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R. D. Jarrard - One of the best experts on this subject based on the ideXlab platform.
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Petrophysical investigations on sediment Core CRP-2A from the Ross Sea, Antarctica, supplement to: Brink, Jason; Jarrard, Richard D (2000): Petrophysics of Core Plugs from CRP-2A drillhole, Victoria Land Basin, Antarctica. Terra Antartica, 7(3), 231-
2020Co-Authors: J. Brink, R. D. JarrardAbstract:A suite of petropysical measurements - velocity versus pressure, bulk density, porosity, matrix density, and magnetic susceptibility -was undertaken on 63 Core Plugs from CRP-2A. These data are used to calibrate neutron, resistivity, and magnetic susceptibility well logs. Agreement between Core-Plug magnetic susceptibility measurements and both well-log and whole-Core data is excellent. Comparison of Core-Plug bulk densities with continious well-log density records shows very good agreement. Core-Plug measurements of matrix density permit conversion of the well-log and whole-Core density records to porosity. Sands and muds exhibit similar downhole compaction patterns, and both patterns are consistent with 250 ± 150 m of exhumation. Pervasive cementation, particularly in the lower half of the Core, has affected many CRP-2A petrophysical parameters:(1) fractional porosities are reduced by about 0.05 - 0.10 in the lower part of the hole;(2) velocity and porosity rebound are much smaller than is usually observed for unconsolidated sediments with burial depths similar to CRP-2A;(3) velocities are unusually insensitive to pressure, suggesting that any exhumation-induced microcracks have been scaled subsequently;(4) the velocity/porosity relationship lacks the characteristic signature of exhumation-induced microcracks;(5) the velocity/porosity relationship changes with depth, indicating downhole increase in consolidation;(6) Vp/Vs ratios of the highest-porosity sediments are unusually low, implying enhancement of framework stiffness.
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Petrophysics of Core Plugs from CRP-2A drillhole, Victoria Land Basin, Antarctica
1998Co-Authors: J. Brink, R. D. JarrardAbstract:A suite of petrophysical properties velocity, resistivity, bulk density, porosity, and matrix density – was measured on 88 Core Plugs from the CRP-3 drillhole. Core-Plug bulk densities were used to recalibrate both whole-Core and downhole bulk density logs. Core-Plug measurements of matrix density permit conversion of the whole-Core and downhole bulk density logs to porosity. Both velocity and formation factor (a normalized measure of resistivity) are strongly correlated with porosity. The velocity/porosity pattern is similar to that for the lower part of CRP-2A and is consistent with the empirical relationship for sandstones. Core-Plug and whole-Core measurements of P-wave velocity at atmospheric pressure exhibit excellent agreement. Measurements of velocity as a function of pressure indicate a significantly higher velocity sensitivity to pressure than has been observed at CRP-1 and CRP-2A; rebound or presence of microcracks at CRP-3 may be responsible. The percentage difference between velocities at in situ pressures and atmospheric pressures increases downhole from 0% at the seafloor to 9% at the bottom. This pattern can be used to correct whole-Core velocity data, measured at atmospheric pressure, to in situ velocities for depth-to-time conversion and associated comparison to the seismic profile across the drillsite.
Bruce J. Balcom - One of the best experts on this subject based on the ideXlab platform.
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Controlling susceptibility mismatch effects, signal lifetimes, and SNR through variation of B0 in MRI of rock Core Plugs
Journal of Magnetic Resonance, 2019Co-Authors: Razieh Enjilela, Bryce Macmillan, Michael Mcaloon, Oleg V. Petrov, S. Vashaee, Bruce J. BalcomAbstract:Abstract 1H relaxometry measurements of petroleum Core Plugs are commonly performed on low field magnets ( 3 Tesla) are typically employed in small animal MRI studies to improve SNR and image resolution. For many rock Core Plug samples, susceptibility mismatch effects can be severe at these higher fields leading to decreased T2 and T2*. In this work we seek an answer to the general question of what is the best field for MRI of rock Core Plugs, anticipating that it will be both sample and measurement method dependent. Free Induction Decay (FID) relaxation time measurements were undertaken to investigate the conditions under which the SNR in Centric Scan SPRITE (Single Point Ramped Imaging with T1 Enhancement) MRI measurements is maximized. The image SNR benefits from greater signal at higher fields, but is negatively impacted by the correspondingly shorter signal lifetimes. Depending on the noise regime of the sample, the maximum SNR may be predicted for Centric Scan SPRITE MRI with T2* being B0 field dependent. In this work we describe a series of simple experimental considerations to determine the optimal B0 field for SPRITE MRI. Selection of the best field is aided by a new generation of superconducting magnets which allows the experimentalist to readily vary the field strength. Such magnets allow one to experimentally control sample magnetization for high sensitivity MRI measurements of Core Plug samples, while controlling the effect of susceptibility mismatch on the signal lifetimes.
