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Author : Bahiya Jabbar
Publisher :
ISBN 13 :
Total Pages : 77 pages
Book Rating : 4.:/5 (92 download)
Download or read book Poroelastic Effect on Gas Transport and Storage in Organic Rich Shale Reservoir written by Bahiya Jabbar and published by . This book was released on 2014 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : E.H. Rutter
Publisher : Geological Society of London
ISBN 13 : 1786203162
Total Pages : 369 pages
Book Rating : 4.7/5 (862 download)
Download or read book Geomechanical and Petrophysical Properties of Mudrocks written by E.H. Rutter and published by Geological Society of London. This book was released on 2017-10-09 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: A surge of interest in the geomechanical and petrophysical properties of mudrocks (shales) has taken place in recent years following the development of a shale gas industry in the United States and elsewhere, and with the prospect of similar developments in the UK. Also, these rocks are of particular importance in excavation and construction geotechnics and other rock engineering applications, such as underground natural gas storage, carbon dioxide disposal and radioactive waste storage. They may greatly influence the stability of natural and engineered slopes. Mudrocks, which make up almost three-quarters of all the sedimentary rocks on Earth, therefore impact on many areas of applied geoscience. This volume focuses on the mechanical behaviour and various physical properties of mudrocks. The 15 chapters are grouped into three themes: (i) physical properties such as porosity, permeability, fluid flow through cracks, strength and geotechnical behaviour; (ii) mineralogy and microstructure, which control geomechanical behaviour; and (iii) fracture, both in laboratory studies and in the field.
Author : Reza Rezaee
Publisher : John Wiley & Sons
ISBN 13 : 1119039266
Total Pages : 417 pages
Book Rating : 4.1/5 (19 download)
Download or read book Fundamentals of Gas Shale Reservoirs written by Reza Rezaee and published by John Wiley & Sons. This book was released on 2015-07-01 with total page 417 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides comprehensive information about the key exploration, development and optimization concepts required for gas shale reservoirs Includes statistics about gas shale resources and countries that have shale gas potential Addresses the challenges that oil and gas industries may confront for gas shale reservoir exploration and development Introduces petrophysical analysis, rock physics, geomechanics and passive seismic methods for gas shale plays Details shale gas environmental issues and challenges, economic consideration for gas shale reservoirs Includes case studies of major producing gas shale formations
Author : John Peter Vermylen
Publisher : Stanford University
ISBN 13 :
Total Pages : 143 pages
Book Rating : 4.F/5 ( download)
Download or read book Geomechanical Studies of the Barnett Shale, Texas, USA written by John Peter Vermylen and published by Stanford University. This book was released on 2011 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents five studies of a gas shale reservoir using diverse methodologies to investigate geomechanical and transport properties that are important across the full reservoir lifecycle. Using the Barnett shale as a case study, we investigated adsorption, permeability, geomechanics, microseismicity, and stress evolution in two different study areas. The main goals of this thesis can be divided into two parts: first, to investigate how flow properties evolve with changes in stress and gas species, and second, to understand how the interactions between stress, fractures, and microseismicity control the creation of a permeable reservoir volume during hydraulic fracturing. In Chapter 2, we present results from adsorption and permeability experiments conducted on Barnett shale rock samples. We found Langmuir-type adsorption of CH4 and N2 at magnitudes consistent with previous studies of the Barnett shale. Three of our samples demonstrated BET-type adsorption of CO2, in contrast to all previous studies on CO2 adsorption in gas shales, which found Langmuir-adsorption. At low pressures (600 psi), we found preferential adsorption of CO2 over CH4 ranging from 3.6x to 5.5x. While our measurements were conducted at low pressures (up to 1500 psi), when our model fits are extrapolated to reservoir pressures they reach similar adsorption magnitudes as have been found in previous studies. At these high reservoir pressures, the very large preferential adsorption of CO2 over CH4 (up to 5-10x) suggests a significant potential for CO2 storage in gas shales like the Barnett if practical problems of injectivity and matrix transport can be overcome. We successfully measured permeability versus effective stress on two intact Barnett shale samples. We measured permeability effective stress coefficients less than 1 on both samples, invalidating our hypothesis that there might be throughgoing flow paths within the soft, porous organic kerogen that would lead the permeability effective stress coefficient to be greater than 1. The results suggest that microcracks are likely the dominant flow paths at these scales. In Chapter 3, we present integrated geological, geophysical, and geomechanical data in order to characterize the rock properties in our Barnett shale study area and to model the stress state in the reservoir before hydraulic fracturing occurred. Five parallel, horizontal wells were drilled in the study area and then fractured using three different techniques. We used the well logs from a vertical pilot well and a horizontal well to constrain the stress state in the reservoir. While there was some variation along the length of the well, we were able to determine a best fit stress state of Pp = 0.48 psi/ft, Sv = 1.1 psi/ft, SHmax = 0.73 psi/ft, and Shmin = 0.68 psi/ft. Applying this stress state to the mapped