Development of a High-Temperature Resistant Polymer Gel System for Conformance Control in Jidong Oilfield

摘要

The PG reservoir in Jidong Oilfield is at a depth of around 15,000 ft with an extremely high-temperature of about 300 °F. The average water cut has reached nearly 80%, but the oil recovery is less than 10% only after two years of water flooding process. It is of great importance to developing a high-temperature resistant plugging system to improve the reservoir conformance and control water production. An in-situ polymer gel system formed by the terpolymer and a new crosslinker system was developed, and its properties were systematically studied under the condition of extremely high temperature (300 °F). Suitable gelation time and favorable gel strength were obtained by adjusting the concentration of the terpolymer (0.4%-1.0%) and the crosslinker system (0.4%-0.7%). An increase of polymer and crosslinker concentration would decrease the gelation time and increase the gel strength. The gelant could form continuous three-dimensional network structures and thus have an excellent long-time thermal stability. The syneresis of this gel system was very little even after being heated for five months at the temperature of 300 °F. The gel system could maintain most of the initial viscosity and viscoelasticity even after experiencing the mechanical shear or the porous media shear. Core flow experiments showed that the gel system could plug the fractures and reduce the permeability in the higher permeability regions, and diverted the injection water flow to the lower permeability regions, and thus improve the conformance.