Relations Between Pore Size Fluid and Matrix Properties, and NML Measurements

1970 ◽  
Vol 10 (03) ◽  
pp. 268-278 ◽  
Author(s):  
J.D. Loren ◽  
J.D. Robinson
Keyword(s):  
Relaxation Time ◽  
Pore Size ◽  
Pore Space ◽  
Laboratory Data ◽  
Thermal Relaxation ◽  
Residual Oil ◽  
Mercury Injection ◽  
Order Of Magnitude ◽  
Water Response ◽  
Mercury Injection Capillary Pressure

Abstract A theory relating proton relaxation times for water and hydrocarbons confined to rock pores to the pore size distribution of rocks and providing the basis for Nuclear Magnetism Log (NML) interpretation is presented. A model proposed by Senturia and Robinson relates the thermal relaxation time (T1) of the proton spins of molecules in the liquid state to proton spins of molecules in the liquid state to geometrical and physical properties of a liquid-filled porous solid. Four parameters enter their theory, namely, jump distance and correlation time of the liquid molecules, radius of the confining region a, and the probability (1-p) for proton spin-flip at the liquid-solid interface. In this report the theoretical model of Ref. 1 is used to analyze thermal relaxation measurements on a suite of liquid-saturated porcelain samples. The assumption that pore size is inversely proportional to mercury injection capillary pressure proportional to mercury injection capillary pressure (Pc) enables the T1 of the liquid-saturated porous solid to be expressed as where l/r is the thermal relaxation time of the bulk liquid, and is a parameter containing, p and a constant of proportionality. The suite of porcelain samples have mercury injection displacement pressures ranging from 20 to 200 psi; yet values of pressures ranging from 20 to 200 psi; yet values of derived from the measured values of T1, r and Pc are relatively constant as predicted by the theory. When the identical porcelain samples are saturated with decane rather than water, there is an order of magnitude decrease in; this leads to the conclusion that the T1 of a water-wet, hydrocarbon-saturated rock is relatively insensitive to pore size. Values of determined for a suite of water-saturated sandstones with widely varying pore sizes range from 0.13 psi-1 sec-1 to 0.44 psi-1 sec-1. Measurements on samples with both a water and an oil phase present illustrate the insensitivity of the T1 of the oil phase to the geometry of the confining pore space. pore space. Within carbonates, the observed value of is an order of magnitude less than in sands. This reduction could be brought about by either a change in the factor of proportionality relating pore size to pore entry size, or by a decrease in the probability for relaxation at the surface. Within rocks containing both water and oil, the known values of and the assumption that the oil phase occupies the larger pores permits thermal phase occupies the larger pores permits thermal relaxation curves to be calculated which fit observed data. A method for quantitatively determining residual oil involves use of a paramagnetic aqueous phase to effectively kill the water response and phase to effectively kill the water response and permit the remaining signal to be attributed to the permit the remaining signal to be attributed to the oil phase. This theory provides the basis for NML interpretation. For example, application of the theory permits a pore size histogram to be determined from permits a pore size histogram to be determined from a thermal relaxation curve derived histogram is dependent upon the uncertainty associated with each point on the thermal relation curve; and the fraction of the total proton magnetization observed. Another application is the quantitative determination of residual oil from down-hole thermal relaxation data. Introduction The signal recorded on an NML is obtained directly from fluids contained in the pores of a rock. A proper understanding of the relation between the observed response and matrix and fluid properties is essential for the interpretation of the log. In this report, a physical model is presented which provides this relation. Laboratory data from provides this relation. Laboratory data from porcelain and natural cores containing both water and porcelain and natural cores containing both water and hydrocarbon are analyzed in terms of the model. SPEJ p. 268

Salinity dependence of the complex surface conductivity of the Portland sandstone

Geophysics ◽  
2016 ◽  
Vol 81 (2) ◽  
pp. D125-D140 ◽  
Author(s):  
Qifei Niu ◽  
André Revil ◽  
Milad Saidian
Keyword(s):  
Relaxation Time ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Pore Space ◽  
Complex Surface ◽  
Surface Conductivity ◽  
Formation Factor ◽  
Polarization Model ◽  
Fluid Conductivity

