scholarly journals Cement / rock interaction in geothermal wells

2021 ◽  
Author(s):  
◽  
João Ricardo Marques Conde da Silva
Keyword(s):  
Driving Forces ◽  
Volcanic Rocks ◽  
Drilling Mud ◽  
Rock Permeability ◽  
Rock Interaction ◽  
Geothermal Wells ◽  
Physical Interactions ◽  
Geothermal Environments ◽  
Cement Formulation ◽  
The Way

<p>One of the main issues associated with the exploitation of geothermal energy is the durability of the cement that is used downhole to cement the steel casing to the formation. Cement durability can have a major impact on the lifetime of geothermal wells, which do not usually last as long as desirable. The cement formulations used in the construction of geothermal wells are designed to provide mechanical support to the metallic well casings and protect them against the downhole harsh environment, which often leads to corrosion. This research is focused on the way that these formulations interact with the surrounding rock formation in geothermal environments, and aims to understand whether these are likely to affect the cement durability and, consequently, the geothermal well lifetime. The experimental work in this thesis consists of examining the changes in the interfacial transition zone (ITZ) that forms between geothermal cements and the volcanic rocks, after hydrothermal treatment. Holes were drilled in blocks of volcanic rocks and cement slurries with distinct formulations were poured into the cavities. The assemblages were autoclaved under typical geothermal conditions. The main variables under study were the cement formulation, the temperature of curing (150°C and 290°C), the presence of drilling mud, CO₂ exposure and the type of rock. The results show that with all the Portland cement based systems a series of chemical reactions occur at the interface between the cement and the rock, the ITZ, where migration of Ca²⁺ and OH⁻ ions occurs from the cement into the rock pores. These reactions are ongoing, which occur faster during the first days/few weeks of curing, mostly driven by physical process of cement movement into the rock, followed by a slower second stage, controlled mostly by chemical driving forces. This work highlights the interdependence between the chemical and physical interactions between geothermal cements and volcanic rocks which are complex. Variables such as temperature and time of curing and silica addition affect the cement phases that form, while the amount of amorphous silica and rock permeability dictate the extent of rock interaction. The presence of carbon dioxide influences the extent of rock/cement interaction and this can be controlled by the rock permeability and cement formulation. Consequently, most of the above mentioned variables were found to have an impact on the geothermal cement durability, which depends on the way these factors are combined.</p>

scholarly journals Cement / rock interaction in geothermal wells

2021 ◽  
Author(s):  
◽  
João Ricardo Marques Conde da Silva
Keyword(s):  
Driving Forces ◽  
Volcanic Rocks ◽  
Drilling Mud ◽  
Rock Permeability ◽  
Rock Interaction ◽  
Geothermal Wells ◽  
Physical Interactions ◽  
Geothermal Environments ◽  
Cement Formulation ◽  
The Way

<p>One of the main issues associated with the exploitation of geothermal energy is the durability of the cement that is used downhole to cement the steel casing to the formation. Cement durability can have a major impact on the lifetime of geothermal wells, which do not usually last as long as desirable. The cement formulations used in the construction of geothermal wells are designed to provide mechanical support to the metallic well casings and protect them against the downhole harsh environment, which often leads to corrosion. This research is focused on the way that these formulations interact with the surrounding rock formation in geothermal environments, and aims to understand whether these are likely to affect the cement durability and, consequently, the geothermal well lifetime. The experimental work in this thesis consists of examining the changes in the interfacial transition zone (ITZ) that forms between geothermal cements and the volcanic rocks, after hydrothermal treatment. Holes were drilled in blocks of volcanic rocks and cement slurries with distinct formulations were poured into the cavities. The assemblages were autoclaved under typical geothermal conditions. The main variables under study were the cement formulation, the temperature of curing (150°C and 290°C), the presence of drilling mud, CO₂ exposure and the type of rock. The results show that with all the Portland cement based systems a series of chemical reactions occur at the interface between the cement and the rock, the ITZ, where migration of Ca²⁺ and OH⁻ ions occurs from the cement into the rock pores. These reactions are ongoing, which occur faster during the first days/few weeks of curing, mostly driven by physical process of cement movement into the rock, followed by a slower second stage, controlled mostly by chemical driving forces. This work highlights the interdependence between the chemical and physical interactions between geothermal cements and volcanic rocks which are complex. Variables such as temperature and time of curing and silica addition affect the cement phases that form, while the amount of amorphous silica and rock permeability dictate the extent of rock interaction. The presence of carbon dioxide influences the extent of rock/cement interaction and this can be controlled by the rock permeability and cement formulation. Consequently, most of the above mentioned variables were found to have an impact on the geothermal cement durability, which depends on the way these factors are combined.</p>

