Recent Submissions

  • Metadata Analysis Reveals Major Worldwide Trends in Industrial and Academic Geophysics

    Eltsov, Timofey; Yutkin, Maxim; Patzek, Tadeusz (Energies, MDPI AG, 2020-12-28) [Article]
    We summarize our metadata analysis of the last 38 well-attended annual conferences, organized by the Society of Exploration Geophysicists. In 2018, Schlumberger and Saudi Aramco had the highest number of publications among service and production companies. In 2019, BGP and PetroChina took the lead. Throughout history, US academics have had the highest number of publications, but in 2019 Chinese academia came close to taking the lead. Analysis of the publication activity of oil-producing and oilfield service companies provides insights into the state of geophysical research. The number of publications from industrial companies in the energy sector reflects their financial standing and aspirations for the near future. Publications from academia in different countries tell us about state and private funding of research in each country, and indirectly reflect the geopolitical situation in the world. The changing number of publications over time reflects the dynamics of the transformation of research in geophysics, and allows us to understand better what is happening and make forecasts.
  • Soil Response during Globally Drained and Undrained Freeze–Thaw Cycles under Deviatoric Loading

    Kim, Sang Yeob; Park, Junghee; Cha, Wonjun; Lee, Jong-Sub; Santamarina, Carlos (Journal of Geotechnical and Geoenvironmental Engineering, American Society of Civil Engineers (ASCE), 2020-12-12) [Article]
    Sediments experience shear and volumetric strains during freeze–thaw cycles. Measurements during globally drained and undrained cycles under constant deviatoric stresses show that the asymptotic shear and volumetric response vary with sediment type and drainage conditions. In particular, the sediment response is intimately related to the ice pore habit that results from effective stress and the ice capillary pressure σ′z/Δuiw. Pore-invasive ice formation in coarse-grained soils may trigger some contraction during the first freeze–thaw cycle, even in sands denser than the critical state. Grain-displacive ice growth in fine-grained soils causes cryogenic consolidation of the surrounding sediment; subsequent melting of the segregated ice lenses yields a high increase in pore water pressure during undrained thawing, a pronounced volume contraction under drained conditions, and preferential shear deformation along melting ice lenses in either case. Both dilative sand and normally consolidated (NC) clay specimens subjected to deviatoric loading exhibit unceasing vertical strain accumulation (i.e., ratcheting) during freeze–thaw cycles; the void ratio evolves toward asymptotic values in all cases. The freezing rate relative to the pressure diffusion rate Π=DT/Cv regulates drainage conditions during freeze–thaw cycles; globally drained freezing and thawing are anticipated in coarse-grained sediments.
  • Thermal Conductivity of Sand–Silt Mixtures

    Roshankhah, Shahrzad; Garcia, Adrian; Santamarina, Carlos (Journal of Geotechnical and Geoenvironmental Engineering, American Society of Civil Engineers (ASCE), 2020-12-12) [Article]
    Heat flow controls the design and operation of a wide range of engineered geosystems. This study uses transient thermal probe measurements to determine the evolution of the thermal conductivity of air-dry and water-saturated sand–silt mixtures as a function of effective stress. Results confirm that the thermal conductivity of soils varies with state of stress, dry mass density, mineralogy, and pore fluid properties and highlight the effect of thermal contact resistance on the thermal conductivity of granular materials. Thermal conductivity follows a linear relationship with the logarithm of effective stress as a consequence of fabric compaction, increased coordination number, contact deformation, and reduced thermal contact resistance. The bulk thermal conductivity of water-saturated soils is more than seven times that of air-dry soils for the same fines content (FC) and effective stress. Pore-filling fines contribute conduction paths and interparticle coordination; the peak in thermal conductivity takes place at FC≈0.4; this mixture range corresponds to the transition from fines-controlled to coarse-controlled mechanical response (i.e., both fines and coarse grains are load bearing), in agreement with the revised soil classification system.
  • The critical role of pore size on depth-dependent microbial cell counts in sediments