Induced polarization can be used to estimate surface conductivity by assuming a universal linear relationship between the surface and quadrature conductivities of porous media. However, this assumption has not yet been justified for conditions covering a broad range of fluid conductivities. We have performed complex conductivity measurements on Portland sandstone, an illite- and kaolinite-rich sandstone, at 13 different water salinities (NaCl) over the frequency range of 0.1 Hz to 45 kHz. The conductivity of the pore water [Formula: see text] affected the complex surface conductivity mainly by changing the tortuosity of the conduction paths in the pore network from high to low salinities. As the fluid conductivity decreases, the magnitude of the surface conductivity and quadrature conductivity was observed to decrease. At relatively high salinities ([Formula: see text]), the ratio between the surface conductivity and quadrature conductivity was roughly constant. At low salinities ([Formula: see text]), the ratio decreased slightly with the decrease of the salinity. A Stern layer polarization model was combined with the differential effective medium (DEM) theory to describe this behavior. The tortuosity entering the complex surface conductivity was salinity dependent following the prediction of the DEM theory. At high salinity, it reached the value of the bulk tortuosity of the pore space given by the product of the intrinsic formation factor and the connected porosity. The relaxation time distributions were also obtained at different salinities by inverting the measured spectra using a Warburg decomposition. The mode of the relaxation time probability distribution found a small but clear dependence on the salinity. This salinity dependence can be explained by considering the ions exchange between Stern and diffuse layers during polarization of the former. The pore-size distribution obtained from the distribution of the relaxation time agreed with the pore-size distribution from nuclear magnetic resonance measurements.

Effects of Thermomechanical Coupling and Relaxation Times on Wave Spectrum in Dynamic Theory of Generalized Thermoelasticity

1998 ◽  
Vol 65 (3) ◽  
pp. 605-613 ◽  
Author(s):  
C. S. Suh ◽  
C. P. Burger
Keyword(s):  
Relaxation Time ◽  
Wave Spectrum ◽  
Relaxation Times ◽  
Thermal Relaxation ◽  
Generalized Thermoelasticity ◽  
Thermomechanical Coupling ◽  
Order Of Magnitude ◽  
Relaxation Time Constants ◽  
Thermoelastic Waves ◽  
Insight Into

A spectral study is performed to gain insight into the effects of relaxation times and thermomechanical coupling on dynamic thermoe Iastic responses in generalized thermoelasticity. The hyperbolic thermoelastic theories of Lord and Schulman (LS) and Green and Lindsay (GL) are selected for the study. A generalized characteristic equation is derived to investigate dispersion behavior of thermoelastic waves as functions of thermomechanical coupling and relaxation time constants. Thermomechanical coupling is found to impose a significant influence on phase velocities. The GL model implicitly indicates that the order of magnitude of the thermomechanical relaxation time can never be greater than that of thermal relaxation time.

The impact of pore-scale magnetic field inhomogeneity on the shape of the nuclear magnetic resonance relaxation time distribution

Geophysics ◽  
2016 ◽  
Vol 81 (5) ◽  
pp. EN43-EN55 ◽  
Author(s):  
Denys Grombacher ◽  
Emily Fay ◽  
Matias Nordin ◽  
Rosemary Knight
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Pore Size ◽  
Time Distribution ◽  
Pore Space ◽  
Relaxation Times ◽  
Magnetic Field Inhomogeneity ◽  
Field Inhomogeneity ◽  
Relaxation Time Distribution ◽  
Measured Relaxation

Measurements of the nuclear magnetic resonance (NMR) signal’s behavior with time provide powerful noninvasive insight into the pore-scale environment. The time dependence of the NMR signal, which is a function of parameters called relaxation times, is intimately linked to the geometry of the pore space and has been used successfully to estimate pore size and permeability. The basis for the pore size and permeability estimates is that interactions occurring at the grain surface often function as the primary mechanism controlling the time dependence of the NMR signal. In this limit, called the fast diffusion limit, and when each pore can be considered to be isolated, the measured relaxation times are often interpreted as representative of pore sizes. In heterogeneous media, where the NMR signal is described by a distribution of relaxation times, the measured relaxation time distribution is often interpreted as representative of the underlying pore-size distribution. We have explored a scenario in which an additional relaxation mechanism, which arises due to magnetic field inhomogeneity across the pore space, violates the assumption that interactions occurring at the grain surface are the dominant relaxation mechanism. Using both synthetic and laboratory studies, we demonstrate that magnetic field inhomogeneity can lead to a complex relationship between the measured relaxation time distribution and the underlying pore-size distribution. Magnetic field inhomogeneity is observed to lead to a spatially heterogeneous magnetization density across the pore space requiring multiple eigenmodes to describe the evolution of the magnetization within a single pore during the NMR experiment. This results in a breakdown of the validity of the interpretation of the relaxation time distribution as representative of the underlying pore-size distribution for sediments with high magnetic susceptibility.

scholarly journals Ocena parametrów przestrzeni porowej łupków menilitowych z odsłonięcia w Birczy