natural fractures indicates that there is significant potential for induced shear slip on natural fracture planes in this region of the Barnett, particularly close to the main hydraulic fracture where the pore pressure increase during hydraulic fracturing is likely to be very high. In Chapter 4, we present new techniques to quantify the robustness of hydraulic fracturing in gas shale reservoirs. The case study we analyzed involves five parallel horizontal wells in the Barnett shale with 51 frac stages. To investigate the numbers, sizes, and types of microearthquakes initiated during each frac stage, we created Gutenberg-Richter-type magnitude distribution plots to see if the size of events follows the characteristic scaling relationship found in natural earthquakes. We found that slickwater fracturing does generate a log-linear distribution of microearthquakes, but that it creates proportionally more small events than natural earthquake sources. Finding considerable variability in the generation of microearthquakes, we used the magnitude analysis as a proxy for the "robustness" of the stimulation of a given stage. We found that the conventionally fractured well and the two alternately fractured wells ("zipperfracs") were more effective than the simultaneously fractured wells ("simulfracs") in generating microearthquakes. We also found that the later stages of fracturing a given well were more successful in generating microearthquakes than the early stages. In Chapter 5, we present estimates of stress evolution in our study reservoir through analysis of the instantaneous shut-in pressure (ISIP) at the end of each stage. The ISIP increased stage by stage for all wells, but the simulfrac wells showed the greatest increase and the zipperfrac wells the least. We modeled the stress increase in the reservoir with a simple sequence of 2-D cracks along the length of the well. When using a spacing of one crack per stage, the modeled stress increase was nearly identical to the measured stress increase in the zipperfrac wells. When using three cracks per stage, the modeled final stage stress magnitude matched the measured final stage stress magnitude from the simulfrac wells, but the rate of stress increase in the simulfrac wells was much more gradual than the model predicted. To further investigate the causes of these ISIP trends, we began numerical flow and stress analysis to more realistically model the processes in the reservoir. One of our hypotheses was that the shorter total time needed to complete all the stages of the simulfrac wells was the cause of the greater ISIP increase compared to the zipperfrac wells. The microseismic activity level measured in Chapter 4 also correlates with total length of injection, suggesting leak off into the reservoir encouraged shear failure. Numerical modeling using the coupled FEM and flow software GEOSIM was able to model some cumulative stress increase the reservoir, but the full trend was not replicated. Further work to model field observations of hydraulic fracturing will enhance our understanding of the impact that hydraulic fracturing and stress change have on fracture creation and permeability enhancement in gas shales.
Author : Nirjhor Chakraborty
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (11 download)
Download or read book Fundamental Investigation of Gas Storage and Transport in Shales written by Nirjhor Chakraborty and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Gas storage and transport in shales is very different from sandstones or limestones. This is not only due to their inherently lower porosity and substantially lower permeability, but also because more complex and fundamentally different physical mechanistic phenomena govern both storage and transport. We use gas injection porosimetry to measure the storage of several single-component gases at supercritical pressures and temperatures on whole core plugs of Marcellus, Haynesville, Mancos, and Bakken shales. We find that the storage capacities of all gases far exceed helium storage in most shales. This is indicative of densification of gas that is taken up by the samples. Possible mechanisms for this densification such as confinement induced-supercriticality, adsorption, and capillary condensation are evaluated and the case for each is presented. Assuming the excess storage, beyond helium derived pore or free-gas volumes, is adsorption, adsorbed methane gas is found to account for between 12-75% of total gas-in-place (GIP) and is more than 40% of GIP in most cases. Despite being a noble gas, argon storage is found to be almost the same as methane. Ethylene gas storage in the Marcellus sample is found to be over 96% of GIP. Closer analysis of the data in conjunction with pore surface area estimates from LPSA measurements indicates a multilayer adsorption mechanism. This raises questions on the applicability of the Langmuir monolayer-model to describe storage in shales. Compositional and textural characterization indicates that organic content is a moderately important factor controlling gas storage behavior. However, three-dimensional spatial maps indicate that high storage is not limited to organic-rich regions. Pore size, rather than composition, appears to be a better predictor of storage behavior, with storage being proportional to the prevalence of nanopores and to total pore surface area. Gas transport in shale is also multi-mechanistic and cannot be separated from the underlying storage mechanisms. A numerical model is developed accounting for free-gas and adsorbed-phase diffusion, as well as adsorption-desorption kinetics. The model is validated on dynamic in-situ gas concentration data obtained via x-ray CT imaging of the Marcellus Shale. Modeling results suggest that concentration-dependent surface diffusion is the dominant mechanism controlling gas transport in the Marcellus. It is observed that the surface diffusion coefficient can exceed the free-gas diffusion coefficient by up to ten times.
