https://orcid.org/0000-0003-1677-1961
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ABSTRACT
Micropore and pore evolution both severely influence pore structure and transport properties. The micropore connects isolated pores to predominate connected pore cluster while the pore evolution generates isolated pores. Therefore, investigating separate impacts of predominate and remaining pore clusters is the first step to modify the existing electrical resistivity and permeability models with consideration of the micropore and pore evolution.
The main pore clusters in six porous media including sandstone and carbonate were first extracted. Then, the pore geometry, topology, electrical resistivity and permeability from the main pore cluster compared with them from all the pore clusters in the same porous medium. The calculations of pore morphological and the petrophysical properties were all based on the pore networks extracted from the porous media by maximal ball method.
The predominant pore cluster mainly determined the pore geometry, electrical resistivity and permeability of the corresponded porous medium. However, the isolated pore clusters from pore evolution undermined the pore connectivity. The developments of the remaining pore clusters slightly affected the electrical resistivity and permeability while seriously impacted the porosity exponents. Therefore, the micropore could increase the pore connectivity, and then slightly increase the permeability and reduce the electrical resistivity.
Nomenclature
| MB | = | – maximal ball |
| RW | = | – random walk |
| X-CT | = | – X-ray computerized tomography |
| 3D | = | – three dimensions |
| 2D | = | – two dimensions |
| PTAR | = | – pore to throat cross sectional area ratio |
| G | = | – shape factor |
| SSA | = | – specific surface area |
| FF | = | – formation factor |
| As | = | – surface area of pore or throat |
| V | = | – volume of pore or throat |
| L | = | – Length |
| A | = | – cross-sectional area |
| R | = | – radius of pore or throat |
| N | = | – number of isolated objects |
| C | = | – number of redundant connections within the pore space |
| H | = | – number of totally enclosed cavities |
| χ | = | – Euler number |
| Nnode | = | – number of nodes connected at least by one bond |
| Nbond | = | – number of bonds |
| d | = | – dimensionality of the space |
| <r2> | = | – mean-square displacement |
| D | = | – diffusion coefficient of walkers |
| t | = | – time step |
| a | = | – electric current flow |
| ve | = | – voltage |
| ge | = | – electrical conductance |
| R0 | = | – resistivity of rock fully saturated by a single phase |
| p | = | – single phase in rock |
| ats | = | – macroscopic total current flow |
| ΔVe | = | – voltage drop |
| Ap | = | – cross sectional area occupied by single phase p |
| Rp | = | – resistivity of the single phase p |
| Rw | = | – resistivity of the brine |
| σw | = | – conductivity of the brine |
| σ0 | = | – conductivity of the porous medium full of brine |
| K | = | – absolute permeability |
| μp | = | – viscosity of single phase p |
| qtsp | = | – total flow rate of single phase, p |
| Фinlet | = | – potential in the inlet |
| Фoutlet | = | – potential in the outlet |
| qp | = | – flow rate of single phase p |
| gp | = | – fluid conductance of single phase p |
| Ф | = | – phase potential |
| lij | = | – distance between two pore centers |
| li | = | – pore body length of pore i from the pore-throat interface to the pore center |
| lj | = | – pore body length of pore j from the pore-throat interface to the pore center |
| lt | = | – throat length purely existing in the throat |
| ϕ | = | – porosity |
| τ | = | – tortuosity |
| CD | = | – conductance |
| CDt | = | – conductance of the porous medium |
| CD1 | = | – conductance of the first tube in the porous medium |
| CD2 | = | – conductance of the second tube in the porous medium |
| CDw | = | – conductance of the porous medium with porosity equal to 100% |
Acknowledgments
This investigation is financially supported by National Science &Technology Major Special Project (NO.2016ZX05006-002), China Postdoctoral Science Fund (No. 2018M632716), Shengli Oilfield Postdoctoral Fund (GKB1611) and Shandong Province Postdoctoral Innovative Project Special Fund.
August 14, 2018
Disclosure statement
No potential conflict of interest was reported by the author.