scholarly journals Mechanical zonation of rock properties and the development of fluid migration pathways: implications for enhanced geothermal systems in sedimentary-hosted geothermal reservoirs

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Oladoyin Kolawole ◽  
Ion Ispas ◽  
Folarin Kolawole ◽  
Christophe Germay ◽  
John D. McLennan
Keyword(s):  
Mechanical Properties ◽  
Hydrothermal Fluid ◽  
Sedimentary Basins ◽  
Geothermal Reservoir ◽  
Fluid Migration ◽  
Fluid Circulation ◽  
Hydraulic Stimulation ◽  
Mean Values ◽  
The Past ◽  
Mechanical Stratigraphy

AbstractOil and gas operations in sedimentary basins have revealed the occurrence of significant temperature anomalies at depth, raising the possibility of major geothermal resource potential in the sedimentary sequences. The efficient development of such a resource may require enhancement by hydraulic stimulation. However, effective stimulation relies on an initial assessment of in situ mechanical properties and a model of the rock response. Here, we examine the distribution of mechanical properties (unconfined compressive strength, UCS; ultrasonic velocity-derived Poisson ratio, ν; and, scratch toughness, Ks) along the cored interval of a sedimentary formation with a known low-to-medium temperature geothermal anomaly in the Permian Basin, U.S. Our results reveal the presence of mechanical stratigraphy along the core, demonstrated by the alternation of distinct soft–hard (i.e.,less stiff-to-stiff) mechanical zone couplets composed of: (1) mechanically softer 0.17-m-thick Zone-A and 0.18-m-thick Zone-C with mean values of UCS = 110 MPa, ν = 0.25, Ks = 1.89 MPa·√m; and (2) mechanically harder 0.41-m-thick Zone-B and 0.15-m-thick Zone-D which show mean values of UCS = 166 MPa, ν = 0.22, and Ks = 2.87 MPa·√m. Although X-ray diffraction analyses of the samples suggest that the entire rock matrix is dominated by dolomite, the harder zones show an abundance of quartz cement (> 30%) and relatively lower phyllosilicate mineral content (< 2%) than the softer zones. Further, we observe that the mechanically harder zones have the greatest occurrences and thicknesses of hydrothermal alterations (anhydrite veins and nodules), indicating that the rock had experienced hydrothermal fluid circulation (basinal brines) in the past. We infer that the mechanical stratigraphy most likely influenced the spatial clustering of fractures that facilitated hydrothermal fluid migration in the past, and provides insight that is relevant for the exploitation of geothermal energy resources in sedimentary basins. We suggest that the harder zones or formation intervals with higher ratios of the hard zones relative to soft zones represent viable targets for hydraulic stimulation of a sedimentary-hosted geothermal reservoir, both for the emplacement of new fractures and the linkage of pre-existing fractures to allow efficient fluid circulation. Our findings in this study provide insight that is relevant for understanding the complexity of pre-existing mechanical heterogeneity in sedimentary-hosted geothermal reservoir targets in other places.

Mechanical Zonation of Rock Properties and the Development of Hydrothermal Fluid Circulation Pathways: Implications for Enhanced Geothermal Systems

2020 ◽  
Author(s):  
Oladoyin Kolawole ◽  
Ion Ispas ◽  
Folarin Kolawole ◽  
Christophe Germay ◽  
John D McLennan
Keyword(s):  
Mechanical Properties ◽  
Hydrothermal Fluid ◽  
Sedimentary Basins ◽  
Geothermal Reservoir ◽  
Rock Properties ◽  
Initial Assessment ◽  
Fluid Circulation ◽  
Hydraulic Stimulation ◽  
Stimulation Of