Nafta-Gaz ◽  
2021 ◽  
Vol 77 (10) ◽  
pp. 633-640
Author(s):  
Lidia Dudek ◽  
◽  
Konrad Ziemianin ◽  
Keyword(s):  
Specific Surface ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Capillary Pressure ◽  
Size Distribution ◽  
Surface Area ◽  
Specific Surface Area ◽  
Mercury Injection ◽  
Mercury Injection Capillary Pressure

Celem pracy było scharakteryzowanie przestrzeni porowej łupków menilitowych występujących w odsłonięciach powierzchniowych z rejonu Birczy w jednostce skolskiej. Wszystkie próbki zostały pobrane z całego profilu stratygraficznego w jednym odsłonięciu w Birczy o długości 1 m. Struktura porowa próbek łupków wygrzanych w 105°C była mierzona metodą porozymetrii rtęciowej (ang. mercury injection capillary pressure, MICP) w temperaturze otoczenia oraz metodą adsorpcji azotu w temperaturze wrzenia ciekłego azotu. Ze względu na deformację przestrzeni porowej pod wpływem wysokich ciśnień roboczych rtęci, z krokami ciśnienia od 0 do 4136,84 bara, mikropory i mezopory można błędnie interpretować. Jako metodę uzupełniającą zastosowano więc pomiar adsorpcji azotu w celu prawidłowego obliczenia całkowitej połączonej objętości porowej. Na wykresach dV/dD (pochodnych objętości względem średnicy) połączono wyniki z obu technik pomiarowych, uzyskując pełniejszy obraz rozkładu objętości porów. W pracy przedstawiono możliwość dokładniejszego obliczenia objętości porów na podstawie nowego podejścia do analizy wykresów pochodnych. Obie metody zapewniają również kompleksową ocenę parametrów struktury porów, w tym powierzchni właściwej (ang. specific surface area, SSA), objętości mikro- i mezoporów oraz rozszerzonego zakresu rozkładu wielkości porów (ang. pore size distribution, PSD). Porównując wyniki metody adsorpcyjnej z użyciem azotu z wynikami porozymetrii rtęciowej, należy pamiętać o różnicach w zakresach obu technik badawczych oraz o tym, że azot i rtęć rejestrują struktury porowe w znacząco odmienny sposób. Zatłaczanie rtęci do struktury porowej jest regulowane przez przewężenia porów, podczas gdy zjawisko adsorpcji jest kontrolowane przez powierzchnię porów. Zastosowanie porozymetrii rtęciowej i adsorpcji azotu do łupków menilitowych pokazuje, jak użycie tych dwóch metod może wpłynąć na uzyskanie wzajemnie uzupełniających się informacji, które weryfikują obliczenia objętości porowej głównej skały macierzystej dla karpackich rop naftowych.

scholarly journals Evidence from Spectra of Bright Fireballs

1971 ◽  
Vol 13 ◽  
pp. 89-102 ◽  
Author(s):  
Zdeněk Ceplecha
Keyword(s):  
Relaxation Time ◽  
Spectral Data ◽  
Laboratory Data ◽  
Absolute Magnitude ◽  
Boltzmann Distribution ◽  
Luminous Efficiency ◽  
The Self ◽  
Oscillator Strengths ◽  
Spontaneous Radiation ◽  
Order Of Magnitude

Spectral data with dispersions from 11 to 94 Å/mm on 4 fireballs of actual brightness of —4 to —12 magnitude and with velocities of about 30 km/s at 70 to 80 km heights are used for studies of meteor radiation problems. Previously published analyses need revision for two main reasons: (a) the absolute values of oscillator strengths of Fe I lines from laboratory data were recently recognized to be 1 order of magnitude lower, (b) the luminous efficiency factor τ of Fe I is now much better known from several different experiments. The radiation of fireballs is found to be strongly affected by self-absorption. But if the emission curve of growth is used for correction oj the self-absorption of Fe I lines, a great discrepancy between spectral data and efficiency data for total Fe I light is found. If one assumes that the self-absorption is superposed on another effect, a decrease of the dimensions of the radiating volume with increasing lower potential E1, the spectral data on Fe I lines will be in agreement with the luminous efficiency of total Fe I meteor radiation. Formulas for emission curve of growth and Boltzmann distribution including this effect are derived. This effect is important for fireballs brighter than about —1 or — 2 magnitude, while self-absorption seems to be important even for fainter meteors. The optically thin radiation of all Fe I lines might be expected for meteors fainter than +5 magnitude. Excitation temperature of 5500° K and relaxation time of 0.02 s were found as typical values for the Fe I radiation of fireballs studied. The light of fireballs is emitted during a relatively long relaxation time, which is many orders of magnitude longer than the time necessary for spontaneous radiation of excited Fe I atoms. The dimensions of the radiating volume of Fe I gas for lines with E1 = 0 were found to be 0.3X9 m at 0 absolute magnitude and 2×60 m at —10 absolute magnitude. It ivas not possible to determine any realistic abundances of other elements due to small numbers of lines for an analysis independent of Fe I, while the Fe I curve of growth cannot be used for other elements, because the radiation originates mainly from the effective surface of the radiating volume. A general formula for meteor radiation is also derived and compared with the conventional luminosity equation.