Author : Kun Sang Lee
Publisher : Gulf Professional Publishing
ISBN 13 : 0128178612
Total Pages : 150 pages
Book Rating : 4.1/5 (281 download)
Download or read book Transport in Shale Reservoirs written by Kun Sang Lee and published by Gulf Professional Publishing. This book was released on 2019-02-20 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transport in Shale Reservoirs fills the need for a necessary, integrative approach on shale reservoirs. It delivers both the fundamental theories of transport in shale reservoirs and the most recent advancements in the recovery of shale oil and gas in one convenient reference. Shale reservoirs have distinctive features dissimilar to those of conventional reservoirs, thus an accurate evaluation on the behavior of shale gas reservoirs requires an integrated understanding on their characteristics and the transport of reservoir and fluids. Updates on the various transport mechanisms in shale, such as molecular diffusion and phase behavior in nano-pores Applies theory to practice through simulation in both shale oil and gas Presents an up-to-date reference on remaining challenges, such as organic material in the shale simulation and multicomponent transport in CO2 injection processes
Author : Hoss Belyadi
Publisher : Gulf Professional Publishing
ISBN 13 : 0128176660
Total Pages : 632 pages
Book Rating : 4.1/5 (281 download)
Download or read book Hydraulic Fracturing in Unconventional Reservoirs written by Hoss Belyadi and published by Gulf Professional Publishing. This book was released on 2019-06-18 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydraulic Fracturing in Unconventional Reservoirs: Theories, Operations, and Economic Analysis, Second Edition, presents the latest operations and applications in all facets of fracturing. Enhanced to include today’s newest technologies, such as machine learning and the monitoring of field performance using pressure and rate transient analysis, this reference gives engineers the full spectrum of information needed to run unconventional field developments. Covering key aspects, including fracture clean-up, expanded material on refracturing, and a discussion on economic analysis in unconventional reservoirs, this book keeps today's petroleum engineers updated on the critical aspects of unconventional activity. Helps readers understand drilling and production technology and operations in shale gas through real-field examples Covers various topics on fractured wells and the exploitation of unconventional hydrocarbons in one complete reference Presents the latest operations and applications in all facets of fracturing
Author : Reza Rezaee
Publisher : MDPI
ISBN 13 : 3039285807
Total Pages : 522 pages
Book Rating : 4.0/5 (392 download)
Download or read book Development of Unconventional Reservoirs written by Reza Rezaee and published by MDPI. This book was released on 2020-04-16 with total page 522 pages. Available in PDF, EPUB and Kindle. Book excerpt: The need for energy is increasing and but the production from conventional reservoirs is declining quickly. This requires an economically and technically feasible source of energy for the coming years. Among some alternative future energy solutions, the most reasonable source is from unconventional reservoirs. As the name “unconventional” implies, different and challenging approaches are required to characterize and develop these resources. This Special Issue covers some of the technical challenges for developing unconventional energy sources from shale gas/oil, tight gas sand, and coalbed methane.
Author : John Peter Vermylen
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (742 download)
Download or read book Geomechanical Studies of the Barnett Shale, Texas, USA written by John Peter Vermylen and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents five studies of a gas shale reservoir using diverse methodologies to investigate geomechanical and transport properties that are important across the full reservoir lifecycle. Using the Barnett shale as a case study, we investigated adsorption, permeability, geomechanics, microseismicity, and stress evolution in two different study areas. The main goals of this thesis can be divided into two parts: first, to investigate how flow properties evolve with changes in stress and gas species, and second, to understand how the interactions between stress, fractures, and microseismicity control the creation of a permeable reservoir volume during hydraulic fracturing. In Chapter 2, we present results from adsorption and permeability experiments conducted on Barnett shale rock samples. We found Langmuir-type adsorption of CH4 and N2 at magnitudes consistent with previous studies of the Barnett shale. Three of our samples demonstrated BET-type adsorption of CO2, in contrast to all previous studies on CO2 adsorption in gas shales, which found Langmuir-adsorption. At low pressures (600 psi), we found preferential adsorption of CO2 over CH4 ranging from 3.6x to 5.5x. While our measurements were conducted at low pressures (up to 1500 psi), when our model fits are extrapolated to reservoir pressures they reach similar adsorption magnitudes as have been found in previous studies. At these high reservoir pressures, the very large preferential adsorption of CO2 over CH4 (up to 5-10x) suggests a significant potential for CO2 storage in gas shales like the Barnett if practical problems of injectivity and matrix transport can be overcome. We successfully measured permeability versus effective stress on two intact Barnett shale samples. We measured permeability effective stress coefficients less than 1 on both samples, invalidating our hypothesis that there might be throughgoing flow paths within the soft, porous organic kerogen that would lead the permeability effective stress coefficient to be greater than 1. The results suggest that microcracks are likely the dominant flow paths at these scales. In Chapter 3, we present integrated geological, geophysical, and geomechanical data in order to characterize the rock properties in our Barnett shale study area and to model the stress state in the