    Park, Junghee; Santamarina, Carlos (Scientific Reports, Springer Science and Business Media LLC, 2020-12-10) [Article]
    AbstractCell counts decrease with sediment depth. Typical explanations consider limiting factors such as water availability and chemistry, carbon source, nutrients, energy and temperature, and overlook the role of pore size. Our analyses consider sediment self-compaction, the evolution of pore size with depth, and the probability of pores larger than the microbial size to compute the volume fraction of life-compatible pores. We evaluate cell counts vs. depth profiles gathered at 116 sites worldwide. Results confirm the critical role of pore size on cell counts in the subsurface and explain much of the data spread (from ~ 9 orders of magnitude range in cell counts to ~ 2 orders). Cells colonize pores often forming dense biofilms, thus, cell counts in pores are orders of magnitude higher than in the water column. Similar arguments apply to rocks.
  • Shales: Comprehensive Laboratory Characterization

    Gramajo, Eduardo (2020-12) [Dissertation]
    Advisor: Santamarina, Carlos
    Committee members: Vahrenkamp, Volker C.; Mai, Paul Martin; Frost, David; Finkbeiner, Thomas
    Unconventional formations have become an increasingly important source of energy resources. Proper rock mechanic characterization is needed not only to identify the most promising areas for stimulation, but to increase our understanding of the sealing capabilities of cap-rock formations for carbon geological storage. However, shale assessment is challenging with current standard techniques. This research explores the index and rock mechanic properties of different shale specimens considered as source rocks for oil and gas (Eagle Ford, Wolfcamp, Jordanian, Mancos, Bakken, and Kimmeridge), and presents an in-depth analysis of tools and protocols to identify inherent biases. New test protocols proposed in this thesis provide robust and cost-effective measurement techniques to characterize shale formations in general; these include: 1) new energy methods computed from the area under the stress-strain curve or proposed boundary asymptotes (strength and stiffness) to assess brittle/ductile conditions in the field, 2) tensile strength analyses to determine anisotropy in shale formations, 3) Coda wave analysis to monitor pre-failure damage evolution during compression, and 4) a combination of index tests to anticipate the complicated geology or layered characteristics, which include high-resolution imaging, hardness, and scratch tests. Experimental results combined with extensive databases provide unprecedented information related to the mechanical behavior of shale formations needed for the enhanced design and analysis of geo-engineering applications. Calcareous shales display strong interlayer bonding and lower compressive strength anisotropy than siliceous shales. Tensile strength anisotropy is more pronounced than in compressive strength and reflects bedding orientation and loading conditions that affect fracture propagation and ensuing failure surface topography.
  • A Semi-Analytical Approach to Model Drilling Fluid Leakage Into Fractured Formation

    Albattat, Rami; Hoteit, Hussein (arXiv, 2020-11-05) [Preprint]
    Loss of circulation while drilling is a challenging problem that may interrupt operations, reduce efficiency, and may contaminate the subsurface. When a drilled borehole intercepts conductive faults or fractures, lost circulation manifests as a partial or total escape of drilling, workover, or cementing fluids, into the surrounding rock formations. Loss control materials (LCM) are often used in the mitigation process. Understanding the fracture effective hydraulic properties and fluid leakage behavior is crucial to mitigate this problem. Analytical modeling of fluid flow in fractures is a tool that can be quickly deployed to assess lost circulation and perform diagnostics, including leakage rate decline, effective fracture conductivity, and selection of the LCM. Such models should be applicable to Newtonian and non-Newtonian yield-stress fluids, where the fluid rheology is a nonlinear function of fluid flow and shear stress. In this work, a new semi-analytical solution is developed to model the flow of non-Newtonian drilling fluid in a fractured medium. The solution model is applicable for various fluid types exhibiting yield-power-law (Herschel-Bulkley). We use high-resolution finite-element simulations based on the Cauchy equation to verify our solutions. We also generate type-curves and compare them to others in the literature. We demonstrate the applicability of the proposed model for two field cases encountering lost circulations. To address the subsurface uncertainty, we combine the developed solutions with Monte-Carlo and generate probabilistic predictions. The solution method can estimate the range of fracture conductivity, parametrized by the fracture hydraulic aperture, and time-dependent fluid loss rate that can predict the cumulative volume of lost fluid. The proposed approach is accurate and efficient enough to support decision-making for real-time drilling operations.
  • Probing Chemical Interactions of Asphaltene-like Compounds with Silica and Calcium Carbonate in the Context of Improved Oil Recovery

