scholarly journals Pore connectivity, electrical conductivity, and partial water saturation: Network simulations

2015 ◽  
Vol 120 (6) ◽  
pp. 4055-4068 ◽  
Author(s):  
M. Li ◽  
Y. B. Tang ◽  
Y. Bernabé ◽  
J. Z. Zhao ◽  
X. F. Li ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Water Saturation ◽  
Pore Connectivity ◽  
Network Simulations ◽  
Partial Water

A physically based model for the electrical conductivity of partially saturated porous media

2020 ◽  
Vol 223 (2) ◽  
pp. 993-1006
Author(s):  
Luong Duy Thanh ◽  
Damien Jougnot ◽  
Phan Van Do ◽  
Nguyen Van Nghia A ◽  
Vu Phi Tuyen ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Porous Media ◽  
Fractal Dimension ◽  
Water Saturation ◽  
Theoretical Models ◽  
Fluid Composition ◽  
Physically Based Model ◽  
Partially Saturated ◽  
Proposed Model ◽  
Physically Based

SUMMARY In reservoir and environmental studies, the geological material characterization is often done by measuring its electrical conductivity. Its main interest is due to its sensitivity to physical properties of porous media (i.e. structure, water content, or fluid composition). Its quantitative use therefore depends on the efficiency of the theoretical models to link them. In this study, we develop a new physically based model that takes into account the surface conductivity for estimating electrical conductivity of porous media under partially saturated conditions. The proposed model is expressed in terms of electrical conductivity of the pore fluid, water saturation, critical water saturation and microstructural parameters such as the minimum and maximum pore/capillary radii, the pore fractal dimension, the tortuosity fractal dimension and the porosity. Factors influencing the electrical conductivity in porous media are also analysed. From the proposed model, we obtain an expression for the relative electrical conductivity that is consistent with other models in literature. The model predictions are successfully compared with published experimental data for different types of porous media. The new physically based model for electrical conductivity opens up new possibilities to characterize porous media under partially saturated conditions with geoelectrical and electromagnetic techniques.

Seismic AVO variations related to partial water saturation during a pumping test

2007 ◽  
Author(s):  
Steven D. Sloan ◽  
Georgios P. Tsoflias ◽  
Don W. Steeples
Keyword(s):  
Water Saturation ◽  
Pumping Test ◽  
Partial Water

Test Study on the Multi-Pulse Loading Fracturing Technology for Development of Shallow CBM

2011 ◽  
Vol 361-363 ◽  
pp. 212-216
Author(s):  
Jin Jun Wu ◽  
Xiao San Chu ◽  
Li Cai Liu ◽  
Guo Hua Zhao
Keyword(s):  
New Technologies ◽  
Water Saturation ◽  
High Energy ◽  
Pulse Loading ◽  
Coal Bed ◽  
Pore Connectivity ◽  
Gas Formation ◽  
Test Study ◽  
Test Application ◽  
Strong Adsorption

In China, the coal gas formation is characterized as low permeability, low pressure and low water saturation. The coal bed methane (CBM) has strong adsorption and is difficult to develop. Hydraulic fracture is currently the main measure to improve its permeability, drain the liquid and lower the pressure, which promotes desorption of CBM. But it is not efficient. Based on the principle of high energy gas fracturing (HEGF) and the study of new methods, we proposed the test application of the multi-pulse loading fracturing technology for development of shallow CBM. The mechanism of the technology is that it generates high-temperature and high-pressure gas in the target coal bed to produce a long multi-fracture system with effects of multi-pulse loading. It can also produce strong impulse oscillation acting on formation matrix to loose formation pressure, improve the pore connectivity and permeability of coal bed, which promotes pressure drawdown and desorption of CBM. Thus, the goal of increasing the yield of CBM wells is achieved. This paper focuses on the research ideas, mechanism, process design and feasibility. We carried out analysis combined with field test applications. The study provides a new direction to explore new technologies for China’s CBM development.

scholarly journals Depth characterization of shallow aquifers with seismic reflection, Part II—Prestack depth migration and field examples

Geophysics ◽  
2002 ◽  
Vol 67 (1) ◽  
pp. 98-109 ◽  
Author(s):  
John H. Bradford ◽  
D. S. Sawyer
Keyword(s):  
Seismic Reflection ◽  
Water Saturation ◽  
Compressional Wave ◽  
Unconsolidated Sediments ◽  
Prestack Depth Migration ◽  
Improve Image Quality ◽  
Depth Migration ◽  
Shallow Seismic ◽  
Partial Water

It is common in shallow seismic studies for the compressional‐wave velocity in unconsolidated sediments to increase by a factor of four or more at the transition from dry or partial water saturation to full saturation. Under these conditions, conventional NMO velocity analysis fails and leads to large depth and layer thickness estimates if the Dix equation is assumed valid. Prestack depth migration (PSDM) is a means of improving image accuracy. A comparison of PSDM with conventional NMO processing for three field examples from differing hydrogeologic environments illustrates that PSDM can significantly improve image quality and accuracy.