reservoir before hydraulic fracturing occurred. Five parallel, horizontal wells were drilled in the study area and then fractured using three different techniques. We used the well logs from a vertical pilot well and a horizontal well to constrain the stress state in the reservoir. While there was some variation along the length of the well, we were able to determine a best fit stress state of Pp = 0.48 psi/ft, Sv = 1.1 psi/ft, SHmax = 0.73 psi/ft, and Shmin = 0.68 psi/ft. Applying this stress state to the mapped natural fractures indicates that there is significant potential for induced shear slip on natural fracture planes in this region of the Barnett, particularly close to the main hydraulic fracture where the pore pressure increase during hydraulic fracturing is likely to be very high. In Chapter 4, we present new techniques to quantify the robustness of hydraulic fracturing in gas shale reservoirs. The case study we analyzed involves five parallel horizontal wells in the Barnett shale with 51 frac stages. To investigate the numbers, sizes, and types of microearthquakes initiated during each frac stage, we created Gutenberg-Richter-type magnitude distribution plots to see if the size of events follows the characteristic scaling relationship found in natural earthquakes. We found that slickwater fracturing does generate a log-linear distribution of microearthquakes, but that it creates proportionally more small events than natural earthquake sources. Finding considerable variability in the generation of microearthquakes, we used the magnitude analysis as a proxy for the "robustness" of the stimulation of a given stage. We found that the conventionally fractured well and the two alternately fractured wells ("zipperfracs") were more effective than the simultaneously fractured wells ("simulfracs") in generating microearthquakes. We also found that the later stages of fracturing a given well were more successful in generating microearthquakes than the early stages. In Chapter 5, we present estimates of stress evolution in our study reservoir through analysis of the instantaneous shut-in pressure (ISIP) at the end of each stage. The ISIP increased stage by stage for all wells, but the simulfrac wells showed the greatest increase and the zipperfrac wells the least. We modeled the stress increase in the reservoir with a simple sequence of 2-D cracks along the length of the well. When using a spacing of one crack per stage, the modeled stress increase was nearly identical to the measured stress increase in the zipperfrac wells. When using three cracks per stage, the modeled final stage stress magnitude matched the measured final stage stress magnitude from the simulfrac wells, but the rate of stress increase in the simulfrac wells was much more gradual than the model predicted. To further investigate the causes of these ISIP trends, we began numerical flow and stress analysis to more realistically model the processes in the reservoir. One of our hypotheses was that the shorter total time needed to complete all the stages of the simulfrac wells was the cause of the greater ISIP increase compared to the zipperfrac wells. The microseismic activity level measured in Chapter 4 also correlates with total length of injection, suggesting leak off into the reservoir encouraged shear failure. Numerical modeling using the coupled FEM and flow software GEOSIM was able to model some cumulative stress increase the reservoir, but the full trend was not replicated. Further work to model field observations of hydraulic fracturing will enhance our understanding of the impact that hydraulic fracturing and stress change have on fracture creation and permeability enhancement in gas shales.
Author : Siavash Khosh Sokhan Monfared
Publisher :
ISBN 13 :
Total Pages : 183 pages
Book Rating : 4.:/5 (911 download)
Download or read book Microporoelastic Modeling of Organic-rich Shales written by Siavash Khosh Sokhan Monfared and published by . This book was released on 2015 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to their abundance, organic-rich shales are playing a critical role in re-defining the world's energy landscape leading to shifts in global geopolitics. However, technical challenges and environmental concerns continue to contribute to the slow growth of organic-rich shale exploration and exploitation worldwide. The engineering and scientific challenges arise from the extremely heterogeneous and anisotropic nature of these naturally occurring geo-composites at multiple length scales. Specifically, the anisotropic poroelastic behavior of organic-rich shales becomes of critical importance for petroleum engineers. Thus, the focus of this thesis is to capture mechanisms of first-order contribution to the effective anisotropic poroelasticity of organic-rich shales which can pave the way for more efficient and effective exploration and exploitation. We introduce an original approach for micromechanical modeling of organic-rich shales which accounts for the effect of organic maturity on the overall anisotropic poroelasticity through morphology considerations. This morphology contribution is captured by means of an effective media theory that bridges the gap between immature and mature systems through the choice of the system's micro-texture; namely a matrix-inclusion morphology (Mori-Tanaka) for immature systems and a polycrystal/ granular morphology for mature systems. Also, we show that interfaces play a role on the effective elasticity of mature organic-rich shales. The models are calibrated by means of ultrasonic pulse velocity measurements of elastic properties and validated by means of lab measured nanoindentation data. Sensitivity analyses using Spearman's Partial Rank Correlation Coefficient show the importance of porosity and Total Organic Carbon (TOC) as key input parameters for accurate model predictions. These models' developments provide a mean to define a "unique" set of clay elasticity. They also highlight the importance of the depositional environment, burial and diagenetic processes on overall mechanical and poromechanical behavior of organic-rich shales.