    Hassan, Saleh (2020-11) [Dissertation]
    Advisor: Patzek, Tadeusz
    Committee members: Hoteit, Hussein; Sun, Shuyu; Radke, Clayton J.
    Crude oil recovery is related to surface wettability, which is controlled by crude interactions with rock surfaces. Understanding these interactions is associated with studying the complex asphaltenes that (1) are irreversibly deposited from oil-brine interfaces onto reservoir mineral surfaces, (2) are bulky super-molecules and (3) incorporate several chemical groups by stacking aromatic rings together. This is a difficult task because of varying crude oil composition, asphaltene interfacial and chemical activity, and the potential of irreversibly contaminating analytical equipment by such substances. To overcome these challenges, we split the problem into parts by studying how different mono- and poly-functional groups mimic asphaltene interaction with mineral surfaces, such as silica and calcium carbonate. The amine, carboxylate, and sulfate groups were identified as the highest potential functional groups responsible for asphaltene adsorption. Experiments included quartz crystal micro-balance with dissipation, bulk adsorption, and core samples. Adsorption tests for the mono-functional surfactants studied were fully reversible and, therefore, not representative of asphaltenes. Poly-functional compounds demonstrated irreversible adsorption, mimicking asphaltenes, through ion exchange and ion-bridging, depending on the type of functional group, chain length, mineral surface, and brine ionic composition. Poly-amines adsorb irreversibly onto silica and calcium carbonate surfaces regardless of the brine ionic composition or surface charge. However, irreversible adsorption of poly-sulfates and poly-carboxylates onto surfaces requires (1) sufficiently long chains and (2) an abundant presence of calcium ions in solution to allow ion-bringing mechanism. These findings suggest that crudes containing amine groups and long chains of carboxylates or sulfates have a higher tendency to be adsorbed onto surfaces and change wettability. This is important for designing an efficient detachment of asphaltenic oil from rock surfaces, where no complete desorption or drastic wettability change is required. The weakening of asphaltene interactions may be sufficient to induce spontaneous imbibition and consequently increase the efficiency of two-phase displacement. This work emphasizes the importance of understating crude-brine-rock interactions for the purpose of oil recovery. In summary, evaluating potential candidates for deploying enhanced oil recovery, such as low salinity waterflooding, should consider rock and crude types, as successful implementation requires “specific” properties collaborating together to enable incremental oil production
  • Particle-laden fluid flow through porous media - Clogging

    Hafez, Ahmed (2020-11) [Dissertation]
    Advisor: Santamarina, Carlos
    Committee members: Hoteit, Hussein; Thoroddsen, Sigurdur T; Finkbeiner, Thomas; O'Sullivan, Catherine
    Colloids and suspensions are frequently encountered in energy geo-engineering applications, from natural processes such as fine particles suspended in subsurface water and oil, to engineered fluids such as drilling muds and proppants. Transported particles can clog porous media and alter the medium permeability and flow paths. This research explores particle laden fluids using pore- and fracture-scale experimental, analytical and numerical techniques. Particle shape emerges as an important dimension in bridge formation at the pore-scale. Experiments show that cubical particles and 3D crosses are the most prone to clogging because of their ability to interlock and to develop torque-resisting contacts. Simulation results reveal the complex arch geometries and associated force chains formed by different particle shapes. A large-scale parallel-plate configuration mimics particle-laden radial fluid flow at the fracture-scale. Experimental and numerical simulation results show the development of a negative pressure annular zone away from the central injection point as a result of fluid inertial effects at high Reynolds numbers. Gravity and inertial retardation cause particles to deviate from the fluid streamlines, which changes the local particle concentration and enhances clogging. Conventional treatments prevent fluid leakage into the subsurface for small-aperture fractures, but are inefficient for large openings. Magnetically-controlled aggregation emerges as a viable clogging alternative. Tests with a newly designed magnetorheological mud show that the suspended iron particles accumulate around magnetic poles and gradually form a plug that stops fluid flow (flow resumes once the magnetic field is removed). The complementary study investigates the granular self-assembly of engineered magnetic particles to form large architectures in a bubble-column reactor; results show the stochastic nature of collision-limited aggregation and the role of boundaries in constraining potential configurations. Bentonite-cement-oil mixtures exhibit surprisingly fast hydration and may be used for fluid loss control into large-aperture fractures. Linear and radial flow experiments reveal the complex interactions between concurrent processes: spontaneous imbibition, the release of hydrated ions during cement hydration, bentonite flocculation, and enhanced permeability. Complementary oedometer and cone penetration tests show the evolving swelling pressure and plug strength.
  • The Harrat volcanic Fields on the Arabian Peninsula: their geologic setting, petrology, and suitability for carbon disposal

