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Fractured vuggy carbonate reservoirs are one of the most important reserves in the world, which hold great importance for increasing reserves and production. However, fractured vuggy reservoir has greatly different reservoir space and flow patterns challenging low recovery. Three types of reservoir space, including matrix pores, fractures, and vugs, coexist with strong heterogeneity, and the...
Dissolution of CO2 in brine, one of the key mechanisms for securely storing CO2 in the subsurface, involves diffusion of CO2 into the brine and subsequent buoyancy-driven convective migration. The stable stratification along the CO2-brine interface, predominated by diffusion, stimulates the density-driven convection, resulting in an enhanced dissolution rate. In fractured porous media, the...
To solve the problem of rapid decline in conductivity of sand filled fractures in deep shale, based on the mechanical process of compression and deformation of proppant pile, the constitutive equation of deformation and fracture of proppant pile was established, and the transfer matrix of gradation curve after fracture of proppant pile was established based on fractal theory. Combined with KC...
The capillary pressure curve is essential for predicting multiphase flow processes in geological systems. At low saturations, wetting films form and become important, but how wetting films control this curve remains inadequately understood. In this study, we combine microfluidic experiments with pore-network modeling to investigate the impact of corner-bridge flow on the capillary pressure...
Granite is considered a suitable host rock for a deep geological repository for radioactive waste. Since fractures are the main flow pathways for solute transport in this material, accurate and efficient calculation of solute transport and retention phenomena is essential for predictions related to the safety case of the repository. A key issue is the effect of cross-scale surface topography...
Underground gas storage (UGS) exhibits various transport mechanisms due to their multi-cycle injection and production, often overlooked in numerical simulations. In fractured-vuggy UGS, certain mechanisms may have a stronger effect. L underground gas storage is crucial to China's first fractured-vuggy UGS group. A simulation study was conducted to investigate the effect of three transport...
The technology of multi-stage, multi-well pad fracturing is an effective way to increase the stimulated volume and recoverable reserves in shale reservoirs. During the fracturing treatments, there are common phenomena of well interferences from the multi-well pad. However, there still lacks an effective tool to analyze the parent-child interactions and to evaluate the fracture parameters...
While isolated fractures are difficult to fully characterize in subsurface formations, they serve as highly conductive long-range flow conduits and thus may have a strong influence on flow and transport. Recently, we have proposed a new model for flow in fractured formations that provides predictions of the expected flow field. Unlike existing methods, this model accounts for the non-local...
For deep fractured-vuggy carbonate reservoirs, foam flooding is an effective oil recovery method. However, the connectivity and anisotropy of the fractured-vuggy network affect the plugging performance of foam and the ability to adjust the displacement profile. Therefore, it is necessary to conduct a comprehensive investigation on the migration characteristics of foam, in order to provide...
In order to enhance acid penetration depth and fracture conductivity, acid fracturing techniques involving the alternating injection of non-reactive fluids (fracturing fluids) or weakly reactive fluids (self-generated acid) with acid are considered a pivotal enhanced oil recovery rate in carbonate reservoirs. In recent years, the CO2-enhanced acid fracturing technique has gained prominence in...
The release of trapped bubbles from dead-end porous media filled with nonvolatile liquid holds extensive applications in gas‒liquid reactors, CO2-assisted srteam flooding, ceramic sintering, and droplet microcarriers. Since traditional pressure-driven flow fails to induce bubble transport in dead-end pores, this study investigates the potential use of heating to control the release of bubbles...
To address the scientific problems of fracture initiation and expansion of hydraulic fractures in the process of shale gas reservoir extraction, this paper focuses on the influence of shale minerals on fracture initiation and expansion of hydraulic fractures under the influence of mineral interface, establishes a geometric model of random distribution of shale minerals at the microscopic...
Fractures can facilitate or alter fluid flow and transport in subsurface reservoirs. Consequently, their accurate characterisation is crucial for various applications, including geothermal heat extraction and carbon sequestration. Yet, direct measurement of relevant fracture parameters is difficult. Access is limited to wells, leading to significant uncertainties, particularly in estimating...
We consider single-phase flow in a fractured porous medium governed by Darcy's law with spatially varying matrix-valued hydraulic conductivities in both bulk and fractures. In particular, we account for general fracture geometries parameterized by aperture functions on a submanifold of codimension one. Given a fracture with a width-to-length ratio of the order of a small parameter...