Author : Zhiwei Qian
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (93 download)
Download or read book Geophysical Responses of Organic-rich Shale and the Effect of Mineralogy written by Zhiwei Qian and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Total organic carbon (TOC) is one of the most important parameters for indicating the resource potential of unconventional shale reservoirs. Because of the low density and velocity of organic matter, some seismic attributes like P-wave impedance (Ip) and Vp/Vs ratio would respond to high TOC content. So we can use these seismic attributes to remotely identify organic-rich areas. However, these attributes are not equally efficient for all shale formations. The behavior of the geophysical response on TOC content may vary due to mineral variations of different shale plays. So, it is important to understand the mineral composition, study their impact on geophysical responses, and choose the right seismic attributes for the interpretation of a certain shale play. A rock physics modeling can be applied to link the in-situ rock parameters like mineral composition, TOC content, porosity etc. with the geophysical response. In this thesis work, I study the geophysical response of Barnett shale. In addition, I study the impacts of the mineral variations within an individual shale reservoir on geophysical response. Certain relationships between TOC and volume percentage of clay and quartz were observed, which should be taken into account when performing rock physics modeling, as opposed to assuming the mineral composition changing randomly.
Author : Mark D. Zoback
Publisher : Cambridge University Press
ISBN 13 : 1107087074
Total Pages : 495 pages
Book Rating : 4.1/5 (7 download)
Download or read book Unconventional Reservoir Geomechanics written by Mark D. Zoback and published by Cambridge University Press. This book was released on 2019-05-16 with total page 495 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive overview of the key geologic, geomechanical and engineering principles that govern the development of unconventional oil and gas reservoirs. Covering hydrocarbon-bearing formations, horizontal drilling, reservoir seismology and environmental impacts, this is an invaluable resource for geologists, geophysicists and reservoir engineers.
Author : Khalid R. Alnoaimi
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (944 download)
Download or read book Influence of Cracks and Microcracks on Flow and Storage Capacities of Gas Shales at Core-level written by Khalid R. Alnoaimi and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Economical shale gas production is only possible via hydraulic fracturing in which a fluid is injected in the subsurface at a pressure large enough to penetrate the near wellbore region. Hydraulic fracturing activates subsets of cracks and microcracks that facilitate transfer of gas to exit the matrix. This process creates stress sensitive flow dynamics between various media with their respective flow paths. This complex interplay of transport in media with different size scales poses challenges for modeling. Understanding the mechanisms of flow as the reservoir fluid pressure increases during fracturing or decreases during flow back is key for quantifying the production forecast and the volume of reserves. Gas transport in shales is believed to be driven by complex physical mechanisms including Darcy flow, Knudsen diffusion, and adsorption through fractures, microcracks, and matrix. Understanding the interplay of gas transport in these media at increased pore pressure and constant net effective stress, as well as at increased net effective stress (i.e. during depletion) is the goal of this work. This research work investigates the interplay of gas transport in the cracks, microcracks, and matrix of shale using He and CO2 via transient upstream pressure pulse decay experiments. The cracks and microcracks are natural in the sense no lab pretreatment created them. A novel setup of the pressure pulse decay experiment was used to determine the storage and flow capacities simultaneously. Experimentally, the pressure signals are used to define time-dependent pore volume partitioning between the microcracks and the matrix. A dual continuum simulator is constructed to decouple the flow and storage capacity at early-time pressure where the gas flows simultaneously in both media. This is done via a history-matching process that quantifies the pore volume partitioning of the microcracks and matrix, the permeability in the microcracks, and the diffusivity of gas in the matrix. A series of experiments were conducted at constant net effective stress (500 psi) and increasing net effective stress (500, 1000, 2000 psi) to study the evolution of the pore volume partitioning, the permeability in the microcracks, and the diffusion in the matrix. The experiments were conducted on samples from the Eagle Ford and Haynesville shale plays. Results have shown that the pore volume partitioning in the microcracks in sample 180Ha (Eagle Ford) was between 8 - 24.1% of the total pore volume in all experiments at constant and variable net effective stresses. Sample TWG 1-3 (Haynesville) had a percentage of microcracks between 84.5 - 87.0% of the total pore volume. Sample TWG 3-3 had a microcracks portion between 68.8 - 83.1% of the total pore volume. These proportions were found to be related to the magnitude of permeability and void volumes in the system. The greater the permeability and the smaller the void volumes, the smaller is the microcracks pore volume. Samples 180Ha, TWG 1-3, TWG 3-3 had a liquid permeability of 396.3, 1.63, and 16.59 micro Darcy. The gas transport in the matrix was expressed volumetrically via a "diffusional transport group" parameter. This history-match parameter was found to increase generally with pore pressure at constant net effective stress and decrease with increased net effective stress. The role of adsorption was also investigated using CO2 in the same experimental apparatus and conditions. It was found that the influence of pore volume partitioning is suppressed by the large adsorption capacity in the shale samples. The adsorption capacity was a history-match parameter in the analysis. It was found that adsorption occurs in the microcracks in permeabilities less than 50 micro Darcy along with adsorption in the matrix. For permeabilities greater than that value, adsorption had no importance on microcracks. Adsorption in both media required different adsorption-pressure functions. The CO2 permeability was found to be smaller than the He permeability by a 2-3 factors.
