Pore Bridging Research Articles

A mitigation strategy for productivity impairment in sandstone reservoirs with varying clay mineralogy

The interaction between drilling fluids and oil and gas reservoir formations can result in the reduction or blockage of the micropore structural network, leading to a consequent decrease in permeability. Due to the negative economic impact of formation damage on hydrocarbon production, formulating drilling fluids with characteristics that minimise formation damage has been a major focus of the petroleum industry and researchers since the 1970s–1980s. Formation damage can significantly affect the ultimate productivity in hydrocarbon-bearing formations, especially in sandstone reservoirs with varying clay mineralogy such as kaolinite, smectite, illite, and mixed layer (illite + smectite) clay mineralogy in the micropore structural networks. These clay minerals are highly unstable/reactive and often appear as pore lining, pore bridging, and pore-filling along the walls of the micropore structural, inevitably coming into contact with drilling fluids (both solids and filtrates) that have invaded the micropore structure. Existing studies on the understanding of the relationship between drilling fluid formulation and formation damage mechanisms have not adequately addressed the role of individual species of clay minerals and their varying physicochemical properties during the formulation of drilling fluids for sandstone reservoirs with varying clay minerals. Instead, clay minerals are often treated as a whole or a single group. The work presented in this paper aims to examine and quantifies the impact of three drilling fluids (PAC-UL water-based, potassium formate, and halide drilling fluids) on productivity impairment in kaolinitic sandstone reservoirs and in kaolinitic and mixed-layer (illitic + smectitic) sandstone reservoirs. To achieve this, a high-temperature, high-pressure (HTHP) formation damage testing facility was designed and built to determine the initial and return permeability of selected hydrocarbon reservoirs using core samples. The formation damage mechanisms resulting from the interaction of the reservoir rocks with different formulations of drilling fluids are fully characterized using a combination of scanning electron microscopy, energy dispersive X-ray and micro-computed tomography. For all three drilling fluid formulations, the results showed an enhanced return permeability of the kaolinitic sandstone after interaction with the specially formulated halide drilling fluid.

Experimental study and small-sample-regression prediction on effect of carbon-based reinforcements on thermal conductivity of composite mortar

To reveal the impact of various sizes of inert reinforcement on the pore structure, hydration products, and microscopic morphology of mortar. To explore its effect on mortar's thermal conductivity. Investigated by microscopic tests and small sample regression modeling. It is found that nanoscale materials have a nanocore effect, which can effectively enhance hydration, but the filling and bridging of larger pores is inadequate, leading to lower thermal conductivity in the early stage. The release of their properties is limited by the dispersion technique. Micron-reinforcing-phase, easily dispersed and with adsorption, can effectively fill capillary pores, and adsorb the hydration products to advance the hydration process. Milli-reinforcing-phase, flocculent fiber water absorption is obvious, resulting in the reduction of the real water-cement ratio, hydration process is delayed. With age growth and water precipitation, the fiber surface produces nucleation sites, which will accelerate the hydration rate. For thermal conductivity, porosity is the main influence factor in the early curing stage; when the porosity changes are small, the internal microstructure and hydration products will become the dominant factors. The sample set is expanded by feature enhancement and data synthesis to improve the generalization ability. The predicted model R2 can reach 0.75, demonstrating that a limited sample of experimental data can make reliable predictions.

Clay-induced permeability decline in sandstone reservoirs: Insights from a coupled NMR-SEM experimental approach

The blockage induced by solid particles transport and deposition is one of the main causes of injectivity decline in geothermal sandstone reservoirs during reinjection. This paper investigates clay-induced clogging mechanisms to provide a better understanding to formation damage problems encountered in geothermal fields. In-depth NMR measurements were carried out during core-flooding experiments where illite clay particles (120 nm) were injected in sand-packed columns. SEM imaging was performed to compare the porous space before and after damage and study the morphology and distribution of the deposited particles in the sand column. Pressure drop measurements and NMR T2 relaxation time distributions revealed that clogging occurs in two stages: surface deposition and pore bridging. This was further confirmed by SEM images showing that pore-blocking illite ribbons were formed in the porous space.

