No abstract

Corrosion inhibition performance of synthesized amino acid compounds, namely, (Z)-2-(2-oxoindolin-3-ylideneamino)acetic acid (OYAA) and 2-(2-oxoindolin-3-ylideneamino)-3-phenylpropanoic acid (OYPA) on mild steel in 15-% HCl solution was investigated by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Potentiodynamic polarization studies showed that both studied inhibitors were mixed types in nature. The adsorption of inhibitors on the mild steel surface obeyed Langmuir's adsorption isotherm. The potential of zero charge (E PZC ) for the mild steel was determined via EIS to discuss the adsorption mechanism. Scanning electron microscopy, energy dispersion X-ray spectroscopy and atomic force microscopy were used to characterize the surface morphology of uninhibited and inhibited mild steel specimens. The density functional theory was employed for theoretical calculations.

No abstract

No abstract

Summary Determining the rheology of drilling fluid under subsurface conditions—that is, pressure > 103.4 MPa (15,000 psi) and temperature > 450 K (350°F)—is very important for safe and trouble-free drilling operations of high-pressure/high-temperature (HP/HT) wells. As the severity of HP/HT wells increases, it is challenging to measure downhole rheology accurately. In the absence of rheology measurement tools under HP/HT conditions, it is essential to develop an accurate rheological model under extreme conditions. In this study, temperature- and pressure-dependence rheology of drilling fluids [i.e., shear viscosity, apparent viscosity (AV), and plastic viscosity (PV)] are predicted at HP/HT conditions using the fundamental momentum transport mechanism (i.e., kinetic theory) of liquids. Drilling fluid properties (e.g., density, thermal decomposition temperature, and isothermal compressibility), and Fann® 35 Viscometer (Fann Instrument Corporation, Houston, USA) readings at surface conditions, are the only input parameters for the proposed HP/HT shear viscosity model. The proposed model has been tested using 26 different types of HP/HT drilling fluids, including water, formate, oil, and synthetic oil as base fluids. The detailed error and the sensitivity analysis have been performed to demonstrate the accuracy of the proposed model and yield comparative results. The proposed model is quite simple and may be applied to accurately predict the rheology of numerous drilling fluids. In the absence of subsurface rheology under HP/HT conditions, the proposed viscosity model may be used as a reliable soft-sensor tool for the online monitoring and control of rheology under downhole conditions while drilling HP/HT wells.