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A comparative analysis of numerical simulation and analytical modeling of horizontal well cyclic steam injectionRavago Bastardo, Delmira Cristina 29 August 2005 (has links)
The main objective of this research is to compare the performance of cyclic steam injection using horizontal wells based on the analytical model developed by Gunadi against that based on numerical simulation. For comparison, a common reservoir model was used. The reservoir model measured 330 ft long by 330 ft wide by 120 ft thick, representing half of a 5-acre drainage area, and contained oil based on the properties of the Bachaquero-01 reservoir (Venezuela). Three steam injection cycles were assumed, consisting of a 20-day injection period at 1500 BPDCWE (half-well), followed by a 10-day soak period, and a 180-day production period. Comparisons were made for two cases of the position of the horizontal well located on one side of the reservoir model: at mid-reservoir height and at reservoir base.
The analytical model of Gunadi had to be modified before a reasonable agreement with simulation results could be obtained. Main modifications were as follows. First, the cold horizontal well productivity index was modified to that based on the Economides-Joshi model instead of that for a vertical well. Second, in calculating the growth of the steam zone, the end-point relative permeability??s of steam and oil were taken into consideration, instead of assuming them to be the same (as in the original model of Gunadi).
Main results of the comparative analysis for both cases of horizontal well positions are as follows. First, the water production rates are in very close agreement with results obtained from simulation. Second, the oil production rates based on the analytical model (averaging 46,000 STB), however, are lower than values obtained from simulation (64,000 STB). This discrepancy is most likely due to the fact that the analytical model assumes residual oil saturation in the steam zone, while there is moveable oil based on the simulation model. Nevertheless, the analytical model may be used to give a first-pass estimate of the performance of cyclic steam injection in horizontal wells, prior to conducting more detailed thermal reservoir simulation.
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Reservoir Simulation Used to Plan Diatomite Developement in Mountainous RegionPowell, Richard 2012 August 1900 (has links)
In Santa Barbara County, Santa Maria Pacific (an exploration and production company) is expanding their cyclic steam project in a diatomite reservoir. The hilly or mountainous topography and cut and fill restrictions have interfered with the company's ideal development plan. The steep hillsides prevent well pad development for about 22 vertical well locations in the 110 well expansion plan. Conventional production performs poorly in the area because the combination of relatively low permeability (1-10 md) and high viscosity (~220 cp) at the reservoir temperature. Cyclic steam injection has been widely used in diatomite reservoirs to take advantage of the diatomite rocks unique properties and lower the viscosity of the oil. Some companies used deviated wells for cyclic steam injection, but Santa Maria Pacific prefers the use only vertical wells for the expansion. Currently, the inability to create well pads above 22 vertical well target locations will result in an estimated $60,000,000 of lost revenue over a five year period.
The target locations could be developed with unstimulated deviated or horizontal wells, but expected well rates and expenses have not been estimated. In this work, I use a thermal reservoir simulator to estimate production based on five potential development cases. The first case represents no development other than the cyclic wells. This case is used to calibrate the model based on the pilot program performance and serves as a reference point for the other cases. Two of the cases simulate a deviated well with and without artificial lift next to a cyclic well, and the final two cases simulate a horizontal well segment with and without artificial lift next to a cyclic well.
The deviated well with artificial lift results in the highest NPV and profit after five years. The well experienced pressure support from the neighboring cyclic well and performed better with the cyclic well than without it. Adding 22 deviated wells with artificial lift will increase the project's net profit by an estimated $7,326,000 and NPV by $2,838,000 after five years.