Associations Between Driving Forces to Adopt ICT and Benefits Derived from that Adoption in Medical Practices in Australia

2011 ◽  
pp. 652-668
Author(s):  
R. C. MacGregor ◽  
P. N. Hyland ◽  
C. Harvie
Keyword(s):  
Decision Making ◽  
Information And Communication Technology ◽  
Communication Technology ◽  
Driving Forces ◽  
Perceived Benefits ◽  
Medical Practices ◽  
The Past ◽  
Ict Adoption ◽  
Information And Communication ◽  
The Way

Information and Communication Technology (ICT) is today seen as a catalyst for change in the way work is carried out. Over the past decade there have been a number of studies examining both the decision-making behind ICT adoption (the driving forces for adoption) as well as the perceived benefits from that adoption. However, no studies have attempted to determine, or indeed map whether emphasis given to specific driving forces have manifested in differing perceptions of perceived benefits. The purpose of this chapter is to examine whether emphasis on particular driving forces for ICT adoption are associated with the perception of particular benefits. A study was undertaken amongst 198 Australian GPs. Results suggest that greater emphasis on improving communications gives rise to higher perceived benefits both in terms of communications and practice effectiveness, while emphasis on other drivers does not significantly alter the perception of benefits derived from adoption.

scholarly journals Surface and Groundwater Hydrochemistry of the Menengai Caldera Geothermal Field and Surrounding Nakuru County, Kenya

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3131 ◽  
Author(s):  
Nelly Montcoudiol ◽  
Neil M. Burnside ◽  
Domokos Györe ◽  
Nicholas Mariita ◽  
Thecla Mutia ◽  
...  
Keyword(s):  
Ionic Composition ◽  
Sampling Period ◽  
Geothermal Field ◽  
Wet Season ◽  
Lake Nakuru ◽  
Rock Interaction ◽  
Geothermal Wells ◽  
Groundwater Hydrochemistry ◽  
Hydrological System ◽  
Oxygen Isotopic

In order to assess the sustainability and impact of production from geothermal reservoirs on hydrological systems, a thorough understanding of local and regional hydrogeological systematics is a prerequisite. The Menengai Caldera in the Kenya Great Rift Valley is one of the largest explored geothermal fields in the country. This paper presents a hydrochemical investigation of the Menengai Caldera geothermal field and the ground and surface waters of the surrounding Nakuru County. Our results demonstrated a similar, sodium-alkaline dominated, ionic composition across all water types. Geothermal wells return the highest cation/anion concentrations and largely demonstrate a meteoric source from their δ18O and δ2H signature. Wells MW-09 (central part of the caldera), MW-18 (eastern part) and MW-20 (central part) showed a more evaporitic signature, closely matching with our own calculated Lake Evaporation Line, suggesting an increased mixing influence of Lake Nakuru waters. MW-09 also showed evidence of high-temperature oxygen isotopic exchange and significant water-rock interaction. Lake samples largely demonstrated seasonal shifts in ionic and isotopic values. Lake Nakuru ionic composition and isotopic values increased throughout the 12-month wet–dry–wet season sampling period. This correlated with a decrease in area which suggests a lessening of water inflow and facilitates increased evaporation. Groundwaters demonstrated clear evidence of mixing between meteoric, irrigation and lake waters. These observations enhanced the understanding of the hydrological system surrounding the Menengai Caldera and, when combined with future studies, will provide a powerful tool to assess the sustainability and impact of soon-to-be completed geothermal power production operations.

Traveling Policies: Hijacked in Central Asia

2005 ◽  
Vol 4 (1) ◽  
pp. 50-59 ◽  
Author(s):  
Iveta Silova
Keyword(s):  
Soviet Union ◽  
Education Reform ◽  
Central Asia ◽  
Driving Forces ◽  
Local Policy ◽  
Reform Agenda ◽  
The Soviet Union ◽  
Central Asian ◽  
National Boundaries ◽  
The Way

Since the collapse of the Soviet Union, Central Asian education reform discourses have become increasingly similar to distinctive Western policy discourses traveling globally across national boundaries. Tracing the trajectory of ‘traveling policies' in Central Asia, this article discusses the way Western education discourses have been hybridized in the encounter with collectivist and centralist cultures within post-socialist environments in Kazakhstan, Tajikistan, and Turkmenistan. In the context of international aid relationships, the article considers different motivations and driving forces for reforms, the way pre-Soviet and Soviet traditions are affirmed within the reforms, as well as how these reforms speak back to Western reform agenda. Emphasizing the historical legacy of Soviet centralist traditions, this article reveals how traveling policies have been ‘hijacked’ by local policy makers and used for their own purposes nationally.

