Fractal analyses on saturation exponent in Archie's law for electrical properties of hydrate-bearing porous media

2021 ◽  
Vol 196 ◽  
pp. 107642
Author(s):  
Zhun Zhang ◽  
Lele Liu ◽  
Chengfeng Li ◽  
Jianchao Cai ◽  
Fulong Ning ◽  
...  
Keyword(s):  
Porous Media ◽  
Electrical Properties ◽  
Archie’S Law ◽  
Fractal Analyses ◽  
Saturation Exponent

scholarly journals Effects of Foam Microbubbles on Electrical Resistivity and Capillary Pressure of Partially Saturated Porous Media

Molecules ◽  
2020 ◽  
Vol 25 (15) ◽  
pp. 3385 ◽  
Author(s):  
Abdulrauf R. Adebayo ◽  
Abubakar Isah ◽  
Mohamed Mahmoud ◽  
Dhafer Al-Shehri
Keyword(s):  
Porous Media ◽  
Electrical Resistivity ◽  
Capillary Pressure ◽  
Oil Recovery ◽  
Water Saturation ◽  
Porous Plate ◽  
Fluid Distribution ◽  
Cross Sectional ◽  
Injection Process ◽  
Saturation Exponent

Laboratory measurements of capillary pressure (Pc) and the electrical resistivity index (RI) of reservoir rocks are used to calibrate well logging tools and to determine reservoir fluid distribution. Significant studies on the methods and factors affecting these measurements in rocks containing oil, gas, and water are adequately reported in the literature. However, with the advent of chemical enhanced oil recovery (EOR) methods, surfactants are mixed with injection fluids to generate foam to enhance the gas injection process. Foam is a complex and non-Newtonian fluid whose behavior in porous media is different from conventional reservoir fluids. As a result, the effect of foam on Pc and the reliability of using known rock models such as the Archie equation to fit experimental resistivity data in rocks containing foam are yet to be ascertained. In this study, we investigated the effect of foam on the behavior of both Pc and RI curves in sandstone and carbonate rocks using both porous plate and two-pole resistivity methods at ambient temperature. Our results consistently showed that for a given water saturation (Sw), the RI of a rock increases in the presence of foam than without foam. We found that, below a critical Sw, the resistivity of a rock containing foam continues to rise rapidly. We argue, based on knowledge of foam behavior in porous media, that this critical Sw represents the regime where the foam texture begins to become finer, and it is dependent on the properties of the rock and the foam. Nonetheless, the Archie model fits the experimental data of the rocks but with resulting saturation exponents that are higher than conventional gas–water rock systems. The degree of variation in the saturation exponents between the two fluid systems also depends on the rock and fluid properties. A theory is presented to explain this phenomenon. We also found that foam affects the saturation exponent in a similar way as oil-wet rocks in the sense that they decrease the cross-sectional area of water available in the pores for current flow. Foam appears to have competing and opposite effects caused by the presence of clay, micropores, and conducting minerals, which tend to lower the saturation exponent at low Sw. Finally, the Pc curve is consistently lower in foam than without foam for the same Sw.

RANDOM NETWORKS AND MIXING LAWS

Geophysics ◽  
1976 ◽  
Vol 41 (6) ◽  
pp. 1104-1125 ◽  
Author(s):  
Theodore R. Madden
Keyword(s):  
Porous Media ◽  
Heterogeneous Media ◽  
General Trend ◽  
Geometric Mean ◽  
Fundamental Property ◽  
Total Porosity ◽  
Random Networks ◽  
Embedded Networks ◽  
Archie’S Law ◽  
Wide Range

Random networks are investigated as models of heterogeneous media. A general approximate structure is used where the networks are described as a system of embedded networks, and the critical behavior and averaging behavior of such networks are developed. These results are applied to a study of the electrical conductivity of porous media, with special attention to an Archie's law behavior. It appears that the wide range of crack and pore widths in rocks makes the resulting conductivity relatively insensitive to the topology of their interconnections and allows one to make reasonable predictions of rock conductivities, given the distribution of crack and pore widths. It also appears that with low porosity rocks the conductivity is controlled by the microcrack population which only accounts for a fraction of the total porosity. It would seem, therefore, that Archie's law is a feature of some general trend between porosity and crack and pore width distributions rather than a fundamental property of porous media. The law of the geometric mean is an accurate predictor of the physical properties of a mixture of different materials. This mixing law can result from an equal balance of series and parallel arrangements which can be produced by an appropriate distribution of shapes. A brief look is given to problems of anisotropic distributions for the conductivity problem and it is shown how the averaging process greatly dilutes the microscopic anisotropy in producing the macroscopic properties.

Effects of pore structure and wettability on the electrical resistivity of partially saturated rocks—A network study

Geophysics ◽  
1997 ◽  
Vol 62 (4) ◽  
pp. 1151-1162 ◽  
Author(s):  
Ravi J. Suman ◽  
Rosemary J. Knight
Keyword(s):  
Pore Structure ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Network Model ◽  
Water Saturation ◽  
Archie’S Law ◽  
Partially Saturated ◽  
Saturation Exponent ◽  
Wetting Film

