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Simulation study of areal sweep efficiency versus a function of mobility ratio and aspect ratio for staggered line-drive waterflood patternGuliyev, Ruslan 10 October 2008 (has links)
Pattern geometry plays a major role in determining oil recovery during waterflooding
and enhanced oil recovery operations. Although simulation is an important tool for
design and evaluation, the first step often involves rough calculations based upon areal
sweep efficiencies of displacements in homogeneous, two-dimensional, scaled, physical
models. These results are available as a function of the displacement pattern and the
mobility ratio M.
In this research I studied the effect of mobility ratios on five-spot and staggered
waterflood patterns behavior for areal (2D) displacement in a reservoir that is
homogeneous and isotropic containing no initial gas saturation. Simulation was
performed using Eclipse 100 simulator.
Simulation results are presented as graphs of areal sweep efficiency at breakthrough
versus Craig mobility ratio for various staggered line drive aspect ratios.
The main results of the study are presented in the form of a graph of areal sweep
efficiency at breakthrough as a function of staggered line drive aspect ratio. This should
enable engineers to utilize the results in a convenient manner.
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Development of a 2-D black-oil reservoir simulator using a unique grid-block systemChong, Emeline E 12 April 2006 (has links)
The grid orientation effect is a long-standing problem plaguing reservoir simulators that employ finite difference schemes. A rotation of the computational grids yields a substantially different solution under certain circumstances. For example, in a five-spot pattern, the predicted recovery, water cut performance and the locations of the fronts depend on the type of grid system used. A Cartesian grid with one axis parallel to the line joining an injector and producer gives a solution significantly different from a grid that has the axes oriented at 45° to this line.
This study develops a unique grid-block assignment where rectangular grid blocks are interspersed with octagonal grid blocks. This grid block system is called the Hybrid Grid Block (HGB) system. The objective of this study is to evaluate the grid orientation effect of the HGB grid to see whether it is an improvement over the conventional Cartesian grid system.
In HGB, flow can progress in four directions in the octagonal grid blocks and two in the square grid blocks. The increase in the number of flow directions in the octagonal grid blocks is expected to reduce the grid orientation effect in the model. Hence, this study also evaluates the grid orientation effect of the HGB and compares it with the Cartesian grid system.
To test the viability of HGB, a general purpose finite difference IMPES-formulated two-dimensional black oil simulator was developed in this study, while retaining the familiar finite-difference discretization of the flow equations. Several simulation cases were conducted to compare HGB and conventional grid block systems. Comparisons with commercial simulator are also made. Despite the fact that the reservoir is isotropic and homogeneous, grid orientation effect was still observed when rectangular Cartesian grid models are run at mobility ratio, M = 1.0. Grid refinement can help to reduce the grid orientation effect in rectangular Cartesian grid models when there are favorable mobility ratios, i.e. M = 1.0 or less. However, at an unfavorable mobility ratio of M = 10.0, it is found that neither parallel nor diagonal orientation can be used reliably for the displacement problems run in this study. This is because as the number of grid blocks is increased, the performance of diagonal and parallel models actually diverges for the grid spacings investigated here. On the other hand, HGB grid is able to reduce the grid orientation effect even for unfavorable mobility ratio displacement problems (up to M = 50.0), with maximum relative difference in pore volume recovered of 6% between parallel and diagonal HGB grid models for all the cases run in this study. Comparisons between the conventional Cartesian and HGB grid show that the HGB grid is more effective in reducing the grid orientation effect than the Cartesian grid. The HGB grid performs better by consistently giving a smaller relative difference between HGB parallel grid and HGB diagonal grid in pore volume recovered (6.0, 4.5, 3.3, and 2.2%) compared to the relative difference between Cartesian parallel grid and Cartesian diagonal grid in pore volume recovered (17.0, 13.0, 9.3, 7.9%) at similar averaged area per grid block for all the four comparison cases studied.
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An Experimental and Numerical Study to Investigate the Impact of Capillarity on Fluid Flow in Heterogeneous Porous MediaAlabdulghani, Ahmad 10 1900 (has links)
Although the global energy demand is shifting towards a well-balanced energy mix, fossil fuels will continue to have a significant role in this transition and will maintain a big share in the energy mix portfolio. The production of oil and gas has already reached the apex in the time that most of the conventional giant reservoirs are depleting, and discoveries for new reserves have shrunk down. In conventional reservoirs, it is estimated that about two-thirds of the Original Oil in Place (OOIP) will not be produced within the field lifecycle, corresponding to an average Recovery Factor (RF) between 20% and 40%. This low recovery factors from traditional methods trigger more investments in the Enhanced Oil Recovery (EOR) techniques.
Waterflooding is one of the most commonly used technique to increase RF by raising or maintaining reservoir pressure. Lack of comprehending the driving forces in Naturally Fractured Reservoirs and reservoir heterogeneity may lead to serious conformance problems in which dealing with excessive undesirable water production becomes very challenging. Chemical EOR through an injection of a polymer solution is amongst the tested options that can be used to improve sweep efficiency. Ultimately, understanding the reservoir characteristics and having the know-how to implement the best recovery option will help to maximize the field’s lifecycle and increase the RF.
Therefore, this study investigates some key elements that have a significant influence on the overall fluid flow behavior. The work reveals insights on the impact of capillarity and wettability in heterogeneous porous media. An experimental lab-scale consisting of a 2D sandbox model, which mimics a water-wet fractured system with injection and production ports, was designed, fabricated, and tested in single-phase and two-phase flow scenarios including the injection of water and polymer solutions.
