT-PPGs) for chemical enhanced oil recovery. HT-PPG described herein can swell more than 30 times its initial volume in brines of different ionic strengths. We systematically evaluated the effect of variables like temperature, pH, salinity, monovalent vs divalent ions on swelling behavior. The HT-PPGs are mechanically robust in nature with storage moduli (G’) of over 3000 Pa at about 90 percent water content. Additionally, HT-PPGs showed excellent thermal stability at 150 °C for more than 12 months in monovalent and divalent ion containing brines at all swelling ratios. HT-PPGs exhibit exceptional hydrolytic thermal stability for more than 18 months in 2% KCl brine (at water content of greater than 93 percent) at 150 °C. Coreflooding tests were performed in a fractured core and showed good plugging efficiency, helped to reduce the permeability of fracture and did not wash out, were not eluted, during the test. HT-PPG discussed in this work, is a unique product with excellent features which makes it an ideal candidate for conformance control of reservoirs with harsh temperature, salinity conditions.