NMR AND ULTRASONIC STUDIES IN CORE PLUG SAMPLES FROM CARBONATES AND SANDSTONES’TIGHT FORMATIONS

摘要

Core plug samples of carbonates and sandstones tight formations have been studied using ultrasonic P waves,analysed in frequency domain,and low field NMR transversal relaxation,in order to find information about lithology,presence of fractures and petrophysical properties.The main production mechanism of these formations is due to fractures.The Fast Fourier Spectra of P waves indicate higher amplitudes in the samples presenting microfractures than in non-fractured ones,because of less energy lost into S waves when open fractures are present.The T2 distribution times show characteristic behaviour determined by the grain size in sandstone samples and additionally by the presence of vugs in carbonates with complex lithology.