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Adequate description of heavy oil viscosities and a method to assess optimal steam cyclic periods for thermal reservoir simulationMago, Alonso Luis 16 August 2006 (has links)
A global steady increase of energy consumption coupled with the decline of conventional oil resources points to a more aggressive exploitation of heavy oil. Heavy oil is a major source of energy in this century with a worldwide base reserve exceeding 2.5 trillion barrels. Management decisions and production strategies from thermal oil recovery processes are frequently based on reservoir simulation. A proper description of the physical properties, particularly oil viscosity, is essential in performing reliable modeling studies of fluid flow in the reservoir. We simulated cyclic steam injections on the highly viscous Hamaca oil, with a viscosity of over 10,000 cp at ambient temperature, and the production was drastically impacted by up to an order of magnitude when using improper mixing rules to describe the oil viscosity. This thesis demonstrates the importance of these mixing rules and alerts reservoir engineers to the significance of using different options simulators have built in their platforms to describe the viscosity of heavy oils. Log linear and power mixing rules do not provide enough flexibility to describe the viscosity of extra heavy oil with temperature. A recently implemented mixing rule in a commercial simulator has been studied providing satisfactory results. However, the methodology requires substantial interventions, and cannot be automatically updated. We provide guidelines to improve it and suggest more flexible mixing rules that could easily be implemented in commercial simulators. We also provide a methodology to determine the adequate time for each one of the periods in cyclic steam injection: injection, soaking and production. There is a lot of speculation in this matter and one of the objectives of this thesis is to better understand and provide guidelines to optimize oil production using proper lengths in each one of these periods. We have found that the production and injection periods should be similar in time length. Nevertheless, the production period should not be less than the injection period. On the other hand, the soaking period should be as short as possible because it is unproductive time in terms of field oil production for the well and therefore it translates into a negative cash flow for a company.
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Adequate description of heavy oil viscosities and a method to assess optimal steam cyclic periods for thermal reservoir simulationMago, Alonso Luis 16 August 2006 (has links)
A global steady increase of energy consumption coupled with the decline of conventional oil resources points to a more aggressive exploitation of heavy oil. Heavy oil is a major source of energy in this century with a worldwide base reserve exceeding 2.5 trillion barrels. Management decisions and production strategies from thermal oil recovery processes are frequently based on reservoir simulation. A proper description of the physical properties, particularly oil viscosity, is essential in performing reliable modeling studies of fluid flow in the reservoir. We simulated cyclic steam injections on the highly viscous Hamaca oil, with a viscosity of over 10,000 cp at ambient temperature, and the production was drastically impacted by up to an order of magnitude when using improper mixing rules to describe the oil viscosity. This thesis demonstrates the importance of these mixing rules and alerts reservoir engineers to the significance of using different options simulators have built in their platforms to describe the viscosity of heavy oils. Log linear and power mixing rules do not provide enough flexibility to describe the viscosity of extra heavy oil with temperature. A recently implemented mixing rule in a commercial simulator has been studied providing satisfactory results. However, the methodology requires substantial interventions, and cannot be automatically updated. We provide guidelines to improve it and suggest more flexible mixing rules that could easily be implemented in commercial simulators. We also provide a methodology to determine the adequate time for each one of the periods in cyclic steam injection: injection, soaking and production. There is a lot of speculation in this matter and one of the objectives of this thesis is to better understand and provide guidelines to optimize oil production using proper lengths in each one of these periods. We have found that the production and injection periods should be similar in time length. Nevertheless, the production period should not be less than the injection period. On the other hand, the soaking period should be as short as possible because it is unproductive time in terms of field oil production for the well and therefore it translates into a negative cash flow for a company.
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Thermal Enhanced Oil Recovery and Potential Benefits for Use of Produced Water for Agriculture and Food Security: A Case Study of Oil Fields in South SudanLado, Flora Eyoha Severino 11 February 2021 (has links)
This research covers simulation of Cyclic Steam Stimulation (CSS) Thermal Enhanced Oil Recovery (TEOR) and potential benefits for use of produced water in agriculture and food security, using a case study of oil fields in South Sudan. Oil production in many oil fields in South Sudan is declining, has high water cut, and low recovery factor. It is costly to manage the produced water. At the same time, agriculture in South Sudan is almost entirely rainfed, and this affects food security. Produced water can be managed by using it for TEOR and agriculture to solve water management issues, enhance oil production, reduces competition over water resources, and improve food security.
Field A is a deep reservoir in South Sudan with oil gravity between 25 and 31 API. There are limited and mixed results from applications of TEOR methods in deep reservoirs. As such history matching and sensitivity analysis, and CSSS TEOR simulations were performed to examine most uncertain reservoir properties and the compatibility of Field A properties with CSS TEOR method. The results of simulation show that aquifer volume (AQV) and productivity index (PI) are the most uncertain property that affect reservoir pressure; cumulative oil, gas, and water production; water cut; and gas oil ratio. CSS TEOR simulation was not successfully due to the high API gravity suggesting that Field A is not a good candidate for CSS TEOR.
