Sensitivity Analysis of the Effect of Pore Structure and Geometry on Petrophysical and Electrical Properties of Tight Media: Random Network Modeling

Several methodologies published in the literature can be used to construct realistic pore networks for simple rocks, whereas in complex pore geometry formations, as formed in tight reservoirs, such a construction still remains a challenge. A basic understanding of pore structure and topology is essential to overcome the challenges associated with the pore scale modeling of tight porous media. A stochastic random generation algorithm was employed to assess the effects of certain pore structure and geometries on the estimation of petrophysical and electrical properties of tight media through physically realistic 3D random networks. A Weibull truncated equation was used to predict the distribution of network pores and throats. An equivalent 3D pore network of Berea Sandstone was generated based on published pore and throat size distributions. The estimated porosity, absolute permeability, and formation factor of the reconstructed pore network are in good agreement with published laboratory measurements. Moreover, the estimated drainage and imbibition relative permeability curves are in a good match with corresponding experimental relative permeability curves. Subsequently, the effect of pore structure on basic core properties is evaluated by varying the Berea network pore size, throat size, and coordination number (connectivity) distributions. Finally, the effect of pore and throat geometries on two phase flow properties is investigated. The study shows the importance of taking into consideration the internal pore structure for petrophysical and electrical properties estimation

X-Ray Fluoroscopy Measurements and CFD Simulation of Hydrodynamics in a Two Dimensional Gas-Solids Fluidized Bed

X-ray fluoroscopy measurements and CFD simulation were used to characterize the hydrodynamics in a pseudo 2-D gas-solids bubbling fluidized bed using polyethylene resin and glass beads. Bubble properties, such as bubble frequency, bubble size, bubble number distribution and bubble diameter distribution, were estimated from X-ray images and compared to those from CFD simulation

Hydrodynamics of Gas-Solids Bubbling Fluidized Beds Using Polyethylene Resin

Pressure fluctuations were measured in three gas-solids bubbling fluidized beds (10cm, 20cm, and 30cm diameter, 1.0m high) using polyethylene particles of different sizes and particle size distributions. Both bed scale and particle size distribution significantly affect the gas-solids flow behavior. Bubble diameters measured from X-ray fluoroscopy in the 10cm diameter column were compared to various correlations in the literature

Laboratory Investigation of Pipeline/Soil Interactions Using X-Ray Computer Assisted Tomography

X-ray Computer Assisted Tomography (CAT or CT) Scanning has been used successfully for the determination of physical properties of porous rocks and for flow visualization in a variety of porous media including soils. CAT scanning has also been demonstrated as an effective tool for the visualization of different stress conditions in porous rocks with greater accuracy when dealing with unconsolidated media. This success was the motivation in trying to expand the diagnostic capabilities of CAT scanning in the phenomena associated with pipeline / soil interactions. For this purpose, a physical model was built. The model consisted of a x-ray transparent holder which had two pistons, one at each end. The pistons were mounted on a cylindrical rod of variable diameter. The holder was then filled with sand. The entire apparatus was placed in the CAT scanner gantry. A series of experiments were performed whereby the rod was forced through the sand pack. The holder was scanned from end to end and the images of various cross-sections were acquired and analyzed for bulk density and porosity. The experiments were coupled with calibration experiments where a uniformly packed sand was loaded under hydrostatic load in given increments. As the sand pack compacted, its bulk density increased. The normalized change in density (strain) was monitored as a function of the pressure load (stress). The results of the calibration tests were used to identify the levels of stress on the sand surrounding the moving rod. It was discovered that areas of compaction ahead of the moving rod and dilation behind the moving rod could be successfully identified and mapped. The stress / strain calibration data allowed the translation of the bulk density images into stress maps around the pipeline. Although the system and materials used in this work were utilized only for demonstration, it was evident that this type of experimental work could be successfully used to calibrate complicated field scale computer models that are very difficult to tune because of the lack of experimental data

