High-temperature conditions drastically compromise the physical properties of cement, especially, its strengths. In this work, the influence of adding nanoclay (NC) particles to Saudi class G oil well cement (OWC) strength retrogression resistance under high-temperature condition (300 °C) is evaluated. Six cement slurries with different concentrations of silica flour (SF) and NC were prepared and tested under conditions of 38 °C and 300 °C for different time periods (7 and 28 days) of curing. The changes in the cement matrix compressive and tensile strengths, permeability, loss in the absorbed water, and the cement slurry rheology were evaluated as a function of NC content and temperature, the changes in the structure of the cement surfaces were investigated through the optical microscope. The results revealed that the use of NC (up to 3% by weight of cement (BWOC)) can prevent the OWC deterioration under extremely high-temperature conditions. Incorporating more than 3% of NC severely damaged the cement matrix microstructure due to the agglomeration of the nanoparticles. Incorporation of NC particles increased all the cement slurry rheological properties.
Durability and long-term integrity of oil well cement are the most important parameters to be considered while designing the cement slurry, especially in the high-pressure and high-temperature (HPHT) environments. In this study, the effect of adding the polypropylene fiber (PPF) to Saudi Class G cement is evaluated under HPHT conditions. The effect of the PPF on the cement compressive and tensile strength, thickening time, density, free water, porosity, and permeability was studied. The effect of the PPF particles on the cement sheath microstructure was studied through powder X-ray diffraction (XRD) and scanning electron microscope. The results obtained showed that PPF did not affect the cement rheology, density, and free water. The addition of PPF considerably decreased the thickening time and improved the tensile and compressive strength of the cement. 0.75% by weight of cement (BWOC) of PPF reduced the thickening time by 75%, from 317 to 78 min. The compressive strength of the cement increased by 17.8% after adding 0.5% BWOC of PPF, while the tensile strength increased by 18% when 0.75% of PPF is used which is attributed to the formation of stable forms of calcium silicate hydrates because of the ability of PPF to accelerate cement hydration process as indicated by the XRD results. The ability of the PPF to decrease the cement thickening time along with its ability to improve the cement strength suggests the use of PPF as an alternative for silica floor in shallow wells where a reduction in thickening time will decrease the wait on cement time. Porosity and permeability of the base cement were also decreased by incorporating PPF because of the pores filling effect of PPF particles as indicated by the microstructure analysis.
CO 2 -enhanced oil recovery (EOR) has demonstrated significant success over the last decades; it is one of the fastest-growing EOR techniques in the USA accounting for nearly 6% of oil production. A large quantity of CO 2 gas is required for the EOR process and sometimes other gases such as hydrocarbons, air, flue gases, CO 2 , N 2 , and mixtures of two or more gases are used for injection. It is also realized that the injection of CO 2 and N 2 combines advantage in reducing CO 2 concentrations in the atmosphere and improving the oil recovery by sequestering it underground. However, there are a number of variables involved in the successful design of the CO 2 -EOR process. The objective of this study is to investigate the effect of CO 2 /N 2 mixture composition on interfacial tension (IFT) of crude oil. Experiments were performed to measure the IFT of the CO 2 /N 2 mixtures and crude oil for different compositions of gas by varying the system pressure at a fixed temperature. The effect of CO 2 /N 2 mixture composition and pressure on the IFT of crude oil is evaluated. The experimental results show that an increase in the mole fraction of CO 2 in the gas mixture results in a decrease in IFT between CO 2 −oil, irrespective of the system pressure. However, because of an increase in the mole fraction of N 2 in the gas mixture, an increase in IFT was observed and this change is opposite to the effect of the CO 2 mole fraction. Also, the change in IFT is consistent with the pressure, which means that the IFT decreases with an increase in the pressure at a given temperature. The effect of the CO 2 mole fraction is more profound compared to the N 2 fraction and with the pressure at which experiments were conducted in this study. The finding of this study helps in designing the CO 2 -EOR process in which achieving miscibility conditions is vital for taking advantage of the CO 2 injection. Also, the presence of N 2 and its influence on the IFT that must be considered in the CO 2 -EOR were addressed in this study.
for their financial support. Without their support, this work would not have been possible. Additional gratitude is also extended to all professors. Special thanks are extended to the staff at LSU's Petroleum Engineering Research and Technology Transfer Laboratory (PERTTL), especially Gerry Masterman and Darryl A. Bourgoyne for their help to set the lab equipment and hours spent on this project. Also, I would like to thank to Mr. Fenelon Nunes for his support and presence at the department. Special thanks to Stepan Co., Northfield, IL, and Baker-Petrolite, Sugar Land, TX, for providing products and information to develop this research. I wish to thank to my country, Serbia, because through the University of Belgrade and companies Energoproject and PM Lucas I received the academic knowledge and professional experience to be successful in my life. This work is dedicated to my parents, Vladimir and Javorka, my sister Gordana and her son Andrej.
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