Uso da cinza da casca do arroz em tampões de cimento para abandono de poços petrolíferos

Abstract

When an oil well reaches the end of life cycle, due to low economic return or failure of its mechanical integrity, a series of plugs are designed and placed inside the wellbore to isolate formations that have potential to flow to the surface or to adjacent formations and, thus, guarantee the sealing and permanent abandonment. The present work aims to use the Ash of the Rice Husk (RHA) as an alternative material to compose cement paste systems for application in oil well abandonment buffer. Samples containing RHA and reference samples were submitted for seven days at 40ºC, 60ºC, 80ºC, 110ºC and 300ºC, respectively, according to temperature ranges established by the UK Guidelines on Qualification of Materials for the Abandonment of Wells, Issue 2. Performance these paste systems were evaluated for compressive strength (RC) and gas permeability. These two parameters were chosen, due to the relevance they present in the approval of Portland cement-based materials, for plug and abandonment operations. TGA and XRD tests were performed to assist in understanding the observed phenomena. The alternative material RHA gave superior or equivalent results in compressive strength in all conditions tested. Another positive factor observed was that, due to the physical characteristics of the mixtures containing RHA, good performances were obtained in cases where more water has been added, with less consumption of Portland cement and lighter pastes, when compared to the usual systems. The systems containing RHA showed low permeability values in their hydrated matrix, in some cases, being inferior to the reference pastes. Due to the possibility of composing lighter paste systems, but without compromising resistance, the pastes are also suitable for work in depleted wells. The alternative systems have shown promise to compose well barriers (WB) necessary to guarantee the correct plug and abandonment and well integrity, even at the end of life cycle. The systems also proved to be versatile, as they have high performance, both at low and at very high temperatures, while conventional systems need specific compositions for each situation