Abstract Oil and gas operations in sedimentary basins have revealed significant temperatures at depth, raising the possibility of major geothermal resource potential in the sedimentary sequences. The efficient development of such a resource may require enhancement by hydraulic stimulation. However, effective stimulation relies on an initial assessment of in-situ mechanical properties and a Discrete Fracture Network (DFN) model of the rock response. Here, we examine the distribution of mechanical properties (unconfined compressive strength, UCS ; ultrasonic velocity-derived Poisson ratio, ν; and, scratch-derived fracture toughness, K s ) along the cored interval of a sedimentary formation with a known geothermal anomaly in the Permian Basin, U.S. Our results reveal the mechanical heterogeneity of the rock, demonstrated by four distinct alternating mechanical zones, which include: (1.) mechanically weaker 0.17 m-thick Zone-A and 0.18 m-thick Zone-C with mean UCS = 110 MPa, ν = 0.25, K s = 1.89 MPa·√m; and (2.) mechanically stronger 0.41 m-thick Zone-B and 0.15 m-thick Zone-D which show mean UCS = 166 MPa, ν = 0.22, and K s = 2.87 MPa·√m. Although X-ray Diffraction analyses of the samples suggest that the entire rock matrix is dominated by dolomite, the stronger zones show a higher abundance of quartz (>30%) and relatively lower phyllosilicate mineral content (<2%) than the weaker zones. Further, we observe that the mechanically stronger zones have the greatest occurrences of hydrothermal alterations (anhydrite veins and nodules ), indicating that the cored interval had experienced hydrothermal fluid circulation in the past. We infer that the denser clustering of fractures in the stronger zones which facilitated the hydrothermal vein development was due to the influence of mechanical stratigraphy on the brittle deformation and alteration of the sedimentary-hosted hydrothermal reservoir. Thus, we suggest that the stronger zones represent viable targets for hydraulic stimulation of a geothermal reservoir, both for the emplacement of new fractures and the linkage of pre-existing fractures. Our findings in this study provide an analog for hydraulic stimulation of viable geothermal reservoir targets at higher in-situ temperatures and higher geothermal gradients.

scholarly journals Understanding ion-induced assembly of cellulose nanofibrilllar gels through shear-free mixing and in situ scanning-SAXS

2021 ◽  
Author(s):  
Tomas Rosén ◽  
Ruifu Wang ◽  
HongRui He ◽  
Chengbo Zhan ◽  
Shirish Chodankar ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Building Block ◽  
Cellulose Nanofibrils ◽  
Advanced Materials ◽  
The Past

During the past decade, cellulose nanofibrils (CNFs) have shown tremendous potential as a building block to fabricate new advanced materials that are both biocompatible and biodegradable. The excellent mechanical properties...

The Structure and Mechanical Properties of Aluminum Cellular Metal With Periodic Cubic Cells

2016 ◽  
Author(s):  
Xiaobing Dang ◽  
Ruxu Du ◽  
Kai He ◽  
Qiyang Zuo
Keyword(s):  
Mechanical Properties ◽  
Relative Density ◽  
Sheet Metal ◽  
Light Weight ◽  
Practical Applications ◽  
Sheet Metal Stamping ◽  
High Stiffness ◽  
The Past ◽  
Cellular Metal ◽  
Metal Stamping

As a light-weight material with high stiffness and strength, cellular metal has attracted a lot of attentions in the past two decades. In this paper, the structure and mechanical properties of aluminum cellular metal with periodic cubic cells are studied. The aluminum cellular metal is fabricated by sheet metal stamping and simple adhesion. Two sizes of specimens with cell sizes of 3mm and 5mm are fabricated. Their relative density and mechanical properties are tested by means of experiments. The results show that the cubic-cell cellular metal has high and predictable strength and hence, can be used for many practical applications.

scholarly journals Roles of Lanthanum and Cerium in Grain Refinement of Steels during Solidification

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 884 ◽  
Author(s):  
Yunping Ji ◽  
Ming-Xing Zhang ◽  
Huiping Ren
Keyword(s):  
Mechanical Properties ◽  
Grain Refinement ◽  
Rare Earths ◽  
Heterogeneous Nucleation ◽  
The Past ◽  
Cast Steels ◽  
Steel Castings ◽  
Similarity And Difference

Refinement of as-cast structures is one of the most effective approaches to improve mechanical properties, formability, and surface quality of steel castings and ingots. In the past few decades, addition of rare earths (REs), lanthanum and cerium in particular, has been considered as a practical and effective method to refine the as-cast steels. However, previous reports contained inconsistent, sometime even contradictory, results. This review summaries the major published results on investigation of the roles of lanthanum or/and cerium in various steels, provides reviews on the similarity and difference of previous studies, and clarifies the inconsistent results. The proposed mechanisms of grain refinement by the addition of lanthanum or/and cerium are also reviewed. It is concluded that the grain refinement of steels by RE additions is attributed to either heterogeneous nucleation on the in-situ formed RE inclusions, a solute effect, or the combined effect of both. The models/theories for evaluation of heterogeneous nucleation potency and for solute effect on grain refinement of cast metals are also briefly summarized.

scholarly journals Quantifying sea surface temperature ranges of the Arabian Sea for the past 20 000 years