Author : Youssef Magdy Abdou Mohamed Elkady
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (12 download)
Download or read book Multiscale Investigation of Fluid Transport and Enhanced Recovery in Shale written by Youssef Magdy Abdou Mohamed Elkady and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In 2019, the U.S. produced 75% of its natural gas from shales and 59% of its oil from tight oil resources. Multistage hydraulic fracturing along with horizontal pad drilling enabled operators to increase significantly production from these resources. Despite the vastness of shale resources, recovery factors are small typically, amounting to 5-10% for oil and ~25% for gas. In this work we examine various enhanced recovery techniques across multiple length scales to gain a better understanding of enhanced resource recovery mechanisms resulting from injection of gas, such as carbon dioxide (CO2). In doing so, we develop in-house shale characterization experimental methods to quantify fluid flow, storage, and recovery in the laboratory. An experimental workflow is presented for rock characterization (porosity, permeability, and adsorption) to quantify accurately gas storage and flow needed for enhanced gas recovery (EGR) experiments. Both pulse decay and Computed Tomography (CT) were used independently to establish consistency between results derived from each method. New image processing routines for CT data were developed that better match mass balance derived porosity and storativity results compared to conventional CT methods. Measured porosity values using helium (He) for each sample proved to be constant at various equilibrium pore pressures justifying its use as a reference gas for excess adsorption computations for other gases studied. Nitrogen (N2), methane (CH4), krypton (Kr), and CO2 apparent permeability and storativity at different pore pressures were determined. All adsorptive gases, except CO2, exhibited monolayer Langmuir adsorption behavior. CO2 uniquely showed multilayer behavior that was observed in two cores (Eagle Ford (EF1) and Wolfcamp (WC2)). The impact of adsorption on gas permeability was captured in our experiments showing a negative correlation between adsorption affinity and permeability. For instance, Kr and CO2 reduced the liquid-like permeability value determined using He by factors of 2 and 8, respectively, for sample EF1. Finally, a persistent five-fold reduction in permeability was observed in sample WC2 after CO2 exposure that is attributed to kerogen swelling or matrix softening. The degree of kerogen swelling is impacted by the affinity of the gas to adsorb and its ability to dissolve into kerogen. Matrix softening, on the other hand, enhances compaction of the pore space under constant effective stresses. Diverse diagnostics across multiple scales were used to examine the impact of CO2-water fluids on oil recovery and matrix flow on both core and micron scales. Enhanced oil recovery (EOR) was investigated on a Utica (W2-2) core that was artificially split and saturated with crude oil for 3 months. The core was cut to create a conductive pathway and to increase surface area to help oil saturate the sample. Core-scale examinations using pulse decay, injection experiments, and CT showed no material enhancement to matrix fluid flow or oil recovery using dry supercritical CO2, water-saturated CO2, or carbonated water. Approximately 87% of the in-situ oil was recovered using dry supercritical CO2 initially without any further recovery. CT visualizations showed that most of the oil resided in the main fracture with small amounts of oil residing in the matrix. Potential enhancement in core-scale matrix flow was investigated by conducting He pressure pulses before and after a carbonate-rich Eagle Ford (EF-1) sample was exposed to carbonated water for 6 months. Measured permeability values were identical before and after exposure to the acidic fluid. Micron-scale findings, on the other hand, using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and micro-CT showed vugs and pits, from calcite dissolution, ranging from 1 micro-m to 10's micro-m in size in samples exposed to carbonated water. These samples were exposed to carbonated water in either a batch reactor setting or a core-scale carbonated water injection experiment. The wet supercritical CO2 phase did not induce any observable carbonate dissolution in the shale sample tested. Finally, it was determined that gold coating of the sample (a preparation step needed for SEM imaging) has no impact on fluid-rock interaction during our experiments. A novel experimental setup was designed for investigating EGR in shale cores. The detailed sample characterization conducted on both samples (EF1 and WC2) was used to assess initial rock storativity, adsorption, and permeability that are vital for proper experimental planning given the small pore volumes in shales. Experiments were run with Kr or CH4 as in-situ gases and CO2 or N2 as injection gases. Continuous Kr gas injection experiments showed consistent results between mass balance and CT-derived results establishing reliability in our CT depictions. CO2 gas injection had a better initial displacement efficiency compared to N2 when displacing in-situ Kr. Homogeneous sample WC2 required approximately four times fewer pore volume injections to produce the entire original gas in place compared to sample EF1 that had two CT-visible conductive pathways or microcracks. Finally, core-scale findings reveal that continuous gas injection is more effective than huff-n-puff for enhancing gas recovery on a pore volume injected basis. Core-scale simulations using CMG GEM were created to mimic and validate lab pulse decay and EGR experiments. Porosity, permeability, and adsorption values were validated for various pressure pulses across both cores (EF1 and WC2) using all the gases investigated (He, N2, Kr, CH4, and CO2). Coal bed methane modeling in CMG GEM was utilized for matching highly adsorptive gases (Kr and CO2) due to a delayed downstream response given the experimentally determined porosity, permeability, and adsorption values. Another critical parameter, diffusion characteristic