Effect of hydrocarbon on evaluating formation pore structure using nuclear magnetic resonance (NMR) logging

Xiao, Liang; Mao, Zhiqiang; Li, Junran; Yu, Ho‐Shing

doi:10.1016/j.fuel.2017.12.020

Cited by 39 publications

(7 citation statements)

References 22 publications

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“…The size of the transverse relaxation time can reflect the pore size of the rock, and the longer the relaxation time, the larger the pore size. The signal intensity reflects the number of hydrogen protons, which is proportional to the volume of the fluid in the pore . By measuring the T 2 spectrum of the core in the process of imbibition, it can obtain the pore fluid distribution characteristics.…”

Section: Methodsmentioning

confidence: 99%

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Effects of Fracture Characteristics on Spontaneous Imbibition in a Tight Reservoir

et al. 2021

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Horizontal well fracturing technology is widely used in the development of shale gas resources. After the fracturing operations, natural and artificial fractures exist in the reservoir at the same time, which has significant effects on spontaneous imbibition to increase shale gas production. Based on nuclear magnetic resonance technology, this work studies the spontaneous imbibition property of fractured shale, including artificial and natural fractures, surface cemented minerals, boundary conditions, etc. The results show that the relaxation time spectra reflect the characteristics of water and gas migration in the rock pore space. The micropores and the small pores are the main storage space for water in shale. After water imbibition starts, the imbibition volume is roughly proportional to the square root of time. Through the comparative experiments on artificial fractures, natural fractures, and seamless cores, it is found that the existence of fractures can significantly promote water imbibition, and the imbibition speed of artificial fractured cores is faster than those of others. Because of the existence of artificial and natural fractures, the number of pores for gas discharge increases, and the imbibed volume is slightly more. When the cemented minerals such as quartzite and calcite are attached to the core surface, they have poor water sensitivity and block some of the pores, thus resulting in a slower imbibition speed. Different boundary conditions will not only affect the contact area between the core and water but also influence the types of imbibition, which changes the water flow path and imbibition speed. This study provides an important insight into spontaneous imbibition in gas shale after the fracturing operations.

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Section: Methodsmentioning

confidence: 99%

“…The signal intensity reflects the number of hydrogen protons, which is proportional to the volume of the fluid in the pore. 43 By measuring the T 2 spectrum of the core in the process of imbibition, it can obtain the pore fluid distribution characteristics. 2.2.2.…”

mentioning

confidence: 99%

Effects of Fracture Characteristics on Spontaneous Imbibition in a Tight Reservoir

et al. 2021

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“…Therefore, the invasion of mud filtrate only has a great impact on the T 2 spectrum of NMR logging corresponding to macropores but has little impact on the T 2 spectrum of NMR logging of bound fluid in small pores [ 27 ]. Therefore, this study corrected the movable fluid part of the T 2 spectrum of formation NMR logging after the invasion of oil-based mud filtrate and combined it with the T 2 spectrum of NMR logging of the original bound fluid part to obtain the complete NMR T 2 spectrum after morphological correction [ 28 ].…”

Section: Methodsmentioning

confidence: 99%

Study on Nuclear Magnetic Resonance Logging T2 Spectrum Shape Correction of Sandstone Reservoirs in Oil-Based Mud Wells

Sun

Cai²,

Feng

et al. 2021

Molecules

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The oil-based mud filtrate will invade the formation under the overbalanced pressure during drilling operations. As a result, alterations will occur to the nuclear magnetic resonance (NMR) response characteristics of the original formation, causing the relaxation time of the NMR T2 spectrum of the free fluid part to move towards a slower relaxation time. Consequently, the subsequent interpretation and petrophysical evaluation will be heavily impacted. Therefore, the actual measured T2 spectrum needs to be corrected for invasion. For this reason, considering the low-porosity and low-permeability of sandstone gas formations in the East China Sea as the research object, a new method to correct the incorrect shape of the NMR logging T2 spectrum was proposed in three main steps. First, the differences in the morphology of the NMR logging T2 spectrum between oil-based mud wells and water-based mud wells in adjacent wells were analyzed based on the NMR relaxation mechanism. Second, rocks were divided into four categories according to the pore structure, and the NMR logging T2 spectrum was extracted using the multidimensional matrix method to establish the T2 spectrum of water-based mud wells and oil-based mud wells. Finally, the correctness of the method was verified by two T2 spectrum correction examples of oil-based mud wells in the study area. The results show that the corrected NMR T2 spectrum eliminates the influence of oil-based mud filtrate and improves the accuracy of NMR logging for calculating permeability.

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“…Since the NMR T 2 is very short, and the difference of T 2 between solid and fluid is large, Therefore, T 2 has been used to describe the inner structure of rock. When rock samples are completely saturated, they are placed into uniform magnetic field and the short echo time is adopted in NMR test, the NMR relaxation mechanism of the fluid inside rock can be approximately considered to be only related to the surface relaxation of pores inside rock [22]- [25]. The relaxation rate is expressed as Eq.…”

Section: Experimental Principles a Nmr Technologymentioning

confidence: 99%

Investigation on Microstructure and Damage of Sandstone Under Cyclic Dynamic Impact

Jiang

Deng

et al. 2019

IEEE Access

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In order to study the microscopic damage evolution of rock under the cyclic dynamic impact, red sandstone was selected as samples, and Split Hopkinson Pressure Bar (SHPB) loaded with impact pressure of 0.3 MPa was adopted to exert cyclic dynamic impact on samples. After each dynamic impact, nuclear magnetic resonance (NMR) system was then applied to test the microscopic structure of samples, and then, the parameters of red sandstone, including porosity, transverse relaxation time (T 2 ) spectrum, permeability, and magnetic resonance images (MRI) after each dynamic impact, were obtained. The results show that both porosity and permeability increase with the number of dynamic impacts that red sandstone undertakes, and the increasing range of them also increases gradually. The T 2cutoff value gradually decreases when the number of dynamic impacts increases and their decrease range increases gradually, which is consistent with the trend of microscopic damage represented by porosity and permeability. Also, it is found through analyzing the T 2 spectrum that the dynamic impact produced by the impact pressure of 0.3 Mpa leads to the gradual increase of primary pore size, an increase of macro pores, and enhancement of samples' connectivity, rather than the generation of new microspores. The MRI images reveal that cyclic dynamic impact leads to the generation of microcracks in red sandstone, which coalesces and extends with the number of dynamic impact increase and forms larger micro crack zones finally.INDEX TERMS Cyclic dynamic impact, connectivity of pores, microscopic damage, MRI, NMR.

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Effect of hydrocarbon on evaluating formation pore structure using nuclear magnetic resonance (NMR) logging

Cited by 39 publications

References 22 publications

Effects of Fracture Characteristics on Spontaneous Imbibition in a Tight Reservoir

Effects of Fracture Characteristics on Spontaneous Imbibition in a Tight Reservoir

Study on Nuclear Magnetic Resonance Logging T2 Spectrum Shape Correction of Sandstone Reservoirs in Oil-Based Mud Wells

Investigation on Microstructure and Damage of Sandstone Under Cyclic Dynamic Impact

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