Sistema a base de resina poliéster para aplicação em poços petrolíferos: desenvolvimento de metodologia para análise da resistência à compressão pelo método ultrassônico (UCA)

Abstract

Historically, Portland cement is widely used to conduct the most varied interventions in oil wells. The numerous advantages of using this material are well known, however, in recent years, the use of alternative materials for some types of interventions has been growing, as is the case of some abandonments, as they have specific characteristics for application in scenarios where the use of cement is limited to its performance. Among the alternative materials to cement for oil wells, resins have been gaining prominence due to their compatibility with the fluids contained in the wells. The resins are free of solids, and this results in superior performance for well abandonment operations whose injectivity is too low for the penetration of conventional cement slurry. Another very interesting characteristic of the resins is their compressive strength, which is high when compared to conventional cement paste systems, in addition to their extremely low permeability. One of the biggest challenges for the application of alternative materials to replace Portland cement is the control and characterization of its technological properties. The API (American Petroleum Institute) standards, specifically SPEC 10A and RP 10B-2, were developed decades ago with a focus on testing for Portland cement. The adaptation of some procedures for the characterization of alternative materials, such as resins, is the key point to guarantee operational success during field application, especially the compressive strength. Based on the above, in this work a methodology was developed to analyze the compressive strength (CS) by the ultrasonic method in polyester-based resin systems. The control of the CS of the resin systems was conducted through the addition of the chemical inhibitor 4-tert-butylcatechol (TBC). The response to the addition of TBC in the polyester resin system was quite consistent, as it was possible to observe a variation in the time of onset of CS development, proportional to the percentage of TBC in the system. The polyester resin samples showed CS results after 24 hours between 6,000 psi and 6,500 psi, high above the results of conventional Portland cement slurry systems, whose CS after 24 hours do not reach 2,000 psi. In addition to the difference in absolute values, the almost instantaneous gain in CS of the analyzed polyester resin is notable in comparison with the slow gain, of at least 15 hours, for the CS of the Portland cement to reach stability.