    Petrova, Miliausha V. (2020-11) [Thesis]
    Advisor: Hoteit, Hussein
    Committee members: Van der Zwan, Froukje M.; Afifi, Abdulkader M.; Arkadakskiy, Serguey
    This thesis evaluates the suitability of the Late Miocene-Recent basalts on the Harrat volcanic elds of Saudi Arabia for the disposal of CO2 emitted from industrial sources. For this evaluation, topography, geological setting, hydrology, and petrology of the Harrat basalts are the most important parameters. The basalts must have su cient thickness of at least 500 m of which at least 400 m must be saturated with groundwater in order to completely dissolve CO2 at the injection depth. The basalts must be reactive with dissolved CO2 and must have su cient matrix or fracture permeability. In addition, the basalts must be located near a xed industrial source of CO2, and there must be su cient supply of water for injection. All the volcanic elds in western and northern Saudi Arabia are evaluated in this study, amounting to 17 individual elds. The basalt elds were grouped in an older and younger generation, each with speci c geological characteristics. The basalts are reactive with CO2, because they are relatively unaltered. Field observations con rm that the basalts are su ciently permeable, particularly in tu s, agglomerates near vents, in distal lava ows along natural shrinkage joints and along vesicular margins of individual ows. The total thickness of basalt within lava elds was mapped using the digital elevation model by subtracting the base elevation from the surface elevation. The level of the groundwater table was estimated from Google Earth observations of the local topography and well data. Most elds did not have su cient basalt thickness and/or groundwater for the process. Harrat Rahat meets most of the requirements for 5 the CarbFix process, having su ciently thick basalts in three areas and an extensive groundwater aquifer. However, the maximum height of the groundwater aquifer in basalts is estimated to be 225 meters, which is less than optimal. This study concludes that 16 out of the 17 basalt elds in Saudi Arabia are not suitable for carbon mineralization by the CarbFix process, mainly because they are too thin and located higher than the local groundwater table. However, this pioneering study establishes a baseline for additional research in new technologies using CarbFix or other processes.
  • Investigation of Subsurface Systems of Polygonal Fractures

    Zhu, Weiwei (2020-11) [Dissertation]
    Advisor: Patzek, Tadeusz
    Committee members: Hoteit, Hussein; Bertotti, Giovanni; Sun, Shuyu
    Abstract: Fractures are ubiquitous in the subsurface, and they provide dominant pathways for fluid flow in low permeability formations. Therefore, fractures usually play an essential role in many engineering fields, such as hydrology, waste disposal, geother-mal reservoir and petroleum reservoir exploitation. Since fractures are invisible and have variable sizes from micrometers to kilometers, there is limited knowledge of their structure. We aim to deepen the understanding of fracture networks in the subsurface from their topological structures, hydraulic connectivity and characteristics at differ-ent scales. We adopt the discrete fracture network method and develop an efficient C++ code, HatchFrac, to make in-depth investigations possible. We start from generating stochastic fracture networks by constraining fracture geometries with dif-ferent stochastic distributions. We apply percolation theory to investigate the global connectivity of fracture networks. We find that commonly adopted percolation pa-rameters are unsuitable for the characterization of the percolation state of complex fracture networks. We implement the concept of global efficiency to quantify the impact of fracture geometries on the connectivity of fracture networks. Furthermore, we constrain the fracture networks with geological data and geomechanics principles. We investigate the correlation of fracture intensities with different dimensionality and find that it is not feasible to obtain correct 3D intensity parameters from 1D or 2D samples. We utilize a deep-learning technique and propose a pixel-based detection algorithm to automatically interpret fractures from raw outcrop images. Interpreted fracture maps provide abundant resources to investigate fracture intensities, lengths, orientations, and generations. For large scale faults, we develop a method to generate fault segments from a rough fault trace on a seismic map. Accurate fault geome-tries have significant impacts on damage zones and fault-related flow problems. For small scale fractures, we consider the impact of fracture sealing on the percolation state of orthogonal fracture networks. We emphasize the importance of non-critically stressed and partially sealed fractures, which are usually neglected because usually they are nonconductive. However, with significant stress perturbations, those non-critically stressed and partially sealed fractures can also contribute to the production by enlarging the stimulated reservoir volume.
  • Depth-Dependent Seabed Properties: Geoacoustic Assessment

