Cavity Porosity Research Articles

Use digital rock physics to characterize velocity and attenuation signatures of deep cavity-fracture carbonate reservoirs

Abstract Conventional rock physics experiments and well logging analyses face challenges in deep carbonate formation containing meter-scale cavity-fracture system, since it is unfeasible to extract representative samples from targeted formation. In this study, differing from the conventional digital rock models at the core scale, we construct a digital rock model from realistic outcrop images with meter-scale heterogeneity of cavities and fractures. Using a dynamic stress–strain simulation, we investigate how reservoir type, fracture density and spacing, cavity porosity and size, fluid saturation, and connectivity influence wave dispersion and attenuation. By selecting the simulation frequency of 0.3 MHz approximately corresponding to the field seismic measuring frequency of 30 Hz, the simulation results can reflect the realistic seismic velocity and attenuation characteristics of deep carbonate reservoir rocks. We find that the P-wave velocity decreases linearly with increasing fracture and cavity porosity. The P-wave attenuation is sensitive to variations in fracture density but shows limited sensitivity to changes in cavity porosity and size. Fractures with narrower spacing result in higher attenuation when fracture density remains constant. Deep carbonate rocks with cavity-fracture systems saturated with two immiscible fluids display enhanced attenuation compared to fully saturated conditions. The velocity demonstrates an almost linear increase with water saturation, while attenuation initially increases before decreasing at a peak water saturation of 70%–80%. The connectivity between fractures and cavities significantly influences the attenuation behavior. Our simulation results provide valuable guidance for seismic data processing and interpretation of deep carbonate reservoir rocks with cavity-fracture systems.

Convection flow of nano-encapsulated phase change material in wavy chamber with double sliding walls, flame-shaped heating source, and magnetic force

This article aims to improve the convection flow within a two-dimensional chamber by utilizing nano-encapsulated phase change material (NEPCM). The chamber center contains a flame-shaped heating source, and the bottom wall is wavy. Forced convection occurs due to the motion of the chamber's side walls, while natural convection arises from the thermal gradient across the side walls. The Galerkin-finite element (GFEM) approach was employed to analyze the system's governing equations. The study investigates the impact of the following factors on heat transfer: wall velocity (Re = 10–1000), wall movement directions (both walls moving in a positive direction, both walls moving in a negative direction, and one wall negative and the other positive), intensity of the magnetic field (Ha = 0–100), and cavity porosity (Da = 10−5 – 10−2). The results demonstrate that increasing Re and Da improves the average Nusselt number (NuAvg). Conversely, raising the intensity of the magnetic field and moving the side walls in the opposite direction reduces NuAvg. At Re = 1000, increasing Da (10−2 instead of 10−5) leads to a 139% increase in NuAvg, and decreasing Ha and moving walls in the same directions increase NuAvg by 11.5% and 640%, respectively.

Magnetic field impact on double diffusive mixed convective hybrid-nanofluid flow and irreversibility in porous cavity with vertical wavy walls and rotating solid cylinder

Mixed convective heat transfer due to rotating surface has sustainable importance in improving cooling efficiency of thermal engineering equipment. In this investigation, hydromagnetic double diffusive mixed convection in a wavy porous cavity filled with hybrid nanofluid having rotating heat source is numerically studied. A solid cylindrical rotating heat source is positioned at the center of the wavy cavity. The fluid domain inside the cavity is heated from the rotating heat source and partially heated bottom wall. The governing partial differential equations are simulated using finite element method. The computational technique is validated performing rational comparisons. The results indicate that the pattern of streamlines circulation, isotherms and local entropy generation are significantly influenced with the rotating heat source. The flow velocity is observed increasing rapidly with cylinder rotation speed which is maximized with increasing cavity porosity and permeability but minimized with magnetic field impact and amalgamating hybrid nanoparticles. Heat transfer enhancement is found increasing by 682.07% with rotating heat source for varying Darcy number (Da = 10−4 to 10−1) in absence of magnetic field (Ha = 0) which reduces to 504.02% in presence of magnetic field (Ha = 100). Moreover, 45.62% heat transfer enhancement is achieved for varying of cavity porosity (ε = 0.3 to 0.9) which declines to 22.83% in presence of magnetic field (Ha = 100). In addition, 90.04% more heat transfer enhancement is estimated in hybrid nanofluid of 5% volume fraction than base fluid water. The entropy generations components are affected significantly with higher values of physical parameters. The Bejan number is found declining for all influential parameters studied. Accordingly, the study has significant impact on the controlling and optimizing of fluid flow and heat transfer in hybrid nanofluid filled improved designing and is applicable in improving the performance of thermal equipment such as high-performance heat exchangers, electronic device cooling, energy storage systems, thermal mixing, space thermal management, crystal growth, float glass production, solidifications, solar technologies, and reactor safety devices, etc.