A network model of porous media is used to assess the effects of pore structure and matrix wettability on the resistivity of partially saturated rocks. Our focus is the magnitude of the saturation exponent n from Archie's law and the hysteresis in resistivity between drainage and imbibition cycles. Wettability is found to have the dominant effect on resistivity. The network model is used to investigate the role of a wetting film in water‐wet systems, and the behavior of oil‐wet systems. In the presence of a thin wetting film in water‐wet systems, the observed variation in n with saturation is reduced significantly resulting in lower n values and reduced hysteresis. This is attributed to the electrical continuity provided by the film at low‐water saturation between otherwise physically isolated portions of water. Oil‐wet systems, when compared with the water‐wet systems, are found to have higher n values. In addition, the oil‐wet systems exhibit a different form of hysteresis and more pronounced hysteresis. These differences in the resistivity response are attributed to differences in the pore scale distribution of water. The effects of pore structure are assessed by varying pore size distribution and standard deviation of the pore size distribution and considering networks with pore size correlation. The most significant parameter is found to be the pore size correlation. When the sizes of the neighboring pores of the network are correlated positively, the magnitude of n and hysteresis are reduced substantially in both the water‐wet and oil‐wet systems. This is attributed to higher pore accessibility in the correlated networks. The results of the present study emphasize the importance of conducting laboratory measurements on core samples with reservoir fluids and wettability that is representative of the reservoir. Hysteresis in resistivity can be present, particularly in oil‐wet systems, and should be considered in the interpretation of resistivity data.

The effects of pore structure on the electrical properties of sand-based porous media

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Weibiao Xie ◽  
Qiuli Yin ◽  
Xiaojiao Pang ◽  
Guiwen Wang ◽  
Song Wang
Keyword(s):  
Porous Media ◽  
Electrical Properties ◽  
Pore Structure

scholarly journals Development and validation of an acoustic-electrical joint testing system for hydrate-bearing porous media

2020 ◽  
Vol 12 (3) ◽  
pp. 168781402090898
Author(s):  
Lanchang Xing ◽  
Tai Zhu ◽  
Jiale Niu ◽  
Changling Liu ◽  
Bin Wang
Keyword(s):  
Porous Media ◽  
Electrical Properties ◽  
Sound Velocity ◽  
Ultrasonic Wave ◽  
Electrical Impedance ◽  
Hydrate Formation ◽  
Experimental System ◽  
Sampled Data ◽  
Impedance System ◽  
Hydrate Bearing Sediments

Acoustic and electrical properties are fundamental and important physical properties to characterize hydrate-bearing sediments. A new experimental system called Ultrasound Combined with Electrical Impedance was developed for jointly testing the ultrasonic wave parameters and electrical impedance of hydrate-bearing porous media in the hydrate formation and decomposition processes. The Ultrasound Combined with Electrical Impedance system features its novel ultrasonic-electrical compound sensors and sensor array, fully controllable instruments, variety of sampled data, and flexible working modes. Experiment was carried out with methane gas as the hydrate former, meanwhile the acoustic/electrical parameters were derived. The acoustic/electrical properties were characterized with the aid of typical models such as the time-average equation, Wood’s equation, weighted equation, and Archie’s formula. It has been shown by the results that key parameters such as the sound velocity and electrical impedance can be used to characterize the acoustic and electrical properties of hydrate-bearing sediments conjointly, demonstrating the applicability of the proposed Ultrasound Combined with Electrical Impedance system. The wavelet-analysis based denoising approach and singularity detection method are effective denoising methods to filter the ultrasound signals and to identify the arriving time of the ultrasonic wave. The weighted equation and Archie’s formula with a segmented regression method are recommended for modeling the relations between the hydrate saturation and sound velocity/impedance modulus, respectively.

Sensitivity of the high-frequency sounding method to variations in electrical properties

Geophysics ◽  
2010 ◽  
Vol 75 (4) ◽  
pp. WA189-WA197
Author(s):  
Erin L. Wallin
Keyword(s):  
Magnetic Field ◽  
Electrical Properties ◽  
High Frequency ◽  
Low Frequency ◽  
Vertical Magnetic Field ◽  
Depth Of Penetration ◽  
Archie’S Law ◽  
Dense Nonaqueous Phase Liquid ◽  
Sensitivity Curves ◽  
Ground Penetrating

Instrumentation for high-frequency sounding (HFS) was developed by the U.S. Geological Survey (USGS) in the late 1980s, continuing until 2006. To aid in this development, forward modeling and sensitivity analysis of vertical magnetic fields to electromagnetic (EM) properties between [Formula: see text] and [Formula: see text] were completed. Because these frequencies encompass the transition between the diffusion and propagation regimes, the HFS method ought to be sensitive to all properties contained in the EM wavenumber — namely, electrical conductivity, dielectric permittivity, and magnetic permeability as well as layer thickness. The models consist of three layers that simulate the contam-ination and remediation of dense nonaqueous-phase liquid (DNAPL) contaminants by oxidation. This scenario provides values of [Formula: see text] that would attenuate ground-penetrating radar signals and a range of [Formula: see text] which is a parameter that direct-current resistivity and low-frequency electromagnetic-induction (EMI) techniques are insensitive to. Conductivity and permittivity parameters are calculated with Archie’s law and the Bruggeman-Hanai-Sen (BHS) mixing formula. The importance of thickness and electrical properties to vertical-magnetic-field response of the models initially was addressed using numerical differencing between models containing slight perturbations in electrical properties. Results from this procedure were oscillatory and hence problematic, so analytic partial derivatives of the vertical magnetic field with respect to each parameter were computed for the same scenarios. The derivatives show that the sensitivity to the second-layer permittivity is less than the sensitivity to other properties, and the response is sensitive to slightly magnetic soils. It is also evident that sensitivity and resolution are limited by depth of penetration. The sensitivity curves and plots of the real and imaginary portions of the EM wavenumber demonstrate that propagation begins near [Formula: see text].

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