Desenvolvimento de sistemas à base de sulfato de cálcio para aplicação em poços de petróleo

Abstract

The Portland Cement (PC) production is directly linked to different environmental impacts. Those impacts are associated with different extraction phases going from the raw material stage to the clinquerization stage, having the emission of large volumes of CO2 and very high energy utilized. The search to alternative cement materials may have similar technological properties and with less aggression to the environment, has become the target of several segments to Portland Cement industry. Calcium sulfate hemi-hydrate (HH) is a binder with reduced environmental impacts linked to both its production and use, presented as a less aggressive material to the environment. Calcium sulfate systems can be used both in their pure form and can have their properties improved upon partial replacement by Portland cement and other materials can also be used as an agent of pozzolanic activity, as a Rice Husk Ash (RHA). This paper is aimed to develop and analyze systems based on pure calcium sulfate and with the addition of Portland Cement and Rice Husk Ash (RHA), as an alternative to the formulations used in cementation of wells shallow of Petroleum. For the development of this study, slurrys with water/gypsum factors (FAGs) between 0.5-0.6 were prepared, being submitted to different cures ages (24 hours, 7 and 28 days) and temperatures (27, 38 and 60ºC). The slurrys were aditived using a handle retarder (sodium tetraborate) and superplasticizer (polycarboxylate), in order to obtain the technological properties required for application in the petroleum industry. These formulations were evaluated through tests of compressive strength, rheological parameters and permeability, besides the use of thermal characterization techniques (TG / DTG), X-ray diffraction (XRD), scanning electron microscopy (SEM-EDS) HH and its formulations with CCA and CP. The results showed that the system based on pure calcium sulfate type HH-α and HH-β with 30% substitution for CCA and cement, present satisfactory results of compressive strength, with higher values, compared to the PC formulation traditionally used in cementing operations. The systems showed technological properties applicable to operations for wells with low depth (500-800 m) and/or initial stages of deeper wells with softer conditions of temperature and pressure. In addition, there is the matrix cost factor, in which HH is usually 60-70% cheaper than the CP currently used.