    Lyu, Chuangxin; Park, Junghee; Santamarina, Carlos (Journal of Geotechnical and Geoenvironmental Engineering, American Society of Civil Engineers (ASCE), 2020-10-24) [Article]
    Offshore geoengineering requires reliable sediment parameters for analysis and design. This study proposes a robust framework for effective stress-dependent geotechnical and geoacoustic properties for seabed analysis based on geophysical models, new experimental data, and extensive data sets compiled from published studies that cover a wide range of marine sediments and depths. First, effective stress-dependent porosity versus depth profiles are computed using compaction models that are valid for a wide stress range. Then, P- and S-wave velocity data are analyzed in the context of effective stress-controlled density, shear stiffness, and bulk modulus within a Hertzian-Biot-Gassmann framework. Finally, this study selects six distinct “reference sediments” that range from clean sands to highplasticity clays and assigns self-consistent compaction and shear stiffness properties using well-known correlations reported in the literature in terms of specific surface, plasticity, and grain characteristics. Results show that robust physical models for compaction and stiffness adequately predict depth-dependent geotechnical and geoacoustic properties according to sediment type. The asymptotic void ratio at low effective stress eL determines the sediment density ρo at the sediment–water boundary. New experimental studies show that the characteristic asymptotic sediment density ρo at very low effective stress σ 0z → 0 controls the high-frequency acoustic reflection used for bathymetric imaging. The proposed analysis of geoacoustic data can be used to obtain first-order estimates of seafloor sediment properties and to produce sediment-type seafloor maps. D
  • Novel Approach to Study the Impact of Asphaltene Properties on Low Salinity Flooding

    Hassan, Saleh F.; Yutkin, Maxim; Kamireddy, Sirisha; Radke, Clayton J.; Patzek, Tadeusz (Society of Petroleum Engineers, 2020-10-21) [Conference Paper]
    Low salinity water flooding (LSW) has gained significant attention, because of its advantages compared with other enhanced oil recovery (EOR) methods. LSW's positive contribution to recovery factor has been demonstrated in the literature at lab and field scales. However, LSW flooding does not always increment oil recovery. It is a specific combination of properties of an asphaltenic crude oil, chemically equilibrated brine, and rock surface that may explain the success or failure of LSW. In this work, we introduce a novel experimental approach to study asphaltene-like chemical interactions with surfaces rock minerals to evaluate the effectiveness of applying LSW. When studying the impact of asphaltene properties on incremental recovery, one aims to detach some of the immobile oil, which is semi-irreversibly stuck on rock surface. This is a difficult task, because of varying crude oil composition, as well as asphaltene interfacial and chemical properties. To overcome these issues, we split the problem into several parts. We study how mono- and poly-functional chemical compounds mimic asphaltene interactions with mineral surfaces, like silica and calcium carbonate, which are proxies for sandstones and limestones, respectively. For example, amines, quaternary ammonia or carboxylates represent asphaltene functional groups that are mainly responsible for crude oil base and acid numbers, respectively. Adsorption of polymers and oligomers containing such groups mimics the irreversible asphaltene deposition onto rock surface through formation of chemically active polymerlike structures at the oil-brine interface. The silica surface is negatively charged in brines with pH above 2. Silica attracts positively charged ammonia salts, such as cetrimonium chloride (CTAC). However, negatively charged mono-functional carboxylates, i.e. anionic surfactants, like sodium hexanoate (NaHex), hardly adsorb onto silica, even in the presence of a bridging ion, like calcium. In contrast to silica, calcium carbonate surface has both positive and negative charges on its surface. We found that CTAC adsorbs onto calcium carbonate in any brine tested. NaHex shows minimal adsorption onto calcium carbonate only in the presence of calcium ions suggesting a contribution of an ion-bridging mechanism. Adsorption of all studied mono-functional surfactants is fully reversible and, consequently not representative of asphaltenes. Multifunctional compounds, i.e., polymers, demonstrate irreversible, asphaltene-like, adsorption. We studied adsorption of carbohydrates decorated with individual amines and quaternary ammonia functional groups. The carbohydrates with amine functional groups adsorb irreversibly on calcium carbonate and silica in all tested brines with pH up to 10. Therefore, a lower base number (BN) in crude oils indicates a higher potential for LSW. Our findings demonstrate the proof of concept that contribution of different functional groups to asphaltene adsorption/deposition can be studied using functionalized water-soluble polymers. This framework is useful for assessment of adsorption strength vs. number of active groups as well as screening of efficient detachment process of asphaltenic crude oils from rock surface
  • Interfacial Viscoelasticity in Crude Oil-Water Systems to Understand Incremental Oil Recovery