The produced water is sufficient to irrigate large areas of farms and watering thousands of livestock. However, analysis results from untreated water; water treated by demulsifer-defoamer and bioremediation shows high total dissolved solids (TDS) and sodium absorption ratio (SAR) values. Therefore, reverse osmosis (RO) membrane technology was applied to treat the produced water. RO rejected more than 90% of elements in the produced water with exception of elements B, Cu, Pb, and Ca. Consequently, water from RO does not meet food and agriculture organization (FAO) standards for all uses in agriculture. ANOVA showed that there was no significant difference in TDS reductions between the different applied treatment technologies. Therefore, caution is needed when using statistical analysis to verify operationalization of RO technology which rejected more than 90% of the elements in the produced water. / Doctor of Philosophy / This research discusses how to increase oil production by injecting steam in the reservoir and leaving it to soak before the next injection and start of oil production, along with potential benefits for use of produced water in agriculture and food security, all using a case study of oil fields in South Sudan. In many oil fields in South Sudan the volume of oil produced is decreasing while that of water is increasing rapidly, so that now nearly 90% of the total fluids produced is water. Management of produced water can be very costly. Despite the large quantities of produced water, agriculture in South Sudan still depends on rain water, and this dependency on rain water can affect crop production and food security, and also cause conflict amongst nomads and farmers over water resources during the dry season. These problems can be mitigated by using produced water to increase oil production and then be applied for agricultural uses.
The first study simulated steam injection in the reservoir in Oil Field A. The results showed that process of injection did not work well due to the properties of the oil in that formation, and therefore other methods may be needed to increase oil production in Field A.
In the second study, water which is produced together with oil (produced water) was analyzed to check its quality. This analysis determined that the water has very high concentration of total dissolved solids. Treatment methods that have been applied in the oil fields for treating produced water do not currently make the water clean enough to be use for agriculture use. Therefore, reverse osmosis membrane technology was applied to reduce the concentration of the elements in the water. Reverse osmosis treatment technology is capable of removing 90 % concentration of most elements in the produced water, but some potentially harmful elements, such as boron, remained. As a result, the water treated by reverse osmosis can only be used for livestock watering unless additional treatment methods are adopted to reduce boron concentrations to acceptable level.
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Estudo de sistemas multicomponentes no processo de inje??o c?clica de vaporCarvalho, Tiago Pinheiro de 18 September 2010 (has links)
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Previous issue date: 2010-09-18 / In Brazilian Northeast there are reservoirs with heavy oil, which use steam flooding as a
recovery method. This process allows to reduce oil viscosity, increasing its mobility and
consequently its oil recovery. Steam injection is a thermal method and can occurs in
continues or cyclic form. Cyclic steam stimulation (CSS) can be repeated several times.
Each cycle consisting of three stages: steam injection, soaking time and production
phase. CSS becomes less efficient with an increase of number of cycles. Thus, this work
aims to study the influence of compositional models in cyclic steam injection and the
effects of some parameters, such like: flow injection, steam quality and temperature of
steam injected, analyzing the influence of pseudocomponents numbers on oil rate,
cumulative oil, oil recovery and simulation time. In the situations analyzed was
compared the model of fluid of three phases and three components known as Blackoil .
Simulations were done using commercial software (CMG), it was analyzed a
homogeneous reservoir with characteristics similar to those found in Brazilian
Northeast. It was observed that an increase of components number, increase the time
spent in simulation. As for analyzed parameters, it appears that the steam rate, and
steam quality has influence on cumulative oil and oil recovery. The number of
components did not a lot influenced on oil recovery, however it has influenced on gas
production / No Nordeste brasileiro existem reservat?rios de ?leos pesados, nos quais se utiliza a inje??o
de vapor como m?todo de recupera??o. Este processo permite diminuir a viscosidade do ?leo,
aumentando a sua mobilidade e melhorando o volume de ?leo a ser recuperado. A inje??o de
vapor ? um m?todo t?rmico e ocorre na forma cont?nua ou c?clica. A inje??o c?clica de vapor
pode ser repetida diversas vezes. Cada ciclo consiste de tr?s etapas distintas: a fase de inje??o,
fase de fechamento (soaking) e fase de produ??o. A inje??o c?clica se torna menos eficiente ?
