scholarly journals Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

Solid Earth ◽  
2016 ◽  
Vol 7 (4) ◽  
pp. 1109-1124 ◽  
Author(s):  
Tobias Kling ◽  
Da Huo ◽  
Jens-Oliver Schwarz ◽  
Frieder Enzmann ◽  
Sally Benson ◽  
...  
Keyword(s):  
Preferential Flow ◽  
Input Parameter ◽  
Matrix Material ◽  
Core Sample ◽  
Core Flooding ◽  
Ct Scanner ◽  
Fracture Permeability ◽  
Sandstone Sample ◽  
X Ray ◽  
Stress Dependent

Abstract. Various geoscientific applications require a fast prediction of fracture permeability for an optimal workflow. Hence, the objective of the current study is to introduce and validate a practical method to characterize and approximate single flow in fractures under different stress conditions by using a core-flooding apparatus, in situ X-ray computed tomography (CT) scans and a finite-volume method solving the Navier–Stokes–Brinkman equations. The permeability of the fractured sandstone sample was measured stepwise during a loading–unloading cycle (0.7 to 22.1 MPa and back) to validate the numerical results. Simultaneously, the pressurized core sample was imaged with a medical X-ray CT scanner with a voxel dimension of 0.5  ×  0.5  ×  1.0 mm3. Fracture geometries were obtained by CT images based on a modification of the simplified missing attenuation (MSMA) approach. Simulation results revealed both qualitative plausibility and a quantitative approximation of the experimentally derived permeabilities. The qualitative results indicate flow channeling along several preferential flow paths with less pronounced tortuosity. Significant changes in permeability can be assigned to temporal and permanent changes within the fracture due to applied stresses. The deviations of the quantitative results appear to be mainly caused by both local underestimation of hydraulic properties due to compositional matrix heterogeneities and the low CT resolution affecting the accurate capturing of sub-grid-scale features. Both affect the proper reproduction of the actual connectivity and therefore also the depiction of the expected permeability hysteresis. Furthermore, the threshold value CTmat (1862.6 HU) depicting the matrix material represents the most sensitive input parameter of the simulations. Small variations of CTmat can cause enormous changes in simulated permeability by up to a factor of 2.6 ± 0.1 and, thus, have to be defined with caution. Nevertheless, comparison with further CT-based flow simulations indicates that the proposed method represents a valuable method to approximate actual permeabilities, particularly for smooth fractures (< 35 µm). However, further systematic investigations concerning the applicability of the method are essential for future studies. Thus, some recommendations are compiled by also including suggestions of comparable studies.

scholarly journals Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

2016 ◽  
Author(s):  
Tobias Kling ◽  
Da Huo ◽  
Jens-Oliver Schwarz ◽  
Frieder Enzmann ◽  
Sally Benson ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Preferential Flow ◽  
Input Parameter ◽  
Matrix Material ◽  
Core Sample ◽  
High Porosity ◽  
Sandstone Sample ◽  
X Ray ◽  
The Matrix ◽  
Stress Dependent

Abstract. The objective of the current study is to investigate and validate stress-dependent single fluid flow in a fractured core sample using in situ X-ray computed tomography (CT) scans and a finite-volume method solving the Navier-Stokes-Brinkman equations. The permeability of the fractured sandstone sample was measured stepwise during a loading-unloading cycle (0.7 MPa to 22.1 MPa and back) to validate the numerical results. Simultaneously, the pressurized core sample was imaged with a medical X-ray CT scanner with a voxel dimension of 0.5 × 0.5 × 1.0 mm3. Fracture geometries were obtained by CT images based on the Missing Attenuation (MA) approach. Simulation results revealed both, qualitative plausibility and a quantitative approximation of the experimentally derived permeabilities. The qualitative results indicate flow channeling along several preferential flow paths with less pronounced tortuosity. Significant changes in permeability can be assigned to temporal and permanent changes within the fracture due to applied stresses. The applied fluid flow simulations also incorporate potential fracture-matrix interaction and permeability anisotropy within the matrix caused by high-porosity layers. The deviations of the quantitative results appear to be mainly caused by the low resolution affecting the accurate capturing of sub-grid scale features and the reproduction of the actual connectivity. Furthermore, the threshold value CTmat (1862.6 HU) depicting the matrix material represents the most sensitive input parameter of the simulations. Small variations of CTmat (±17.7 HU in this study) can cause enormous changes in simulated permeability by up to a factor of 2.6 ± 0.1 and, thus, has to be defined with caution. Finally, our results are also compared with other studies showing similar results. Based on these observations various recommendations to improve CT image quality, model quality, aperture calibration and validation of qualitative fluid flow are provided.

