Occurrence characteristics of the movable fluid in heterogeneous sandstone reservoir based on fractal analysis of NMR data: A case study of the Chang 7 Member of Ansai Block, Ordos Basin, China

Zang, Qibiao; Liu, Cheng‐Lin; Awan, Rizwan Sarwar; Yang, Xiya; Li, Guoxiong; Wu, Yuping; Lu, Zhendong; Feng, Dehao

doi:10.1016/j.petrol.2022.110499

Cited by 24 publications

(18 citation statements)

References 77 publications

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“…Taking B62 as an example, the red dashed line is the porosity cumulative distribution of the sample in the saturated water state, and the blue dashed line is the porosity cumulative distribution of the sample in the centrifugal state after the centrifugation at 267 psi. The tangent line of the red dashed line intersects with the blue dashed line, and the T 2 value corresponding to this intersection point is the T 2 cutoff value of this sample [27][28][29] (Figure 3).…”

Section: Experiments Methods and Proceduresmentioning

confidence: 84%

“…In the previous studies, scholars usually selected the empirical T 2 cutoff value of the target region as the T 2 cutoff of the study samples. However, due to the strong heterogeneity among Chang 7 tight reservoir samples, sophisticated assembly of pore and throat structure as well as seepage characteristics and T 2 cutoff for the actual samples can be very different from the regional empirical value [9,28].…”

Section: Experiments Methods and Proceduresmentioning

confidence: 99%

“…experimental results are presented in Table 2, where the T 2 cutoff varies greatly between different samples, ranging from 3.92 ms to 18.04 ms, which also indicates that it is not advisable to evaluate the characteristics of movable fluid distribution for variable samples according to the experience value or the T 2 cutoff of the same sample. For a more visible characterization of the reservoir's movable fluid content, the movable fluid porosity (Φm) parameter is introduced [27,28,31], which is numerically Φm = Sm × Φ/100. The Sm of the samples is distributed which varied between 19.07% and 32.52%, with an average of 26.23%.…”

Section: Nmr T 2 Spectrummentioning

confidence: 99%

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Characterization of Movable Fluid Distribution in Tight Oil Reservoirs by NMR and Centrifugation

et al. 2023

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The reservoir of Chang 7 Member of Yanchang Formation in the Ordos Basin is rich in tight oil resources, with well-developed micro-nanopore throats, strong heterogeneity, and complex fluid distribution characteristics. In this paper, a combination of nuclear magnetic resonance and centrifugation experiments is carried out to qualitatively and quantitatively analyze and evaluate the distribution characteristics of the movable fluid in Chang 7 reservoirs in Baibao Block. With different centrifugal forces, the NMR T2 spectrum characteristics of saturated water state and different centrifugal force state can be obtained, and the movable fluid distribution characteristics under the control of different centrifugal forces and different pore throat intervals can be obtained. The research results demonstrate that the NMR T2 spectrum of the Chang 7 tight oil reservoir in the study area presents a double-peak or triple-peak shape. With the increase of centrifugal force, the water saturation value of the corresponding sample gradually decreases. The overall movable fluid saturation ranged from 19.07% to 32.52%, with an average of 26.23% and a low degree of movability. The submicron (0.1~1 μm) and nanoscale (0.075~0.1 μm) pore throats were the main pore throat intervals controlling the movable fluid saturation of the studied samples, accounting for an average of 18.31% and 5.57%, respectively, and micron-scale pore throats ( r > 1 μ m ) accounted for an average of 2.35% of the movable fluid distribution.

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Section: Experiments Methods and Proceduresmentioning

confidence: 84%

Section: Experiments Methods and Proceduresmentioning

confidence: 99%

Section: Nmr T 2 Spectrummentioning

confidence: 99%

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Characterization of Movable Fluid Distribution in Tight Oil Reservoirs by NMR and Centrifugation

et al. 2023

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“…Nuclear magnetic resonance (NMR) is a significant technique to investigate water occurrence, which when associated with a high-speed centrifugation machine can distinguish the pore size distribution of movable and irreducible liquid. − The principle of NMR is based on the fact that liquid in large pores has a longer relaxation time, and liquid in small pores has a short relaxation time. Thus, the whole pore size distribution can be obtained. − NMR T 2 relaxation time can only reflect the pore size distribution, but the real pore size can be obtained by a converting factor, which can convert the T 2 value into the real pore size . Because the converting factors are different among various methods, usually the T 2 value was used directly to represent the pore size.…”

Section: Introductionmentioning

confidence: 99%

Rock Fabric of Tight Sandstone and Its Influence on Irreducible Water Saturation in Eastern Ordos Basin

