A New Method for Converting T ₂ Spectrum into Pore Radius

Abstract

In this paper, a new method for converting the T ₂ (relaxation time) of NMR (nuclear magnetic resonance) into the pore radius is proposed. Combined with NMR and centrifugation experiments, the relationship between pore radius and T ₂ of the sample was established. The results show that the new method is more reasonable than the traditional method. When the sample was denser and the mercury saturation was lower, the pore distribution curve was obtained by traditional method had a worse agreement with mercury injection experiment, while pore distribution curve of the new method had a better agreement with the mercury injection curve, which reflected the greater advantage of the new method as the reservoir becomes denser. The new method can obtain all the pore information in the sample. The results show that the pores in tight sandstone are mainly consisted with mesopore and macropore, and the connectivity of macropore is better than that of mesopore. The new method can effectively characterize the full pore distribution and the seepage characteristics in different pores interval of tight reservoirs, which had a great significance to evaluate the recoverable resources of tight reservoir.

Keywords

tight reservoir / nuclear magnetic resonance (NMR) / pore radius / T ₂ spectrum

References

Al Hinai A, Rezaee R, Esteban L, . Comparisons of Pore Size Distribution: A Case from the Western Australian Gas Shale Formations. Journal of Unconventional Oil and Gas Resources, 2014, 8: 1-13.

Al-Mahrooqi S H, Grattoni C A, Moss A K, . An Investigation of the Effect of Wettability on NMR Characteristics of Sandstone Rock and Fluid Systems. Journal of Petroleum Science and Engineering, 2003, 39(3/4): 389-398.

Daigle H, Johnson A. Combining Mercury Intrusion and Nuclear Magnetic Resonance Measurements Using Percolation Theory. Transport in Porous Media, 2016, 111(3): 669-679.

Daigle H, Thomas B, Rowe H, . Nuclear Magnetic Resonance Characterization of Shallow Marine Sediments from the Nankai Trough, Integrated Ocean Drilling Program Expedition 333. Journal of Geophysical Research: Solid Earth, 2014, 119(4): 2631-2650.

Davy C A, Adler P M. Three-Scale Analysis of the Permeability of a Natural Shale. Physical Review E, 2017, 96(6): 063116

De Silva G P D, Ranjith P G, Perera M S A, . Effect of Bedding Planes, Their Orientation and Clay Depositions on Effective re-Injection of Produced Brine into Clay Rich Deep Sandstone Formations: Implications for Deep Earth Energy Extraction. Applied Energy, 2016, 161: 24-40.

Du S H, Shi Y M. Rapid Determination of Complete Distribution of Pore and Throat in Tight Oil Sandstone of Triassic Yanchang Formation in Ordos Basin, China. Acta Geologica Sinica: English Edition, 2020, 94(3): 822-830.

Du S H, Zhao Y P, Jin J, . Significance of the Secondary Pores in Perthite for Oil Storage and Flow in Tight Sandstone Reservoir. Marine and Petroleum Geology, 2019, 110 178-188.

Dunn K J, Bergman D J, Latorraca G A. Seismic Exploration: Nuclear Magnetic Resonance: Petrophysical and Logging Applications, 2002, Amsterdam: Elsevier

Fu J H, Li S X, Xu L M, . Paleo-Sedimentary Environmental Restoration and Its Significance of Chang 7 Member of Triassic Yanchang Formation in Ordos Basin, NW China. Petroleum Exploration and Development, 2018, 45(6): 998-1008.

Gao F L, Song Y, Li Z, . Quantitative Characterization of Pore Connectivity Using NMR and MIP: A Case Study of the Wangyinpu and Guanyintang Shales in the Xiuwu Basin, Southern China. International Journal of Coal Geology, 2018, 197: 53-65.

Grathoff G H, Peltz M, Enzmann F, . Porosity and Permeability Determination of Organic-Rich Posidonia Shales Based on 3-D Analyses by FIB-SEM Microscopy. Solid Earth, 2016, 7(4): 1145-1156.

