Pore characteristics of the carbonate shoal from fractal perspective

Wei, Duan; Gao, Zhiqian; Zhang, Chi; Tang, Fan; Karubandika, Grace Muzee; Meng, Ming

doi:10.1016/j.petrol.2018.11.059

Cited by 20 publications

(10 citation statements)

References 34 publications

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“…The fractal dimensions derived from HPMI reflects the changes in the pore structure of sandstone rocks. 32,35,37,40,41 42 The results demonstrated that macropores and mesopores were relatively well developed in type A core samples, while all the three kinds of pores were developed in type B core samples. Additionally, the total fractal dimension D 0 and D HPMI were obtained from the slopes of the straight lines of the logarithmic scatter points and eqs 7 and 8, respectively.…”

Section: Resultsmentioning

confidence: 94%

Effects of the Sandstone Pore Structure on Spontaneous Imbibition: A Systematic Experimental Investigation Based on Fractal Analysis

Zhang

Lai

et al. 2021

Energy Fuels

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Pore structure is one of the most fundamental properties in reservoir characterization and is closely related to spontaneous imbibition recovery. This work utilized tight sandstone reservoir rock samples in the Ordos Basin to probe the influencing factors of the pore structure and fractal characteristics on imbibition efficiency. A series of experiments including high-pressure mercury injection (HPMI) and low-pressure nitrogen gas adsorption (LP-N 2 GA) were performed to systematically characterize the pore structure of the tight sandstone rocks. Then, the effects of pore structures and fractal dimensions on the imbibition recovery factor were elaborately discussed. These factors were further ranked using the gray correlation analysis. Results indicated a relatively high imbibition recovery, which ranged from 64.91 to 89.88%. Mesopores were more conducive to gas production, accounting for up to 56.88%. The combination of HPMI and LP-N 2 GA data synergistically characterized pores in the entire range, from micro-to macropores of the subjected reservoir (0.02-10 μm). Sensitivity analyses showed that imbibition recovery correlated with the homogeneity coefficient, reservoir quality index, skew coefficient (S kp ), sorting coefficient (S p ), micropore volume, displacement pressure, specific surface area, and Swanson parameter. Additionally, the gray correlation analysis further suggested that imbibition efficiency was highly related to the fractal dimension, and gas production recovery was mainly governed by the mesopore fractal dimension. This work provides insights into how the pore structure affects spontaneous imbibition efficiency in tight sandstone reservoirs from a fractal perspective.

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Section: Resultsmentioning

confidence: 94%

Effects of the Sandstone Pore Structure on Spontaneous Imbibition: A Systematic Experimental Investigation Based on Fractal Analysis

Zhang

Lai

et al. 2021

Energy Fuels

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“…This is possibly because a relatively higher fraction of larger pores would contribute greatly to the brine absolute permeability compared to smaller pores. In addition, low-field NMR measurements were performed to understand the distribution of pore sizes because of the correlation between the transverse relaxation time ( T 2 ) and pore size. , The carbonate rock pores can be categorized as micropores ( T 2 < 100 ms), mesopores, and macropores ( T 2 > 100 ms). , In this study, four sections (<10 ms, 10–100 ms, 100–1000 ms, and >1000 ms) of the T 2 spectrum were divided in order to compare these samples in detail, as indicated in Table . Sample A-5 has the relatively higher increment porosity at T 2 > 1000 ms and fall in the range of 2–5%, whereas these samples have a lower increment porosity at T 2 < 100 ms in comparison with sample A-2 and A-6, as can be seen in Figure .…”

Section: Results and Discussionmentioning

confidence: 99%

“…In addition, low-field NMR measurements were performed to understand the distribution of pore sizes because of the correlation between the transverse relaxation time (T 2 ) and pore size. 43,44 The carbonate rock pores can be categorized as micropores (T 2 < 100 ms), mesopores, and macropores (T 2 > 100 ms). 43,45 In this study, four sections (<10 ms, 10−100 ms, 100−1000 ms, and >1000 ms) of the T 2 spectrum were divided in order to compare these samples in detail, as indicated in Table 4.…”

Section: Effect Of Rpm Concentration 231 Brine or DI Water Flooding (...mentioning

confidence: 99%

Further Insights into the Performance of Silylated Polyacrylamide-Based Relative Permeability Modifiers in Carbonate Reservoirs and Influencing Factors