Meng

Shen

et al. 2023

Energy Fuels

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After flowback, the residual fracturing fluid will reduce the gas seepage space and influence natural gas production, which attracts widespread attention. In this study, the irreducible water saturation was investigated, and its controlling factors were clarified. We target the Upper Paleozoic Taiyuan and Shihezi Formations, which belong to a tight gas reservoir in the eastern Ordos Basin. The main experiments include porosity, permeability, mineral composition, nitrogen adsorption, mercury intrusion porosimetry, nuclear magnetic resonance, and high-speed centrifugation. The specific surface area is very low and varies from 0.95 to 4.03 m 2 /g, and the median pore-throat diameter ranges from 28.6 to 698.6 nm. Through the T 2 cutoff value, the water saturation can be divided into movable water saturation (S mov ) and irreducible water saturation (S irr ). Furthermore, the S irr can be divided into water saturation in large pores controlled by the small throat (S irrl ) and water saturation controlled by the capillary force (S irrc ). In both formations, the S irr has a negative relationship with porosity, permeability, and average pore diameter and exhibits a positive relationship with the specific surface area. The S irrl has a positive relationship with the median pore-throat diameter in Taiyuan Formation, but the S irrl has a weak relationship with the median pore-throat diameter in Shihezi Formation. The S irrc has a negative relationship with porosity, permeability, and average pore diameter and displays a positive relationship with the specific surface area in Taiyuan Formation, but the S irrc has a weak relationship with these parameters in Shihezi Formation. The relationship difference between Taiyuan and Shihezi Formations was mainly caused by the pore structure, demonstrated by the amplitude ratio in three peaks. Based on the above analysis, this study is conducive to understanding the mechanism of water occurrence and its controlling factors.

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“…The method of mathematical statistics cannot effectively describe the pore‐throat structure of the reservoir. It is necessary to calculate the fractal dimension with the help of fractal theory, so as to describe the complexity of pore‐throat structure, the roughness of pore surface and the heterogeneity of the reservoir (Dong et al, 2022; Guo et al, 2019; H. Li, Zhou, et al, 2022; X. M. Li, Wang, et al, 2022; Qu et al, 2020; E. Z. Wang et al, 2022; Zang et al, 2022; K. X. Zhang et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Pore‐throat structure characteristics and fluid mobility analysis of tight sandstone reservoirs in Shaximiao Formation, Central Sichuan

et al. 2023

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The pore‐throat structure and fluid mobility are the key factors of tight sandstone reservoir classification and evaluation. Taking the Jurassic Shaximiao Formation tight sandstone reservoir in Central Sichuan Basin as an example, 19 samples were analysed by casting thin sections, scanning electron microscopy, high‐pressure mercury injection and nuclear magnetic resonance to clarify the pore‐throat structure, the fluid motility and its controlling factors. The results show that the pore type of Shaximiao Formation tight sandstone reservoir consist of intergranular pores, dissolved pores and a few microfractures. Based on the feature of capillary pressure curve, the pore‐throat structure was classified into three types, corresponding to different movable fluid characteristics. The Type I has large pore and throat radius, good pore‐throat connectivity, small fractal dimension, weak reservoir heterogeneity and strong fluid motility. The distribution range of pore‐throat radius is mainly from 0.3 to 1.1 μm and the average movable fluid porosity (MFP) and movable fluid saturation (MFS) are 6.04% and 49.93%. The Type II has poor pore‐throat sorting, weak fluid motility and the distribution range of pore‐throat radius is 0.01–0.03 μm and 0.2–0.8 μm. The average MFP and MFS of Type II are 1.13% and 14.3%. The Type III has the smallest pore‐throat radius and the largest fractal dimension, corresponding to the most complex pore‐throat structure, which lead to the worst fluid mobility. The average MFP and MFS are 0.49% and 12.76%. The fluid mobility of the tight sandstone reservoir is affected by physical properties and pore‐throat structure. The reservoirs with large pore‐throat size, good connectivity between pore and throat, and low heterogeneity have higher MFP and saturation. Moreover, the mineral compositions have different effects on fluid mobility of the tight sandstone. The feldspar positively affects fluid mobility, while the clay minerals negatively affect fluid mobility.

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Occurrence characteristics of the movable fluid in heterogeneous sandstone reservoir based on fractal analysis of NMR data: A case study of the Chang 7 Member of Ansai Block, Ordos Basin, China

Cited by 24 publications

References 77 publications

Characterization of Movable Fluid Distribution in Tight Oil Reservoirs by NMR and Centrifugation

Characterization of Movable Fluid Distribution in Tight Oil Reservoirs by NMR and Centrifugation

Rock Fabric of Tight Sandstone and Its Influence on Irreducible Water Saturation in Eastern Ordos Basin

Pore‐throat structure characteristics and fluid mobility analysis of tight sandstone reservoirs in Shaximiao Formation, Central Sichuan

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