The Power of Characterizing Pore-Fluid Distribution for Microscopic CO2 Injection Studies in Tight Sandstones

The microscopic structure of low-permeability tight reservoirs is complicated due to diagenetic processes that impact the pore-fluid distribution and hydraulic properties of tight rocks. As part of an ongoing study of carbon dioxide-enhanced oil and gas recovery (CO2-EOR/EGR) and CO2 sequestration, this research article adopts an integrated approach to investigate the contribution of the micropore system in pore-fluid distribution in tight sandstones. A new dimensionless number, termed the microscopic confinement index (MCI), was established to select the right candidate for microscopic CO2 injection in tight formations. Storativity and containment indices were essential for MCI estimation. A set of experiments, including routine core analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), mercury injection capillary pressure (MICP), and nuclear magnetic resonance (NMR), was performed on three tight sandstone rock samples, namely Bandera, Kentucky, and Scioto. Results indicate that the presence of fibrous illite acting as pore bridging in Bandera and Kentucky sandstone samples reduced the micropore-throat proportion (MTMR), leading to a significant drop in the micropore system confinement in Kentucky and Bandera sandstone samples of 1.03 and 0.56, respectively. Pore-filling kaolinite booklets reduced the micropore storativity index (MSI) to 0.48 in Kentucky and 0.38 in Bandera. On the other hand, the absence of fibrous illite and kaolinite booklets in Scioto sandstone led to the highest micropore system capability of 1.44 MTMR and 0.5 MSI to store and confine fluids. Therefore, Scioto sandstone is the best candidate for CO2 injection and storage among the tested samples of 0.72 MCI.

Impact of clay mineralogy on the petrophysical properties of tight sandstones

A full petrographic and petrophysical characterization of tight sandstones has been conducted as part of ongoing study of Carbon Dioxide Enhanced Oil and Gas Recovery (CO2-EOR/EGR) and CO2sequestration. The main purpose of this study is to give novel perception into the interplay of the rock characteristics and fluid flow in tight formations, which are candidates for EOR/EGR processes (macroscopic sweep vs. microscopic displacement efficiency). To achieve this, several experimental techniques, including routine core analysis, X-ray diffraction (XRD), X-ray fluorescence (XRF), thin sections petrography, Scanning Electron Microscopy (SEM) and capillarity/pore size distributions by using Mercury Injection Capillary Pressure (MICP), Nuclear Magnetic Resonance (NMR), and Micro-Computed Tomography (Micro-CT), were conducted. Three tight sandstone rock samples (Bandera, Kentucky, and Scioto) were used in this work and particular attention was paid to the impact of clay content on rock's pore system and other petrophysical characteristics and hence fluids flow during production process.Results indicate that the presence of fibrous illite clay acting as pore bridging in Bandera and Kentucky samples have blocked the overall micro-pore system causing a significant reduction in the micro-pore throat system to 36% in Bandera sand and 50.9% in Kentucky sample. On the other hand, absence of fibrous illite and the presence of illite platelets in the Scioto sandstone led to a clear preservation of the sample's micro-pore throat attributing to a total of 59.1% of the total pore throat system.A new dimensionless number (dimensionless micro-pore throat modality) was established, defined as the ratio of micro-to macro-pore sizes. This shows that Scioto has the highest value of 1.44 implying that both macro- and micro-pore systems contribute to flow. Therefore, the mitigation of oil bypass from smaller pores should be a key criterion in selecting the proper recovery methods. Results show the effect of clay mineralogy on pore system considering a part of the physical and spatial properties the pore/grain framework of the tight sandstones.

3D extrusion printing of density gradients by variation of sinusoidal printing paths for tissue engineering and beyond.