et al. 2021

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We have previously used surface chemistry analysis techniques to optimize the functionalization of carbonate rocks with a silylated polyacrylamide-based relative permeability modifier (RPM). The RPM is expected to selectively reduce the permeability to water in a hydrocarbon reservoir setting, resulting in a reduction in the amount of produced water while maintaining the production of oil/gas. This study will focus on using core flooding techniques with brine/crude oil under reservoir conditions (i.e., 1500 psi pore pressure and 60 °C temperature) to understand the impact of a silylated polyacrylamide-based RPM on the fluid transport properties in carbonate rocks. The effects of RPM concentration, brine salinity, rock permeability, and pore structure on permeability characteristics were studied. Scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDX) provided visual images of the polymer adsorbed onto the rock surfaces and confirmed the attachment of the polymer on the surface of the rock pore space after treatment. The relative percentage of Si increased from 1.65 to 13.55%, and the relative percentage of N increased to 4.54%. Core flooding showed that increasing the PAM-co-AA (poly acrylamide-co-acrylic acid partial sodium salt) concentration resulted in residual resistance factors for oil (RRFoil) and brine (RRFbrine) that were greater than 1. However, there was a modest decrease in the disproportionate permeability reduction (DRP) ratio (RRFbrine/RRFoil) from 1.75 to 1.60 when the polymer concentration was increased from 0.05 to 0.1 wt %. Furthermore, the RRFbrine values decreased slightly from 120 to 62 with increasing salinity (i.e., 1–10% NaCl) because of electrostatic shielding caused by charged ions in brine and the RPM. The cross-over points of relative permeability in these four samples shifted to the right because of the larger decrease in relative water permeability compared with relative oil permeability. End-point relative permeability to water in sample C-5 decreased by 80%, showing a reduction greater than that in the sample C-2 (i.e., 74%). Kr curves indicated a stronger formation damage in sample C-1, C-2, and C-4 than in sample C-5. Rock samples with a higher initial permeability exhibited a higher RRFbrine to RRFoil ratio (i.e., 3.05) under similar test conditions. This can be attributed to a larger pore radius, which was verified by nuclear magnetic resonance (NMR) measurements. Furthermore, a detailed mechanism has been proposed to understand the effects of the RPM on fluid transport in porous carbonate cores. In this study, SEM–EDX and NMR measurements combined with core flooding tests provide insights into the performance of silylated polyacrylamide-based RPMs and benefit its future implementation in carbonate reservoirs.

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“…In recent years, it has been widely used in the shale pore structure field (Li et al, 2019a;Liu et al, 2020;Li, 2021;Liu et al, 2021). Pore image data, gas or liquid flow test data (such as nitrogen adsorption and mercury intrusion tests), and NMR data can be used to study the pore fractal characteristics (Yang et al, 2017;Liu J. S. et al, 2018;Tang et al, 2019;Wei et al, 2019). For different types of shale reservoir spaces, researchers have attempted to use different models such as the Frenkel-Halsey-Hill (FHH) model, Newton-Kantorovich (NK) model, and Neimark model to carry out fractal research on the shale pore structures (Ahmad and Mustafa, 2006;Pan et al, 2021;Chang et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

Pore structure and fractal characteristics of the marine shale of the longmaxi formation in the changning area, Southern Sichuan Basin, China

Jiling²,

Mou

et al. 2022

Front. Earth Sci.

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The pore structure is an important factor affecting reservoir capacity and shale gas production. The shale reservoir of the Longmaxi Formation in the Changning area, Southern Sichuan Basin, is highly heterogeneous and has a complex pore structure. To quantitatively characterize the shale’s pore structure and influencing factors, based on whole rock X-ray diffraction, argon ion polishing electron microscopy observations, and low-temperature nitrogen adsorption-desorption experiments, the characteristics of the shale pore structure are studied by using the Frenkel-Halsey-Hill (FHH) model. The research reveals the following: 1) The pores of the Longmaxi Formation shale mainly include organic pores, intergranular pores, dissolution pores and microfractures. The pore size is mainly micro-mesoporous. Both ink bottle-type pores and semiclosed slit-type pores with good openness exist, but mainly ink bottle-type pores are observed. 2) The pore structure of the Longmaxi Formation shale has self-similarity, conforms to the fractal law, and shows double fractal characteristics. Taking the relative pressure of 0.45 (P/P0 = 0.45) as the boundary, the surface fractal dimension Dsf and the structural fractal dimension Dst are defined. Dsf is between 2.3215 and 2.6117, and the structural fractal dimension Dst is between 2.8424 and 2.9016. The pore structure of micropores and mesopores is more complex. 3) The mineral components and organic matter have obvious control over the fractal dimension of shale, and samples from different wells show certain differences. The fractal dimension has a good positive correlation with the quartz content but an obvious negative correlation with clay minerals. The higher the total organic carbon content is, the higher the degree of thermal evolution, the more complex the pore structure of shale, and the larger the fractal dimension. The results have guiding significance for the characterization of pore structure of tight rocks.

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Pore characteristics of the carbonate shoal from fractal perspective

Cited by 20 publications

References 34 publications

Effects of the Sandstone Pore Structure on Spontaneous Imbibition: A Systematic Experimental Investigation Based on Fractal Analysis

Effects of the Sandstone Pore Structure on Spontaneous Imbibition: A Systematic Experimental Investigation Based on Fractal Analysis

Further Insights into the Performance of Silylated Polyacrylamide-Based Relative Permeability Modifiers in Carbonate Reservoirs and Influencing Factors

Pore structure and fractal characteristics of the marine shale of the longmaxi formation in the changning area, Southern Sichuan Basin, China

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