scholarly journals CO2-brine injectivity tests in high co2 content carbonate field, sarawak basin, offshore east Malaysia

2019 ◽  
Vol 89 ◽  
pp. 04005 ◽  
Author(s):  
A Giwelli ◽  
MZ Kashim ◽  
MB Clennell ◽  
L Esteban ◽  
R Noble ◽  
...  
Keyword(s):  
Packed Column ◽  
Core Sample ◽  
Chemical Analyses ◽  
Core Flooding ◽  
Flow Rates ◽  
X Ray ◽  
The Core ◽  
Reservoir Conditions ◽  
Post Test ◽  
Porosity And Permeability

We conducted relatively long duration core-flooding tests on three representative core samples under reservoir conditions to quantify the potential impact of flow rates on fines production/permeability change. Supercritical CO2 was injected cyclically with incremental increases in flow rate (2─14 ml/min) with live brine until a total of 7 cycles were completed. To avoid unwanted fluid-rock reaction when live brine was injected into the sample, and to mimic the in-situ geochemical conditions of the reservoir, a packed column was installed on the inflow accumulator line to pre-equilibrate the fluid before entering the core sample. The change in the gas porosity and permeability of the tested plug samples due to different mechanisms (dissolution and/or precipitation) that may occur during scCO2/live brine injection was investigated. Nuclear magnetic resonance (NMR) T2 determination, X-ray CT scans and chemical analyses of the produced brine were also conducted. Results of pre- and post-test analyses (poroperm, NMR, X-ray CT) showed no clear evidence of formation damage even after long testing cycles and only minor or no dissolution (after large injected pore volumes (PVs) ~ 200). The critical flow rates (if there is one) were higher than the maximum rates applied. Chemical analyses of the core effluent showed that the rock samples for which a pre-column was installed do not experience carbonate dissolution.

Determination of Optimum Parameters for Anaerobic Thermophilic Bacterium Injection using Commercial Simulator: Core Flooding Validation and Sensitivity

2020 ◽  
Author(s):  
A. Koto
Keyword(s):  
Oil Recovery ◽  
Simulation Experiment ◽  
Previous Experiment ◽  
Core Sample ◽  
Thermophilic Bacterium ◽  
Injection Rate ◽  
Core Flooding ◽  
Optimum Parameters ◽  
Result Show

The objective of this paper is to determine the optimum anaerobic-thermophilic bacterium injection (Microbial Enhanced Oil Recovery) parameters using commercial simulator from core flooding experiments. From the previous experiment in the laboratory, Petrotoga sp AR80 microbe and yeast extract has been injected into core sample. The result show that the experiment with the treated microbe flooding has produced more oil than the experiment that treated by brine flooding. Moreover, this microbe classified into anaerobic thermophilic bacterium due to its ability to live in 80 degC and without oxygen. So, to find the optimum parameter that affect this microbe, the simulation experiment has been conducted. The simulator that is used is CMG – STAR 2015.10. There are five scenarios that have been made to forecast the performance of microbial flooding. Each of this scenario focus on the injection rate and shut in periods. In terms of the result, the best scenario on this research can yield an oil recovery up to 55.7%.

scholarly journals Micro-Fabric Analyzer (MFA): A New Semiautomated ArcGIS-Based Edge Detector for Quantitative Microstructural Analysis of Rock Thin-Sections

2021 ◽  
Vol 10 (2) ◽  
pp. 51 ◽  
Author(s):  
Roberto Visalli ◽  
Gaetano Ortolano ◽  
Gaston Godard ◽  
Rosolino Cirrincione
Keyword(s):  
Physical Properties ◽  
Electron Backscatter Diffraction ◽  
Microstructural Analysis ◽  
Image Features ◽  
Elemental Distribution ◽  
Edge Detector ◽  
Sandstone Sample ◽  
Thin Sections ◽  
X Ray ◽  
Distribution Maps

