New Chemistry for the Placement of Chromium(III)/Polymer Gels in High-Temperature Reservoirs

Abstract

Summary: Coordination chemistry concepts have been used in the development of Cr+3/polymer solutions that meet the delayed-gelation requirements for in-depth treatment of high-temperature reservoirs. Use of the malonate complex of Cr+3, Cr(malonate)3)3, provides gelation delays at elevated temperature much greater than those obtained with either the hydrated Cr+3 ion or Cr(acetate)3. Inclusion of additional, uncomplexed malonate ions in the formulations provides a means for further, and predictable, extension of the gelation time. The gelation delays obtained over the temperature range of 90 to 135 °C are equal to or greater than those that can be achieved with the best gelation delay technologies described previously. The dependence of the gelation time on temperature, pH, and the Cr+3 and malonate ion concentrations has been investigated. Preliminary results indicate that the thermal decomposition of the delaying ligand, malonate, plays an important role in determining the gelation rate. The use of a Cr+3 complex of relatively low toxicity rather than the carcinogenic Cr+6 ion to control gelation rate is an amctive feature of the new technology.