Entropy generation due to hydromagnetic buoyancy-driven hybrid-nanofluid flow in partially heated porous cavity containing heat conductive obstacle

Hydromagnetic natural convection heat transfer in an improved designing has sustainable importance in high performance thermal equipment and geothermal energy systems. This investigation explores the fluid flow and temperature behaviours along with entropy generation for buoyancy driven flow of hybrid nanofluid in a partially heated cavity saturated by porous medium having heat conductive cylinder in presence of external magnetic field. Effective thermal conductivity model is formulated based on Brownian motion of Cu and Al2O3 nanoparticles. The developed governing equations are solved implementing Galerkin finite element method. Results-based discussion is presented through streamlines, temperature contours, heat transfer rate and entropy generation tools, respectively. The results endorse that fluid flow and temperature and also local entropy generation are phenomenally influenced with higher buoyancy parameter but these impacts are correlated with magnetic field strength, amount of hybrid nanoparticles and also cavity permeability. The heat transfer rate and average entropy generation components are increased with the increase in Rayleigh number and these trends are expedited with the increase in cavity porosity and volume fraction but reverse trend is found for magnetic field effect except magnetic-irreversibility. In addition, Bejan number is declined for increasing Rayleigh and Darcy numbers but increased for higher Hartmann number and amount of hybrid nanoparticles.

Accurate meso-scale simulation of mixed convective heat transfer in a porous media for a vented square with hot elliptic obstacle: An LBM approach

In the present study, heat and fluid flow of water in a vented cavity with elliptical hot obstacle is numerically investigated using Lattice Boltzmann Method (LBM). This flow is assumed to be laminar, 2D and incompressible. The main purpose in this work is to investigate the effect of utilizing porous medium on mixed convective heat transfer in an obstructed vented cavity. The simulations are performed for Richardson number of 0.1, 1 and 10, porosity of 0.5, 0.7 and 0.9, and solid-to-fluid conductivity ratios of 10, 33.3, 66.7 and 100. The results are presented by streamlines, temperature contours, and Nusselt number curves. Results show that by increasing Richardson number, due to the dominance of natural convective heat transfer compared with that of the forced case, the heat penetration in fluid layers in all areas of the cavity is increased. Moreover, as the Richardson number increases, due to limitation of forced heat transfer, the temperature gradients in the cavity rise and the growth of thermal boundary layer becomes significant. This behavior has an undesirable effect on heat transfer of hot obstacle especially around the cavity outlet and right side of the obstacle. By decreasing the cavity porosity, the areas around the hot obstacle will experience higher heat penetration into the fluid and consequently the heat transfer is reduced. In this study, the highest Nusselt number is obtained for Richardson number of Ri=0.1 and porosity of Po=0.5 and the increase in Richardson number and porosity coefficient results in reduced Nusselt number in all areas around the hot obstacle. The porosity changes have more significant effect on heat transfer in smaller Richardson numbers. This results in Nusselt number higher about 79% in best condition at conductivity ratio of 33.33 (Ri=0.1) while it changes the Nusselt number about 17.4% at conductivity ratio of 10 (Ri=10).