Micro-Fabric Analyzer (MFA) is a new GIS-based tool for the quantitative extrapolation of rock microstructural features that takes advantage both of the characteristics of the X-ray images and the optical image features. Most of the previously developed edge mineral grain detectors are uniquely based on the physical properties of the X-ray-, electron-, or optical-derived images; not permitting the exploitation of the specific physical properties of each image type at the same time. More advanced techniques, such as 3D microtomography, permit the reconstruction of tridimensional models of mineral fabric arrays, even though adjacent mineral grain boundaries with the same atomic density are often not detectable. Only electron backscatter diffraction (EBSD) allows providing high-performing grain boundary detection that is crystallographically differentiated per mineral phase, even though it is relatively expensive and can be executed only in duly equipped microanalytical laboratories by suitably trained users. Instead, the MFA toolbox allows quantifying fabric parameters subdivided per mineral type starting from a crossed-polarizers high-resolution RGB image, which is useful for identifying the edges of the individual grains characterizing rock fabrics. Then, this image is integrated with a set of micro-X-ray maps, which are useful for the quantitative extrapolation of elemental distribution maps. In addition, all this is achieved by means of low-cost and easy-to-use equipment. We applied the tool on amphibolite, mylonitic-paragneiss, and -tonalite samples to extrapolate the particle fabric on different metamorphic rock types, as well as on the same sandstone sample used for another edge detector, which is useful for comparing the obtained results.

A New Procedure for Quick Estimation of Porosity and Density of Hydrate-bearing Sediments by Using Medical X-ray CT Scanner

2018 ◽  
Author(s):  
Lallan Gupta ◽  
Wataru Tanikawa ◽  
Yohei Hamada ◽  
Takehiro Hirose ◽  
Naokazu Ahagon ◽  
...  
Keyword(s):  
Ct Scanner ◽  
X Ray ◽  
Hydrate Bearing Sediments

Experimental investigation of the effect of compliant pores on reservoir rocks under hydrostatic and triaxial compression stress states

2019 ◽  
Vol 56 (7) ◽  
pp. 983-991
Author(s):  
Hua Yu ◽  
Kam Ng ◽  
Dario Grana ◽  
John Kaszuba ◽  
Vladimir Alvarado ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Triaxial Compression ◽  
Matrix Material ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Differential Pressure ◽  
Sandstone Sample ◽  
Stress States ◽  
Rock Springs ◽  
Stage 1

The presence of compliant pores in rocks is important for understanding the stress–strain behaviors under different stress conditions. This paper describes findings on the effect of compliant pores on the mechanical behavior of a reservoir sandstone under hydrostatic and triaxial compression. Laboratory experiments were conducted at reservoir temperature on Weber Sandstone samples from the Rock Springs Uplift, Wyoming. Each experiment was conducted at three sequential stages: (stage 1) increase in the confining pressure while maintaining the pore pressure, (stage 2) increase in the pore pressure while maintaining the confining pressure, and (stage 3) application of the deviatoric load to failure. The nonlinear pore pressure – volumetric strain relationship governed by compliant pores under low confining pressure changes to a linear behavior governed by stiff pores under higher confining pressure. The estimated compressibilities of the matrix material in sandstone samples are close to the typical compressibility of quartz. Because of the change in pore structures during stage 1 and stage 2 loadings, the estimated bulk compressibilities of the sandstone sample under the lowest confining pressure decrease with increasing differential pressure. The increase in crack initiation stress is limited with increasing differential pressure because of similar total crack length governed by initial compliant porosity in sandstone samples.

High temperature fatigue characteristics of P/M and hot-forged W-Re and TZM for X-ray target of CT scanner

2018 ◽  
Vol 137 ◽  
pp. 335-344 ◽  
Author(s):  
Mohd Azhar Harimon ◽  
Yukio Miyashita ◽  
Yuichi Otsuka ◽  
Yoshiharu Mutoh ◽  
Shinichi Yamamoto
Keyword(s):  
High Temperature ◽  
Ct Scanner ◽  
X Ray ◽  
High Temperature Fatigue ◽  
Fatigue Characteristics

scholarly journals Optimization of the imaging protocol of an X-ray CT scanner for evaluation of normoxic polymer gel dosimeters

2006 ◽  
Vol 31 (2) ◽  
pp. 72 ◽  
Author(s):  
Brindha Subramanian ◽  
PaulB Ravindran ◽  
Clive Baldock
Keyword(s):  
Polymer Gel ◽  
Ct Scanner ◽  
Imaging Protocol ◽  
X Ray
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