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An MR/MRI Compatible Core Holder with the RF Probe Immersed in the Confining Fluid
Journal of Magnetic Resonance, 2017Co-Authors: Mojtaba Shakerian, Bruce J. BalcomAbstract:• A new high pressure/temperature metal MR/MRI Core holder which significantly simplifies MR/MRI Core Plug measurements at reservoir conditions.
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k-t acceleration in pure phase encode MRI to monitor dynamic flooding processes in rock Core Plugs.
Journal of Magnetic Resonance, 2014Co-Authors: Dan Xiao, Bruce J. BalcomAbstract:Abstract Monitoring the pore system in sedimentary rocks with MRI when fluids are introduced is very important in the study of petroleum reservoirs and enhanced oil recovery. However, the lengthy acquisition time of each image, with pure phase encode MRI, limits the temporal resolution. Spatiotemporal correlations can be exploited to undersample the k -t space data. The stacked frames/profiles can be well approximated by an image matrix with rank deficiency, which can be recovered by nonlinear nuclear norm minimization. Sparsity of the x -t image can also be exploited for nonlinear reconstruction. In this work the results of a low rank matrix completion technique were compared with k- t sparse compressed sensing. These methods are demonstrated with one dimensional SPRITE imaging of a Bentheimer rock Core Plug and SESPI imaging of a Berea rock Core Plug, but can be easily extended to higher dimensionality and/or other pure phase encode measurements. These ideas will enable higher dimensionality pure phase encode MRI studies of dynamic flooding processes in low magnetic field systems.
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region of interest selection of long Core Plug samples by magnetic resonance imaging profiling and local t2 measurement
Measurement Science and Technology, 2014Co-Authors: S. Vashaee, Bruce J. Balcom, O V Petrov, Benedict NewlingAbstract:Magnetic resonance imaging (MRI) is increasingly employed as a Core analysis technique by the oil and gas industry. In axial profiling of petroleum reservoir Core samples and Core Plugs, the sample of interest may frequently be much longer than the natural field of view (FOV) defined by the radio frequency (RF) sensor and region of constant magnetic field gradient. Profiling such samples with a low field MRI will result in distorted, non-quantitative axial profiles near the edge of the FOV with data from outside the desired FOV folding back into the image, when the gradient magnetic field homogenity region is shorter than the region of RF excitation. The quality of MRI as a Core analysis technique is increased if imaging can be performed on intact samples with the FOV reduced to the region of interest (ROI), either to increase the image resolution or to reduce the total time for imaging. A spatially selective adiabatic inversion pulse is applied in the presence of a slice selective magnetic field gradient to restrict the FOV to an ROI that is a small portion of a long sample. Slice selection is followed by a 1D centric-scan SPRITE measurement to yield an axial fluid density profile of the sample in the ROI. By employing adiabatic pulses, which are immune to RF field non-uniformities, it is possible to restrict the ROI to a region of homogeneous RF excitation, facilitating quantitative imaging. The method does not employ conventional selective excitation, but a subtraction based on images acquired with and without adiabatic inversion slice selection. The adiabatic slice selection lends itself to a selective T2 distribution measurement when a CPMG pulse sequence follows the slice selection. The inversion pulse selects a slice on the order of 1 cm at an arbitrary position. The local T2 distributions measured are of similar quality to bulk CPMG. This method is an alternative to MRI-based techniques for T2 mapping in short relaxation time samples in porous media when T2 is required to be measured at only a few positions along the sample, and a resolution of 1 cm is acceptable.
