DBPapers
DOI: 10.5593/sgem2017H/15/S06.050

PORTABLE NUCLEAR MAGNETIC RESONANCE RELAXOMETRY IN THE STUDY OF PETROPHYSICAL PROPERTIES OF RESERVOIR ROCKS

L. Muravyev, S. Zhakov, D. Byzov
Thursday 23 November 2017 by Libadmin2017

References: 17th International Multidisciplinary Scientific GeoConference SGEM 2017, www.sgemviennagreen.org, SGEM2017 Vienna GREEN Conference Proceedings, ISBN 978-619-7408-26-3 / ISSN 1314-2704, 27 - 29 November, 2017, Vol. 17, Issue 15, 397-404 pp; DOI: 10.5593/sgem2017H/15/S06.050

ABSTRACT

Reliable estimation of hydrocarbon feedstock reserves is based on determining the reservoir’s fluid recoverability, which is done by laboratory studying the microscopic structure of the core samples. Impulse nuclear magnetic resonance relaxometery (NMR) is one of the most perspective methods for studying petrophysical properties of rocks. We developed a portable NMR relaxometer, which can be used both in the laboratory and in the field while drilling. NMR analysis of the drill mud can be done directly on the well in real time. For mud sizes of 3-5 mm, the results coincide with the analysis of the core. We present methodical issues of laboratory investigations with NMR relaxometer. We propose a method for NMR experiment parameters selecting providing the maximum level of the observed signal. We have developed a method for inversion of relaxation curves based on the Fletcher-Reeves minimization (conjugate gradients). The software is running on a high-performance computer complex including an NVIDIA video adapter. For sufficient accuracy of NMR spectra approximation we used the function f(T2), belonging to three classes: discrete, piecewise-constant and piecewise-linear. Software for processing and geological-geophysical interpretation of relaxation curves is taking into account medium models and preliminary geological information. Proposed analysis method allows working with core in laboratory and with mud directly in the drilling site. Reliable initial data obtained during NMR studies of the petrophysical properties of reservoir rocks allow us to refine the empirical relationships between the relaxation time distribution and the pore space characteristics of the geological media studied. This makes it possible to increase the reliability of the analysis of reservoir properties of core samples, to increase the validity of assessments of reserves of hydrocarbon deposits and their oil recovery ratio.

Keywords: Nuclear Magnetic Resonance, Capacitive Properties, Petrophysics, relaxation time, CPMG