The interplay between fracture roughness, topology, and permeability is of major interest in hydrogeology, and models that account for the roughness and tortuosity of fractures to upscale hydraulic apertures that represent the microscale aperture distribution have been the focus of many studies in the past decades (He et al., 2021). However, these models often overlook the tensorial aspects of...
Fluid-driven fracturing plays a vital role in the exploitation of geo-energy sources (geothermal, gas and oil), while also posing challenges for CO2 sequestration and underground energy storage. While the variational phase-field models have shown their power in modeling the involved crack nucleation and propagation coupled with hydro processes, the diffused representation of the cracks impedes...
The prediction of the permeability enhancement that can be achieved in a geothermal system (EGS) is challenging and computationally expensive because it requires the quantification of distributed frictional sliding and tensile opening in fracture networks with a practically relevant level of complexity. Yet, modelling these processes is indispensable for determining dynamic fracture aperture...
In this research, we present a novel numerical framework for hydraulic fracturing that incorporates thermo-hydro-mechanical coupled effects. Unlike previous studies that have employed the phase-field method for hydraulic fracturing modeling, our work introduces a THM coupling scheme grounded in the variational phase-field approach, a significant advancement in the field. The THM coupling is...
Dam failures and landslides can be caused by erosional processes. Suffusion, a special type of internal erosion (Yang et al., 2019), is the initial stage of a backward erosion process (van Beek, 2015) which may lead to creeping degradation of the dam’s stability and in the end to catastrophic outcomes like the Brumadinho tailings dam collapse in Brazil 2019 (Silva Rotta et al., 2020)....
Flow in fractured porous media plays an important role in applications ranging from geothermal energy production to the selection of suitable underground CO$_2$ storage sites. Predictions of flow and transport are central in these applications and often times corresponding models are applied that rely on effective permeabilities. In subsurface formations, where fractures extend over distances...
SC-CO2 (supercritical carbon dioxide) has attracted much attention in subsurface engineering process, such as CO2 sequestration, enhanced oil recovery and geothermal development. Using micro-particle as proppant in SC-CO2 fracturing is a new fracturing technology in unconventional oil and gas reservoirs. Despite the multiphase flow of SC-CO2 in porous media has been widely studied in recent...
Particle transport in rough natural fractures has seen diversified potentials and applications in environmental engineering and resource development engineering.
Despite intensive and outstanding research on their transport phenomena, the impact
of surface attachment and confined space of rough natural fractures on particle
transport remains poorly understood.
In this study, we...
Abstract:
Fractured media can be found in various natural and engineering systems, and the presence of fractures and fracture networks has a significant impact on the flow and transport processes at different scales. However, the complex nature of fractures poses challenges for theoretical modeling and numerical analysis. In this study, we propose a new hybrid upscaling workflow that...
We developed a parallel thermo-hydraulic-mechanical (THM) model of fully coupled multiphase fluid and heat flow and geomechanics as well as associated fracturing processes in porous and fractured media to simulate cryogenic fracturing with liquid nitrogen in hot reservoirs. This included enhancing our THM simulator and developing a physical property module for nitrogen-water systems and...
Understanding methane adsorption behavior on deep shales is crucial for estimating the original gas in place and enhancing gas recovery in deep shale gas formations. However, the methane adsorption behavior on deep shales under high pressure is challenging, and many uncertainties still exist in the process. In this study, the methane adsorption on deep shales within the Lower Silurian Longmaxi...
Interface-coupled dissolution and precipitation (ICDP) [1] occur in various subsurface applications, e.g., serpentine carbonation in the context of CO2 sequestration, the carbonation of concrete causing degradation, anoxic steel corrosion in geological disposal facilities for nuclear waste, or during groundwater remediation using permeable reactive barriers. ICDP is characterized by the...
Wettability can dramatically impact on the immiscible fluids flow in permeable media, including subsurface technologies to microfluidics. Previous studies have profoundly revealed this effect on flow in porous media, but so far, few systematic results on how the wettability controls flow in rough fracture are reported. Here, we conduct the visualization experiment to investigate the immiscible...
Tracer testing is commonly used to characterize fracture flow and transport processes. The interpretation of tracer data requires numerous forward simulations of tracer transport in a 3D fracture-matrix model, leading to significant computational burden. As matrix permeability is generally several magnitudes smaller than fracture permeability, some studies only considered a 2D fracture model...
