Thermosetting Polymer Based Flexible Synthetic Cement for Successful Zonal Isolation in Thermal Wells – A New Approach
- R. Shanbhag (University of Southern California) | Z. Melrose (University of Southern California) | S. Nutt (University of Southern California) | M. Cleveland (Schlumberger) | R. Keese (Schlumberger)
- Document ID
- Society of Petroleum Engineers
- SPE Thermal Well Integrity and Design Symposium, 23-25 November, Banff, Alberta, Canada
- Publication Date
- Document Type
- Conference Paper
- 2015. Society of Petroleum Engineers
- 0.2.1 Wellbore integrity, 4.3.4 Scale, 0.2 Wellbore Design
- High Strength, Zonal Isolation, Flexible, Synthetic Cement
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Conventional Portland cements present significant challenges in thermal wells due to a high degree of brittleness, low strength, and inconsistent strength development following set. These challenges are further compounded by progressive degradation of the material with repeated thermo-mechanical loading. A new, highly flexible synthetic cement based on a thermosetting polymer, that overcomes many of these challenges, is presented. The material exhibits significantly higher strength and lower modulus (thus, a higher elastic strain to failure) than conventional cements and also shows a very high degree of resilience to thermal as well as mechanical fatigue. Further, the material exhibits right angle set and immediate strength development following set.
The material was tested for various mechanical properties in tension as well as in compression. Rheological testing was conducted and the effect of variability in BHCT as well as in initiator concentrations on cure kinetics was determined. A yard test was conducted using conventional oilfield equipment to assess suitability of large-scale deployment of the cement.
Typical compressive strength, tensile strength and compressive modulus values are greater than 8,000 psi, greater than 1,500 psi, and less than 500 ksi, respectively. The density of the material can be modified in the 10.0 to 17.0 pounds/gallon range. In this paper, the 12.0 and 14.5 pound/gallon variations were tested. Poisson's ratio of the material was determined to be 0.27 at 77°F and increases at higher temperatures, showing a very high degree of flexibility. The material exhibits a right angle set at a range of temperatures with little variation in set times due to variations in bottom hole circulating temperature and initiator concentration. Further, the strength development is immediate following set in each case. The system also exhibits zero shrinkage upon cure, an important attribute in preventing vent flow.
The high strength and flexibility, high temperature performance, as well as the "set on demand", zero shrink and "right angle set" properties of the material render it ideal for placement in thermal wells where wellbore integrity is of concern. Further, use of conventional oilfield equipment in placement allows for an easy deployment of this new solution that may solve a number of problems associated with thermal wells.
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