    Saad, Ahmed M.; Aime, Stefano; Mahavadi, Sharath C.; Song, Yi-Qiao; Patzek, Tadeusz; Weitz, David (Society of Petroleum Engineers, 2020-10-21) [Conference Paper]
    Improved oil recovery from asphaltenic oil reservoirs may provide the world with a significant source of lower-cost energy over many decades. However, the mechanisms through which the surface-active components in crude oil, such as asphaltenes and organic acids, affect incremental oil production are still unclear. In this study, we investigate crude oil/water interfacial films using shear and dilational rheology for mechanical properties and Fourier-Transform Infrared Spectroscopy (FTIR) to better understand its molecular species present at the interface that contribute to the development of viscoelastic behaviors. Dilational rheology has proven to be more sensitive to early time development of elasticity. In contrast, shear rheology provided more insights regarding the formation of elastic films at the macroscopic scale and late time interfacial changes. The presence of salts such as sodium chloride in the aqueous phase played a critical role in altering the dynamics of both the rheological properties development and the interfacial tension.
  • Assessment of polymer-induced formation damage using microfluidics

    Sugar, Antonia; Torrealba, Victor; Buttner, Ulrich; Hoteit, Hussein (Society of Petroleum Engineers, 2020-10-21) [Conference Paper]
    Polymers have been successfully deployed in the oil&gas industry in various field implementations, including mobility control in waterflood, flow divergence, and well conformance control. However, lab and field applications of polymer injections often encounter polymer-induced formation damage related to pore-throat clogging from polymer entrapments, leading to permeability reduction. This phenomenon manifests as a loss of injectivity, which can diminish the recovery performance. The first principles of polymer interaction with porous rocks are poorly understood. In this work, we use microfluidics to assess formation damage induced by polymer flood. Microfluidic techniques offer convenient tools to observe polymer flow behavior and transport mechanisms through porous media. The microfluidic chips were designed to mimic the pore-size distribution of oil-bearing conventional reservoir rocks, with pore-throats ranging from 1 to 10 µm. The proposed fabrication techniques enabled us to transfer the design onto a silicon wafer substrate, through photolithography. The constructed microfluidic chip, conceptually known as "Reservoir-on-a-Chip", served as a two-dimensional flow proxy. With this technique, we overcome the inherent complexity of the three-dimensional aspects of porous rocks to study the transport mechanisms occurring at the pore-scale. We performed various experiments to assess the mechanisms of polymer-rock interaction. The polymer flow behavior was compared to that of the water-flood baseline. Our observations showed that prolonged injection of polymer solutions could clog pore-throats of sizes larger than the measured mean polymer-coil size, which is consistent with lab and field observations. This finding highlights a major limitation in some polymer screening workflows in the industry that suggest selecting the candidate polymers based solely on their molecular size and the size distribution of the rock pore-throats. This work emphasizes the need for careful core-flood experiments to assess polymer entrapment mechanisms and their implication on short- and long-term injectivity.
  • Electrification at water–hydrophobe interfaces