2011 ◽  
Vol 7 (4) ◽  
pp. 1337-1349 ◽  
Author(s):  
G. M. Ganssen ◽  
F. J. C. Peeters ◽  
B. Metcalfe ◽  
P. Anand ◽  
S. J. A. Jung ◽  
...  
Keyword(s):  
Arabian Sea ◽  
Isotope Composition ◽  
Planktonic Foraminifera ◽  
Sediment Cores ◽  
Maximum Temperature ◽  
Physical Parameters ◽  
Seasonal Temperature ◽  
Mean Values ◽  
The Past ◽  
Temperature Ranges

Abstract. The oxygen isotopic composition of planktonic foraminifera tests is one of the widest used geochemical tools to reconstruct past changes of physical parameters of the upper ocean. It is common practice to analyze multiple individuals from a mono-specific population and assume that the outcome reflects a mean value of the environmental conditions during calcification of the analyzed individuals. Here we present the oxygen isotope composition of individual specimens of the surface-dwelling species Globigerinoides ruber and Globigerina bulloides from sediment cores in the Western Arabian Sea off Somalia, inferred as indicators of past seasonal ranges in temperature. Combining the δ18O measurements of individual specimens to obtain temperature ranges with Mg/Ca based mean calcification temperatures allows us to reconstruct temperature extrema. Our results indicate that over the past 20 kyr the seasonal temperature range has fluctuated from its present value of 16 °C to mean values of 13 °C and 11 °C for the Holocene and LGM, respectively. The data for the LGM suggest that the maximum temperature was lower, whilst minimum temperature remained approximately constant. The rather minor variability in lowest summer temperatures during the LGM suggests roughly constant summer monsoon intensity, while upwelling-induced productivity was lowered.

scholarly journals A bio-based phosphaphenanthrene-containing derivative modified epoxy thermosets with good flame retardancy, high mechanical properties and transparency

RSC Advances ◽  
2021 ◽  
Vol 11 (49) ◽  
pp. 30943-30954
Author(s):  
Wei Peng ◽  
Yu-xuan Xu ◽  
Shi-bin Nie ◽  
Wei Yang
Keyword(s):  
Mechanical Properties ◽  
Flame Retardant ◽  
Flame Retardancy ◽  
Epoxy Resins ◽  
Flame Retardants ◽  
The Past ◽  
Phosphorus Containing ◽  
Modified Epoxy

Phosphorus-containing flame retardants have received huge interest for improving the flame retardant behavior of epoxy resins (EP) over the past few decades.

scholarly journals Fresh and Mechanical Properties of Self-Consolidating Concrete Incorporating Silica Fume and Metakaolin

2021 ◽  
Author(s):  
Syed Ahmed
Keyword(s):  
Mechanical Properties ◽  
Construction Industry ◽  
Silica Fume ◽  
High Flow ◽  
Self Consolidating Concrete ◽  
Supplementary Cementing Materials ◽  
The Past

Self-consolidating concrete (SCC) has been gaining greater interest over the past decades with its excellent offerings of efficiency, beauty, and savings. Due to its high flow ability, resistance to bleeding, and non-segregating properties, SCC holds tremendous potential for use in the construction industry. SCC requires no vibration and can fill capacities, including the ones with even the most congested reinforcements. Since SCC can be obtained by incorporating supplementary cementing materials (SCMs) such as silica fume and metakaolin. It is crucial to develop and test different SCC mixtures with different volumes of SCMs to evaluate fresh and mechanical properties. Although silica fume is used in the production of SCC, the use of metakaoline in SCC is new. In this project, eleven SCC mixtures having different volumes of silica fume and metakaolin are developed. In addition, the influence of the above mentioned pozzolans (silica fume and metakaolin) on the fresh and mechanical properties are analyzed. Recommendations on fresh and mechanical properties of silica fume and metakaoline based SCC mixtures are also provided.

scholarly journals Porcelain enamel coatings, from the past to the future: solved and unsolved issues for the improvement of their mechanical properties.