medida que o n?mero de ciclos aumenta. Neste sentido, este trabalho visa estudar a influ?ncia
de modelos composicionais na inje??o c?clica de vapor e os efeitos de alguns par?metros, tais
como: vaz?o de inje??o, qualidade do vapor e temperatura do vapor injetado; analisando a
influ?ncia do n?mero de pseudocomponentes, no que diz respeito ? vaz?o de ?leo, produ??o
acumulada de ?leo, fator de recupera??o e tempo de simula??o. Nas situa??es analisadas foi
comparado o modelo de fluido de tr?s fases e tr?s componentes conhecido como Black-oil .
Foram realizadas simula??es, utilizando um simulador comercial a partir de um modelo de
reservat?rio homog?neo com caracter?sticas similares ?s encontradas no Nordeste brasileiro.
Observou-se que quanto maior o n?mero de componentes, maior ? o tempo gasto na
simula??o. J? para os par?metros analisados, verifica-se que a vaz?o de inje??o de vapor e a
qualidade do vapor influenciam na produ??o acumulada de ?leo e no fator de recupera??o. O
n?mero de componentes n?o exerceu muita influ?ncia na produ??o acumulada, nem no fator
de recupera??o de ?leo, por?m foi significativa na produ??o de g?s do sistema
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Otimiza??o da inje??o c?clica de vapor em reservat?rio de ?leo pesadoQueiroz, Gertrudes Oliveira de 16 December 2005 (has links)
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Previous issue date: 2005-12-16 / Thermal methods made heavy oil production possible in fields where primary recovery failed. Throughout the years steam injection became one of the most important alternatives to increase heavy oil recovery. There are many types of steam injection, and one of them is the cyclic steam injection, which has been used with success in several countries, including Brazil. The process involves three phases: firstly, steam is injected, inside of the producing well; secondly, the well is closed (soak period); and finally, the well is put back into production. These steps constitute one cycle. The cycle is repeated several times until economical production limit is reached. Usually, independent of reservoir type, as the number of cycles increases the cyclic injection turns less efficient. This work aims to analyze rock and reservoir property influence in the cyclic steam injection. The objective was to study the ideal number of cycles and, consequently, process optimization. Simulations were realized using the STARS simulator from the CMG group based in a proposed reservoir model. It was observed that the reservoir thickness was the most important parameter in the process performance, whilst soaking time influence was not significant / Os m?todos t?rmicos viabilizaram a produ??o de ?leo pesado em campos considerados n?o comerciais pelos m?todos convencionais de recupera??o. A inje??o de vapor, em particular, veio a se consagrar ao longo dos anos e ? hoje uma das principais alternativas economicamente vi?vel para o aumento da recupera??o dos ?leos pesados. Dentre as ramifica??es da inje??o de vapor existentes a inje??o c?clica tem sido utilizada com sucesso em escalas comerciais em v?rios pa?ses, incluindo o Brasil. O processo envolve tr?s fases: a primeira ? a inje??o de vapor na qual o vapor ? injetado, dentro do po?o produtor, por um per?odo espec?fico de tempo; em seguida, o po?o ? fechado por um curto per?odo de tempo ( soak period ); e finalmente, o po?o ? recolocado em produ??o durante meses a anos. Esse processo constitui um ciclo. O ciclo ? repetido um n?mero de vezes at? que o limite econ?mico na produ??o seja alcan?ado. Independente do tipo de reservat?rio, a inje??o c?clica geralmente se torna menos eficiente ? propor??o que o n?mero de ciclos aumenta. Este trabalho visa analisar a influ?ncia de algumas propriedades de rocha e reservat?rio na inje??o c?clica de vapor a fim de estudar o n?mero ideal de ciclos e, conseq?entemente, otimizar o processo. Foram realizadas simula??es, utilizando o simulador STARS do grupo CMG, a partir de um modelo de reservat?rio proposto. Observou-se que o efeito da espessura do reservat?rio foi o par?metro que mais influenciou no desempenho do processo, enquanto que para o tempo de soaking essa influ?ncia n?o foi significativa
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The techno-economics of bitumen recovery from oil and tar sands as a complement to oil exploration in Nigeria / E. OrireOrire, Endurance January 2009 (has links)
The Nigeria economy is wholly dependent on revenue from oil. However, bitumen has been discovered in
the country since 1903 and has remained untapped over the years. The need for the country to
complement oil exploration with the huge bitumen deposit cannot be overemphasized. This will help to
improve the country's gross domestic product (GDP) and revenue available to government. Bitumen is
classifled as heavy crude with API (American petroleum Institute) number ranging between 50 and 110
and occurs in Nigeria, Canada, Saudi Arabia, Venezuela etc from which petroleum products could be
derived.
