scholarly journals Influence of the Addition of Silica Nanoparticles on the Compressive Strength of Cement Slurries under Elevated Temperature Condition

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5493
Author(s):  
Anna Pikłowska ◽  
Jan Ziaja ◽  
Marcin Kremieniewski

Drilling ever deeper, and thus in increasingly difficult conditions, is associated with restrictive requirements that must be met by cement slurries. This implies the need to use advanced, innovative measures that will significantly improve the performance parameters of the cement slurry and cement stone. Due to its unique properties, an admixture of nanosilica improves the properties of the cement stone and allows for appropriate zone insulation. The article presents the results of strength tests of cement stone samples with the addition of silica nanoparticles deposited in an environment of increased temperature of 90 °C. In all three cases of modification with an admixture of nanosilica (type 1, 2 and 3, concentration 0.5%, 1% and 5%), the cement stone shows an improvement in mechanical properties, which is manifested by an increase in compressive strength. The most homogeneous results of strength measurements are for cement slurries with an admixture of type 3 nanosilica (the highest average strength: 132–149% in relation to the base sample). They show the smallest stretch marks and deviations from the average. The highest average increase in strength is for the sample with the addition of 1% nanosilica (on average 124% in relation to the base sample). This amount causes the greatest increase in strength with no significant deterioration of rheological parameters.

Nafta-Gaz ◽  
2021 ◽  
Vol 77 (5) ◽  
pp. 323-331
Author(s):  
Miłosz Kędzierski ◽  
◽  
Marcin Rzepka ◽  

The article presents the results of the influence of carbon nanotubes on the mechanical parameters of cement stones under high temperature and pressure conditions (150°C, 90 MPa). The tests used multi-walled carbon nanotubes (MWCNTs) with an external diameter of 10–20 nm and a length of 10–30 μm. Cement slurries contained 0.1% of CNTs bwoc (by the weight of cement). Laboratory tests of cement slurries were carried out at the Oil and Gas Institute – National Research Institute. The tests were carried out under conditions of increased pressure and temperature at 150°C, 90 MPa. Cement slurries were prepared on the basis of class G drilling cement. Developing recipes were guided by the requirements to be met by cement slurry for the cementing of casing in the conditions of high temperature and reservoir pressures. The densities of tested slurries ranged from 1900 kg/m3 to 2250 kg/m3 (slurries with the addition of hematite). The cement slurries were tested for density, fluidity, rheological parameters, filtration and thickening time. Compressive strength tests and measuring adhesion were carried out after 2, 7, 14 and 28 days. Cement slurry recipes with very good technological parameters were developed and after curing (after 28 days of hydration) had very high values of compressive strength, reaching up to 45 MPa. Cements were characterized by high values of adhesion to pipes reaching up 7 MPa after 28 days. The research showed significant information about possible applications of carbon nanotubes to modify the cement slurry under conditions of high temperature and pressure. The conducted tests confirmed that the addition of even small amounts of CNTs improves the mechanical parameters of the cement stone compared to the base sample without such addition, and also reduces the thickening time of cement slurries and reduces filtration. It is investigated that CNTs addition increases the viscosity and yield point of cement slurry. As a result, slurries with the addition of MWCNTs will more effectively displace the mud from the borehole and significantly affect the quality of cementation.


2016 ◽  
Vol 847 ◽  
pp. 510-518
Author(s):  
Zao Yuan Li ◽  
Hong Hua Liu ◽  
Xiao Yang Guo ◽  
Xiao Wei Cheng ◽  
Hong Juan Ou ◽  
...  