Correlating Blocking Temperatures in Single Molecule Magnets with Raman Relaxation

2018 ◽  
Author(s):  
Marcus J. Giansiracusa ◽  
Andreas Kostopoulos ◽  
George F. S. Whitehead ◽  
David Collison ◽  
Floriana Tuna ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Single Molecule ◽  
Energy Barrier ◽  
Thermal Relaxation ◽  
Relaxation Mechanism ◽  
Blocking Temperature ◽  
Single Molecule Magnets ◽  
Single Molecule Magnet ◽  
Key Parameter

We report a six coordinate DyIII single-molecule magnet<br>(SMM) with an energy barrier of 1110 K for thermal relaxation of<br>magnetization. The sample shows no retention of magnetization<br>even at 2 K and this led us to find a good correlation between the<br>blocking temperature and the Raman relaxation regime for SMMs.<br>The key parameter is the relaxation time (𝜏<sub>switch</sub>) at the point where<br>the Raman relaxation mechanism becomes more important than<br>Orbach.

Petrographic and Petrophysical Characteristics of the Upper Devonian Three Forks Formation, Southern Nesson Anticline, North Dakota

2017 ◽  
Vol 54 (3) ◽  
pp. 181-201
Author(s):  
Rebecca Johnson ◽  
Mark Longman ◽  
Brian Ruskin
Keyword(s):  
Relaxation Time ◽  
Pore Size ◽  
Water Saturation ◽  
Average Pore Size ◽  
Total Porosity ◽  
Average Pore ◽  
Pore Sizes ◽  
Three Forks Formation ◽  
Three Forks ◽  
Intercrystalline Pores