During extrusion printing of pasty biomaterials, internal geometries are mainly adjusted by positioning of straightly deposited strands which does not allow realization of spatially adaptable density gradients in x-, y- and z-direction for anisotropic scaffolds or anatomically shaped constructs. Herein, an alternative concept for printing patterns based on sinusoidal curves was evaluated using a clinically approved calcium phosphate cement (CPC). Infill density in scaffolds was adjusted by varying wavelength and amplitude of a sinus curve. Both wavelength and amplitude factors were defined by multitudes of the applied nozzle diameter. For CPC as a biomaterial ink in bone application, porosity, mechanical stiffness and biological response by seeded immortalized human mesenchymal stem cells - adhesion and pore bridging behavior - were investigated. The internal structure of a xyz-gradient scaffold was proven via X-ray based micro computed tomography (µCT). Silicone was used as a model material to investigate the impact of printing velocity and strand distance on the shape fidelity of the sinus pattern for soft matter printing. The impact of different sinus patterns on mechanical properties was assessed. Density and mechanical properties of CPC scaffolds were successfully adjusted without an adverse effect on adhesion and cell number development. In a proof-of-concept experiment, a sinus-adjusted density gradient in an anatomically shaped construct (human vertebral body) defined via clinical computed tomography (CT) data was demonstrated. This fills a technological gap for extrusion-based printing of freely adjustable, continuously guidable infill density gradients in all spatial directions. STATEMENT OF SIGNIFICANCE: 3D extrusion printing of biomaterials allows the generation of anatomically shaped, patient-specific implants or tissue engineering scaffolds. The density of such a structure is typically adjusted by the strand-to-strand distance of parallel, straight-meandered strands in each deposited layer. By printing in a sinusoidal pattern, design of density gradients is possible with a free, spatial resolution in x-, y- and z-direction. We demonstrated that porosity and mechanical properties can be freely adapted in this way without an adverse effect on cell adhesion. With the example of a CT dataset of a human spine, the anisotropic pattern of a vertebral body was resembled by this printing technique that can be translated to various patterns, materials and application.

3D Plotting of Calcium Phosphate Cement and Melt Electrowriting of Polycaprolactone Microfibers in One Scaffold: A Hybrid Additive Manufacturing Process.

The fabrication of patient-specific scaffolds for bone substitutes is possible through extrusion-based 3D printing of calcium phosphate cements (CPC) which allows the generation of structures with a high degree of customization and interconnected porosity. Given the brittleness of this clinically approved material, the stability of open-porous scaffolds cannot always be secured. Herein, a multi-technological approach allowed the simultaneous combination of CPC printing with melt electrowriting (MEW) of polycaprolactone (PCL) microfibers in an alternating, tunable design in one automated fabrication process. The hybrid CPC+PCL scaffolds with varying CPC strand distance (800–2000 µm) and integrated PCL fibers featured a strong CPC to PCL interface. While no adverse effect on mechanical stiffness was detected by the PCL-supported scaffold design; the microfiber integration led to an improved integrity. The pore distance between CPC strands was gradually increased to identify at which critical CPC porosity the microfibers would have a significant impact on pore bridging behavior and growth of seeded cells. At a CPC strand distance of 1600 µm, after 2 weeks of cultivation, the incorporation of PCL fibers led to pore coverage by a human mesenchymal stem cell line and an elevated proliferation level of murine pre-osteoblasts. The integrated fabrication approach allows versatile design adjustments on different levels.

A water permeability model of nano-reinforced cement pastes based on general effective media theory and multifractals

A theoretical model to predict the water permeability of nano-reinforced cement pastes from the pore structure (including the pore size distribution, pore interconnection, porosity and microcracks) is presented. The model is based on the general effective media (GEM) theory and multifractals, considering both the bridging of microcracks and capillary pores and the filling of nano gel pores of cement pastes reinforced with nano-admixtures. To validate the model, water permeability experiments were conducted using a cementitious composite reinforced with graphene oxide and multi-walled carbon nanotubes. The calculated results showed good agreement with the experimental measurements, with a decrease in the maximum error from 67.8% to 9.7% compared with the previously proposed GEM theory. Moreover, the theoretical calculations suggest that the reinforcing roles of nano-admixtures in cement paste to improve permeability-related properties may be mainly due to bridging effects in microcracks and capillary pores, rather than the filling of nano gel pores. The findings of this study enrich understanding of the mechanism of reinforcing cement-based materials with nano-admixtures. In addition, the permeability of cementitious composites can be measured directly, rather than the use if other using time-consuming methods.

Wetting-Induced Polyelectrolyte Pore Bridging.

