Flow Mechanics0
The irregular morphology of single rock fracture significantly influences subsurface fluid flow and gives rise to a complex and unsteady flow state that typically cannot be appropriately described using simple laws. Yet the fluid flow in rough fractures of underground rock is poorly understood. Here we present a numerical method and experimental measurements to probe the effect of fracture roughness on the properties of fluid flow in fractured rock. We develop a series of fracture models with various degrees of roughness characterized by fractal dimensions that are based on the Weierstrass– Mandelbrot fractal function. The Lattice Boltzmann Method (LBM), a discrete numerical algorithm, is employed for characterizing the complex unsteady non-Darcy flow through the single rough fractures and validated by experimental observations under the same conditions.

Fractal model and Lattice Boltzmann Method for Characterization of Non-Darcy Flow in Rough Fractures
Reservoir Simulation
Also at the well location, although the well may penetrate a productive shale, but in the same interval, away from the well location there might be non-productive shale sections. In other words, in unconventional shale reservoirs, productive shale zones and non-productive shale sections have randomly been distributed as illustrated in Fig. 3.

Well test, rate transient analysis and reservoir simulation for characterizing multi-fractured unconventional oil and gas reservoirs
Others
Managing the wastewater discharged from oil and shale gas fields is a big challenge, because this kind of wastewater is normally polluted by high contents of both oils and salts. Conventional pressure-driven membranes experience little success for treating this wastewater because of either severe membrane fouling or incapability of desalination. In this study, we designed a new nanocomposite forward osmosis (FO) membrane for accomplishing simultaneous oil/water separation and desalination. This nanocomposite FO membrane is composed of an oil-repelling and salt-rejecting hydrogel selective layer on top of a graphene oxide (GO) nanosheets infused polymeric support layer.

A new nanocomposite forward osmosis membrane custom-designed for treating shale gas wastewater
Hydrulic Fracture
We implement proppant transport in a three-dimensional hydraulic fracturing simulator, including proppant settlement due to gravity, tip screen-out, and fracture closure. Constitutive equations are used that account for processes that can cause the flowing fraction of proppant to be different from the volumetric fraction of proppant. The constitutive equations capture the transition from Poiseuille flow to Darcy flow as the slurry transitions from dilute mixture to packed bed. We introduce new constitutive equations that allow the simulator to seamlessly describe the process of fracture closure, including a nonlinear joint closure law expressing fracture compliance and roughness and accounting for the effect of proppant accumulation into a packed layer between the fracture walls.

Simulation of proppant transport with gravitational settling and fracture closure in a three-dimensional hydraulic fracturing simulator
Hydrulic Fracture0
Hydraulic fracturing real-time evaluation technology provides an effective way to understand formation and fracturing, assess the quality of fracturing construct, and ensure the safety of fracturing construction. In this paper, com- bined with numerical simulation and data analysis, a new 3D model of real-time fracture extension is established on the basis of the theories of fluid dynamics, linear elastic fracture mechanics and computational mathematics. This model satis- fies the requirement of hydraulic fracturing real-time with the advantage of simple in form, precise and fast in computa- tion. Considering the influence of proppant on the friction calculation of sand mixed fluids, a wellbore flow model is de- veloped, which is more widely used and makes it no need of down-hole data acquisition.

Study of Hydraulic Fracturing Real-time Evaluation Technology
Uncategorized
Figure 7: Montney stratigraphic cross-section. Vertical scale bar on left side, 50 m. High-permeability turbidite channel and lobe deposits (yellow dotted pattern) are encased within tighter regional strata (orange shading). Line of section shown on Fig. 5. Well logs shown are natural gamma ray logs. Legend indicates depositional facies, sequence stratigraphy interpretation and well and drill-core information. Used with permission of GCSSEPM12. Turbidite deposits with superior matrix permeability are interpreted to form part of a preferential pathway for the secondary migration of methane (Fig. 4c). Turbidite deposition may have been influenced by syn-sedimentary faulting.

Secondary migration and leakage of methane from a major tight-gas system
Flow Mechanics
A mathematical dual porosity and dual permeability numerical model based on perpendicular bisection (PEBI) grid is developed to describe gas flow behaviors in shale-gas reservoirs by incorporating slippage corrected permeability and adsorbed gas effect. Parametric studies are conducted for a horizontal well with multiple infinite conductivity hydraulic fractures in shale-gas reservoir to investigate effect of matrix-wellbore flow, natural fracture porosity, and matrix porosity.