This dissertation looked at the Canadian experience by comparing the oil and tar sand deposit found in Canada with particular reference to Athabasca (Grosmont, Wabiskaw McMurray and Nsiku) with
that in Nigeria with a view of transferring process technology from Canada to Nigeria. The Nigeria and Athabasca tar sands occur in the same type of environment. These are the deltaic, fluvial marine deposit in an incised valley with similar reservoir, chemical and physical properties. However, the Nigeria tar sand is more asphaltenic and also contains more resin and as such will yield more product volume during
hydro cracking albeit more acidic. The differences in the components (viscosity, resin and asphaltenes
contents, sulphur and heavy metal contents) of the tar sands is within the limit of technology adaptation.
Any of the technologies used in Athabasca, Canada is adaptable to Nigeria according to the findings of this research.
The techno-economics of some of the process technologies are. x-rayed using the PTAC (petroleum
technology alliance Canada) technology recovery model in order to obtain their unit cost for Nigeria
bitumen. The unit cost of processed bitumen adopting steam assisted gravity drainage (SAGD), in situ
combustion (ISC) and cyclic steam stimulation (CSS) process technology is 40.59, 25.00 and 44.14
Canadian dollars respectively. The unit cost in Canada using the same process technology is 57.27, 25.00
and 61.33 Canadian dollars respectively. The unit cost in Nigeria is substantively lesser than in Canada.
A trade off is thereafter done using life cycle costing so as to select the best process technology for the
Nigeria oil/tar sands. The net present value/internal rate of return is found to be B$3,062/36.35% for
steam assisted gravity drainage, B$I,570124.51 % for cyclic steam stimulation and B$3,503/39.64% for in
situ combustion. Though in situ combustion returned the highest net present value and internal rate of
return, it proved not to be the best option for Nigeria due to environmental concern and response time to
production. The best viable option for the Nigeria tar sand was then deemed to be steam assisted gravity
drainage.
An integrated oil strategy coupled with cogeneration using MSAR was also seen to considerably amplify
the benefits accruable from bitumen exploration; therefore, an investment in bitumen exploration in
Nigeria is a wise economic decision. / Thesis (M.Ing. (Development and Management))--North-West University, Potchefstroom Campus, 2010.
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The techno-economics of bitumen recovery from oil and tar sands as a complement to oil exploration in Nigeria / E. OrireOrire, Endurance January 2009 (has links)
The Nigeria economy is wholly dependent on revenue from oil. However, bitumen has been discovered in
the country since 1903 and has remained untapped over the years. The need for the country to
complement oil exploration with the huge bitumen deposit cannot be overemphasized. This will help to
improve the country's gross domestic product (GDP) and revenue available to government. Bitumen is
classifled as heavy crude with API (American petroleum Institute) number ranging between 50 and 110
and occurs in Nigeria, Canada, Saudi Arabia, Venezuela etc from which petroleum products could be
derived.
This dissertation looked at the Canadian experience by comparing the oil and tar sand deposit found in Canada with particular reference to Athabasca (Grosmont, Wabiskaw McMurray and Nsiku) with
that in Nigeria with a view of transferring process technology from Canada to Nigeria. The Nigeria and Athabasca tar sands occur in the same type of environment. These are the deltaic, fluvial marine deposit in an incised valley with similar reservoir, chemical and physical properties. However, the Nigeria tar sand is more asphaltenic and also contains more resin and as such will yield more product volume during
hydro cracking albeit more acidic. The differences in the components (viscosity, resin and asphaltenes
contents, sulphur and heavy metal contents) of the tar sands is within the limit of technology adaptation.