    Nauruzbayeva, Jamilya; Sun, Zhonghao; Gallo Junior, Adair; Ibrahim, Mahmoud; Santamarina, Carlos; Mishra, Himanshu (Nature Communications, Springer Science and Business Media LLC, 2020-10-20) [Article]
    Abstract The mechanisms leading to the electrification of water when it comes in contact with hydrophobic surfaces remains a research frontier in chemical science. A clear understanding of these mechanisms could, for instance, aid the rational design of triboelectric generators and micro- and nano-fluidic devices. Here, we investigate the origins of the excess positive charges incurred on water droplets that are dispensed from capillaries made of polypropylene, perfluorodecyltrichlorosilane-coated glass, and polytetrafluoroethylene. Results demonstrate that the magnitude and sign of electrical charges vary depending on: the hydrophobicity/hydrophilicity of the capillary; the presence/absence of a water reservoir inside the capillary; the chemical and physical properties of aqueous solutions such as pH, ionic strength, dielectric constant and dissolved CO2 content; and environmental conditions such as relative humidity. Based on these results, we deduce that common hydrophobic materials possess surface-bound negative charge. Thus, when these surfaces are submerged in water, hydrated cations form an electrical double layer. Furthermore, we demonstrate that the primary role of hydrophobicity is to facilitate water-substrate separation without leaving a significant amount of liquid behind. These results advance the fundamental understanding of water-hydrophobe interfaces and should translate into superior materials and technologies for energy transduction, electrowetting, and separation processes, among others.
  • Text Analysis Reveals Major Trends in Exploration Geophysics

    Eltsov, Timofey; Yutkin, Maxim; Patzek, Tadeusz (Energies, MDPI AG, 2020-09-02) [Article]
    Evolution of professional language reveals advances in geophysics: researchers enthusiastically describe new methods of surveying, data processing techniques, and objects of their study. Geophysicists publish their cutting-edge research in the proceedings of international conferences to share their achievements with the world. Tracking changes in the professional language allows one to identify trends and current state of science. Here, we explain our text analysis of the last 30 annual conferences organized by the Society of Exploration Geophysicists (SEG). These conferences are among the largest geophysical gatherings worldwide. We split the 21,864 SEG articles into 52 million words and phrases, and analyze changes in their usage frequency over time. For example, we find that in 2019, the phrase “neural network” was used more often than “field data.” The word “shale” became less commonly used, but the term “unconventional” grew in frequency. An analysis of conference materials and metadata allows one to identify trends in a specific field of knowledge and predict its development in the near future.
  • A Physics Based Model of Enhanced Gas Production in Mudrocks

    Haider, Syed; Patzek, Tadeusz (American Association of Petroleum Geologists, 2020-08-20) [Conference Paper]
    Gas flow in mudrocks depends on the complex, multiscale connectivity among nanopores, microfractures and macrofractures. Hydraulic fractures stimulate reservoir volume near a horizontal well and create other fractures at all scales. Elsewhere, we have described the Stimulated Reservoir Volume (SRV) as a fractal with its own fracture network that accesses the organic-rich matrix. In the practically impermeable mudrock, the known volume of fracturing water (and proppant) must create an equal volume of fractures at all scales. Thus, we can constrain the physical structure of SRV, i.e., the number of macrofractures and surface area created after hydrofracturing. Nanopores in the organic matrix act as the source of almost all gas. Here, we present a comprehensive, physics-based microscale model of (a) the increased permeability to gas flow in a mudrock and (b) the effects of smallest nanopores on well production rates and gas storage capacity in this mudrock.
  • Shale Reservoir Simulation in Basins with High Pore Pressure and Small Differential Stress

    Arias, Daniela (2020-08) [Thesis]
    Advisor: Patzek, Tadeusz
    Committee members: Hoteit, Hussein; Finkbeiner, Thomas; Klimkowski, Lukasz
    Hydrocarbon production from mudrock (“shale”) reservoirs is fundamental in the global energy supply. Extracting commercial amounts of hydrocarbons from shale plays requires a combination of horizontal well drilling, hydraulic fracturing, and multi-stage completions. This technology creates conductive hydrofractures that may interact with pre-existing natural fractures and bedding planes. Microseismic studies and field pilots have uncovered evidence of complex hydrofracture geometries that can lead to unsatisfactory wellbore flow performance. This study examines the effects of three hydrofracture geometries (”scenarios”) on wellbore production in overpressured shale oil reservoirs using a commercial reservoir simulator (CMG IMEX). The first scenario is our reference case. It comprises ideal ized and vertical hydrofractures. The second scenario has an orthogonal hydrofracture network made up of vertical hydrofractures with perpendicular secondary fractures. The third scenario has vertical hydrofractures with horizontal bedding plane frac tures. We generated additional simulation models that aim to capture the effect on hydrocarbon production of different fracture properties, such as natural fracture ori entation and spacing, number of hydrofractures per stage, number of perpendicular secondary fractures and horizontal fractures, and fracture closure mechanism. The results show that ideal planar fractures are an oversimplification of the hydrofracture geometry in anisotropic shale plays. They fail to represent the complex geometry in reservoir simulation and lead to unexpected hydrocarbon production forecasting. They also show that the generation of unpropped horizontal fractures harms hydro carbon productivity, while perpendicular secondary fractures enhance initial reservoir 5 fluid production. The generation of horizontal hydrofractures is a particular scenario that may occur in reservoirs with high pore pressure and transitional strike-slip to reverse faulting regime. These conditions have been reported in unconventional source rock plays, like the Marcellus shale in northeast Pennsylvania and southwest Virginia, and the Tuwaiq Mountain formation in the Jafurah Basin in Saudi Arabia. Our findings reveal that the presence of horizontal hydrofractures might reduce the cumulative hydrocarbon production by 20%, and the initial hydrocarbon production by 55% compared to the reference case. Our work shows unique reservoir simulations that enable us to assess the impact of different variables on wellbore production performance and understand the effects of varied hydrofracture geometries on hydrocarbon production.
  • Planetary Health for the Arabian Peninsula: The Environmental Limits of Human Population.