2020 ◽  
Author(s):  
Stefano Rossi ◽  
Francesca Russo
Keyword(s):  
Mechanical Properties ◽  
Industrial Revolution ◽  
Chemical Degradation ◽  
Protective Properties ◽  
The Past ◽  
Enhanced Resistance ◽  
Mechanical Study ◽  
The Future ◽  
Ancient Times

Porcelain enamel coatings have their origins in ancient times when they were mainly used for decorative and ornamental purposes. From the industrial revolution onwards, these coatings have started to be used also as functional layers, ranging from home applications up to the use in high-technological fields, such as in chemical reactors. The excellent properties of enamel coatings, such as fire resistance, protection of the substrate from corrosion, resistance to atmospheric and chemical degradation, mainly depend and originate from the glassy nature of the enamel matrix itself. On the other side, the vitreous nature of enamel coatings limits their application in many fields, where mechanical stress and heavy abrasion phenomena could lead to nucleation and propagation of cracks inside the material, thus negatively affecting the protective properties of this coating. Many efforts have been made to improve the abrasion resistance of enamelled materials. On this regard, researchers showed encouraging results and proposed many different improvement approaches. Now it is possible to obtain enamels with enhanced resistance to abrasion. Differently, the investigation of the mechanical properties of enamel coatings remains a poorly studied topic. In the literature, there are interesting methodological ideas, which could be successfully applied to the mechanical study of enamelled materials and could allow to have further insights on their behaviour. Thus, the path that should be followed in the future includes the mechanical characterization of these coatings and the search for new solutions to address their brittle behaviour.

scholarly journals Development of PLA Fibers as an Antimicrobial Agent with Enhanced Infection Resistance using Electrospinning/Plasma Technology

2020 ◽  
Author(s):  
Abdelrahman Mahmoud ◽  
Mohammed Naser ◽  
Mahmoud Abdelrasool ◽  
Khalid Jama ◽  
Mohamed Hussein ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Three Dimensional ◽  
Plasma Technology ◽  
Energy Increase ◽  
The Past ◽  
Unit Cells ◽  
Infection Resistance ◽  
Dimensional Shape ◽  
Fiber Dimensions ◽  
Three Dimensional Shape

Humans are vulnerable and easily prone to all kind of injuries, diseases, and traumas that can be damaging to their tissues (including its building unit, cells), bones, or even organs. Therefore, they would need assistance in healing or re-growing once again. Medical scaffolds have emerged over the past decades as one of the most important concepts in the tissue-engineering field as they enable and aide the re-growth of tissues and their successors. An optimal medical scaffold should be addressing the following factors: biocompatibility, biodegradability, mechanical properties, scaffold architecture/porosity, precise three-dimensional shape and manufacturing technology. There are several materials utilized in the fabrication of medical scaffolds, but one of the most extensively studied polymers is polylactic acid (PLA). PLA is biodegradable thermoplastic aliphatic polyester that is derived from naturally produced lactic acid. PLA is characterized with its excellent mechanical properties, biodegradability, promising eco-friendly, and excellent biocompatibility. PLA can be fabricated into nanofibers for medical scaffolds used through many techniques; electrospinning is one of the widely used methods for such fabrication. Electrospinning is a favorable technique because in the preparation of scaffolds, some parameters such as fiber dimensions, morphology, and porosity are easily controlled. A problem that is associated with medical scaffolds, such as inflammation and infection, was reported in many cases resulting in a degradation of tissues. Therefore, a surface modification was thought of as a needed solution which mostly focuses on an incorporation of extra functionalities responsible for the surface free energy increase (wettability). Therefore, plasma technique was a favorable solution for the surface treatment and modification. Plasma treatment enables the formation of free radicals. These radicals can be easily utilized for grafting process. Subsequently, ascorbic acid (ASA) could be incorporated as anti-inflammatory and anti-infection agent on the plasma pretreated surface of scaffolds.

On Bayesian model selection for INGARCH models viatrans-dimensional Markov chain Monte Carlo methods

2021 ◽  
pp. 1471082X2110347
Author(s):  
Panagiota Tsamtsakiri ◽  
Dimitris Karlis
Keyword(s):  
Time Series ◽  
Model Selection ◽  
Bayesian Model ◽  
Linear Models ◽  
Simulation Experiment ◽  
Mean Values ◽  
The Past ◽  
Competing Models ◽  
Selection For ◽  
Log Linear

There is an increasing interest in models for discrete valued time series. Among them, the integer autoregressive conditional heteroscedastic (INGARCH) is a model that has found several applications. In the present article, we study the problem of model selection for this family of models. Namely we consider that an observation conditional on the past follows a Poisson distribution where its mean depends on its past mean values and on past observations. We consider both linear and log-linear models. Our purpose is to select the most appropriate order of such models, using a trans-dimensional Bayesian approach that allows jumps between competing models. A small simulation experiment supports the usage of the method. We apply the methodology to real datasets to illustrate the potential of the approach.

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