Any of the technologies used in Athabasca, Canada is adaptable to Nigeria according to the findings of this research.
The techno-economics of some of the process technologies are. x-rayed using the PTAC (petroleum
technology alliance Canada) technology recovery model in order to obtain their unit cost for Nigeria
bitumen. The unit cost of processed bitumen adopting steam assisted gravity drainage (SAGD), in situ
combustion (ISC) and cyclic steam stimulation (CSS) process technology is 40.59, 25.00 and 44.14
Canadian dollars respectively. The unit cost in Canada using the same process technology is 57.27, 25.00
and 61.33 Canadian dollars respectively. The unit cost in Nigeria is substantively lesser than in Canada.
A trade off is thereafter done using life cycle costing so as to select the best process technology for the
Nigeria oil/tar sands. The net present value/internal rate of return is found to be B$3,062/36.35% for
steam assisted gravity drainage, B$I,570124.51 % for cyclic steam stimulation and B$3,503/39.64% for in
situ combustion. Though in situ combustion returned the highest net present value and internal rate of
return, it proved not to be the best option for Nigeria due to environmental concern and response time to
production. The best viable option for the Nigeria tar sand was then deemed to be steam assisted gravity
drainage.
An integrated oil strategy coupled with cogeneration using MSAR was also seen to considerably amplify
the benefits accruable from bitumen exploration; therefore, an investment in bitumen exploration in
Nigeria is a wise economic decision. / Thesis (M.Ing. (Development and Management))--North-West University, Potchefstroom Campus, 2010.
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Otimiza??o e an?lise mec?nica de pastas geopolim?ricas para uso em po?os sujeitos ? inje??o c?clica de vaporPaiva, Maria das Dores Macedo 28 October 2008 (has links)
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Previous issue date: 2008-10-28 / Oil wells subjected to cyclic steam injection present important challenges for the development of well cementing systems, mainly due to tensile stresses caused by
thermal gradients during its useful life. Cement sheath failures in wells using conventional high compressive strength systems lead to the use of cement systems that are more flexible and/or ductile, with emphasis on Portland cement systems with latex addition. Recent research efforts have presented geopolymeric systems as alternatives. These cementing systems are based on alkaline activation of amorphous aluminosilicates such as metakaolin or fly ash and display advantageous properties such as high compressive strength, fast setting and
thermal stability. Basic geopolymeric formulations can be found in the literature,
which meet basic oil industry specifications such as rheology, compressive strength and thickening time. In this work, new geopolymeric formulations were developed, based on metakaolin, potassium silicate, potassium hydroxide, silica fume and mineral fiber, using the state of the art in chemical composition, mixture modeling and additivation to optimize the most relevant properties for oil well
cementing. Starting from molar ratios considered ideal in the literature (SiO2/Al2O3 = 3.8 e K2O/Al2O3 = 1.0), a study of dry mixtures was performed,based on the compressive packing model, resulting in an optimal volume of 6% for the added solid material. This material (silica fume and mineral fiber) works both as an additional silica source (in the case of silica fume) and as mechanical
reinforcement, especially in the case of mineral fiber, which incremented the tensile strength. The first triaxial mechanical study of this class of materials was performed. For comparison, a mechanical study of conventional latex-based cementing systems was also carried out. Regardless of differences in the failure mode (brittle for geopolymers, ductile for latex-based systems), the superior uniaxial compressive strength (37 MPa for the geopolymeric slurry P5 versus 18 MPa for the conventional slurry P2), similar triaxial behavior (friction angle 21?