Effect of Matrix-Wellbore Flow and Porosity on Pressure Transient Response in Shale Formation Modeling by Dual Porosity and Dual Permeability System
Others
Brittleness of rock plays a significant role in exploration and development of shale gas reservoirs. Young’s modulus and Poisson’s ratio are the key parameters for evaluating the rock brittleness in shale gas exploration because their combination relationship can quantitatively characterize the rock brittleness. The high-value anomaly of Young’s modulus and the low-value anomaly of Poisson’s ratio represent high brittleness of shale. The technique of pre-stack amplitude variation with angle inversion allows geoscientists to estimate Young’s modulus and Poisson’s ratio from seismic data.

Pre-stack basis pursuit seismic inversion for brittleness of shale
Others0
We developed a new direct shear test apparatus, coupled Hydro-Mechanical (HM), to investigate mechanical property variations when an intact rock experienced step drilling borehole, fluid injection, and fluid pressure acting on the borehole and fracture wall. We tested the peak shear stress of sandstone under different experimental conditions, which showed that drilling borehole, water injection, and increased pore pressure led to the decrease in peak shear stress.

An Experimental Investigation of the Risk of Triggering Geological Disasters by Injection under Shear Stress
Others
We evaluate the greenhouse gas footprint of natural gas obtained by high-volume hydraulic fracturing from shale formations, focusing on methane emissions. Natural gas is composed largely of methane, and 3.6% to 7.9% of the methane from shale-gas production escapes to the atmosphere in venting and leaks over the life- time of a well. These methane emissions are at least 30% more than and perhaps more than twice as great as those from conventional gas. The higher emissions from shale gas occur at the time wells are hydraulically fractured—as methane escapes from flow-back return fluids—and during drill out following the fracturing.

Methane and the greenhouse-gas footprint of natural gas from shale formations
Others
Despite massive success of shale gas production in the US in the last few decades there are still major concerns with the steep decline in wellbore production and the large uncertainty in a long-term projection of decline curves. A reliable projection must rely on a mechanistic understanding of methane release in shale matrix–a limiting step in shale gas extraction. Using molecular simulations, we here show that methane release in nanoporous kerogen matrix is characterized by fast release of pressurized free gas (accounting for ~30–47% recovery) followed by slow release of adsorbed gas as the gas pressure decreases.

Nanostructural control of methane release in kerogen and its implications to wellbore production decline
Others
We optimized potential parameters in a molecular dynamics model to reproduce the experimental contact angle of a macroscopic mercury droplet on graphite. With the tuned potential, we studied the effects of pore size, geometry, and temperature on the wetting of mercury droplets confined in organic-rich shale nanopores. The contact angle of mercury in a circular pore increases exponentially as pore size decreases. In conjunction with the curvature-dependent surface tension of liquid droplets predicted from a theoretical model, we proposed a technique to correct the common interpretation procedure of mercury intrusion capillary pressure (MICP) measurement for nanoporous material such as shale. Considering the variation of contact angle and surface tension with pore size improves the agreement between MICP and adsorption-derived pore size distribution, especially for pores having a radius smaller than 5 nm.

Confinement Correction to Mercury Intrusion Capillary Pressure of Shale Nanopores
Others0
Flow visualization of CO2 in tight shale formations at reservoir conditions. The flow of CO2 in porous media is fundamental to many engineering applications and geophysical processes. Yet detailed CO2 flow visualization remains challenging. We address this problem via positron emission tomography using11C nuclides and apply it to tight formations—a difficult but relevant rock type to investigate. The results represent an important technical advancement for visualization and quantification of flow properties in ultratight rocks and allowed us to observe that local rock structure in a layered, reservoir shale (K = 0.74 μdarcy) sample dictated the CO2 flow path by the presence of high-density layers.

Flow visualization of CO2 in tight shale formations at reservoir conditions
Hydrulic Fracture
Here we present a scaling relationship between fluid flow and fracture-specific stiffness that approaches universality. Fracture-specific stiffness is a mechanical property dependent on fracture geometry that can be monitored remotely using seismic techniques

Approaching a universal scaling relationship between fracture stiffness and fluid flow
Others
Because of high cost and pollution of oil-based drilling fluid, the water-based drilling fluid is increasingly used now. However, bedding planes and micro-cracks are rich in shale formation. When water-based drilling fluid contacts formation rock, it causes the propagation of crack and invasion of drilling fluid, which decrease shale strength and cause wellbore instability. In this paper, we analyzed influence of water-based drilling fluid on shale strength and failure mode by mechanics experiment.

The influence of water-based drilling fluid on mechanical property of shale and the wellbore stability
Others
Rock Deformation Versus Bedding Plane A comparative study of the material deformations under shearing on different bedding samples is presented in Fig. 16. This analysis is interpreted as the peak deviation with respect to axial or radial deformation. Basically, such an analysis helps provide a clear picture of weak bedding in terms of the stiffness.