During shale gas well drilling and completion, the oil based muds (OBMs) would reduce the bonding strength of cement slurry by filter-cake and oil-wettability. At the same time, mixing cement slurry with the OBMs can lead to contamination, and subsequently creates significant problems, such as, reducing the normal thickening time and the compressive strength, and hence affecting the quality of the cementing of the shale gas well. Therefore in the present investigation, the mechanism of the interface displacement, wetting conversion and the contamination was explored by Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD), scanning electron microscope (SEM) and other methods. And then the new materials with the enhanced bonding strength and the contamination relieving by OBMs were obtained. The results showed that the chemical composition of filter-cake determined the properties of chemical preflush, the combined systems (LSS) efficiently flushed filter-cake and increased the bonding strength. It has been found that the reverse wetting agent (APG) has better reverse wetting properties than Tarim Oilfield current application system, which effectively changes the wettability of cementing surface from lipophilicity to hydrophilic. The OBMs and cement slurry mixing generated the emulsion structure and honeycomb structure, and the structures can affect the rheology and the strength of cement slurry; the contaminative relieve agent (SCW) can form a thin film on the surface of the cement stone, the film covers the hole and improves cement compressive strength, thus the SCW can relieve the contamination by OBMs.


2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Jianglin Zhu ◽  
Jiangxiong Wei ◽  
Qijun Yu ◽  
Mingbiao Xu ◽  
Yuwei Luo

Oil well cement is a type of natural brittle material that cannot be used directly in cementing operations. Fiber is a type of material that can effectively improve the strength and toughness of cement stone, and hybrid fiber materials can more effectively improve the performance of a cement sample. To overcome the natural defects of oil well cement, the new mineral fiber, i.e., wollastonite fiber, and common carbon fiber were used in oil well cement, and the micromorphology, mechanical properties, and stress-strain behavior of the cement were evaluated. The experimental results show that carbon fiber and wollastonite fiber are randomly distributed in the cement paste. The mechanical properties of the cement paste are improved by bridging and pulling out. The compressive strength, flexural strength, and impact strength of cement stone containing only carbon fiber or wollastonite fiber are higher than those of the pure cement, but too many fibers are not conducive to the development of mechanical properties. A mixture of 0.3% carbon fiber with 6% wollastonite fiber in oil well cement slurry results in a greater increase in compressive strength, flexural strength, and impact strength. In addition, compared with blank cement stone, the strain of the mixed cement stone increases substantially, and the elastic modulus decreases by 37.8%. The experimental results supply technical support for the design of a high-performance cement slurry system.


2011 ◽  
Vol 17 (1) ◽  
pp. 36-44 ◽  
Author(s):  
Lucyna Domagała

Structural lightweight aggregate concrete (SLWAC) is an alternative building material to normal-weight one, due to its ability to reach a relatively high compressive strength at still significantly lower density. Nevertheless, the application of lightweight aggregate instead of normal-weight one to concrete must result in deterioration of some characteristics of the composite. One of the methods of improving SLWAC properties is incorporation of fibers into concrete. This paper focuses on the influence of steel fibres on modification of properties of structural lightweight concrete with sintered fly ash aggregate. Two different concrete mixtures, producing various levels of matured composite density and compressive strength, were modified with three dosages of fibers: 30, 45 and 60 kg/m3. The applied amounts did not result in significant deterioration of the rheological parameters of concrete mixtures. Despite relatively low volume content of fibres, a considerable increase of flexural and tensile splitting strength was observed. Fibres also improved concrete shrinkage as well as post-peak deformability in uni-axial compression. The effect of steel addition on compressive strength proved to be dependent on specimen type. Nevertheless, it was not as crucial as in the case of the above characteristics. However, the modulus of elasticity of SLWAC was not affected by fibre addition. Santrauka Konstrukcinis su lengvaisiais užpildais betonas (SLWAC) yra normalaus svorio statybinių medžiagų alternatyva, turinti mažesnį tankį ir gebėjimą pasiekti gana didelį gniuždomąjį stiprį. Nepaisant to, lengvieji užpildai, naudojami vietoj normalaus svorio užpildų, realiai gali pabloginti kai kurias kompozito savybes. Vienas iš lengvojo betono SLWAC savybių tobulinimo būdų yra plieninių fibrų įterpimas į betono sudėtį. Šiame darbe aptariamas plieninių fibrų poveikis konstrukcinio lengvojo betono su lakiaisiais pelenais savybėms. Tikslui pasiekti buvo parinktos pagal tankį ir gniuždomąjį stiprį dvi skirtingos betono sudėtys su skirtingais (30, 45 ir 60 kg/m3) plieninių fibrų tankiais. Paruošti bandiniai buvo naudoti gniuždomajam stipriui ir kitoms savybėms nustatyti. Tyrimų rezultatai parodė, kad plieninių fibrų priedas nepablogino reologinių betono mišinio rodiklių. Nepaisant palyginti mažo fibrų kiekio, labai padidėjo bandinių lenkiamasis ir tempiamasis stipris. Fibros taip pat pagerino deformacines betono savybes. Gauto kompozito gniuždomasis stipris iš dalies priklausė nuo naudojamų plieninių fibrų charakteristikų. Tačiau plieninių fibrų priedas nepakeitė SLWAC tamprumo modulio.