for P5 and P2) and lower stifness (in the elastic region 5.1 GPa for P5 versus 6.8 GPa for P2) of the geopolymeric systems allowed them to withstand a similar amount of mechanical energy (155 kJ/m3 for P5 versus 208 kJ/m3
for P2), noting that geopolymers work in the elastic regime, without the microcracking present in the case of latex-based systems. Therefore, the geopolymers studied on this work must be designed for application in the elastic region to avoid brittle failure. Finally, the tensile strength of geopolymers is originally poor (1.3 MPa for the
geopolymeric slurry P3) due to its brittle structure. However, after additivation with mineral fiber, the tensile strength became equivalent to that of latex-based systems (2.3 MPa for P5 and 2.1 MPa for P2). The technical viability of conventional and proposed formulations was evaluated for the whole well life, including stresses due to cyclic steam injection. This analysis was performed using finite element-based simulation software. It was verified that conventional slurries are viable up to 204?F (400?C) and geopolymeric slurries are viable above 500?F
(260?C) / Po?os sujeitos ? inje??o c?clica de vapor apresentam importantes desafios para desenvolvimento de pastas de cimenta??o, devido principalmente aos esfor?os de
tra??o causados pelos gradientes t?rmicos durante a sua vida ?til. Falhas em cimenta??es que empregaram pastas convencionais de elevada resist?ncia ? compress?o levaram ao emprego de pastas mais flex?veis e/ou d?cteis, com destaque para as pastas de cimento Portland com adi??o de l?tex. Recentes pesquisas t?m apresentado pastas geopolim?ricas como alternativa. Estas pastas cimentantes s?o baseadas na ativa??o alcalina de aluminosilicatos amorfos como
o metacaulim ou a cinza volante e possuem propriedades vantajosas como alta resist?ncia ? compress?o, r?pido endurecimento e estabilidade t?rmica. Encontram-se na literatura formula??es geopolim?ricas b?sicas que atendem ?s
especifica??es da ind?stria de petr?leo, incluindo reologia, resist?ncia ? compress?o e tempo de espessamento. Neste trabalho, desenvolveu-se novas formula??es geopolim?ricas ? base de metacaulim, silicato de pot?ssio, hidr?xido de pot?ssio, micross?lica e fibra mineral, utilizando o estado da arte em
composi??o qu?mica, modelagem de misturas e aditiva??o para otimizar as propriedades relevantes para a cimenta??o de po?os. Partindo de raz?es molares
consideradas ideais na literatura (SiO2/Al2O3 = 3,8 e K2O/Al2O3 = 1,0), realizou-se
um estudo de misturas secas baseado no modelo do empacotamento
compress?vel, obtendo-se um volume ?timo de 6% para o material s?lido
adicional. Este material (micross?lica e fibra mineral) serve tanto como fonte de s?lica adicional (no caso da micross?lica) quanto refor?o mec?nico, principalmente no caso da fibra mineral, a qual incrementou a resist?ncia ? tra??o. Realizou-se o
primeiro estudo mec?nico triaxial desta classe de pastas. Para efeito de compara??o, tamb?m foi realizado um estudo mec?nico de pastas convencionais ? base de l?tex. Apesar de diferen?as no modo de ruptura (fr?gil no caso dos geopol?meros, d?ctil no caso das pastas com l?tex), a superior resist?ncia compressiva uniaxial (37 MPa para a pasta geopolim?rica P5 versus 18 MPa para a pasta convencional P2), comportamento triaxial similar (?ngulo de atrito 21?
para P5 e P2) e menor rigidez (na regi?o el?stica 5,1 GPa para P5 versus 6,8 GPa para P2) das pastas geopolim?ricas permitiu uma capacidade de absor??o de energia (155 kJ/m3 para P5 versus 208 kJ/m3 para P2) compar?vel entre as duas, sendo que os geopol?meros atuam no regime el?stico, sem a
microfissura??o presente nas pastas com l?tex. Assim, os geopol?meros estudados neste trabalho devem ser dimensionados para aplica??es no regime el?stico para evitar fraturas fr?geis. Finalmente, a resist?ncia ? tra??o do
geopol?mero ? originalmente pobre (1,3 MPa para a pasta geopolim?rica P3) devido ? sua estrutura fr?gil. Entretanto, ap?s a aditiva??o desse sistema com fibra mineral, a resist?ncia ? tra??o do mesmo tornou-se equivalente (2,3 MPa
para P5 e 2,1 MPa para P2) ? das pastas com l?tex. A viabilidade t?cnica das formula??es convencionais e geopolim?ricas foi avaliada durante toda a vida ?til
do po?o, incluindo os esfor?os devidos ? inje??o c?clica de vapor. Esta an?lise foi feita utilizando um software de simula??o ? base de elementos finitos. Verificou-se que as pastas convencionais s?o vi?veis at? a temperatura de 204?C (400?F) e as geopolim?ricas acima de 260?C (500?F)
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