In the case of single-phase flow, a waterflood baseline scenario was studied with controlled variables, which helped to distinguish the contrast with the polymer flood case. Implementing water injection in a fractured water-wet reservoir showed that water prefers to channel through high permeable streaks, which consequently leads to poor volumetric sweep leading to significant bypassed zones.
Investigating the two-phase flow was the essence of this research. Thus, the same procedures were repeated where water and polymer were used to displace oil. During waterflooding, due to strong capillarity contrast between the matrix and fracture media, flow divergence was found to be faster towards the matrix medium where the matrix gets saturated faster than that the fracture, overriding the high permeability of the fracture. Whereas, polymer flooding exhibited better volumetric sweep in all scenarios. Numerical simulations were used to replicate the experiments. This work can give new visual insights about key recovery mechanisms in heterogeneous reservoirs using polymers.
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[pt] ESTUDO EXPERIMENTAL DA INJEÇÃO DE SOLUÇÃO POLIMÉRICA EM ARENITOS / [en] EXPERIMENTAL STUDY OF POLYMERIC SOLUTION INJECTION IN SANDSTONESADEMIR FREIRE DE MEDEIROS 31 January 2022 (has links)
[pt] Após uma jazida de petróleo ser encontrada, a produção de óleo ou gás é feita
através de um poço produtor que é perfurado até atingir as camadas de rocha onde
os hidrocarbonetos estão alojados. Com a constante produção, a pressão de
reservatório decresce até atingir um nível que é insuficiente para o aproveitamento
econômico. Geralmente, utiliza-se a injeção de água para manter o nível de pressão
do reservatório. Nos estudos de um reservatório de petróleo é fundamental o
conhecimento de propriedades básicas da rocha e dos fluidos nela contidos. São
essas propriedades que determinam as quantidades de fluidos existentes no meio
poroso, a sua distribuição, a capacidade desses fluidos se moverem e, mais
importante, a quantidade de fluidos que pode ser extraída. Através do método
convencional de injeção de água objetiva-se a manutenção da pressão do
reservatório e o deslocamento de óleo em direção aos poços produtores. A água
(fluido deslocante) tende a ocupar gradualmente o espaço antes ocupado pelo óleo
(fluido deslocado), contudo, por efeitos capilares, uma parcela do óleo não é
retirada do meio poroso configurando o que chamamos óleo residual. Em função
da razão de mobilidade da água e do óleo, a frente de deslocamento não é uniforme,
e um grande volume do reservatório não é atingido pela água de injeção. A adição
de polímero à água de injeção visa o aumento da viscosidade da água, e assim,
melhorar a razão de mobilidade água-óleo, aumentando a eficiência de varrido uma
vez que uniformiza a frente de avanço, reduzindo a formação de caminhos
preferenciais no reservatório. Além de diminuir a razão de mobilidade, soluções
poliméricas podem contribuir para um melhor deslocamento de óleo em escala de
poro, a partir de seu efeito elástico, reduzindo, portanto, a saturação de óleo
residual. Contudo, tal mecanismo em micro-escala, ou seja, em escala de poro não
é totalmente compreendido. O presente trabalho preocupa-se principalmente em
analisar o fator de recuperação do óleo e saturação de óleo residual após processo
de deslocamento de óleo por água salgada, solução polimérica de poliacrilamida
parcialmente hidrolisada (HPAM) e solução de glicerina em testemunhos de
Arenito Bentheimer. Um porta-testemunho especial foi utilizado para a realização
dos testes de deslocamento, sendo monitoradas a variação de pressão ao longo da
amostra, além dos volumes de injeção e produção de fluidos em função do tempo. / [en] After an oil deposit is found, oil or gas is produced through a production well
that is drilled until it reaches the rock layers where the hydrocarbons are housed.
With constant oil production, the reservoir pressure decreases until it reaches a level
that is insufficient for economic use. Water injection is generally used to maintain
the reservoir pressure level. It is essential to know the basic rock and fluid properties
to study an oil reservoir. These properties determine the volume of fluids in the
porous medium, their distribution, the ability of these fluids to move, and most
importantly, the volume of fluids that can be extracted. The conventional water
injection method aims to maintain the reservoir pressure and the oil displacement
towards the producing wells. Water (displacing fluid) tends to gradually occupy the
space previously occupied by oil (displaced fluid), however, due to capillary
effects, an oil portion is not removed from the porous medium, configuring what
we call residual oil. Because of the water-oil mobility ratio, the displacement front
is not uniform and a large volume of the reservoir is not reached by the injection
water. Polymer addition in the injection water aims at increasing water viscosity,
and thus, improving the water-oil mobility ratio, increasing the sweeping efficiency
since it unifies the advance front, reducing the formation of preferential paths in the
reservoir. Besides reducing the mobility ratio, polymeric solutions can contribute
to a better oil displacement in pore-scale, based on its elastic effect, reducing
residual oil saturation. However, this mechanism is not fully understood in the
micro-scale. The present work is concerned with analyzing oil recovery factor and
residual oil saturation after the oil displacement process by saltwater, polymeric
solution of partially hydrolyzed polyacrylamide (HPAM), and glycerin solution in
sandstone Bentheimer samples. A special core holder was used to displacement
tests, the injection differential pressure on the sample was monitored, in addition to
the injection volumes and production volume as a function of time.
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