TEMPERATURE CORRECTION MODELS FOR NMR RELAXATION TIME DISTRIBUTION IN CARBONATE ROCKS

The pore structure of cement paste has a relationship with its strength and durability. An appropriate method of measurement is a prerequisite to study the pore structure of cement paste. Among many test methods, Nuclear Magnetic Resonance (NMR) relaxation time is a novel testing methods to study pore structure of cement paste. Different from previous research object is limited to white cement, the test sample in this paper is the blended cement paste containing mineral admixture and has been widely used in practical engineering applications. The factors of pore structure are water to cementitious material ratio, kind of mineral admixture, and mineral admixture content. Measure the same sample at four different ages to obtain the relaxation time distribution to reflect the pore structure. The test results show that, in most cases, the distribution curves of the same kind of paste are in good agreement, and the change of relaxation time distribution of the blended cement paste with different ages can be interpreted as the characteristic of the mineral admixtures in cement paste. So the NMR relaxation time is suitable for study on the blended cement paste. However due to side effects caused by iron content and unsaturated water in gel pore, this method needs further improvement.

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A laboratory study of NMR relaxation times in unconsolidated heterogeneous sediments

Geophysics ◽

10.1190/1.3581094 ◽

2011 ◽

Vol 76 (4) ◽

pp. G73-G83 ◽

Cited By ~ 29

Author(s):

Elliot Grunewald ◽

Rosemary Knight

Keyword(s):

Grain Size ◽

Relaxation Time ◽

Time Distribution ◽

Relaxation Times ◽

Nmr Relaxation ◽

Unconsolidated Sediments ◽

Relaxation Response ◽

Relaxation Time Distribution ◽

Near Surface ◽

Heterogeneous Sediments

Nuclear magnetic resonance (NMR) relaxation-time measurements can provide critical information about the physiochemical properties of water-saturated media and are used often to characterize geologic materials. In unconsolidated sediments, the link between measured relaxation times and pore-scale properties can be complicated when diffusing water molecules couple the relaxation response of heterogeneous regions within a well-connected pore space. Controlled laboratory experiments have allowed us to investigate what factors control the extent of diffusional coupling in unconsolidated sediments and what information is conveyed by the relaxation-time distribution under varied conditions. A range of sediment samples exhibiting heterogeneity in the form of a bimodal mineralogy of quartz and hematite were mixed with varied mineral concentration and grain size. NMR relaxation measurements and geometric analysis of these mixtures demonstrate the importance of two critical length scales controlling the relaxation response: the diffusion length ℓD, describing the distance a water molecule diffuses during the NMR measurement, and the separation length ℓS, describing the scale at which heterogeneity occurs. For the condition of ℓS > ℓD, which prevails for samples with low hematite concentrations and coarser grain size, coupling is weak and the bimodal relaxation-time distribution independently reflects the relaxation properties of the two mineral constituents in the heterogeneous mixtures. For the condition of ℓS < ℓD, which prevails at higher hematite concentrations and finer grain size, the relaxation-time distribution no longer reflects the presence of a bimodal mineralogy but instead conveys a more complex averaging of the heterogeneous relaxation environments. This study has shown the potential extent and influence of diffusional coupling in unconsolidated heterogeneous sediments, and can serve to inform the interpretation of NMR measurements in near-surface environments where unconsolidated sediments are commonly encountered.

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Temperature Dependence of NMR Relaxation Time in Carbonate Reservoirs

10.2118/206184-ms ◽

2021 ◽

Author(s):

Wei Shao ◽

Songhua Chen ◽

Gabor Hursan ◽

Shouxiang Ma

Keyword(s):

Relaxation Time ◽

Ambient Temperature ◽

Temperature Dependence ◽

Carbonate Rocks ◽

Nmr Relaxation ◽

Carbonate Reservoirs ◽

High Quality ◽

T2 Distribution ◽

Nmr Relaxation Time ◽

Data Analytic

Abstract NMR-based carbonate interpretation models are commonly calibrated using laboratory ambient core NMR measurements. For applying the core calibrated models to downhole NMR logging interpretation, the difference between the NMR responses measured at ambient and reservoir conditions needs to be evaluated. The temperature dependence of NMR relaxation time in high-quality carbonate reservoirs was investigated, and NMR temperature dependence models were determined using data analytic methods (Hursan et al, 2019). This paper focuses on temperature dependence of NMR relaxation time in low-quality carbonate formations. For more than 95% of the samples investigated, NMR relaxation time shows a positive correlation with temperature. The correlation is similar to that observed in high-quality carbonate rocks but slightly less significant. Temperature dependent correlations for predicting T2GM from a measured temperature to any other temperature are derived from high- and low-quality carbonate rocks independently first, then a unified T2GM correlation is derived including both the high- and low-quality carbonate reservoirs. Predicting T2 distribution from one temperature to other temperatures is achieved using dimension reduction approach involving principal component analysis (PCA) technique. It is found that the T2 distributions at any given temperature for both the high- and low-quality carbonate reservoirs can be predicted robustly from the T2 distributions at the ambient temperature by representing the T2 distributions with principal components (PCs) at the ambient temperature then using these PCs to predict the PCs at a different temperature. The optimal number of PC components depends on the multimodality of the T2 distribution. This work extends the validity range of a data analytic method that quantifies the temperature dependence of carbonate NMR properties. The new NMR temperature model enables the integration of NMR laboratory studies and dowhole measurements for advanced petrophysical analyses in a wide range of carbonate reservoirs.