2019 ◽  
Vol 11 (7) ◽  
pp. 1923 ◽  
Author(s):  
Salaheldin Elkatatny

Cement slurry segregation has a detrimental impact on the cement matrix efficiency in term of zonal isolation. In this study, synthetic modified phyllosilicate (SMP) dispersant, which is known as laponite RD is suggested to reduce the slurry segregation and enhance the vertical homogeneity of the cement matrix in term of density distribution. Seven cement slurries were prepared with different SMP concentrations using molds with different dimensions based on the targeted test, then cured for 24 h at 140 °C and 3000 psi using a high-pressure and high-temperature curing chamber. After that, the samples’ density distribution was evaluated using a direct density measurement and computer tomography (CT) scan imaging technique, and the effect of SMP on the cement rheological parameters, permeability, and compressive strength and were also evaluated. The performance of SMP was then compared with a commercial dispersant. As a result, 0.3% by weight of cement (BWOC) of SMP is found to considerably reduce the vertical density variation along the cement column to 0.46% compared with a density variation of 4.78% for the slurry with the commercial dispersant. The CT scan images confirmed the vertical homogeneity of the slurry with 0.3% BWOC of SMP. Addition of 0.3% BWOC of SMP increased the yield point of the cement slurry to 60.6 MPa compared with 20.5 MPa for the slurry with 0.25% of the commercial dispersant. Adding 0.3% BWOC of SMP into the cement formulation decreased the permeability by 37.1% compared with the commercial dispersant. The sample with 0.3% BWOC of SMP has a compressive strength of 43.9 MPa.


2021 ◽  
Vol 11 (7) ◽  
pp. 3063
Author(s):  
Shaojun Zheng ◽  
Tianle Liu ◽  
Guosheng Jiang ◽  
Changliang Fang ◽  
Bo Qu ◽  
...  

Changing the water-to-cement ratio is one of the major ways to develop cement slurry with different densities, which in turn will greatly affect the pore structure and mechanical properties of cement slurry. In the current study, the cement hydration model HYMOSTRUC3D was used to investigate the effects of water-to-cement (w/c) ratio (0.40, 0.44, 0.50) on the pore structure evolution and strength development of cement slurry. The microstructure of the cement stone was characterized via scanning electron microscope (SEM) and micro-computed tomography (micro-CT), and the mechanical strength of the cement stone was tested and analyzed via a mechanical tester. The simulated compressive strength and capillary porosity are in good agreement with the measured data, where the relative error between the simulated results and measured results are within 0.6~10.7% and 13.04~25.31%, respectively. The capillary porosity is proved as the main factor affecting the compressive strength of cement stone with different w/c ratios. Herein, the mathematical relationship between the measured capillary porosity and compressive strength could be well fitted via the mathematical prediction models of the Balshin function (R2 = 0.95), Ryshkewitch function (R2 = 0.94), Schiller function (R2 = 0.96), and the linear regression function (R2 = 0.95). Moreover, the linear regression function (y = −2.38x + 82.76) can be used to characterize and predict the quantitative relationship between the compressive strength and capillary porosity of cement stone. The findings in this study will provide a reference value in the fields of oil and gas cementing and building concrete.