time (t*), was identified using this model during the history matching process that quantifies a mass transfer resistance to fracture flow due to fracture-matrix gas exchange. Although our experiments were not designed to measure directly t*, various pressure pulses for CO2 and Kr required a diffusion time of 1.44-1.92 hrs (0.06-0.08 days) to match our pressure pulses using coal bed methane modeling. A continuous gas injection experiment was simulated in CMG GEM that matched the experimental pressure history, recovery results, and CT visualizations for sample EF1. Sensitivity studies on diffusion time revealed its strong influence on recovery in low permeability areas that are predominant during late production. A huff-n-puff experiment was simulated given the same model parameters as the history matched continuous injection experiment. Huff-n-puff had a poorer recovery curve compared to continuous injection due to gas entrapment away from the microcracks with each cycle. Finally, core-scale simulations show that long diffusion times are favorable for huff-n-puff but disadvantageous for continuous injection emphasizing the importance of sample characterization, including transport properties, before evaluating the different EGR techniques. Learnings from core-scale experiments and simulations were translated to assess EGR applicability at field scale. Multiple reservoir uncertainties (porosity, stimulated permeability, diffusion time) and operational decisions (e.g. injection and soak times) were explored to understand their influence on CH4 recovery and CO2 storage for continuous injection and huff-n-puff. A simplified CMG GEM field model was created that utilized 1300 m horizontal wells that have 13 fracture stages with 4 clusters per stage. Field continuous injection scenarios yielded a loss in cumulative CH4 production compared to cases with primary production only over a 20 year period. Injection started after 10 years of primary production; however, the economic benefits from CO2 storage outweighed CH4 losses in cases with short diffusion times (
Author : Craig Matthew Freeman
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (881 download)
Download or read book Study of Multi-scale Transport Phenomena in Tight Gas and Shale Gas Reservoir Systems written by Craig Matthew Freeman and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The hydrocarbon resources found in shale reservoirs have become an important energy source in recent years. Unconventional geological and engineering features of shale systems pose challenges to the characterization of these systems. These challenges have impeded efficient economic development of shale resources. New fundamental insights and tools are needed to improve the state of shale gas development. Few attempts have been made to model the compositional behavior of fluids in shale gas reservoirs. The transport and storage of reservoir fluids in shale is controlled by multiple distinct micro-scale physical phenomena. These phenomena include preferential Knudsen diffusion, differential desorption, and capillary critical effects. Together, these phenomena cause significant changes in fluid composition in the subsurface and a measureable change in the composition of the produced gas over time. In order to quantify this compositional change we developed a numerical model describing the coupled processes of desorption, diffusion, and phase behavior in heterogeneous ultra-tight rocks as a function of pore size. The model captures the various configurations of fractures induced by shale gas fracture stimulation. Through modeling of the physics at the macro-scale (e.g. reservoir-scale hydraulic fractures) and micro-scale (e.g. Knudsen diffusion in kerogen nanopores), we illustrate how and why gas composition changes spatially and temporally during production. We compare the results of our numerical model against measured composition data obtained at regular intervals from shale gas wells. We utilize the characteristic behaviors explicated by the model results to identify features in the measured data. We present a basis for a new method of production data analysis incorporating gas composition measurements in order to develop a more complete diagnostic process. Distinct fluctuations in the flowing gas composition are shown to uniquely identify the onset of fracture interference in horizontal wells with multiple transverse hydraulic fractures. The timescale and durations of the transitional flow regimes in shales are quantified using these measured composition data. These assessments appear to be robust even for high levels of noise in the rate and pressure data. Integration of the compositional shift analysis of this work with modern production analysis is used to infer reservoir properties. This work extends the current understanding of flow behavior and well performance for shale gas systems to encompass the physical phenomena leading to compositional change. This new understanding may be used to aid well performance analysis, optimize fracture and completion design, and improve the accuracy of reserves estimates. In this work we contribute a numerical model which captures multicomponent desorption, diffusion, and phase behavior in ultra-tight rocks. We also describe a workflow for incorporating measured gas composition data into modern production analysis. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151782
Author : Yi Wang
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (1 download)