Active layers of ion separation membranes often consist of charged layers that retain ions based on electrostatic repulsion. Conventional fabrication of these layers, such as polyelectrolyte deposition, can in some cases lead to excess coating to prevent defects in the active layer. This excess deposition increases the overall membrane transport resistance. The study at hand presents a manufacturing procedure for controlled polyelectrolyte complexation in and on porous supports by support wetting control. Pre-wetting of the microfiltration membrane support, or even supports with larger pore sizes, leads to ternary phase boundaries of the support, the coating solution, and the pre-wetting agent. At these phase boundaries, polyelectrolytes can be complexated to form partially freestanding selective structures bridging the pores. This polyelectrolyte complex formation control allows the production of membranes with evenly distributed polyelectrolyte layers, providing (1) fewer coating steps needed for defect-free active layers, (2) larger support diameters that can be bridged, and (3) a precise position control of the formed polyelectrolyte multilayers. We further analyze the formed structures regarding their position, composition, and diffusion dialysis performance.

Rock typing based on hydraulic and electric flow units for reservoir characterization of Nubia Sandstone, southwest Sinai, Egypt

The present work describes and evaluates the reservoir quality of the sandstone of the Nubia Formation at the Gebel Abu Hasswa outcrop in southwest Sinai, Egypt. Hydraulic flow unit (HFU) and electrical flow unit (EFU) concepts are implied to achieve this purpose. The Paleozoic section made up of four formations has been studied. The oldest is Araba Formation followed by Naqus formations (Nubia C and D) overlay by Abu Durba, Ahemir and Qiseib formations (Nubia B), where the Lower Cretaceous (Nubia A) is represented by the Malha Formation. The studied samples have been collected from Araba, Abu Durba, Ahemir and the Malha formations. The hydraulic flow unit (HFU) discrimination was carried out based on permeability and porosity relationship, whereas the electrical flow unit (EFU) differentiation was carried out based on the relationship between formation resistivity factor and porosity. Petrographic investigation of the studied thin sections illustrates that the studied samples are mainly quartz arenite. Important roles to enhance or reduce the pore size and/or pore throats controlling the reservoir petrophysical behavior are due to the diagenetic processes. The present study used the reservoir quality index (RQI) and Winland R35 as additional parameters applied to discriminate the HFUs. The study samples have five hydraulic flow units of different rock types, where the detected electrical flow units are only three. The differences between them are may be due to the cementation process with iron oxides that might act as pore filling, lining and pore bridging, sometimes bridges helping to decrease permeability without serious reduction in porosity. The reduction between the number of EFUs and HFUs comes from the effect of diagenesis processes which is responsible for a precipitation of different cement types such as different clay minerals and iron oxides.

Developing a porosity-permeability relationship for ellipsoidal grains: A correction shape factor for Kozeny-Carman's equation

Rock typing is a process through which reservoir layers are classified into distinct units with similar geological conditions. The Kozeny-Carman's equation is commonly used for rock typing based on the porosity-permeability relationship, but it only considers spherical grains in its calculations which does not give representative results on many occasions. Thus, an attempt was made in this study to develop a new mathematical equation to correct the porosity-permeability relationship in rocks with ellipsoidal grains. To validate this equation, several pore-scale models were analysed using the Discrete Element Method (DEM) where the porosity was calculated under different conditions. The permeability of the pore scale models containing ellipsoidal (spheroidal) grains with different aspect ratios were then determined using the Lattice Boltzmann Method (LBM). This was followed by applying the new equation by incorporating the eccentricity of grains in the correction shape factor of the Kozeny- Carmen's equation. The results obtained indicated that any deviations in the sphericity of the grains (increase or decrease in the aspect ratio) increase the permeability of the model. In other words, the developed pore scale model with the aspect ratio of 1.0 (spherical grains) had the lowest permeability at the same porosity. This could be due to the bridging of pores with the ellipsoidal grains which causes a longer and narrower fluid path. Moreover, the models with the aspect ratio of 0.5 and 2.0 had a similar porosity-permeability correlation which could be linked to their similar packing structure. The new equation was further validated through the literature and numerical studies to ensure its accuracy under different geological conditions.

Three-Dimensional Bioprinting for Tissue Engineering and Regenerative Medicine in Down Under: 2020 Australian Workshop Summary.

Three-Dimensional Bioprinting for Tissue Engineering and Regenerative Medicine in Down Under: 2020 Australian Workshop Summary.