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Parameterization of NMR relaxation curves in terms of logarithmic moments of the relaxation time distribution

Journal of Magnetic Resonance ◽

10.1016/j.jmr.2017.04.009 ◽

2017 ◽

Vol 279 ◽

pp. 29-38 ◽

Cited By ~ 6

Author(s):

Oleg V. Petrov ◽

Siegfried Stapf

Keyword(s):

Relaxation Time ◽

Time Distribution ◽

Nmr Relaxation ◽

Relaxation Time Distribution ◽

Relaxation Curves ◽

Logarithmic Moments

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NMR relaxation time dependency on saturation and wettability of carbonate rocks

10.1190/segam2014-1663.1 ◽

2014 ◽

Cited By ~ 2

Author(s):

Edmilson Rios ◽

Irineu Figueiredo ◽

Vinicius Machado ◽

André Compan ◽

Bernardo Santos ◽

...

Keyword(s):

Relaxation Time ◽

Carbonate Rocks ◽

Nmr Relaxation ◽

Time Dependency ◽

Nmr Relaxation Time

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Temperature Dependence of Nuclear Magnetic Resonance Relaxation Time in Carbonate Reservoirs

SPE Reservoir Evaluation & Engineering ◽

10.2118/206184-pa ◽

2021 ◽

pp. 1-16

Author(s):

Wei Shao ◽

Songhua Chen ◽

Gabor Hursan ◽

Shouxiang Ma

Keyword(s):

Nuclear Magnetic Resonance ◽

Relaxation Time ◽

Temperature Dependence ◽

Carbonate Rocks ◽

Nmr Relaxation ◽

Transverse Relaxation Time ◽

Carbonate Reservoirs ◽

Transverse Relaxation ◽

Nmr Relaxation Time ◽

Data Analytic

Summary Nuclear magnetic resonance (NMR)-based interpretation models are commonly calibrated using laboratory ambient core NMR measurements. For applying the core calibrated models to downhole NMR logging interpretation, the difference between the NMR responses measured at ambient and reservoir temperature needs to be evaluated. The temperature dependence of NMR relaxation time in high-quality (HQ) carbonate reservoirs has been studied, and NMR temperature dependence models were established using data analytic methods. In this paper, we extend our early studies on temperature dependence of NMR relaxation time to low-quality (LQ) carbonate formations. For more than 95% of the LQ samples investigated, NMR relaxation time shows a positive correlation with temperature. The correlation is similar to that observed in HQ carbonate rocks but slightly less significant. Temperature-dependent correlations for predicting the geometric mean of NMR transverse relaxation time (T2,GM) from a measured temperature to any other temperature were derived from HQ to LQ carbonate rocks independently first, then a unified T2,GM correlation was derived including both the HQ and LQ carbonate reservoirs. Predicting NMR transverse relaxation time T2 distribution from one temperature to other temperatures was achieved using a dimension reduction approach involving the principal component analysis (PCA) technique. It was found that the T2 distributions at any given temperature for both HQ and LQ carbonate reservoirs can be predicted robustly from the T2 distributions at the ambient temperature by representing the T2 distributions with principal components (PCs) at the ambient temperature and then using these PCs to predict the PCs at a different temperature. The optimal number of PC components depends on the multimodality of the T2distribution. This work extends the validity range of the data analytic methods, in particular parameter and dimension reduction methods, that quantify the temperature dependence of carbonate NMR properties. The new NMR temperature model enables the integration of NMR laboratory studies and downhole measurements for advanced petrophysical analyses in a wide range of carbonate reservoirs.

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A laboratory study of NMR relaxation times and pore coupling in heterogeneous media

Geophysics ◽

10.1190/1.3223712 ◽

2009 ◽

Vol 74 (6) ◽

pp. E215-E221 ◽

Cited By ~ 45

Author(s):

Elliot Grunewald ◽

Rosemary Knight

Keyword(s):

Relaxation Time ◽

Time Distribution ◽

Heterogeneous Media ◽

Relaxation Times ◽

Nmr Relaxation ◽

Micropore Volume ◽

Heterogeneous Porous Media ◽

Relaxation Time Distribution ◽

Basic Parameters ◽

Nmr Relaxation Times

Nuclear magnetic resonance (NMR) relaxation times of geologic materials are closely related to pore geometry. In heterogeneous media, however, the details of this relationship are poorly understood because of a phenomenon known as pore coupling, which arises when diffusing protons sample multiple pores before relaxing. Laboratory experiments allow us to explore whether surface geochemistry can influence pore coupling and how this process affects the observed relaxation-time distribution. Measurements of the NMR response for microporous silica gel packs, treated with varying amounts of surface-coating iron, demonstrate that samples with less iron exhibit stronger pore coupling than those with abundant iron. When pore coupling is strong, the relaxation-time distribution grossly misrepresents the underlying bimodal pore-size distribution of micropores and macropores. Specifically, the bimodal relaxation-time distribution becomes merged and the relative amplitude of the peaks fails to reflect the true macropore and micropore volume. A reduction in pore coupling, observed with increasing iron content, is attributed to a decrease in the distance protons are able to diffuse before relaxing. Basic parameters describing the shape of the relaxation-time distributions for this range of samples are well-predicted by a 1D analytical model. Experimental results conclusively demonstrate that surface geochemistry is an important factor determining the degree to which pore coupling occurs and illustrate how this phenomenon can affect the interpretation of NMR relaxation measurements in heterogeneous porous media.

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