Andre Souza

Nuclear magnetic resonance (NMR) techniques are key in the study of porous reservoir rocks. They can provide valuable insight into the pore size distribution of the pore space of a given rock sample due to its dependence on the magnetic fluid/matrix interaction. The pore space is often studied at the μm scale through the use of micro-CT images, whi...

NMR techniques are key in the study of porous reservoir rock, both experimentally and numerically. The T2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$T_2$$\end{docum...

Nuclear Magnetic Resonance (NMR) is an important tool to assess physical quantities that characterize porous media such as reservoir rocks. Information about surface-to-volume ratio and micro-connectivity, for instance, are coded in the time-dependent diffusion coefficient of magnetized spins. In this work, we present an efficient computational imp...

One hallmark of modern nuclear magnetic resonance spectroscopy is the use of multi-dimensional correlation experiments typically with only spin Hamiltonians. However, spin systems may be affected by interactions and processes that are not controlled through the spin degree of freedom. This paper demonstrates a correlation spectroscopy between two d...

To characterize a porous medium, it is essential to determine the geometry of its pore space as it controls key properties such as permeability. A standard approach is to saturate the pore space with a fluid and perform NMR relaxation measurements. The standard measurements are sensitive to the low-lying diffusion eigen-modes and they allow an esti...

In a previous work, we showed how to obtain the surface relaxivity as a function of pore size. In the present work, we take a step further and introduce a formulation that uses this surface relaxivity function to convert a T2 distribution into a pore size distribution. We then compare the pore size distribution obtained with the aid of this formula...

Porous media characterized by a hierarchy of length scales are ubiquitous in industry and nature, and include carbonate rocks, cements, heterogeneous catalysts, and biological cells. Nuclear magnetic resonance (NMR) is a popular tool for studying liquid-saturated porous materials, where the spin relaxation rate is generally considered proportional...

Oil-water relative permeability and capillary pressure are key inputs for multiphase reservoir simulations. These data are significantly impacted by the wettability state in the reservoir and by the pore space characteristics of the rock. However, in the laboratory, there are several challenges related to the validation and interpretation of the sp...

The traditional way to enhance signals to noise ratio (SNR) of Nuclear Magnetic Resonance (NMR) signals is to increase the number of scans. However, this procedure increases the measuring time that can be prohibitive for some applications. Therefore, we have tested the use of several post acquisition digital filters to enhance SNR up to one order o...

The economic viability analysis of a possible petroleum reservoir is based on the knowledge about its petrophysical properties, especially the porosity and its relationship with other properties, such as permeability and resistivity. In carbonate systems, the porosity presents a high degree of heterogeneity, which affects other quantities associate...

In the present work, we formulate and solve an inverse problem to recover the surface relaxivity as a function of pore size. The input data for our technique are the distribution measurement and the micro-tomographic image of the rock sample under investigation. We simulate the NMR relaxation signal for a given surface relaxivity function using the...

Irreducible water saturation is a key property for the estimation of original oil and gas-in-place. It is also key to end-point scaling of capillary pressure and relative permeability, with significant impact on simulation results of reservoirs under improved/enhanced oil recovery (IOR/EOR). Several definitions of irreducible water saturation exist...

This work has analyzed, considering the petrophysical point of view, samples of Coquinas obtained in the outcrop of the Morro do Chaves formation(Sergipe-Alagoas Basin). The complex sedimentological aspects for this study have been...Keywords: carbonate, porosity and permeability properties, NMR, electrical resistivity. RESUMO. Esse trabalho analis...

The Presalt carbonate wells of Lula Field, Santos Basin, Offshore Brazil, are currently producing high quality, 28 to 30° API oil at an average rate of 30,000 BOPD. With reservoir pressures over 8,000 psi, and a downhole oil viscosity of 1 cP, the proli¿c Àow rates from these high permeability, lacustrine carbonates have shown no signi¿cant decline...

Introduction The conversion of organic compounds to solid carbon materials is a complex process, which includes a variety of chemical reactions, involving many intermediate stages [1]. Greinke and Lewis [2] studied the carbonization of naphthalene, observing pitch, mesophase and coke formations, mainly through polymerizations with the loss of hydro...

Nuclear magnetic resonance (NMR) measurements have been used as a way to evaluate reservoir rocks based, on the longitudinal and transverse relaxation times, T 1 and T 2 , and the time dependent diffusion coefficient, D(t). Relaxation time distributions can be related to pore sizes and to the free and bound fluid fractions. In addition, there are w...

Nuclear magnetic resonance (NMR) measurements have been used as a way to evaluate reservoir rocks based, on the longitudinal and transverse relaxation times, T1 and T2, and the time dependent diffusion coefficient, D(t). Relaxation time distributions can be related to pore sizes and to the free and bound fluid fractions. In addition, there are well...