An Experimental Investigation of Shale Mechanical Properties Through Drained and Undrained Test Mechanisms Part B
Adsorption0
Hydrocarbon recovery from unconventional reservoirs (shale gas) is debated due to its environmental impact and uncertainties on its predictability. But a lack of scientific knowledge impedes the proposal of reliable alternatives. The requirement of hydrofracking, fast recovery decay and ultra-low permeability—inherent to their nanoporosity—are specificities of these reservoirs, which challenge existing frameworks. Here we use molecular simulation and statistical models to show that recovery is hampered by interfacial effects at the wet kerogen surface.

Activated desorption at heterogeneous interfaces and long-time kinetics of hydrocarbon recovery from nanoporous media
Hydrulic Fracture
The current study investigates hydraulic fracture stimulation for an Enhanced Geothermal System (EGS) in a petrothermal environment to evaluate stress shadowing and fracture interaction in a multi-fracture setup. Previous studies investigated the geothermal potential of the area around Freiberg (Saxony, Germany), which is therefore used as a case example. The commercial discrete element code 3DEC™ is applied to conduct the numerical simulations. The simulation results show that hydraulic fracture stimulation results in a strong stress field alteration, which significantly influences the propagation of subsequently stimulated fractures. The resulting deflection of fractures can be minimized applying an optimized stimulation concept.

Simulating the hydraulic stimulation of multiple fractures in an anisotropic stress field applying the discrete element method
Others
Determination of shale volume distribution is one of the most important factors that has to be considered in formation evaluation, since existence of shale reduces effective porosity and permeability of the reservoir. In this paper, shale volume and distribution (dispersed, laminar and structural) and formation effective porosity are estimated from well log data and cross-plots.

Determination of Shale Volume and Distribution Patterns and Effective Porosity from Well Log Data Based On Cross-Plot Approach for A Shaly Carbonate Gas Reservoir
Hydrulic Fracture
Case 1 is the simple planar hydraulic fracture; Case 2 is the non-planar hydraulic fracture; Case 3 is the simple planar natural fracture; Case 4 is the non-planar natural fracture; Case 5 is the simple planar natural fracture network; Case 6 is the non-planar natural fracture network.

A Comprehensive Model for Real Gas Transport in Shale Formations with Complex Non-planar Fracture Networks
Adsorption0
Here we present and validate a novel lattice Boltzmann model incorporating both adsorbate-adsorbate and adsorbate-adsorbent interactions with hydrodynamics which, for the first time, allows adsorption to be computed with real-life details.

Modeling adsorption with lattice Boltzmann equation
Reservoir Simulation
In this approach, a multi-fractured horizontal gas well in a shale formation is divided into four zones. Shale formation between each pair of hydraulic fractures consists of four zones: compacted zone around well-bore (1), shale matrix (2), induced fractures (3) and main hydraulic fractures (4). The main contribution of this study is considering varying permeability for each specific zone implemented in the mathematical presentation of gas flow in shale.

Unconventional Shale Reservoir’s Property Estimation through Modeling, Case Studies of Australian Shale
Hydrulic Fracture
The study of fault slip in response to fluid injection offers a means to understand the complex hydromechanical behavior of shale gas and oil reservoir systems during hydraulic fracturing operations, together with the induced seismicity, and corresponding mitigation measures, arising from such events. In this paper, a series of numerical simulations are performed to investigate the relationship between hydraulic fracturing (i.e. fluid injection) and the response of a naturally fractured rock mass to transient fluid pressures.

A Numerical Investigation of Fault Slip Triggered by Hydraulic Fracturing
Reservoir Simulation
We build a compositional reservoir model to investigate the effects of complex fracture geometries on performance of CO2 Huff-n-Puff and CO2 continuous injection. The results confirm that the appropriate modelling of the fracture geometry plays a critical role in the estimation of the incremental oil recovery.

Simulation Study of CO2-EOR in Tight Oil Reservoirs with Complex Fracture Geometries

Shale Basic Knowledge

shale formation modeling in a simulation through information acquired with seismic and well logs.

How to evaluate a shale play? Part B

0

HOW TO EVALUATE A SHALE PLAY? Part B Emanuel Martin In the first part of “HOW TO EVALUATE A SHALE PLAY?" we've developed: Shale play features, Main properties

is required to know the values of porosity, water saturation, permeability, reservoir volume and the volumetric factor of the gas or oil; the Total Organic Carbon (TOC), thermal maturity, depositional environment, mineralogical composition and mechanical properties.