Nafta-Gaz ◽  
2021 ◽  
Vol 77 (3) ◽  
pp. 200-2017
Author(s):  
Łukasz Kut ◽  

Works related to the drilling of a deep borehole must take into account the specific conditions at its bottom. This applies especially to high temperatures, exceeding 90–100°C, and pressures of 60–80 MPa. Such difficult downhole conditions have often posed many problems when developing appropriate compositions of cement slurries used for sealing columns of casing pipes. With each passing year, drilling companies make deeper and more complicated boreholes, more and more often exceeding 3000 m, which require the use of specially developed recipes of cement slurries when sealing the casing column. In deep boreholes (with very high temperature and pressure), a serious problem is to ensure a long pumping time of the cement slurry, which should be characterized by low viscosity, little or no free water and the lowest filtration possible. Therefore, it is necessary to select appropriate retardants that are resistant to high temperatures and additives ensuring the appropriate technological parameters of the slurries and cement stone. Pressure and temperature parameters increase with the depth of the borehole. Reservoir waters (brines of different mineralization) largely affect the hardened cement slurry, therefore cement slurries intended for deep boreholes should contain in their composition additives that increase thermal resistance, delay setting, lower filtration and improve resistance to chemical corrosion caused by the action of brines reservoir. The aim of the laboratory research was to develop innovative formulas of cement slurries for sealing boreholes, both crude oil and geothermal, with increased temperatures (up to about 130°C) located in the Carpathian region. During the implementation of the topic, laboratory tests were carried out on both cement slurries and cement stones obtained from them. Due to the industry’s interest in acquiring energy from sources other than crude oil and natural gas, a broader scope of laboratory tests covered cement slurries for sealing geothermal boreholes with controlled rheological parameters, which can be used at high reservoir temperatures to seal deep boreholes. The cement slurries were prepared with tap water with the addition of potassium chloride in the amount of 3, 6 and 10% bwow (in relation to the amount of water). The following agents were successively added to the mixing water: defoaming, adjusting the setting and thickening time, plasticizing and reducing filtration. Cement slurries were made with the addition of 10% latex and a latex stabilizer in the amount of 1% bwoc (both components in relation to the weight of dry cement). The other ingredients: microcement (nanocement), microsilica, hematite and cement were mixed together and then added to the mixing water. All cement slurries were prepared on the basis of drilling cement G. When all components blended, the cement slurry was mixed for 30 minutes followed by laboratory measurements such as: density, fluidity, readings from the Fann apparatus, water retention, filtration, thickening time. From among the developed cement slurries, those with the best rheological parameters were selected, then samples of cement stones were prepared from them. Cement slurries were cured for 48 hours in an environment of high temperature and pressure (downhole conditions). The obtained cement stones were tested for: compressive strength, bending strength, porosity, adhesion of cement stone to steel pipes.


2021 ◽  
Vol 2131 (5) ◽  
pp. 052002
Author(s):  
M Titov ◽  
G Nepomnyashchev ◽  
D Dorofeeva