Carbonate reservoirs often show great heterogeneity in their inner rock structure, and stimulation treatments are often necessary to maintain or establish fluid production. Therefore, core-flow tests are usually conducted to test and model stimulation treatments within a laboratory scale to predict their performance. The visualization of wormholes...

Although nuclear magnetic resonance (NMR) is one of the most powerful analytical techniques, it has not been widely used as a non-destructive, non-contact inline industrial sensor. A short background of NMR spectroscopy fundamentals and instrumentation is presented along with its potential applications and limitations for real-time analysis in the...

In this paper, the Nuclear Magnetic Resonance response of three sedimentary rocks (one sandstone and two carbonates) is modeled through random walk simulations. With this modeling, we aim to improve micro-porosity content and pore size estimation, by taking into account both surface relaxation and diffusive coupling. Experimental Magnetic Resonance...

When estimating permeability (k) from NMR logs, a key assumption is that the surface relaxivity (rho2) parameter, which scales the relationship between transverse relaxation time (T2) and the surface-to-volume ratio (S/V) of the pore system, remains constant. With this assumption, the rho2 parameter can be accounted for in the premultiplier of the...

Whole soil samples from Peruvian bofedales (highland peatlands), located at an average altitude of 3881 m above sea level, were analyzed through 13 C solid-state nuclear magnetic resonance ( 13 C SSNMR) spectroscopy. The objective was to make a semi-quantitative characterization of the predominant organic chemical structures and to compare the...

Existing carbonate classification schemes are based on quantifying rock texture by grain size or pore-throat size. They were developed from visual inspection of cores and cuttings, thin-section microscopy or mercury porosimetry. Recent advances in NMR log and core analysis, complemented by more quantitative use of borehole image logs, have led to t...

The chemical and physical properties of a Brazilian heavy oil submitted to plasma treatment were investigated by 1H low- and high-field nuclear magnetic resonance (NMR) combined to the characterization of rheological properties, thermogravimetry and measurement of basic sediments and water (BSW) content. The crude oil was treated in a dielectric ba...

Several classification schemes have been developed to aid formation evaluation in carbonates, based on quantifying carbonate rock texture by either by grain size,3-2 pore-size3-5 or pore-throat size. 6-7 These schemes were developed from visual inspection of cores and cuttings, thinsection microscopy or mercury porosimetry. Recent advances in nucle...

In this paper, we show that the steady-state free precession sequence can be used to acquire 13C high-resolution nuclear magnetic resonance spectra and applied to qualitative analysis. The analysis of brucine sample using this sequence with 60º flip angle and time interval between pulses equal to 300 ms (acquisition time, 299.7 ms; recycle delay, 3...

The Steady-State Free Precession (SSFP) sequence has been widely used in low-field and low-resolution imaging NMR experiments to increase the signal-to-noise ratio (s/n) of the signals. Here, we analyzed the Scrambled Steady State - SSS and Unscrambled Steady State - USS sequences to suppress phase anomalies and sidebands of the 13C NMR spectrum ac...

This article describes the microstructure and dynamics in the solid state of polyfluorene-based polymers, poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO), a semicrystalline polymer, and poly[(9,9-dioctyl-2,7-divinylene-fluorenylene)-alt-co-{2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene}, a copolymer with mesomorphic phase properties. These struct...

The potential of charcoal and of partially combusted organic waste to mimic the soil organic matter of the Terras Pretas de Índios (Amazonian Dark Earths) from the Amazon Region is discussed. These materials serve as soil conditioners and as sequesterers of carbon in recalcitrant and in reactive forms. Studies carried out by Brazilian and by intern...

This article presents an investigation of the temperature induced modification in the microstructure and dynamics of poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) cast films using Wide-Angle X-ray Scattering (WAXS), solid-state Nuclear Magnetic Resonance (NMR), and Fluorescence Spectroscopy (PL). MEH-PPV chain motions were ch...

In this report, the application of a class of separated local field NMR experiments named dipolar chemical shift correlation (DIPSHIFT) for probing motions in the intermediate regime is discussed. Simple analytical procedures based on the Anderson-Weiss (AW) approximation are presented. In order to establish limits of validity of the AW based formu...

A new method, based on continuous wave-free precession nuclear magnetic resonance, is proposed as a high-throughput technique for measuring the oil content of intact seeds. The method has the potential to analyze more than 20 000 intact seeds per hour and is shown to be applicable even to mixtures of seeds of different species with similar fatty ac...

The use of continuous wave free precession (CWFP) as a practical analytical tool for quantitative determinations in low-resolution nuclear magnetic resonance (LRNMR) is examined. The requirements of this technique are shown to be no more demanding than those prevailing in free-induction decay or spin-echo measurements. It is shown that the substant...