Thermo-mechanical properties of fused borosilicate syntactic foams

The coefficient thermal expansion, a (CTE) of glass microballoon/vinyl ester syntactic foam was determined using dimensional changes of a temperature gradient plot. The CTE was measured and found to be up to 53-63 % lower than the vinyl ester resin matrix when mixing with different weight percentages of the glass microballoon ranging from 2 wt.% to 10 wt.% using a thermomechanical analyzer (TMA). The results of CTE showed that it has a strong relationship with the syntactic foam density (r), radius ration (h) ,cavity porosity (fg) and matrix porosity (fm). Experimental results showed that the CTE decreases when glass microballoons are added into the composites measured at different temperatures ranging from 30 oC to 70 °C. The CTE from the experimental results were also compared with Turner’s modification model for composites for its suitability for thermal expansion of syntactic foams. The results indicate that Turner’s modification model exhibits a close correlation with the reduction up to 80 % of CTE based on experiment.

A case study: Mechanical modeling optimization of cellular structure fabricated using wood flour-filled polylactic acid composites with fused deposition modeling

Wood plastic composites (WPCs) have emerged as environmentally benign filaments for fused deposition modeling (FDM) printing. Using WPCs filaments to print light weight and strong cellular structures could create new application potentials for WPCs and provide sustainable feedstock for cellular materials. In this research, the compression performance of FDM printed circle, square, and voronoi WPCs cellular structures were investigated using finite element simulations and compression experiments. Simulated results did not agree with experimental results due to the presence of cavities in the prints. Cavities were formed in the cellular structures with arcs and curvature. The results showed that the circle cellular structure demonstrated great fluctuations between the simulations and experimental results. The cavity porosity was also found to increase with the increase of the print line width. Further, to improve the accuracy of simulations, the cavity porosity exists in the cellular structures was considered while revising the models. After modification, square cellular models compressed the least, followed by the circle and voronoi ones, which was consistent with the experimental results. Minimizing the print line width could reduce cavity porosity. Nonetheless, thinner print line width and smaller wood fiber size in filaments will likely increase manufacturing cost and difficulty.

Thermal Expansion Properties of Fused Borosilicate Syntactic Foams

The thermal properties such the coefficient thermal expansion, α (CTE) of fused borosilicate syntactic foam was determined using dimensional changes of a temperature gradient plot. The CTE was measured and found to be achieved the value lower than the vinyl ester resin matrix when mixing with different weight percentages of the glass microballoon ranging from 2 wt.% to 10 wt.% using a thermomechanical analyzer (TMA). These results showed that it has a strong relationship with the syntactic foam physical properties such density, radius ration,cavity porosity and matrix porosity. Experimental results showed that the CTE decreases when glass microballoons are added into the composites measured at different temperatures ranging from 30 °C to 70 °C. The CTE from the experimental results were also analysed using Turner’s modification model for composites for its suitability for thermal expansion of syntactic foams.

Solution for geological and technological problems in carbonate sections with developed secondary capacity on the example of Volga-Ural Petroleum and Gas Province deposit

As of today many of the old fields are already depleted. Replenishment of the category of oil and gas reserves from the category of prospective resources proceeds mainly due to revising the state of overor underlying layers in the already developed horizon, rather than by exploiting entirely new deposits. Current methods of allocation of complex reservoirs both according to the data of geological and technological studies and the results of commercial and geophysical studies are relevant. In this paper, solutions of geological and technological problems are considered on the example of the carbonate section of the Volga-Ural Petroleum and Gas Province in absorbing wells. Today, by the methods of borehole geophysics, reservoirs capacity in isotropic environment is effectively calculated. In the presence of fracture and cavity porosity, the standard methods of electrometry prove to be ineffective, even for a qualitative interpretation. Therefore, in the complex reservoir with a secondary porosity space structure, construction of interpretation model is used by the following methods of well logging - neutron method (NM), acoustic method (AK) and gamma-gamma density method (GGM-P). To eliminate absorptions, both standard methods and the latest developments were used. The effectiveness of the use of profile packers in absorbing wells is shown.