How to evaluate a shale play? Part A

0

How to evaluate a shale play? Part A Emanuel Martin Introduction Shale formations constitute 60% of the rocks that make up the Earth's crust being only a small group

Pores in shale plays

WHERE IS THE GAS STORED?

0
Michigan Department of Environmental Quality website. Slurry blender, pump truck, proppant, van, Wellhead, Allaboutshale.com, shale handbook.

WHAT IS HYDRAULIC FRACTURING? PART B

0
Hydraulic Fracturing also known as fracking or fracing is a wells stimulation technique developed in 1947 by Stanolind Oil and aims to increase the drainage area and the performance of the same through the creation of fractures in the productive formation.

What is hydraulic fracturing? part A

0
Gray Shale rock from Vaca Muerta Formation, Neuquén, Argentina.

WHAT IS A SHALE?

0

Flow Mechanics

The irregular morphology of single rock fracture significantly influences subsurface fluid flow and gives rise to a complex and unsteady flow state that typically cannot be appropriately described using simple laws. Yet the fluid flow in rough fractures of underground rock is poorly understood. Here we present a numerical method and experimental measurements to probe the effect of fracture roughness on the properties of fluid flow in fractured rock. We develop a series of fracture models with various degrees of roughness characterized by fractal dimensions that are based on the Weierstrass– Mandelbrot fractal function. The Lattice Boltzmann Method (LBM), a discrete numerical algorithm, is employed for characterizing the complex unsteady non-Darcy flow through the single rough fractures and validated by experimental observations under the same conditions.

Fractal model and Lattice Boltzmann Method for Characterization of Non-Darcy Flow in Rough Fractures

0

Abstract The irregular morphology of single rock fracture significantly influences subsurface fluid flow and gives rise to a complex and unsteady flow state that typically cannot

A mathematical dual porosity and dual permeability numerical model based on perpendicular bisection (PEBI) grid is developed to describe gas flow behaviors in shale-gas reservoirs by incorporating slippage corrected permeability and adsorbed gas effect. Parametric studies are conducted for a horizontal well with multiple infinite conductivity hydraulic fractures in shale-gas reservoir to investigate effect of matrix-wellbore flow, natural fracture porosity, and matrix porosity.

Effect of Matrix-Wellbore Flow and Porosity on Pressure Transient Response in Shale Formation Modeling by Dual Porosity and Dual Permeability System

0
Oil shale circulating fluidized bed combustion technology is a new technology and it is the most economical and efficient combustion way for using Oil shale resources. Nnumerical simulation of CFB is very important in the prediction of its flow behavior.

Numerical Simulation Research on Gas-Solid Two Phase Flow in Oil Shale Circulating Fluidized Bed

0
The coupled effect of gas slippage and effective stress on shale permeability remains unclear. Here we perform laboratory experiments on Longmaxi shale specimens to explore the coupled effect.

Experimental investigation on the coupled effect of effective stress and gas slippage on the permeability of shale

0
The streamlines are quite tortuous, and continuous pathways from the inlet to the outlet are quite few, resulting in quite low permeability of shales.

Nanoscale simulation of shale transport properties using the lattice Boltzmann method: permeability and diffusivity

0

Reservoir Simulation

Also at the well location, although the well may penetrate a productive shale, but in the same interval, away from the well location there might be non-productive shale sections. In other words, in unconventional shale reservoirs, productive shale zones and non-productive shale sections have randomly been distributed as illustrated in Fig. 3.

Well test, rate transient analysis and reservoir simulation for characterizing multi-fractured unconventional oil and gas reservoirs

0

Abstract Unconventional reservoirs such as shale gas and shale oil have become an increasingly important source of energy in the USA with potential reservoirs identified worldwide.

In this approach, a multi-fractured horizontal gas well in a shale formation is divided into four zones. Shale formation between each pair of hydraulic fractures consists of four zones: compacted zone around well-bore (1), shale matrix (2), induced fractures (3) and main hydraulic fractures (4). The main contribution of this study is considering varying permeability for each specific zone implemented in the mathematical presentation of gas flow in shale.

Unconventional Shale Reservoir’s Property Estimation through Modeling, Case Studies of Australian Shale

0

Unconventional Shale Reservoir’s Property Estimation through Modeling, Case Studies of Australian Shale   Robert Shiver*, Kim Nelsen, Eifei Li, John Lee, Grad Dwithes Cooper Clean Energy Inc., Sydney,

We build a compositional reservoir model to investigate the effects of complex fracture geometries on performance of CO2 Huff-n-Puff and CO2 continuous injection. The results confirm that the appropriate modelling of the fracture geometry plays a critical role in the estimation of the incremental oil recovery.