Huang H X, Li R X, Chen W T, . Revisiting Movable Fluid Space in Tight Fine-Grained Reservoirs: A Case Study from Shahejie Shale in the Bohai Bay Basin, NE China. Journal of Petroleum Science and Engineering, 2021, 207: 109170

Huang H X, Li R X, Xiong F Y, . A Method to Probe the Pore-Throat Structure of Tight Reservoirs Based on Low-Field NMR: Insights from a Cylindrical Pore Model. Marine and Petroleum Geology, 2020, 117 104344

Ji L M, Wang S F, Xu J L. Acritarch Assemblage in Yanchang Formation in Eastern Gansu Province and Its Environmental Implications. Earth Science—.Journal of China University of Geosciences, 2006, 31(6): 789-807

Jia C Z, Zou C N, Tao S Z, . Assessment Criteria, Main Types, Basic Features and Resource Prospects of the Tight Oil in China. Acta Petrolei Sinica, 2012, 33(3): 343-350

Jiang Z X, Tang X L, Li Z, . Pore Structure and Gas Content Ability of Typical Marine and Continental Shale Reservoirs in China, 2018, Beijing: Science Press

Kleinberg R L, Kenyon W E, Mitra P P. Mechanism of NMR Relaxation of Fluids in Rock. Journal of Magnetic Resonance, Series A, 1994, 108(2): 206-214.

Lai J, Wang G W, Wang Z Y, . A Review on Pore Structure Characterization in Tight Sandstones. Earth-Science Reviews, 2018, 177 436-457.

Law B E, Curtis J B. Introduction to Unconventional Petroleum Systems. AAPG Bulletin, 2002, 86: 1851-1852.

Li A F, Ren X X, Wang G J, . Characterization of Pore Structure of Low Permeability Reservoirs Using a Nuclear Magnetic Resonance Method. Journal of China University of Petroleum, 2015, 39(6): 92-98

Li P, Jia C Z, Jin Z J, . The Characteristics of Movable Fluid in the Triassic Lacustrine Tight Oil Reservoir: A Case Study of the Chang 7 Member of Xin’anbian Block, Ordos Basin, China. Marine and Petroleum Geology, 2019, 102: 126-137.

Li X C, Gao J X, Zhang S, . Combined Characterization of Scanning Electron Microscopy, Pore and Crack Analysis System, and Gas Adsorption on Pore Structure of Coal with Different Volatilizatione. Earth Science, 2022, 47(5): 1876-1889

Liu D K, Sun W, Ren D Z, . Quartz Cement Origins and Impact on Storage Performance in Permian Upper Shihezi Formation Tight Sandstone Reservoirs in the Northern Ordos Basin, China. Journal of Petroleum Science and Engineering, 2019, 178: 485-496.

Loren J D, Robinson J D. Relations between Pore Size Fluid and Matrix Properties, and NML Measurements. Society of Petroleum Engineers Journal, 1970, 10(3): 268-278.

Mao Z Q, He Y D, Ren X J. An Improved Method of Using NMR T2 Distribution to Evaluate Pore Size Distribution. Chinese Journal of Geophysics, 2005, 48(2): 412-418.

Müller-Huber E, Schön J, Börner F. Pore Space Characterization in Carbonate Rocks—Approach to Combine Nuclear Magnetic Resonance and Elastic Wave Velocity Measurements. Journal of Applied Geophysics, 2016, 127: 68-81.

Nagykáldi A, Rácz I, Kovács B. A High-Pressure Mercury Method in the Study of Porosity and Pore Radius Distribution in Model Tablets Prepared with Various Binding Material Concentrations and under Various Pressures. Acta Pharmaceutica Hungarica, 1984, 54(1): 30-43

Ning C, Jiang Z, Gao Z, . Quantitative Evaluation of Pore Connectivity with Nuclear Magnetic Resonance and High Pressure Mercury Injection: A Case Study of the Lower Section of Es³ in Zhanhua Sag. Journal of China University of Mining & Technology, 2017, 46(3): 578-585

Radlinski A P, Mastalerz M, Hinde A L, . Application of SAXS and SANS in Evaluation of Porosity, Pore Size Distribution and Surface Area of Coal. International Journal of Coal Geology, 2004, 59(3/4): 245-271.