Abstract The aspects, related to the influence of the electrohydraulic shock method use in a water-cement slurry passing in a closed chamber (activation reactor) with a pre-applied pressure to the system under various processing modes are highlighted in the article. In order to test the effect of this method on water-cement slurry, an installation was developed, consisting of: a high-voltage source, a high-voltage diode, capacitor banks, a closing element and an activation reactor. The necessary experiments were carried out on the completed installation. The procedure for conducting experiments is described in the work, shows a schematic diagram of the installation for performing activation, a diagram of the reactor, and the processing modes. Several activation modes were considered, depending on: the number of pulses (1-4), pulse energy (0.5-8 kJ), water-cement ratio (0.2-0.35), time intervals for starting treatment from the moment the cement was mixed with water (0 -120 minutes), volume and shape of the container (activation reactor), holding temperature (20-60°C), etc. According to the results of the data obtained, it was experimentally established that the use of electric pulse treatment of water-cement suspension has a positive effect on strength (cup compressive strength) indicators, obtained as a result of processing cement stone samples at different times of hardening (1-3 days). The compressive strength of the treated specimens’ increases in comparison with the untreated specimens, increase in strength reaches up to 45%, depending on the activation mode. The resulting effect was achieved due to many factors (high pressure, magnetic, temperature, energy, ultrasonic and other influences), which were applied in the most optimal period of time (stage) of the cement grain hydration process.


Author(s):  
A.M. Satarkulova

The assessment and dynamic control over students’ status is a very important task. It allows timely detection of prenosological status prior to pathology and health maintenance in students. The objective of the paper is to assess the adaptive abilities of the body, to analyze changes in heart rate variability indicators in students with various types of autonomic regulation, to identify prenosological status and precursory pathological symptoms. Materials and Methods. The study enrolled 302 students from India, aged 21.54±1.43. Programming complex «Psychophysiologist» was used to register the main HRV parameters within 5 minutes. Health status was evaluated according to the index of functional changes and the scale of functional states. Results. N.I. Shlyk (2009) distinguished two groups of students with different types of autonomic regulation: type 1 (53 %) with moderate and type 2 (5 %) with marked characteristics of central regulation profile, type 3 (35 %) with moderate and type 4 (7 %) with marked characteristics of autonomous regulation profile. Main parameters of HRV and adaptation potential were defined for each student.All the parameters characterized functional and health status. Conclusions. It was shown that 82 % of trial subjects (type 1), 53 % (type 2), 94 % (type 3) and 95 % (type 4) demonstrated satisfactory adaptation and their physiological processes were at an optimal level. 18 % of students (type 1) demonstrated reduced adaptive abilities of the body. Moreover, they were under moderate stress. 47 % of subjects (type 2) were also under a significant stress, which was proven by excessively high SI, low SDNN and TP, and an increased index of functional changes. 5 % of students (type 4) revealed dysfunctional characteristics in the heart rhythm, peculiar to pathology. Keywords: foreign students, heart rate variability, types of autonomic regulation, adaptation potential, functional status. Оценка состояния студентов и динамический контроль за ним является важной задачей, поскольку позволяет своевременно выявлять у студентов донозологические состояния, предшествующие патологии, и способствовать сохранению здоровья. Цель. Оценка адаптивных возможностей организма, анализ изменений показателей вариабельности сердечного ритма у студентов с различными типами вегетативной регуляции, выявление донозологических состояний и ранних признаков патологии. Материалы и методы. В исследовании участвовало 302 студента в возрасте 21,54+1,43 года из Индии. Регистрировались основные параметры ВСР в течение 5 мин с использованием программно-аппаратного комплекса «Психофизиолог». Состояние и уровень здоровья оценивались по индексу функциональных изменений и шкале функциональных состояний. Результаты. По способу, предложенному Н.И. Шлык, выделены группы студентов с различными типами вегетативной регуляции: I (53 %) и II типы (5 %) – с умеренным и выраженным преобладанием центрального контура регуляции соответственно, III (35 %) и IV типы (7 %) – с умеренным и выраженным преобладанием автономного контура регуляции соответственно. У каждого из студентов определены основные параметры ВСР и адаптационного потенциала, характеризующие функциональное состояние и уровень здоровья. Выводы. Показано, что для 82 % обследуемых с I типом, 53 % со II типом, 94 % c III типом и 95 % с IV типом регуляции характерно состояние удовлетворительной адаптации, физиологические процессы сохраняются на оптимальном уровне. В группе студентов I типа у 18 % студентов адаптивные возможности организма снижены, выявлено состояние умеренного напряжения. У 47 % обследуемых II типа также зафиксировано состояние резко выраженного напряжения, индикатором которого является чрезмерно высокое значение SI, низкие величины SDNN и ТP, повышенное значение индекса функциональных изменений. В группе студентов с IV типом у 5 % учащихсяв регуляции ритма сердца выявлены дисфункциональные признаки, характерные для патологии. Ключевые слова: иностранные студенты, вариабельность сердечного ритма, типы вегетативной регуляции, адаптационный потенциал, функциональное состояние.