In low-permeability unsaturated fractured rock, fluid flows predominantly through the interconnected fracture network, with some fluid imbibing into the neighboring matrix rock. Imbibition (driven by capillary pressure gradient) advectively transports chemicals from fractures into the matrix. Diffusion (driven by concentration gradient) can diffusively transport chemicals into the matrix. Once...
Suspended particle migration and clogging processes in rock fractures are ubiquitous in nature and industrial activities like hydraulic fracturing and hole-drilling fluid leakage resistance. As a common type of particle cohesion, the impact of liquid cohesion on clogging in rock fractures and its mechanism remain unclear. We conduct visualized experiments and discover that even if a small...
The fluid dynamics of gas-brine flow within porous media play a crucial role in the recovery of hydrocarbon gas and the sequestration of CO2. Coal seams are targeted as a reservoir rock because of their strong adsorption properties. However, permeability is an issue as they consist of matrix and fracture components, present a complex flow channel system for competing fluids and gases. During...
Acid fracturing is a primary stimulation technique for carbonate reservoirs. Acid selectively etches hydraulic fractures, forming high-conductivity channels capable of transporting oil and gas under the influence of normal closure pressures. Numerous fracture acidization models have focused on factors such as reservoir temperature, acid fluid type, and distribution of carbonate minerals, but...
In complex fracture networks, dynamic fluid-flow patterns arise already at flow velocities in the centimetre-per-second (cm/s) range. Yet, these phenomena get ignored or underestimated when such flows are modelled using Stokes’ equation or steady-state approximations of the Navier Stokes equation (NSE) are used.
Here we apply the Detached-Eddy Simulation technique to solve the NSE in...
In this study, we present a new version of the multi-level discrete fracture model (MLDFM) for multiphase flow in complex fractured systems with features present at various scales. In MLDFM, two levels of unstructured grids conforming with each other are constructed. In a fine-scale grid, both large and small features are represented in conformal DFM manner, and in a coarse grid, only large...
Countercurrent imbibition is the process that the wetting phase spontaneously displace the nonwetting phase in porous media while the nonwetting phase is recovered at the wetting phase inlet[1]. It is a major mechanism of shale oil recovery, where the permeability is so low that co-current imbibition is largely limited[2, 3]. For fractured media, classic dual-porosity model is based on good...
The SF reservoir in China is a naturally fractured but low permeability carbonate gas reservoir with average porosity and permeability about 4.3% and 3.7mD, respectively. Macro- and micro-fracture as well as large vuggy pore all developed in the reservoir making it quite heterogeneous. This reservoir has been converted to underground gas storage (UGS) after 25 years depleted production with...
Abstract: The northern structural zone of the Kuqa Depression exhibits varying lithological characteristics within the Jurassic Ahe Formation, which is predominantly composed of gray to light gray medium-coarse sandstone with high heterogeneity. Based on the structural features of the region, the northern structural zone is divided into the Horst scetion, North slope section, and the Dibei...
Understanding the effect of minerals on the mechanical behavior of granite under thermo-mechanical coupling is of great significance in deep engineering. In this paper, nine thermo-mechanical grain-based models of granite with different mineral contents were established based on particle flow simulation, revealing the influence mechanisms of temperature and mineral on the mechanical properties...
Microbially induced calcium carbonate precipitation (MICP) is an eco-friendly solution in geotechnical engineering, particularly for applications in bioremediation and $CO_{2}$ sequestration. Mathematical models have been developed to describe coupled biochemical processes in geological media. However, there is a lack of numerical methods capable of modeling MICP directly from a single set of...
Dispersion in partially saturated porous media has many applications in scientific and engineering fields. For example, in carbon dioxide capture and storage (CCS), dispersion increases the mass transfer rate and accelerates the dissolution process in large background velocity field (Tsinober, 2022). In this study, we create a steady-state system that mimics a depleted oil field where salty...
In various research fields such as hydrogeology, environmental science and energy engineering, geological formations with fractures are frequently encountered. Accurately characterizing these fractured media is of paramount importance when it comes to tasks that demand precise predictions of liquid flow and the transport of solute and energy within them. Since directly measuring fractured...
The storage space of tight formation after volumetric fracturing is complex, characterized by the coexistence of micro-nano pores and multi-scale fractures. This complexity hinders a clear understanding of pore-scale flow dynamics in the integrated fracturing-shut in-flowback process of tight oil reservoir. To tackle this issue, we introduced the micro-focus CT imaging and digital image...
