Formulação de pasta de cimento flexível utilizando planejamento experimental

Steam injection is an oil recovery method accomplished by introducing steam directly into the oil well to the reservoir. The steam causes dilation of the casing, which, after reduction in temperature, tends to return to the initial dimensions: causing the formation of cracks in the cement and loss of hydraulic isolation.. In this context, the type of the SBR latex is used to improve the flexibility of the cement matrix by reducing the amount of fatigue failure. To prevent these failures, the mechanical resistance parameters should be carefully adjusted to well conditions. This work aims to study the mechanical behavior of cement slurry systems additivated with SBR latex for cementing oil wells subject to steam injection. Through the central composite factorial design was studied the behavior of the compressive strength by varying the density of the paste between 1.75 g /cm³ (14.6 lb/ Gal) and 1.89 g/cm³ (15,8lb / Gal), curing time between 4 days and 28 days and concentration of SBR Latex between 0 L / m³ and 534.722 L / m³ (0 gpc and 4 gpc). The results showed that increasing the concentration of SBR latex, within the given ranges, there was a decreased compression resistance and elastic modulus by increasing the elastic deformability of the slurry. From the results it can determine best slurries formulation conditions in oil well cementing operations subject to steam injection.

Recomendações para o desenvolvimento de uma ferramenta de suporte às primeiras decisões projetuais visando ao desempenho energético de edificações de escritório em clima quente

PEDRINI, Aldomar; SZOKOLAY, Steven. Recomendações para o desenvolvimento de uma ferramenta de suporte às primeiras decisões projetuais visando ao desempenho energético de edificações de escritório em clima quente. Ambiente Construído, Porto Alegre, v. 5, n. 1, p.39-54, jan./mar. 2005. Trimestral. Disponível em: . Acesso em: 04 out. 2010.

Novo método para estimativa do gradiente de fratura para poços de petróleo

The development of oil wells drilling requires additional cares mainly if the drilling is in offshore ultra deep water with low overburden pressure gradients which cause low fracture gradients and, consequently, difficult the well drilling by the reduction of the operational window. To minimize, in the well planning phases, the difficulties faced by the drilling in those sceneries, indirect models are used to estimate fracture gradient that foresees approximate values for leakoff tests. These models generate curves of geopressures that allow detailed analysis of the pressure behavior for the whole well. Most of these models are based on the Terzaghi equation, just differentiating in the determination of the values of rock tension coefficient. This work proposes an alternative method for prediction of fracture pressure gradient based on a geometric correlation that relates the pressure gradients proportionally for a given depth and extrapolates it for the whole well depth, meaning that theses parameters vary in a fixed proportion. The model is based on the application of analytical proportion segments corresponding to the differential pressure related to the rock tension. The study shows that the proposed analytical proportion segments reaches values of fracture gradient with good agreement with those available for leakoff tests in the field area. The obtained results were compared with twelve different indirect models for fracture pressure gradient prediction based on the compacting effect. For this, a software was developed using Matlab language. The comparison was also made varying the water depth from zero (onshore wellbores) to 1500 meters. The leakoff tests are also used to compare the different methods including the one proposed in this work. The presented work gives good results for error analysis compared to other methods and, due to its simplicity, justify its possible application

Metodologia para avaliação de cinemática de partículas gasosas em fluidos de viscosidade variável com o tempo e sua aplicação na construção de poços de petróleo

Many challenges have been presented in petroleum industry. One of them is the preventing of fluids influx during drilling and cementing. Gas migration can occur as result of pressure imbalance inside the well when well pressure becomes lower than gas zone pressure and in cementing operation this occurs during cement slurry transition period (solid to fluid). In this work it was developed a methodology to evaluate gas migration during drilling and cementing operations. It was considered gel strength concept and through experimental tests determined gas migration initial time. A mechanistic model was developed to obtain equation that evaluates bubble displacement through the fluid while it gels. Being a time-dependant behavior, dynamic rheological measurements were made to evaluate viscosity along the time. For drilling fluids analyzed it was verified that it is desirable fast and non-progressive gelation in order to reduce gas migration without affect operational window (difference between pore and fracture pressure). For cement slurries analyzed, the most appropriate is that remains fluid for more time below critical gel strength, maintaining hydrostatic pressure above gas zone pressure, and after that gels quickly, reducing gas migration. The model developed simulates previously operational conditions and allow changes in operational and fluids design to obtain a safer condition for well construction