Download or read book Laboratory Estimation and Modeling of Apparent Permeability for Ultra-Tight Anthracite and Shale Matrix written by Yi Wang and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Gas production from unconventional reservoirs such as gas shale and coalbed methane (CBM) has become a major source of clean energy in the United States. Reservoir apparent permeability is a critical and controlling parameter for the predictions of shale gas and coalbed methane (CBM) productions. Shale matrix and tight anthracite are characterized by ultra-tight pore structure and low permeability at micro- and nano-scale with gas molecules stored by adsorption. Gas transport in shale and anthracite matrices no longer always falls into the continuum flow regime described by Darcys law, rather a considerable portion of transport is sporadic and irregular due to the mean free path of gas is comparable to the prevailing pore scale. Therefore, gas transport in both anthracite and shale will be a complicated nonlinear multi-mechanistic process. A multi-mechanistic flow process is always happening during shale gas and CBM production, including Darcy viscous flow, slip flow, transition flow and Knudsen diffusion and their proportional contributions to apparent permeability are constantly changing with continuous reservoir depletion. The complexity of the gas storage and flow mechanisms in ultra-fine pore structure is diverse and makes it more difficult to predict the matrix permeability and gas deliverability. In this study, a multi-mechanistic apparent-permeability model for unconventional reservoir rocks (shale and anthracite) was derived under different stress boundary conditions (constant-stress and uniaxial-strain). The proposed model incorporates the pressure-dependent weighting coefficients to separate the contributions of Knudsen diffusion and Darcy flow on matrix permeability. A combination of both permeability components was coupled with pressure-dependent weighting coefficients. A stressstrain relationships for a linear elastic gas-desorbing porous medium under hydrostatic stress condition was derived from thermal-elastic equations and can be incorporated into the Darcian flow component, serving for the permeability data under hydrostatic stress. The modeled results well agree with anthracite and shale sample permeability measured data.In this study, laboratory measurements of gas apparent permeability were conducted on coal and shale samples for both helium and CO2 injection/depletion under different stress conditions. At low pressure under constant stress condition, CO2 permeability enhancement due to sorption-induced matrix shrinkage effect is significant, which can be either clearly observed from the pulse-decay pressure response curves or the data reduced by Cui et al.s method. CO2 apparent permeability can be higher than He at pressure higher than 1000 psi, which may be resulted from limited shale adsorption capacity. Helium permeability is more sensitive to the variation of Terzaghi effective stress than CO2 and it is independent of pore pressure. The true effective stress coefficient can be found two values at low pressure region (500 psi) and high pressure region (500 psi). The negative value indicates Knudsen diffusion and slip flow effect have more impact on apparent permeability than Terzaghi stress at low pressure. Additionally, laboratory measurements of gas sorption, Knudsen diffusion coefficient and coal deformation were conducted to break down the key effects that influence gas permeability evolution. Adsorption isotherms of crushed anthracite coal samples was measured using Gibbs adsorption principle at different gas pressures. The adsorption isotherm result showed that the adsorption capacity at low pressure changes with a higher rate and thus brings a significant sorption-induced rock matrix swelling/shrinkage effect. And the isotherm data are important inputs for the Darcy permeability models. The latter was coupled in the apparent-permeability model as the Darcy flow component which involves the sorption-induced strain component. Diffusion coefficients of the pulverized samples were estimated by using the particle method and was used to calculate the effective Knudsen permeability. The Knudsen diffusion flow component in the proposed apparent-permeability model was constructed by transforming Knudsen mass flux into permeability term and used to match the effective Knudsen permeability based on diffusion data. Increasing trends for all results were performed during pressure drop down in the result plots. And the modeling result showed very good agreements with them, giving a solid proof of the availability of Knudsen diffusion component as part of the proposed model. The results of a series of experimental measurements of coal deformation with gas injection and depletion revealed that the coal sorption induced deformation exhibits anisotropy, with larger deformation in direction perpendicular to bedding than those parallel to the bedding planes. The deformation of coal is reversible for helium and methane with injection/depletion, but not for CO2. Based on the modeling results, it was found that application of isotropic deformation in permeability model can overestimate the permeability loss compared to anisotropic deformation. This demonstrates that the anisotropic coal deformation should be considered to predict the permeability behavior of CBM as well as CO2 sequestration/ECBM projects.
Author : Jianchao Cai
Publisher : Elsevier
ISBN 13 : 0128172894
Total Pages : 354 pages
Book Rating : 4.1/5 (281 download)
Download or read book Petrophysical Characterization and Fluids Transport in Unconventional Reservoirs written by Jianchao Cai and published by Elsevier. This book was released on 2019-01-24 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: Petrophysical Characterization and Fluids Transport in Unconventional Reservoirs presents a comprehensive look at these new methods and technologies for the petrophysical characterization of unconventional reservoirs, including recent theoretical advances and modeling on fluids transport in unconventional reservoirs. The book is a valuable tool for geoscientists and engineers working in academia and industry. Many novel technologies and approaches, including petrophysics, multi-scale modelling, rock reconstruction and upscaling approaches are discussed, along with the challenge of the development of unconventional reservoirs and the mechanism of multi-phase/multi-scale flow and transport in these structures. Includes both practical and theoretical research for the characterization of unconventional reservoirs Covers the basic approaches and mechanisms for enhanced recovery techniques in unconventional reservoirs Presents the latest research in the fluid transport processes in unconventional reservoirs