Lithofacies characterization and quantitative mineralogical analysis of the sediments from Sahaiawei-1well in the northern Delta Depobelt of the Niger Delta Basin

The sediments of Sahaiawei-1 Well in the Northern Delta Depobelt are represented by sand and shale alternation. Lithofacies characterization and X-ray diffraction technique were used to characterize the sediments from the well in order to characterize the lithofacies, identify the minerals present, determine environment of deposition and identify potential zones for hydrocarbon exploitation. The lithofacies characterization was based on the textural properties, mineralogical composition, fossil content, homogeneity and heterogeneity of the lithofacies units of the well. The lithofacies analysis for Sahaiawei-1 Well identified four (4) lithofacies types of mainly sandstone, shaly sandstone, sandy shale and shale; and fourteen (14) lithofacies zones. The result of the X-ray diffraction analysis identified the following clay minerals – kaolinite, illite/muscovite, chlorite and sepiolite; carbonates and non-clay minerals. Therefore, due to the high percentage of kaolinite in Sahaiawei-1 Well (2% to 39.87%), it could be concluded that pore filing kaolinite may have more effect on the reservoir quality than the pore bridging illite and pore lining chlorite.
 Keywords: alternation, lithofacies, X-ray diffraction, reservoir, mineralogy

Cell proliferation and migration explain pore bridging dynamics in 3D printed scaffolds of different pore size

Tissue growth in bioscaffolds is influenced significantly by pore geometry, but how this geometric dependence emerges from dynamic cellular processes such as cell proliferation and cell migration remains poorly understood. Here we investigate the influence of pore size on the time required to bridge pores in thin 3D-printed scaffolds. Experimentally, new tissue infills the pores continually from their perimeter under strong curvature control, which leads the tissue front to round off with time. Despite the varied shapes assumed by the tissue during this evolution, we find that time to bridge a pore simply increases linearly with the overall pore size. To disentangle the biological influence of cell behaviour and the mechanistic influence of geometry in this experimental observation, we propose a simple reaction–diffusion model of tissue growth based on Porous-Fisher invasion of cells into the pores. First, this model provides a good qualitative representation of the evolution of the tissue; new tissue in the model grows at an effective rate that depends on the local curvature of the tissue substrate. Second, the model suggests that a linear dependence of bridging time with pore size arises due to geometric reasons alone, not to differences in cell behaviours across pores of different sizes. Our analysis suggests that tissue growth dynamics in these experimental constructs is dominated by mechanistic crowding effects that influence collective cell proliferation and migration processes, and that can be predicted by simple reaction–diffusion models of cells that have robust, consistent behaviours.

The effect of CO2-enriched water salinity on enhancing oil recovery and its potential formation damage: an experimental study on shaly sandstone reservoirs

Many experimental investigations on carbonated water injection (CWI) have shown an increase in oil recovery which CWI is defined as the process of injecting CO2-saturated water in oil reservoirs as a displacing fluid. In every enhanced oil recovery method, the potential formation damage of the injected fluid is considered. This is due to the fact that the injection of incompatible fluids often causes clay swelling and fines migration and thus impairs the formation permeability. Permeability reduction by clay particles mostly depends on its distribution which can be pore lining, pore bridging, dispersed or combination of these causing pore blocking or pore-throat diameter reduction. Besides, fine migration is considered as an important mechanism of recovery improvement during injection of low-salinity water in sandstone oil reservoirs. The present paper investigates the impact of injection of carbonated water and brines with the different salt concentrations on oil recovery and formation damage focusing on permeability variation. The investigation has been done on 12 relatively homogeneous clay-containing sandstone cores, while the compositions of the injection water were varied from 40,000 to 1000 ppm, at 176° F and 2000 psi. The amount of recovery improvement and permeability drop recorded in all tests and the fine effluent of two experiments were analysed using XRD, one for CWI and one for WF (water flooding). In all salinities, CWI has shown more oil recovery improvement than conventional water. CWI of 40,000 ppm showed the minimum permeability reduction of 6 percent, while the highest permeability was obtained by injection of water with 1000 ppm. Maximum ultimate oil recoveries of 61.2% and 42% were achieved by 1000 ppm both for CWI and WF, respectively. In comparison with brine injection, CWI resulted in more permeability drop in salinity above critical salt concentration (CSC), while below CSC, WF has caused more formation damage than CWI. Experimental results also showed that fine migration was the main reason behind formation damage. It was also revealed that permeability was significantly reduced due to fine production in the effluent.

