Thermal and mechanical evaluation of the stability of recycled poly(ethylene terephthalate) applied as sand control agent in petroleum wells

Abstract

In petroleum wells, the granular sand control agents commonly employed are basically inorganic compounds, which are used in operations to prevent the production of sand, from unconsolidated sandstone formations, that contaminates the produced hydrocarbons. In this work the viability of applying recycled poly(ethylene terephthalate) (PETrec) as sand control agent, in an environment that simulated the conditions of the wells, was evaluated. Virgin PET (PETvir) was tested as a standard for comparison means. Pellets of each polymer (PETrec and PETvir) were confined into metallic cells filled with sea water or petroleum, under conditions observed in some sandstone formations that are normally subjected to sand control, in Campos Basin (Rio de Janeiro, Brazil). The cells systems were submitted to a controlled temperature of 70 °C and pressure of 24.1 MPa, and rolled during the experiment period. The total exposure time was approximately six months (172 days), with scheduled sampling periods. Thermal, mechanical and granulometric properties of the pellets before and after the exposition were evaluated. The samples were characterized by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TG). Mechanical experiments were performed, in order to determine the grain pack permeability, by the end of the exposition period, according to API RP 58 and API RP 61 standard methods. Particle size of the grains, before and after the exposure process, was compared. Test results showed that PETrec and PETvir samples did not present significant physical changes or evidences of degradation, nor in water neither in petrol, suggesting that the use of recycled PET as sand control agent seemed to be viable within the experiment conditions.