1970 ◽  
Vol 1 (1) ◽  
pp. 78-82
Author(s):  
Paulo José Oliveira Cortez ◽  
José Elias Tomazini ◽  
Mauro Gonçalves

Introdução: A diminuição da capacidade de exercer esforços por parte dos músculos rotadores pode criar uma variedade de problemas. O conhecimento preciso do nível de força muscular de um indivíduo é importante, tanto para a avaliação da capacidade funcional ocupacional, como para uma apropriada prescrição de exercícios atléticos e de reabilitação. Percebe-se escassez de informação sobre as articulações do ombro, bem como os fatores envolvidos na força muscular dessa região. O objetivo deste estudo foi comparar a força gerada pelos músculos do manguito rotador entre o membro superior direito e o membro superior esquerdo em indivíduos saudáveis. Métodos: Participaram do estudo 22 sujeitos do sexo masculino, com idade de 18 e 19 anos, militares, saudáveis e sem história clínica de patologia ortopédica ou qualquer tipo de lesão no sistema musculoesquelético. Foram aplicados dois testes de força: Rotação Interna e Rotação Externa. Resultado : A força média de rotação interna no membro superior direito (MSD) foi maior que a força média de rotação interna no membro superior esquerdo (MSE) (p=0,723) e a força de rotação externa no MSD foi menor que a força média de rotação externa no MSE (p=0,788). Não houve diferença estatística na comparação dos valores de força de todos os testes de força isométrica. Conclusão: Para amostra estudada e metodologia utilizada na avaliação da força muscular, não houve diferença estatística na comparação da força gerada pelos músculos do manguito rotador do membro superior direito e do membro superior esquerdo.Rotator Cuff Muscle Strength in Healthy Individuals Introduction: Decreased ability to exert efforts by the rotator muscles can create a variety of problems. The precise knowledge of the level of muscular strength of an individual is important for both the functional capacity evaluation for occupational as an appropriate exercise prescription and rehabilitation of athletic. It is perceived scarcity of information on the shoulder joints as well as factors involved in muscle strength in this region. Objective: Develop a device for measuring the strength generated by the muscles of the upper limbs and the verification of efficiency and adaptability of this device through a comparative study of muscle strength in healthy subjects. Methods: The study included 22 male subjects, aged 18 and 19 years, military personnel, body mass between 57.7 and 93 kg (71.8 ± 9.45 kg) and height between 1.67 and 1.90 m (1.75 ± 0.06 m), healthy and without a history of orthopaedic disease or any kind of damage to the musculoskeletal system. Three strength tests were applied: Internal Rotation and External Rotation. For each type of effort three maximum voluntary contractions were required for 10 seconds, with an interval of 30 seconds between each contraction.  Results: Internal rotation in the right upper limb (RUL) was higher than the average strength of internal rotation in the left upper limb (LUL) (p = 0, 723) and the external rotation strength in RUL was lower than the average strength of external rotation in the LUL (p=0,788).  No statistical difference in comparing the strength values of all isometric strength tests. Conclusion: For sample and methodology used to assess muscle strength, there was no statistical difference in comparing the force generated by the muscles of the rotator cuff of the right and left upper limb.


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