2D pore-scale simulation of wide-band electromagnetic dispersion of saturated rocks

Geophysics ◽  
2007 ◽  
Vol 72 (3) ◽  
pp. F97-F110 ◽  
Author(s):  
Emmanuel Toumelin ◽  
Carlos Torres-Verdín
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Permittivity ◽  
Electric Fields ◽  
Electromagnetic Property ◽  
Wide Band ◽  
Geometrical Parameters ◽  
Pore Scale ◽  
Porous Rocks ◽  
Pore Connectivity ◽  
Scale Properties

Effective medium theories (EMTs) are invoked routinely to interpret multifrequency dispersions of dielectric permittivity and electrical conductivity of saturated rocks. However, EMTs exhibit limitations that substantially restrict their validity for petrophysical interpretation. For instance, pore connectivity is of significant interest in the study of subsurface reservoirs, but no existing EMT includes it as an explicit property in the analysis of kilohertz- to gigahertz-range dielectric measurements. We introduce a new approach to quantify the effects of pore geometry and connectivity on the kilohertz-gigahertz frequency dispersion of dielectric permittivity and electrical conductivity of clay-free porous rocks. This approach is based on the numerical solution of the internal electric fields within submicron-resolution pore maps constructed with grain and rock pixels. The discrepancy between the internal fields and electrical currents calculated for ahomogeneous scatterer and those calculated for a given pore map is minimized to yield the effective electrical conductivity and dielectric constant for that pore map. This minimization is performed independently for each frequency and is verified to agree implicitly with Kramers-Kronig's causality relationships. We show that EMTs only predict an average dispersion for given microscopic geometrical parameters (e.g., porosity, pore eccentricity), whereas individual realizations honoring the same parameters are associated with dispersion about average values predicted by EMTs. Unlike any EMT prediction, we show that pore connectivity plays a major role in both the shape and amplitude of wide-band electromagnetic property dispersions. The simulation procedure introduced in this paper provides a systematic method to assess the sensitivity of a multitude of pore-scale properties on the macroscopic wide-band dielectric dispersion of saturated rocks.

Reservoir characterization using crosswell electromagnetic inversion: A feasibility study for the Snorre field, North Sea

Geophysics ◽  
2001 ◽  
Vol 66 (4) ◽  
pp. 1177-1189 ◽  
Author(s):  
G. M. Hoversten ◽  
G. A. Newman ◽  
H. F. Morrison ◽  
E. Gasperikova ◽  
John‐Inge Berg
Keyword(s):  
Electrical Conductivity ◽  
North Sea ◽  
Reservoir Characterization ◽  
Water Saturation ◽  
Numerical Models ◽  
Random Noise ◽  
High Sensitivity ◽  
Quantitative Information ◽  
Two Dimensional ◽  
Reservoir Geometry

The spatial resolution of a commercially available crosswell electromagnetic (EM) system is demonstrated using models derived from three time steps from a reservoir simulation of the Snorre field in the North Sea. The numerical simulation of the Snorre field waterflood shows that crosswell EM field measurements provide high sensitivity to changes in the reservoir over time. This sensitivity is achieved by combining the reservoir geometry derived from surface 3‐D seismic interpretation, reservoir conductivities at well locations, and constrained EM inversion of the reservoir’s electrical conductivity. Inversions of 2‐D and 3‐D numerical models show that the changes in electrical conductivity attributable to changes in water saturation can be quantitatively mapped as a function of time. The inversions provide smooth estimates of the spatial variation of reservoir electrical conductivity that can discriminate between the level of water saturation at different stages of the waterflood. Inversions performed on 2‐D data show that for the Snorre example, 3%–5% Gaussian random noise (depending on the model) can be added without a significant degradation in the inverse models. Two‐dimensional inversions of the full 3‐D data in the Snorre example can map the vertical average electrical conductivity within the reservoir in the interwell region almost as well as when the model is two dimensional (constant in strike direction). The effect of 3‐D structure does not seriously degrade 2‐D inversion in the Snorre example‐even between wells that lie in a line parallel to structure. A series of 2‐D inversions where various constraints and starting models are used demonstrates the importance of incorporating a priori information in the form of starting models and restricting the inversion domain to the reservoir zone. These tests show that totally unconstrained, smooth inversions of the interwell volume provide very limited quantitative information. However, when the reservoir geometry is constrained by seismic data and starting models are provided by linear interpolation of conductivities at well locations, the reservoir’s vertical average electrical conductivity can be predicted to within a few percent by 2‐D inversion. The snorre field consists of a full‐scale reservoir with interwell spacings that exceed 1 km where previous work has demonstrated the applicability of crosswell EM in shallow reservoirs with well separations on the order of 100 m. The simulations show that, given current transmitter and receiver technology, the magnetic fields could be measured in the Snorre field in steel‐cased wells separated from the transmitter by up to 725 m.

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