AN EVALUATION OF THE APPLICATION OF LOW FIELD NMR IN THE CHARACTERIZATION OF CARBONATE RESERVOIRS

ABSTRACT Low field Nuclear Magnetic Resonance (NMR) as an analysis tool for reservoir studies is a relatively new and promising technology that is fast, nondestructive and able to yield a vast amount of information about the reservoir formation. In theory, a single NMR measurement can be used to determine porosity, permeability, and irreducible water saturation. Much of the earlier work with NMR was performed on sands or sandstones. When these models were applied to carbonates, the rock properties predicted were very different from those measured through core analysis, and were often incorrect. Thus the conventional method of interpreting NMR data needs to be changed to accommodate the difference between sandstones and carbonates. This paper details an investigation of the bound and free fluid components of carbonates through the use of NMR and Computed Tomography (CT) analysis. Such information is required for estimates of pore connectivity and recoverable reserves. NMR T 2cutoff values vary in carbonates. Correlations were observed between T 2cutoff and the fully saturated NMR spectrum. These correlations could be used on a logging tool as a rough estimate of moveable fluid volume in different zones. T 2cutoff was also observed to correlate well with the NMR spectrum at S wi , which represents the pores that are not drained. In this manner, NMR T 2cutoff values are thought to be indicative of the connectivity of the pores. To test this hypothesis, CT data were obtained and visually compared to the NMR data in order to confirm the relationship between NMR T 2cutoff and pore connectivity. This verifies that NMR T 2cutoff analysis for estimates of moveable fluid volumes can be used to provide information about pore connectivity in carbonates

Visualization of Chemical Heavy Oil EOR Displacement Mechanisms in a 2D System

This study aims to develop a visual understanding of the macro-displacement mechanisms associated with heavy oil recovery by water and chemical flooding in a 2D system. The sweep efficiency improvements by water, surfactant, polymer, and surfactant-polymer (SP) were evaluated in a Hele-Shaw cell with no local pore-level trapping of fluids. The results demonstrated that displacement performance is highly correlated to the mobility ratio between the fluids. Surfactant and water reached similar oil recovery values at similar mobility ratios; however, they exhibited different flow patterns in the 2D system—reductions in IFT can lead to the formation of emulsions and alter flow pathways, but in the absence of porous media these do not lead to significant improvements in oil recovery. Polymer flooding displayed a more stable front and a higher reduction in viscous fingering. Oil recovery by SP was achieved mostly by polymer rather than due to the effect of the surfactant. The surfactant in the SP slug washed out residual oil in the swept zone without increasing the swept area. This shows the impact of the surfactant on reducing the oil saturation in water-swept zones, but the overall oil recovery was still controlled by the injection of polymer. This study provides insight into the fluid flow behavior in diverging flow paths, as opposed to linear core floods that have limited pathways. The visualization of bulk liquid interactions between different types of injection fluids and oil in the Hele-Shaw cell might assist in the screening process for new chemicals and aid in testing the production process

Visualization of Chemical Heavy Oil EOR Displacement Mechanisms in a 2D System

This study aims to develop a visual understanding of the macro-displacement mechanisms associated with heavy oil recovery by water and chemical flooding in a 2D system. The sweep efficiency improvements by water, surfactant, polymer, and surfactant-polymer (SP) were evaluated in a Hele-Shaw cell with no local pore-level trapping of fluids. The results demonstrated that displacement performance is highly correlated to the mobility ratio between the fluids. Surfactant and water reached similar oil recovery values at similar mobility ratios; however, they exhibited different flow patterns in the 2D system—reductions in IFT can lead to the formation of emulsions and alter flow pathways, but in the absence of porous media these do not lead to significant improvements in oil recovery. Polymer flooding displayed a more stable front and a higher reduction in viscous fingering. Oil recovery by SP was achieved mostly by polymer rather than due to the effect of the surfactant. The surfactant in the SP slug washed out residual oil in the swept zone without increasing the swept area. This shows the impact of the surfactant on reducing the oil saturation in water-swept zones, but the overall oil recovery was still controlled by the injection of polymer. This study provides insight into the fluid flow behavior in diverging flow paths, as opposed to linear core floods that have limited pathways. The visualization of bulk liquid interactions between different types of injection fluids and oil in the Hele-Shaw cell might assist in the screening process for new chemicals and aid in testing the production process