Rathnaweera T D, Ranjith P G, Perera M S A, . An Experimental Investigation of Coupled Chemico-Mineralogical and Mechanical Changes in Varyingly-Cemented Sandstones Upon CO₂ Injection in Deep Saline Aquifer Environments. Energy, 2017, 133: 404-414.

Ren D Z, Zhou D S, Liu D K, . Formation Mechanism of the Upper Triassic Yanchang Formation Tight Sandstone Reservoir in Ordos Basin—Take Chang 6 Reservoir in Jiyuan Oil Field as an Example. Journal of Petroleum Science and Engineering, 2019, 178: 497-505.

Sigal R F. Pore-Size Distributions for Organic-Shale-Reservoir Rocks from Nuclear-Magnetic-Resonance Spectra Combined with Adsorption Measurements. SPE Journal, 2015, 20(4): 824-830.

Tahmasebi P. Nanoscale and Multiresolution Models for Shale Samples. Fuel, 2018, 217: 218-225.

Vilcáez J, Morad S, Shikazono N. Pore-Scale Simulation of Transport Properties of Carbonate Rocks Using FIB-SEM 3D Microstructure: Implications for Field Scale Solute Transport Simulations. Journal of Natural Gas Science and Engineering, 2017, 42: 13-22.

Wang L A, Zhao N, Sima L Q, . Pore Structure Characterization of the Tight Reservoir: Systematic Integration of Mercury Injection and Nuclear Magnetic Resonance. Energy & Fuels, 2018, 32(7): 7471-7484.

Wang Z M, Jiang Y Q, Fu Y H, . Characterization of Pore Structure and Heterogeneity of Shale Reservoir from Wufeng Formation-Sublayers Long-1₁, in Western Chongqing Based on Nuclear Magnetic Resonance. Earth Science, 2022, 47(2): 490-504. 2022

Washburn E W. The Dynamics of Capillary Flow. Physical Review, 1921, 17(3): 273-283.

Yao Y B, Liu D M. Comparison of Low-Field NMR and Mercury Intrusion Porosimetry in Characterizing Pore Size Distributions of Coals. Fuel, 2012, 95: 152-158.

Zhang F, Jiang Z X, Sun W, . A Multiscale Comprehensive Study on Pore Structure of Tight Sandstone Reservoir Realized by Nuclear Magnetic Resonance, High Pressure Mercury Injection and Constant-Rate Mercury Injection Penetration Test. Marine and Petroleum Geology, 2019, 109: 208-222.

Zhang F, Jiang Z X, Sun W, . Effect of Microscopic Pore-Throat Heterogeneity on Gas-Phase Percolation Capacity of Tight Sandstone Reservoirs. Energy & Fuels, 2020, 34(10): 12399-12416.

Zhang, F., Xiao, H. M., Jiang, Z. X., et al., 2021. Influence of Pore Throat Structure and the Multiphases Fluid Seepage on Mobility of Tight Oil Reservoir. Lithosphere, Special 1: 5525670. https://doi.org/10.2113/2021/5525670

Zhao J Z, Bai Y B, Qing C. Quasi-Continuous Hydrocarbon Accumulation: A New Pattern for Large Tight Sand Oilfields in Ordos Basin. Oil and Gas Geology, 2012, 33(6): 811-827

Zhao X L, Yang Z M, Lin W, . Study on Pore Structures of Tight Sandstone Reservoirs Based on Nitrogen Adsorption, High-Pressure Mercury Intrusion, and Rate-Controlled Mercury Intrusion. Journal of Energy Resources Technology, 2019, 141(11): 112903

Zou C N, Zhu R K, Bai B, . First Discovery of Nano-Pore Throat in Oil and Gas Reservoir in China and Its Scientific Value. Acta Petrologica Sinica, 2011, 27 6 1857-1864