    Mitchell, Philip M. (2020-07) [Thesis]
    Advisor: Patzek, Tadeusz
    Committee members: Al Afifi, Abdulkader; Sarathy, Mani
    Human society can be thought of as a heat engine that is powered by fossil fuel and sunlight. The free energy that fossil fuels provide has enabled the development of our modern global human civilization and has artificially raised the human carrying capacity of the planet. Here, I discuss the roots of human population theory in the context of environmental limits, and argue that examining this issue is an essential matter of public health. The Arabian Peninsula is particularly vulnerable to the decline of fossil fuels. Historical records are examined to determine the distribution of population before the fossil fuel age. Then, an agent-based model is developed to examine the increase of carrying capacity and development of trade networks resulting from fossil fuel production. The carrying capacity of the Arabian Peninsula without fossil fuels is between 2.5-6 million people.
  • The Potential for CO2 Disposal in Western Saudi Arabia: The Jizan Group Basalts

    Torres, Jose Eduardo Abreu (2020-07) [Thesis]
    Advisor: Afifi, Abdulkader M.
    Committee members: Hoteit, Hussein; Van der Zwan, Froukje M.; Arkadakskiy, Serguey V.
    This thesis evaluates the technical feasibility of carbon mineralization of industrial CO2 emissions into Oligocene volcanic rocks of the Jizan Group under the Red Sea coastal plain in southwest Saudi Arabia. This area contains several industrial sources of CO2 emissions such as power plants and refineries. The Jizan Group are a thick sequence of basaltic lavas and fragmental rocks which are intruded by coeval subvolcanic basalt dikes, layered gabbros, and granite in the southern part of the Red Sea coastal plain. It outcrops along the eastern foothills of the coastal plain, and dips under Miocene and younger sedimentary rocks towards the coast. It formed in a continental rift environment during the initial stages of separation of Arabia from Africa (Schmidt et al, 1982). The volcanics of the Jizan Group are located close to several CO2 sources and to a supply of seawater needed for co-injection with CO2. Successful carbonate precipitation from rocks reacting with CO2 dissolved in water is highly dependent on several technical and environmental factors. The most significant constraint of this process is the need for CO2 sources to be located near water sources and disposal sites (including igneous complexes with the right mineralogical setting, rich in divalent metal cations such as Ca+2, Mg+2 and Fe+2). Basaltic rocks are the most promising type of rock to dispose of CO2 by this process, due to their high abundance of divalent metal cations. This study concludes that the Jizan Group in the subsurface is technically suitable for CO2 disposal by the CarbFix process due to the favorable combination of the following factors: its predominantly basaltic composition, having sufficient thickness of basalts that are saturated with connate waters, the availability of surface and subsurface data, favorable subcrop geometry under the coastal plain, its location near major fixed sources of CO2 emissions, and availability of seawater needed for injection. However, there are risks that need to be better evaluated, particularly the fracture permeability of the Jizan Group basalts and subvolcanic dikes, and their reactivity with CO2 due to hydrothermal alteration of the basalts. This study identifies the general area east of Jizan Economic City as a potential site for the disposal of CO2. Additional sites are possible between Jizan and Jeddah but are subject to greater geological uncertainty from incomplete subsurface data.

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