Information and Communication Technology Policy in European Cities: A Comparative Approach

2002 ◽  
Vol 29 (5) ◽  
pp. 729-755 ◽  
Author(s):  
Galit Cohen ◽  
Peter Nijkamp
Keyword(s):  
Information And Communication Technology ◽  
Communication Technology ◽  
Technology Policy ◽  
Driving Forces ◽  
Qualitative Content Analysis ◽  
Comparative Approach ◽  
European Cities ◽  
Wide Range ◽  
Information And Communication ◽  
The Way

Information and communication technology (ICT) is widely accepted as a potentially favourable set of instruments, which may improve the welfare and competitiveness of nations and cities. Nowadays, both public and private actors aim to exploit the expected benefits of ICT developments. The authors seek to investigate the potential of ICT use at an urban level and, in particular, to shed more light on various factors that influence urban ICT policies in the public domain. First, a conceptual framework, designed to improve understanding of the driving forces of urban ICT policies, is outlined. It focuses on the way decisionmakers perceive their city, and shape their opinions about ICT; it addresses in particular the way these decisionmakers evaluate the importance of ICT for their city. Next, interviews with urban decisionmakers in different European cities in three countries (Austria, Spain, and the Netherlands) are used to analyse the complex relationship between perceived urban characteristics (for example, nature of problems and urban image), personal attitudes towards ICT, administrative features of the cities concerned, and perceptions of the relevance of ICT to the cities. The authors' main focus is on the identification of a possible systematic relationship between the aforementioned explanatory factors and urban decisionmakers' attitudes towards ICT policies. Understanding the decisionmakers' perceptions is an important step towards grasping the nature and substance of the policy itself, and may explain some of the variance among different cities. Because the ‘urban ICT’ discourse is still relatively new, an open-interview method is used to capture a variety of different views and perceptions on ICT and on the information age in the city. With the aid of qualitative content analysis, the interview results are transformed into a more systematic and comparable form. The results suggest that even interviewees from the same city may have a different understanding of their urban reality whereas, on the other hand, cities with different characteristics may appear to suffer from similar problems. Moreover, the authors found a wide range of attitudes toward ICT and its expected social impacts, although most of the interviewees appeared to be more sceptical than had been expected. The authors identified a clear need for a more thorough investigation of background factors and, therefore an approach originating from the field of artificial intelligence—rough-set analysis—was deployed to offer a more rigorous analysis. This approach helped in the characterisation and understanding of perceptions and attitudes regarding urban policies, problems, and images.

scholarly journals Hola Hola Tawusi Melek, Hola Hola Şehidêt Şingalê: Persecution and the Development of Yezidi Ritual Life

2016 ◽  
Vol 4 (2) ◽  
pp. 155-175 ◽  
Author(s):  
Eszter Spat
Keyword(s):  
Crucial Role ◽  
Driving Forces ◽  
Religious Life ◽  
Sacred Landscape ◽  
Profound Impact ◽  
Ritual Activity ◽  
The Way