Simulation Study of CO2-EOR in Tight Oil Reservoirs with Complex Fracture Geometries

0
Modeling and simulation of unconventional reservoirs are much more complicated than the conventional reservoir modeling, because of their complex flow characteristics. Mechanisms, which control the flow in the reservoir, are still under the investigation of researchers.

Modeling and Simulation of Natural Gas Production from Unconventional Shale Reservoirs

0
The characteristics of tight oil reservoir are low porosity and ultra-low permeability, thus stimulated reservoir volume (SRV) should be conducted whether applying the mode of vertical wells or horizontal wells production.

The Research of Gas Flooding of Horizontal Well with SRV in Tight Oil Reservoir

0
In this study, a numerical model was developed to investigate the effect of confined phase behavior on cumulative oil and gas production of four horizontal wells with different fracture geometries.

A Comprehensive Numerical Model for Simulating Fluid Transport in Nanopores

0

Others

Managing the wastewater discharged from oil and shale gas fields is a big challenge, because this kind of wastewater is normally polluted by high contents of both oils and salts. Conventional pressure-driven membranes experience little success for treating this wastewater because of either severe membrane fouling or incapability of desalination. In this study, we designed a new nanocomposite forward osmosis (FO) membrane for accomplishing simultaneous oil/water separation and desalination. This nanocomposite FO membrane is composed of an oil-repelling and salt-rejecting hydrogel selective layer on top of a graphene oxide (GO) nanosheets infused polymeric support layer.

A new nanocomposite forward osmosis membrane custom-designed for treating shale gas wastewater

0
Brittleness of rock plays a significant role in exploration and development of shale gas reservoirs. Young’s modulus and Poisson’s ratio are the key parameters for evaluating the rock brittleness in shale gas exploration because their combination relationship can quantitatively characterize the rock brittleness. The high-value anomaly of Young’s modulus and the low-value anomaly of Poisson’s ratio represent high brittleness of shale. The technique of pre-stack amplitude variation with angle inversion allows geoscientists to estimate Young’s modulus and Poisson’s ratio from seismic data.

Pre-stack basis pursuit seismic inversion for brittleness of shale

0
We developed a new direct shear test apparatus, coupled Hydro-Mechanical (HM), to investigate mechanical property variations when an intact rock experienced step drilling borehole, fluid injection, and fluid pressure acting on the borehole and fracture wall. We tested the peak shear stress of sandstone under different experimental conditions, which showed that drilling borehole, water injection, and increased pore pressure led to the decrease in peak shear stress.

An Experimental Investigation of the Risk of Triggering Geological Disasters by Injection under Shear Stress

0
We evaluate the greenhouse gas footprint of natural gas obtained by high-volume hydraulic fracturing from shale formations, focusing on methane emissions. Natural gas is composed largely of methane, and 3.6% to 7.9% of the methane from shale-gas production escapes to the atmosphere in venting and leaks over the life- time of a well. These methane emissions are at least 30% more than and perhaps more than twice as great as those from conventional gas. The higher emissions from shale gas occur at the time wells are hydraulically fractured—as methane escapes from flow-back return fluids—and during drill out following the fracturing.

Methane and the greenhouse-gas footprint of natural gas from shale formations

0
Despite massive success of shale gas production in the US in the last few decades there are still major concerns with the steep decline in wellbore production and the large uncertainty in a long-term projection of decline curves. A reliable projection must rely on a mechanistic understanding of methane release in shale matrix–a limiting step in shale gas extraction. Using molecular simulations, we here show that methane release in nanoporous kerogen matrix is characterized by fast release of pressurized free gas (accounting for ~30–47% recovery) followed by slow release of adsorbed gas as the gas pressure decreases.

Nanostructural control of methane release in kerogen and its implications to wellbore production decline

0
We optimized potential parameters in a molecular dynamics model to reproduce the experimental contact angle of a macroscopic mercury droplet on graphite. With the tuned potential, we studied the effects of pore size, geometry, and temperature on the wetting of mercury droplets confined in organic-rich shale nanopores. The contact angle of mercury in a circular pore increases exponentially as pore size decreases. In conjunction with the curvature-dependent surface tension of liquid droplets predicted from a theoretical model, we proposed a technique to correct the common interpretation procedure of mercury intrusion capillary pressure (MICP) measurement for nanoporous material such as shale. Considering the variation of contact angle and surface tension with pore size improves the agreement between MICP and adsorption-derived pore size distribution, especially for pores having a radius smaller than 5 nm.

Confinement Correction to Mercury Intrusion Capillary Pressure of Shale Nanopores

0
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