Avaliação do efeito da temperatura e pressão no combate à perda de circulação utilizando materiais fibrosos e granulares

Abstract

During the process of drilling oil wells, the phenomenon of loss of fluid circulation for the formation can occur. It is a consequence of the loss of drilling fluid through regions of high porosity or fractures, which can be natural or induced by the process, present in the drilled rock formations. As a result, there are partial, severe, or total circulation losses, which can make drilling well unfeasible. The main treatments to contain loss of circulation are the use of materials to strengthen wells or materials to combat loss of circulation. To choose the most efficient technique and materials, it is necessary to understand the material's sealing mechanisms, the flow processes in fractures, and the effects that operating conditions, such as temperature and pressure, affect the effectiveness of the materials. This work aims to evaluate the influence of the effect of pressure and temperature on combating loss of circulation in different methodologies. Four proposals are addressed, being two statically in the bench and two dynamically in the fracture flow simulators. In the static approach, the filtration and gap sealing tests in the HTHP filtration cell were contemplated, varying the temperature at 25, 50, and 75 °C and pressure at 300, 500, and 700 psi. With the filtration tests, it was possible to evaluate the potential for reducing the filtrate of each material and the influence of process conditions on the filtrate volume. In the sealing tests, the influences of temperature, pressure, concentration of pure materials and mixtures on the lost fluid volume for a 2 mm fracture were analyzed. In order to identify the factors and combinations of factors that had the greatest statistical influence on the lost volume. Through predictive modeling, it enabled the prediction of the optimal operating points for the chosen materials, under conditions of high pressure and high temperature. The sealing mechanisms of the two materials were experimentally observed. In addition, it is possible to prove the efficiency of the materials and blends developed. For the dynamic approach, two fracture flow simulators were used, SEF 1.0 at a temperature of 25 °C and a pressure of 60 psi and SEF 2.0 at a differential pressure of 100 psi and temperatures of 25 °C and 50 °C. In the simulators, the fluids are forced to flow under conditions of roughness, tortuosity, temperature and pressure similar to those found in the drilling well. The fractured canals of SEF 1.0 are 1.02 m long and have fractures of 5 and 10 mm in thickness. For the SEF 2.0, despite being modular, 1-meter-long channels and 5 and 10 mm-thick fractures were used. The prepared fluids showed rheological behavior that can be helped by the Power Law model. The data obtained from the simulators were used to analyze the behavior of fluids in flow and trace patterns. These data were also used in the technique of monitoring the fracture sealing by monitoring the hydraulic diameter. Monitoring was effective and the developed Blends were able to seal fractures and sometimes perform better than pure fluids.