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Spatially resolved measurements of mean spin–spin relaxation time constants
Journal of Magnetic Resonance, 2013Co-Authors: Ruben Nechifor, Konstantin Romanenko, Florea Marica, Bruce J. BalcomAbstract:Abstract Magnetic Resonance measurements of the T2 distribution have become very common and they are a powerful way to probe microporous fluid bearing solids. While the structure of the T2 distribution, and changes in the structure, are often very informative, it is common to reduce the T2 distribution to a mean numeric quantity in order to provide a quantitative interpretation of the distribution. Magnetic Resonance Imaging measurements of the T2 distribution have recently been introduced, but they are time consuming, especially for 2 and 3 spatial dimensions. In this paper we explore a direct MRI measurement of the arithmetic mean of 1/T2, characterizing the distribution by using the initial slope of the spatially resolved T2 decay in a CPMG prepared Centric Scan SPRITE experiment. The methodology is explored with a test phantom sample and realistic petroleum reservoir Core Plug samples. The arithmetic mean of 1/T2 is related to the harmonic mean of T2. The mean obtained from the early decay is explored through measurements of uniform saturated Core Plug samples and by comparison to other means determined from the complete T2 distribution. Complementary data were obtained using SE-SPI T2 distribution MRI measurements. The utility of the arithmetic mean 1/T2 is explored through measurements of centrifuged Core Plug samples where the T2 distribution varies spatially. The harmonic mean T2 obtained from the early decay was employed to estimate the irreducible water saturation for Core Plug samples.
T P Blach - One of the best experts on this subject based on the ideXlab platform.
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characterization of tight gas reservoir pore structure using usans sans and gas adsorption analysis
Fuel, 2012Co-Authors: Christopher R. Clarkson, Melissa Freeman, Lilin He, M Agamalian, Yuri B Melnichenko, Maria Mastalerz, Robert Marc Bustin, Andrzej P Radlinski, T P BlachAbstract:Small-angle and ultra-small-angle neutron scattering (SANS and USANS) measurements were performed on samples from the Triassic Montney tight gas reservoir in Western Canada in order to determine the applicability of these techniques for characterizing the full pore size spectrum and to gain insight into the nature of the pore structure and its control on permeability. The subject tight gas reservoir consists of a finely laminated siltstone sequence; extensive cementation and moderate clay content are the primary causes of low permeability. SANS/USANS experiments run at ambient pressure and temperature conditions on lithologically-diverse sub-samples of three Core Plugs demonstrated that a broad pore size distribution could be interpreted from the data. Two interpretation methods were used to evaluate total porosity, pore size distribution and surface area and the results were compared to independent estimates derived from helium porosimetry (connected porosity) and low-pressure N2 and CO2 adsorption (accessible surface area and pore size distribution). The pore structure of the three samples as interpreted from SANS/USANS is fairly uniform, with small differences in the small-pore range (<2000 A), possibly related to differences in degree of cementation, and mineralogy, in particular clay content. Total porosity interpreted from USANS/SANS is similar to (but systematically higher than) helium porosities measured on the whole Core Plug. Both methods were used to estimate the percentage of open porosity expressed here as a ratio of connected porosity, as established from helium adsorption, to the total porosity, as estimated from SANS/USANS techniques. Open porosity appears to control permeability (determined using pressure and pulse-decay techniques), with the highest permeability sample also having the highest percentage of open porosity. Surface area, as calculated from low-pressure N2 and CO2 adsorption, is significantly less than surface area estimates from SANS/USANS, which is due in part to limited accessibility of the gases to all pores. The similarity between N2 and CO2-accessible surface area suggests an absence of microporosity in these samples, which is in agreement with SANS analysis. A Core gamma ray profile run on the same Core from which the Core Plug samples were taken correlates to profile permeability measurements run on the slabbed Core. This correlation is related to clay content, which possibly controls the percentage of open porosity. Continued study of these effects will prove useful in log-Core calibration efforts for tight gas.
