Saturation exponent at various wetting condition: fractal modeling of thin-sections

Abdassah, Doddy; Permadi, Pudji; Sumantri, Y.; Sumantri, R.

doi:10.1016/s0920-4105(98)00014-x

Cited by 12 publications

(7 citation statements)

References 4 publications

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“…Zhou et al [16] used percolation models to show that the saturation exponent in strongly water wet materials is on the order of 1.9, whereas it can increase to over 3.5 for intermediate and oil wet systems. The saturation exponent is dependent on the presence of nonconductive 2 ISRN Geophysics fluid in the pore space and wettability of the rock [12,19]. Although Archie's Law is widely used to determine fluid saturation from resistivity measurements, it is not always valid as the saturation-resistivity relationship depends on the wettability, saturation history, content of clay minerals, salinity of the brine phase and distribution of water and oil in the rock [3,12,15,16].…”

Section: Introductionmentioning

confidence: 99%

The Dependence of Electrical Resistivity-Saturation Relationships on Multiphase Flow Instability

Liu

Moysey

2012

ISRN Geophysics

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We investigate the relationship between apparent electrical resistivity and water saturation during unstable multiphase flow. We conducted experiments in a thin, two-dimensional tank packed with glass beads, where Nigrosine dyed water was injected uniformly along one edge to displace mineral oil. The resulting patterns of fluid saturation in the tank were captured on video using the light transmission method, while the apparent resistivity of the tank was continuously measured. Different experiments were performed by varying the water application rate and orientation of the tank to control the generalized Bond number, which describes the balance between viscous, capillary, and gravity forces that affect flow instability. We observed the resistivity index to gradually decrease as water saturation increases in the tank, but sharp drops occurred as individual fingers bridged the tank. The magnitude of this effect decreased as the displacement became increasingly unstable until a smooth transition occurred for highly unstable flows. By analyzing the dynamic data using Archie's law, we found that the apparent saturation exponent increases linearly between approximately 1 and 2 as a function of generalized Bond number, after which it remained constant for unstable flows with a generalized Bond number less than −0.106.

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Section: Introductionmentioning

confidence: 99%

The Dependence of Electrical Resistivity-Saturation Relationships on Multiphase Flow Instability

Liu

Moysey

2012

ISRN Geophysics

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“…It seems that the values are too low. Even though, the same methodology for determining tortuosity, τ, as described above has been previously used for other sandstones and limestones, yielding τ between 1.56 and 2.76 [21]. These values are within the normal range for real porous rocks [4,37].…”

Section: Resultsmentioning

confidence: 89%

“…Considerations of the development of both fractal theory [12,13] and the complexity of pore morphology have driven many researchers to solve problems of fluid flow in porous media. Among the researchers are [10,[14][15][16][17][18][19][20][21][22][23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

A Study of Sandstone Permeability Anisotropy Through Fractal Concept

Sumantri¹

2018

AJSET

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Most correlation equations of rock permeability are usually based on the Euclidean geometry concept. Pore geometry and structure of most porous rocks are very complex, therefore non-Euclidean geometry concept, e.g. fractal theory, is needed to handle such a complexity. This paper presents a new equation for sandstone permeability involving other properties and fractal dimensions of pore space and surface. The equation is derived by combining Newton's Law of viscosity, Darcy equation, and fractal geometry concept. It is shown that parameters such as tortuosity, internal surface area, and shape factor can be replaced by fractal dimensions. As natural porous media are mostly anisotropic, this study enables us to identify factors that affect the anisotropy. Eighteen sandstone samples with porosity and permeability range from 21 to 37% and 2.76 to 3,644 millidarcies, were employed in this study. The pore space and surface fractal dimensions for each orthogonal direction for each sample was determined by box counting method. The results of this study demonstrate that calculated directional permeability of the high permeability samples is very close to the measured one after corrections were made for pore sizes of less than one micron. This finding suggests that micropores of the samples may be a major factor not contributing to fluid flow. For the low and medium permeability samples, however, an additional pore geometrical correction is needed. The additional correction factor is considerably different for different directions of fluid flow, indicating that the anisotropy is due to the difference in directional pore structural characteristics.

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“…Herein, a comparison with other authors that used Archie's equation in various rocks, such as sandstone, shaly sandstone, carbonate rock, and shale, is of great significance and can promote the understanding of Archie parameters. Initially, the theoretical value of "a" and "m" equaled to 1 and 2 [1,37]. Afterwards, they were assigned different values in literatures based on the best fitting of specific experimental results.…”

Section: Discussionmentioning

confidence: 99%

“…Knackstedt et al stated that the saturation exponent for oil-wet samples was significantly higher than water-wet rocks (n > 5) [36]. Abdassah et al held the same opinion and reported that the saturation exponent was lowest to 1.8 for strongly water-wet rocks and highest to 5.3 for strongly oil-wet rocks [37]. Montaron observed that the I-S w curve behaved nonlinearly in various bending degrees at low water saturation [38].…”

Section: Archie's Equationmentioning

confidence: 98%

A Laboratory Approach Considering Salinity to Investigate Archie’s Parameters in Deep Shale: A Case Study in Longmaxi Formation, Southern Sichuan

Liu

Cai

et al. 2022

Geofluids

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Archie’s parameters are substantial to be investigated in the evaluation of water saturation. Many researchers adhered to the opinion that Archie’s equation can still be applied to water saturation calculation in shale if the accuracy of relative parameters could be improved. External conditions, such as temperature, confining pressure, water salinity, wettability, and displacement, may influence the determination of Archie’s parameters. The aim of the study is to investigate the effect of salinity on Archie’s parameters and their correlation with mineral composition and pore structure. The mineral contents and petrophysical properties were firstly acquired through X-ray diffraction (XRD) and basic measurements. Rock-electric experiments under different salinity were conducted on deep shale samples taken from Longmaxi (LMX) Formation in Luzhou (LZ). The results indicate that Archie’s parameters of “ a ,” “ b ,” “ m ,” and “ n ” under actual brine salinity are assigned to 1.47, 1, 1.26, and 1.6, respectively. Our cementation factor is lower than that in other studies including (shaly) sandstones, carbonates, and shales, probably due to the extremely low porosity in study area. Salinity has a positive effect on cementation factor ( m ) and saturation exponent ( n ), suggesting the traditional assignment to Archie’s parameters is inappropriate. It was concluded that the complicated pore structure and high porosity mainly associated with clay mineral may trigger the increased cementation factor. Further mathematical derivations confirmed that the rock resistivity is inextricable from pore system and establish a physical model. The paper provides a solid evidence base for further understanding and evaluation of water saturation in unconventional shale reservoirs, more significantly, innovatively unveils the research into Archie formula in deep shale reservoirs of southern Sichuan basin.

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Saturation exponent at various wetting condition: fractal modeling of thin-sections

Cited by 12 publications

References 4 publications

The Dependence of Electrical Resistivity-Saturation Relationships on Multiphase Flow Instability

The Dependence of Electrical Resistivity-Saturation Relationships on Multiphase Flow Instability

A Study of Sandstone Permeability Anisotropy Through Fractal Concept

A Laboratory Approach Considering Salinity to Investigate Archie’s Parameters in Deep Shale: A Case Study in Longmaxi Formation, Southern Sichuan

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