Holidays and associated rituals have always played a crucial role in Yezidi religious life. The attack of ISIS on Yezidis and the subsequent displacement of more than half the community has had a profound impact on the way these holidays can be celebrated. The fact that the Sinjari Yezidi community has lost access to its sacred landscape, which is the traditional focus of much ritual activity, as well as a semi-official ban on any public form of rejoicing at a time of mourning, constitute a threat to the continuation of ritual life. However, contrary to expectations, Yezidi religious and ritual life has become more intense rather than declining in the wake of the ISIS attack. The driving forces behind this phenomenon are the need for supernatural help, new opportunities, and a sense of defiance. The daily mixing of the two communities, local Yezidis and Sinjari refugees, with diverse traditions, has also led to an enrichment of ritual life and a new awareness of the multiform nature of Yezidi traditions as people exchange and adopt new customs.Keywords: Yezidis; religion; rituals; ISIS; syncretism.Abstract in KurmanjiHola hola Tawûsî Melek, hola hola şehidêt Şingalê: Zulm û pêkhatina jiyana ayînî ya êzdîCejn û merasimên li wan rojên cejnan bi rê ve diçin hergav xwedanê roleke serekî bûne di jiyana dînî ya êzdiyan de. Êrîşa DAIŞê bi ser êzdiyan û koçberbûna zêdetir ji nîvê cemaeta êzdiyan li dû wê êrîşê tesîreke mezin li ser awayê pîrozkirina wan cejnan kiriye. Cemaeta êzdî ya Şingalê ji devera xwe ya pîroz qût bûye, ku piraniya çalakiyên dînî lê bi rê ve diçin, û herwiha qedexeyeke nîv-resmî li ser her çi awayekî xweşhaliyê heye di vê dema şînê de. Ev herdu eger gefeke mezin in li ser berdewamiya jiyana ayînî an dînî ya cemaetê. Ligel vê jî, ber’eksê ya ku mirov li bendê be, jiyana dînî û ayînî/merasimî ya êzdiyan li dû êrîşa DAIŞê lawaz neketiye, belkî kûrtir û berfirehtir bûye. Li pişt vê diyardeyê sebebên wek pêdiviya alîkariya xwedayî, îmkanên nû, û hesta berxwedanê hene. Têkilbûna herdu cemaetên êzdiyên xwecih û koçberên ji Şingalê, ku xwedanê nerîtên cuda ne, rê li ber dewlemendbûna qewareya merasiman vekiriye û her ku endamên cemaetan dikevine danûstandinê û dab û nerîtên nû dinasin têgihiştineke nû ya tebîetê pir-şiklî ya nerîtên êzdî jî li bal wan peyda dibe.Abstract in Sorani

scholarly journals Challenges to Extension Programming

2005 ◽  
Vol 15 (1) ◽  
pp. 177-180 ◽  
Author(s):  
Raymond A. Cloyd
Keyword(s):  
Invasive Species ◽  
Driving Forces ◽  
New Technology ◽  
Ecological Impacts ◽  
Budget Cuts ◽  
Base Extension ◽  
Computer Based ◽  
Impact Of Technology ◽  
The Impact ◽  
The Way

The way extension specialists and educators conduct programs, such as workshops, and transfer information to their designated clientele, including homeowners, professionals, and specialty groups, has changed within the last decade due to merging departments, budget cuts, reduced operating funds, and lack of refilling vacant positions. These factors have resulted in a number of driving forces that influence the way extension specialists and educators perform their duties, such as accountability, regionalization of extension, impact of technology, and expanding expertise. To be accountable under today's standards, extension specialists and educators must document the impact, relevance, and effectiveness of their programs. Required documentation must include economic, environmental, and human development factors. The effect of downsizing in many states has led to regionalization, which involves sharing extension specialists and educators across state boundaries. Although there are concerns, such as funding issues and evaluation of extension specialists and educators among states, regionalization in general has resulted in collaborative efforts to organize workshops and produce regional publications that serve a wider clientele base. Extension specialists and educators need to use computer-based and electronic technology, such as teleconferencing and distance-education, to present effective programs and address a wider audience, which will reduce the amount of required travel time. Finally, extension specialists and educators need to keep abreast of issues, such as invasive species, and develop programs to increase awareness of the economic and ecological impacts of invasive species in order to effectively serve the clientele base. Extension specialists and educators will more effectively serve their clientele, justify the importance of extension programming, demonstrate extension as a valued resource to administrators, and deal with the challenges of financial constraint existing now and in the foreseeable future by documenting impact, using multi-state programming, adopting new technology, and keeping up with current issues.

Comparative study of chemical stimulation at geothermal wells in the carbonates of the upper jurassic in the Bavarian Molasse Basin

2021 ◽  
Author(s):  
Felicitas Kaplar ◽  
Thomas Baumann
Keyword(s):  
Mass Balance ◽  
Chloride Concentration ◽  
Upper Jurassic ◽  
Chemical Stimulation ◽  
Temporal Development ◽  
Drilling Mud ◽  
Short Term ◽  
Data Set ◽  
Pumping Tests ◽  
Geothermal Wells