Nucleation and Growth Process of Water Adsorption in Micropores of Activated Carbon Revealed by NMR

Properties of liquids at solid interfaces play a central role in numerous important processes in nature. Nuclear magnetic resonance (NMR) is particularly useful for probing liquid/graphitic carbon interfacial properties. In particular, the nucleus-independent chemical shift (NICS) provides a sensitive measure of the distance between adsorbates and the graphitic carbon surface on the subnanometer scale, enabling NMR to acquire subnanometer scale spatial resolution. Here, by combining the information on thermodynamics obtained from in situ NMR-detected water isotherm and spatially resolved information on structure and dynamics obtained by NICS-resolved NMR, the microscopic process of water nucleation and growth inside the micropore of activated carbons is investigated. The formation of water clusters at surface sites, the cooperative growth process of pore bridging, and the final stage of horizontal pore filling are revealed in detail, demonstrating the potential of this comprehensive NMR approach for study...

Simulation of Bridging at the Static Surface Filtration by CFD-DEM Coupling

To achieve a better understanding of the bridging mechanism at the static surface filtration, simulations of particle deposition at a three-dimensional pore model of a filter were performed. The simulations are used to investigate the total filter resistance, which results from interferences between filter medium, particles and fluid. Thereby a CFD (Computational Fluid Dynamics) method for flow simulation was coupled with a Discrete Element Method (DEM) which calculates the particle interactions. The results show that a built particle bridge influences the flow through an unclosed pore. It was concluded that bridging of open pores is hindered at high velocities of approach caused by increasing percentage of closed pores. Moreover, it could be shown, that the total filter resistance depends on the approaching velocity and shape of particles.

Prediction of empirical properties using direct pore-scale simulation of straining through 3D microtomography images of porous media

Summary Understanding the mechanisms of filtration through porous media is relevant in many engineering applications ranging from waste water treatment and aquifer contamination in environmental engineering to estimating the permeability reduction in near wellbore region during drilling or water re-injection in petroleum engineering. In this paper we present a pore-scale approach that models straining through the pore structures extracted from X-ray tomographic images of rock and grain pack samples from the first principles, enabling the examination of current macroscopic models. While continuum models are widely used for fast prediction of the retention profiles and permeability of the host porous medium, they require a number of phenomenological parameters which are derived from matching experimental results. One of these parameters is the rate of entrapment, which is the sink term in the advection–diffusion equation. Here we find the constitutive relationship for the rate of entrapment as a product of the filtration coefficient, velocity, and concentration and validate it by comparing with core flood experiments. Results show that the pore-scale simulation gives close approximations of filtration coefficient when pore bridging and straining are the main particle capture mechanisms.

Fabrication of a multi-layer three-dimensional scaffold with controlled porous micro-architecture for application in small intestine tissue engineering

Various methods can be employed to fabricate scaffolds with characteristics that promote cell-to-material interaction. This report examines the use of a novel technique combining compression molding with particulate leaching to create a unique multi-layered scaffold with differential porosities and pore sizes that provides a high level of control to influence cell behavior. These cell behavioral responses were primarily characterized by bridging and penetration of two cell types (epithelial and smooth muscle cells) on the scaffold in vitro. Larger pore sizes corresponded to an increase in pore penetration, and a decrease in pore bridging. In addition, smaller cells (epithelial) penetrated further into the scaffold than larger cells (smooth muscle cells). In vivo evaluation of a multi-layered scaffold was well tolerated for 75 d in a rodent model. This data shows the ability of the components of multi-layered scaffolds to influence cell behavior, and demonstrates the potential for these scaffolds to promote desired tissue outcomes in vivo.

Transport of a Thermophilic<i> Geobacillus</i> sp. in Sandpack Core as an Enhanced Oil Recovery Material

The effects of temperature, permeability and the presence of a residual oil phase on the transport of the bacterium Geobacillus sp. were investigated experimentally in sandpack cores. A lower reduction in permeability and a higher effluent bacterial concentration were obtained in the higher permeability sandpacks, or at a higher temperature. The bacterial transport could be enhanced by the pulse injection, but reduced with the presence of residual oil. When the injected cell concentration is relatively high (>108 cells/mL), log-jam effect or pore bridging may be the primary mechanism, and the surface adhesion may act as the secondary mechanism of bacteria retention and permeability reduction.