The Three Forks Formation, which is about 230 ft thick along the southern Nesson Anticline (McKenzie County, ND), has four “benches” with distinct petrographic and petrophysical characteristics that impact reservoir quality. These relatively clean benches are separated by slightly more illitic (higher gamma-ray) intervals that range in thickness from 10 to 20 ft. Here we compare pore sizes observed in scanning electron microscope (SEM) images of the benches to the total porosity calculated from binned precession decay times from a suite of 13 nuclear magnetic resonance (NMR) logs in the study area as well as the logarithmic mean of the relaxation decay time (T2 Log Mean) from these NMR logs. The results show that the NMR log is a valid tool for quantifying pore sizes and pore size distributions in the Three Forks Formation and that the T2 Log Mean can be correlated to a range of pore sizes within each bench of the Three Forks Formation. The first (shallowest) bench of the Three Forks is about 35 ft thick and consists of tan to green silty and shaly laminated dolomite mudstones. It has good reservoir characteristics in part because it was affected by organic acids and received the highest oil charge from the overlying lower Bakken black shale source rocks. The 13 NMR logs from the study area show that it has an average of 7.5% total porosity (compared to 8% measured core porosity), and ranges from 5% to 10%. SEM study shows that both intercrystalline pores and secondary moldic pores formed by selective partial dissolution of some grains are present. The intercrystalline pores are typically triangular and occur between euhedral dolomite rhombs that range in size from 10 to 20 microns. The dolomite crystals have distinct iron-rich (ferroan) rims. Many of the intercrystalline pores are partly filled with fibrous authigenic illite, but overall pore size typically ranges from 1 to 5 microns. As expected, the first bench has the highest oil saturations in the Three Forks Formation, averaging 50% with a range from 30% to 70%. The second bench is also about 35 ft thick and consists of silty and shaly dolomite mudstones and rip-up clast breccias with euhedral dolomite crystals that range in size from 10 to 25 microns. Its color is quite variable, ranging from green to tan to red. The reservoir quality of the second bench data set appears to change based on proximity to the Nesson anticline. In the wells off the southeast flank of the Nesson anticline, the water saturation averages 75%, ranging from 64% to 91%. On the crest of the Nesson anticline, the water saturation averages 55%, ranging from 40% to 70%. NMR porosity is consistent across the entire area of interest - averaging 7.3% and ranging from 5% to 9%. Porosity observed from samples collected on the southeast flank of the Nesson Anticline is mainly as intercrystalline pores that have been extensively filled with chlorite clay platelets. In the water saturated southeastern Nesson Anticline, this bench contains few or no secondary pores and the iron-rich rims on the dolomite crystals are less developed than those in the first bench. The chlorite platelets in the intercrystalline pores reduce average pore size to 500 to 800 nanometers. The third bench is about 55 ft thick and is the most calcareous of the Three Forks benches with 20 to 40% calcite and a proportionate reduction in dolomite content near its top. It is also quite silty and shaly with a distinct reddish color. Its dolomite crystals are 20 to 50 microns in size and partly abraded and dissolved. Ferroan dolomite rims are absent. This interval averages 7.1% porosity and ranges from 5% to 9%, but the pores average just 200 nanometers in size and occur mainly as microinterparticle pores between illite flakes in intracrystalline pores in the dolomite crystals. This interval has little or no oil saturation on the southern Nesson Anticline. Unlike other porosity tools, the NMR tool is a lithology independent measurement. The alignment of hydrogen nuclei to the applied magnetic field and the subsequent return to incoherence are described by two decay time constants, longitudinal relaxation time (T1) and transverse relaxation time (T2). T2 is essentially the rate at which hydrogen nuclei lose alignment to the external magnetic field. The logarithmic mean of T2 (T2 Log Mean) has been correlated to pore-size distribution. In this study, we show that the assumption that T2 Log Mean can be used as a proxy for pore-size distribution changes is valid in the Three Forks Formation. While the NMR total porosity from T2 remains relatively consistent in the three benches of the Three Forks, there are significant changes in the T2 Log Mean from bench to bench. There is a positive correlation between changes in T2 Log Mean and average pore size measured on SEM samples. Study of a “type” well, QEP’s Ernie 7-2-11 BHD (Sec. 11, T149N, R95W, McKenzie County), shows that the 1- to 5-micron pores in the first bench have a T2 Log Mean relaxation time of 10.2 msec, whereas the 500- to 800-nanometer pores in the chlorite-filled intercrystalline pores in the second bench have a T2 Log Mean of 4.96 msec. This compares with a T2 Log Mean of 2.86 msec in 3rd bench where pores average just 200 nanometers in size. These data suggest that the NMR log is a useful tool for quantifying average pore size in the various benches of the Three Forks Formation.

Textural and pore size analysis of carbonates from integrated core and nuclear magnetic resonance logging: An Arbuckle study

2015 ◽  
Vol 3 (1) ◽  
pp. SA77-SA89 ◽  
Author(s):  
John Doveton ◽  
Lynn Watney
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Relaxation Time ◽  
Magnetic Resonance ◽  
Pore Size ◽  
Relaxation Times ◽  
T2 Relaxation Time ◽  
T2 Relaxation ◽  
Nmr Logging ◽  
The Core ◽  
Nuclear Magnetic

The T2 relaxation times recorded by nuclear magnetic resonance (NMR) logging are measures of the ratio of the internal surface area to volume of the formation pore system. Although standard porosity logs are restricted to estimating the volume, the NMR log partitions the pore space as a spectrum of pore sizes. These logs have great potential to elucidate carbonate sequences, which can have single, double, or triple porosity systems and whose pores have a wide variety of sizes and shapes. Continuous coring and NMR logging was made of the Cambro-Ordovician Arbuckle saline aquifer in a proposed CO2 injection well in southern Kansas. The large data set gave a rare opportunity to compare the core textural descriptions to NMR T2 relaxation time signatures over an extensive interval. Geochemical logs provided useful elemental information to assess the potential role of paramagnetic components that affect surface relaxivity. Principal component analysis of the T2 relaxation time subdivided the spectrum into five distinctive pore-size classes. When the T2 distribution was allocated between grainstones, packstones, and mudstones, the interparticle porosity component of the spectrum takes a bimodal form that marks a distinction between grain-supported and mud-supported texture. This discrimination was also reflected by the computed gamma-ray log, which recorded contributions from potassium and thorium and therefore assessed clay content reflected by fast relaxation times. A megaporosity class was equated with T2 relaxation times summed from 1024 to 2048 ms bins, and the volumetric curve compared favorably with variation over a range of vug sizes observed in the core. The complementary link between grain textures and pore textures was fruitful in the development of geomodels that integrates geologic core observations with petrophysical log measurements.

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