J. Brink - One of the best experts on this subject based on the ideXlab platform.
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Petrophysical investigations on sediment Core CRP-2A from the Ross Sea, Antarctica, supplement to: Brink, Jason; Jarrard, Richard D (2000): Petrophysics of Core Plugs from CRP-2A drillhole, Victoria Land Basin, Antarctica. Terra Antartica, 7(3), 231-
2020Co-Authors: J. Brink, R. D. JarrardAbstract:A suite of petropysical measurements - velocity versus pressure, bulk density, porosity, matrix density, and magnetic susceptibility -was undertaken on 63 Core Plugs from CRP-2A. These data are used to calibrate neutron, resistivity, and magnetic susceptibility well logs. Agreement between Core-Plug magnetic susceptibility measurements and both well-log and whole-Core data is excellent. Comparison of Core-Plug bulk densities with continious well-log density records shows very good agreement. Core-Plug measurements of matrix density permit conversion of the well-log and whole-Core density records to porosity. Sands and muds exhibit similar downhole compaction patterns, and both patterns are consistent with 250 ± 150 m of exhumation. Pervasive cementation, particularly in the lower half of the Core, has affected many CRP-2A petrophysical parameters:(1) fractional porosities are reduced by about 0.05 - 0.10 in the lower part of the hole;(2) velocity and porosity rebound are much smaller than is usually observed for unconsolidated sediments with burial depths similar to CRP-2A;(3) velocities are unusually insensitive to pressure, suggesting that any exhumation-induced microcracks have been scaled subsequently;(4) the velocity/porosity relationship lacks the characteristic signature of exhumation-induced microcracks;(5) the velocity/porosity relationship changes with depth, indicating downhole increase in consolidation;(6) Vp/Vs ratios of the highest-porosity sediments are unusually low, implying enhancement of framework stiffness.
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Petrophysics of Core Plugs from CRP-2A drillhole, Victoria Land Basin, Antarctica
1998Co-Authors: J. Brink, R. D. JarrardAbstract:A suite of petrophysical properties velocity, resistivity, bulk density, porosity, and matrix density – was measured on 88 Core Plugs from the CRP-3 drillhole. Core-Plug bulk densities were used to recalibrate both whole-Core and downhole bulk density logs. Core-Plug measurements of matrix density permit conversion of the whole-Core and downhole bulk density logs to porosity. Both velocity and formation factor (a normalized measure of resistivity) are strongly correlated with porosity. The velocity/porosity pattern is similar to that for the lower part of CRP-2A and is consistent with the empirical relationship for sandstones. Core-Plug and whole-Core measurements of P-wave velocity at atmospheric pressure exhibit excellent agreement. Measurements of velocity as a function of pressure indicate a significantly higher velocity sensitivity to pressure than has been observed at CRP-1 and CRP-2A; rebound or presence of microcracks at CRP-3 may be responsible. The percentage difference between velocities at in situ pressures and atmospheric pressures increases downhole from 0% at the seafloor to 9% at the bottom. This pattern can be used to correct whole-Core velocity data, measured at atmospheric pressure, to in situ velocities for depth-to-time conversion and associated comparison to the seismic profile across the drillsite.
Benedict Newling - One of the best experts on this subject based on the ideXlab platform.
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region of interest selection of long Core Plug samples by magnetic resonance imaging profiling and local t2 measurement
Measurement Science and Technology, 2014Co-Authors: S. Vashaee, Bruce J. Balcom, O V Petrov, Benedict NewlingAbstract:Magnetic resonance imaging (MRI) is increasingly employed as a Core analysis technique by the oil and gas industry. In axial profiling of petroleum reservoir Core samples and Core Plugs, the sample of interest may frequently be much longer than the natural field of view (FOV) defined by the radio frequency (RF) sensor and region of constant magnetic field gradient. Profiling such samples with a low field MRI will result in distorted, non-quantitative axial profiles near the edge of the FOV with data from outside the desired FOV folding back into the image, when the gradient magnetic field homogenity region is shorter than the region of RF excitation. The quality of MRI as a Core analysis technique is increased if imaging can be performed on intact samples with the FOV reduced to the region of interest (ROI), either to increase the image resolution or to reduce the total time for imaging. A spatially selective adiabatic inversion pulse is applied in the presence of a slice selective magnetic field gradient to restrict the FOV to an ROI that is a small portion of a long sample. Slice selection is followed by a 1D centric-scan SPRITE measurement to yield an axial fluid density profile of the sample in the ROI. By employing adiabatic pulses, which are immune to RF field non-uniformities, it is possible to restrict the ROI to a region of homogeneous RF excitation, facilitating quantitative imaging. The method does not employ conventional selective excitation, but a subtraction based on images acquired with and without adiabatic inversion slice selection. The adiabatic slice selection lends itself to a selective T2 distribution measurement when a CPMG pulse sequence follows the slice selection. The inversion pulse selects a slice on the order of 1 cm at an arbitrary position. The local T2 distributions measured are of similar quality to bulk CPMG. This method is an alternative to MRI-based techniques for T2 mapping in short relaxation time samples in porous media when T2 is required to be measured at only a few positions along the sample, and a resolution of 1 cm is acceptable.