&lt;p&gt;Chemical stimulation of geothermal wells to remove drilling mud and to increase the connection to the reservoir are state of the art. There is hardly any deep geothermal well in the carbonates of the upper jurassic in the pre alpine foreland basin which was not developed using one or more pulses of acid. Several tons of acid are injected into the borehole and followed by a chaser to push the acid into the reservoir. Given the wide use of chemical stimulation measures, mass balance data for the stimulation is rare. This might be due to a rather simple reaction mechanism and the assumption that there is a full stoichiometric reaction and all injected acid is recovered. The efficiency of the stimulation is assessed based on the hydraulic properties derived from the short-term pumping tests following the stimulation. This project compares the full mass balance for chemical stimulation measures and the temporal development of the concentration of relevant ions during the pumping test after stimulation. The data was collected at several sites with a temporal resolution of down to 30 mins. The data includes multiple stimulations as well as stimulation with varying acids and different setup. Using this data set we want to answer the questions whether the acid is fully recovered, whether the assumption of full stochiometric reaction is valid, whether there is a difference in the transport of reactive and conservative ions, what additional value a hydrochemical analysis could add and whether on-site measurements could substitute costly measurements. The evaluation shows a distinct behaviour of the temporal development of the chloride concentration (after stimulation with hydrochloric acid) which can be described by a bi-exponential fit. The fitting parameters of the two exponential terms are getting closer with each stimulation indicating a reduced heterogeneity along the accessible flow paths around the borehole. A comparison of the full scale analysis with on-site sensors was sometimes not possible because the sensors showed a drift during the experiment or were poorly calibrated. As calcium, magnesium, and chloride ion concentrations showed different behaviour, electrical conductivity is not able to cover the full development. The mass balance indicates that a full recovery of the injected acid might take significantly longer than the short term pumping tests. Hydrochemical monitoring provides additional and relevant data about the reservoir in the surrounding of the borehole and allows important predictions about the long-term behaviour, especially if the borehole is used as injection well. For routine applications improved sensors and fast (and cheap) on-site analysis is required.&lt;/p&gt;

Selective mineral dissolution and permeability enhancement of fractured volcanic rocks by chelating agent flooding in geothermal environments 

2021 ◽  
Author(s):  
Luis Salala ◽  
Noriaki Watanabe ◽  
Kaori Takahashi ◽  
Jose Erazo ◽  
Noriyoshi Tsuchiya
Keyword(s):  
Aqueous Solution ◽  
Geothermal Energy ◽  
Volcanic Rocks ◽  
Chelating Agent ◽  
Chemical Stimulation ◽  
Mineral Dissolution ◽  
High Concentration ◽  
Confining Stress ◽  
Permeability Enhancement ◽  
Geothermal Environments

&lt;p&gt;Chemical stimulation using high-concentration hydrofluoric and hydrochloric acids has been a classic method to enhance the permeability of a geothermal reservoir. Our research group has recently proposed a new chemical stimulation using a weakly acidic (moderate-reactivity) aqueous solution containing an environmentally friendly chelating agent to create voids, which are sustained under crustal stress, by selective mineral dissolution with preventing precipitation by chelation of metal ions. In the present study, we have conducted chelating agent flooding experiments using an aqueous solution of pH 4 containing readily biodegradable chelating agent (GLDA) on various types of fractured volcanic rocks at 200 &lt;sup&gt;o&lt;/sup&gt;C and effective confining stress of 15 MPa. The experiments have revealed fast permeability enhancement of up to approximately four times, from the initial value, in two hours. Further analyses have revealed phenocrysts of Fe-bearing minerals (ex. Hematite) dissolved faster than the groundmass of the rocks to create the voids. These results show the possibility of the new chemical stimulation.&lt;/p&gt;&lt;p&gt;Keywords: Chemical stimulation, Chelating agents, Geothermal energy, EGS&lt;/p&gt;

A A New Era of Social Enterprise? A Global Viewpoint

2020 ◽  
Vol 4 (1) ◽  
pp. 79-88
Author(s):  
Jamie Hasall ◽  
Roopinder Oberoi ◽  
Michael Snowden
Keyword(s):  
Social Enterprise ◽  
Driving Forces ◽  
Health Sector ◽  
Vital Role ◽  
The State ◽  
New Era ◽  
The Public ◽  
Global Pandemic ◽  
The World ◽  
The Way

The outbreak of Coronavirus across the world has fundamentally changed the way society functions. The pandemic has shifted the way a capitalist economy works for the state. Drastic measures have had to be put in place; for example, many countries have put extra investment into the health sector and generated support for people who cannot work due to the lockdown rules that have been implemented. More than ever before, the state is playing a vital role. Therefore, various institutions, from charities and non-government organisations, to the public/private sectors, are the driving forces in tackling this pandemic. The aim of this paper is to provide an overview of the ways forward and the ways in which social enterprise will be imperative in this global pandemic.

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