Quantitative image analysis of bubble cavities in iron ore green pellets

Scanning electron microscopy and image analysis was used for quantitative analysis of bubble cavities in iron ore green pellets. Two types of pellets prepared with and without addition of flotation reagent prior to balling were studied. The bubble cavity porosity amounted to 2.8% in the pellets prepared without addition of flotation reagent prior to balling. When flotation reagent was added prior to balling, the bubble cavity porosity increased by a factor of 2.4 and the median bubble diameter was decreased slightly. It was also shown that mercury intrusion porosimetry is not suitable for determination of the distribution of bubble cavities. Finally, our data suggested that the difference in total porosity determined by mercury intrusion porosimetry and pycnometry between the two types of pellets was due to the bubble cavities.

Modelling Carbonate Reservoir Porosity For Enhanced Recovery Schemes

Abstract Most carbonate rock porosity classifications are generic and do not account for features of the pore systems that may affect fluid movement and withdrawal-important factors in the production of hydrocarbons from these rocks. Mercury injection capillary pressure (MICP) analyses of carbonate reservoirs supply valuable information on the interaction between non-wetting fluids and reservoir porosity. Some 200 analyses of a variety of Mississippian carbonate reservoirs in southern Saskatchewan indicate that porosity can be simplified into three types; inter-crystal, cavity and mixed (inter-crystal and cavity). The categories can be recognized by the degree of uniformity of pore throat sizes in the reservoir rock; a high degree of uniformity indicates inter-crystal porosity and a wide variation in pore throat size is representative of cavity porosity. Entry pressure is a second MICP factor that tells something about the reservoir rock. High entry pressures are commonly related to calcitic reservoir rocks with inter-crystal porosity: intermediate entry pressure indicates dolomite with inter-crystal porosity; and low pressures are representative of calcitic or dolomitic rocks with abundant large cavities (mesopores). Pore system/fluid interaction can be shown to influence efficient withdrawal of hydrocarbons from a reservoir, thus productivity may vary markedly due to differences in porosity types over the lateral extent of a producing zone. Introduction During the past ten years, several graduate students in the Department of Geology, University of Regina, and the author have investigated several geological aspects of the Mississippian reservoir rocks in southeastern Saskatchewan. These include studies into the microfacies, diagenesis and nature of the pore systems in the Benson (Midale Beds)(1), Glen Ewen (Midale Beds)(2), Innes (Frobisher Beds)(3,4) and Hummingbird (Ratcliff Beds)(5) oilfields. In addition to these completed investigations, a study is at present being carried out on three Ratcliffe Beds producing areas: Flat Lake, Lake Alma, and Oungre. Most of these studies have been generously supported by the Saskatchewan Department of Energy and Mines, in an effort to establish a readily available source of information on carbonate rock reservoirs for enhanced recovery schemes. The Hummingbird study was financed through a grant to Dr. L. W. Vigrass from Hudson's Bay Oil and Gas Co. Ltd. The pore systems of the reservoirs in these fields have been studied using mercury injection capillary pressure analyses, to establish pore throat size distribution and a variety of fluid response characteristics, including entry pressure, ejection efficiency and unsaturated pore volume. The results of these analyses were enhanced by detailed examination of the reservoir rocks using scanning electron and light microscopy. The variety of carbonate rock types constituting the reservoirs in the Mississippian fields studied have made it possible for the writer to establish a simplified classification of porosity for carbonate reservoir rocks. Because Mississippian rocks are used as the basis for this classification a brief review of their important characteristics is presented below. Geologic Setting Mississippian rocks in southern Saskatchewan were deposited on the northern flank of the Williston Basin in a marine seaway in which paleobathymetry exerted an influence on the distribution of facies.