594 research outputs found
The influence of wettability and carbon dioxide injection on hydrocarbon recovery
This study can be divided into two sections. First, a detailed study of petrophysical
properties and the impact of wettability is performed on cores from a producing
heterogeneous carbonate reservoir from the Middle East. Second, a comparison
between different injection schemes (waterflooding, gas injection, WAG and CO2
injection) for enhanced oil recovery is made for another giant carbonate reservoir in
the Middle East.
Knowledge of the wettability of a reservoir rock and its influence on petrophysical
properties is a key factor for determining oil recovery mechanisms and making
estimates of recovery efficiency. A full suite of experiments on well-characterised
systems, including sandpacks, sandstones and carbonate cores, was performed to
measure capillary pressure, relative permeability, NMR response and resistivity
index. Cores aged in crude oil, with different wettability were studied.
As a preliminary step to investigate the effect of wettability on heterogeneous
carbonates from the Middle East, sandpack and sandstone samples were first tested
because: 1) these samples are known to be quite homogeneous and of a wettability
that can be controlled; 2) To test our experimental methods; and 3) to serve as a
dataset for modelling studies.
First, the static (porosity and permeability) and dynamic (initial water saturation and
residual oil saturation) properties of Leavenseat (LV60) and Ottawa (F-42) sandpacks
were measured. The formation factor and NMR response for these sandpacks were
also determined. These experimental measurements have served as a benchmark for
pore-modelling studies that have reproduced the experimental data.
Fontainebleau sandstones have also been used as a benchmark in the industry
because of its relatively simple pore structure. Mercury injection capillary pressure
(MICP) measurements were performed on this sandstone. The MICP experimental
measurements showed very low pore volume values, indicating very tight
(consolidated) samples. These samples had a diameter of less than 0.02 m which
made the experiments quite difficult.
Once we had confidence in the experimental methodology, five carbonate samples
from a typical Middle East reservoir were imaged and cleaned in order to render
them more water wet. Conventional and special core analyses were performed on all
the samples. The pore throat distribution from capillary pressure was successfully
compared with the pore size distribution inferred from the NMR T2 relaxation curve.
Formation resistivity factor and the formation resistivity index were also measured.
Capillary pressure and relative permeability curves were measured using refined oil
and synthetic formation brine. Then the samples were aged in crude oil from the same field at elevated temperature (120oC) and underwent the same experiments to
evaluate the influence of wettability changes on these properties.
The experimental data show that there is a significant difference in the relative
permeability and capillary pressure of the cleaned and aged samples; the results are
explained in terms of the pore-scale configurations of fluids. In contrast, electrical
resistivity did not encounter significant changes for different wettability, suggesting
that electrical properties in these carbonates are mainly affected by the porosity that
remains water-wet, or is only neutrally-wet. This conclusion is supported by the
significant displacement that is observed in the aged sample at capillary pressures
close to zero.
We show that wettability, imbibition capillary pressure and relative permeability
have major impact on the waterflood sweep efficiency and hence on the distribution
of remaining oil saturation. An incorrect understanding of the distribution of
remaining oil saturation may lead to ineffective reservoir management and IOR/EOR
decisions.
The second part of this thesis is to assess the efficacy of CO2 injection into carbonate
oil fields. The reservoir under study is a layered system. The reservoir consists of two
main units, i.e. a lower zone of generally low permeability layers and an upper zone
of high permeability layers inter-bedded with low permeability layers; the average
permeability of the upper zone is some 10-100 times higher than that of the Lower zone. Under waterflooding, the injected water tends to flow through the upper zone
along the high permeability layers and no or very slow cross flow of water into the
lower zone occurs, resulting in very poor sweep of the lower zone. There is
significant scope for improving oil recovery from such type of heterogeneous mixedwet
carbonate reservoirs. The apparent impediment to water invading the bottom
strata prompts suggests that a miscible fluid could be Injected into the lower zone.
We conducted a series of core-flood experiments to compare the performance of
different displacement process: waterflooding, hydrocarbon gas flooding and wateralternate
gas (WAG) and compared them with CO2 injection. We show that the local
displacement efficiency for CO2 flooding is approximately 97% - much higher than
that obtained from waterflooding or hydrocarbon gas injection, due to the
development of miscibility between CO2 and the oil. We use the results to discuss
the potential of CO2 injection for storage and enhanced oil recovery in the Middle
East carbonate reservoir discussed above, and proposes further research to develop
a fuller understanding of the subsurface behavior of CO2
Analytical approximate solutions for two-dimensional incompressible Navier-Stokes equations
Analytical approximate solutions of the two-dimensional incompressible Navier-Stokes equations by means of Adomian decomposition method are presented. The power of this manageable method is confirmed by applying it for two selected flow problems: The first is the Taylor decaying vortices, and the second is the flow behind a grid, comparison with High-order upwind compact finite-difference method is made. The numerical results that are obtained for two incompressible flow problems showed that the proposed method is less time consuming, quite accurate and easily implemented. In addition, we prove the convergence of this method when it is applied to the flow problems, which are describing them by unsteady two-dimensional incompressible Navier-Stokes equations. Keywords: Navier-Stokes equations, Adomian decomposition, upwind compact difference, Accuracy, Convergence analysis,Taylor's decay vortices, flow behind a grid
Enhanced CNN with Global Features for Fault Diagnosis of Complex Chemical Processes
Convolutional neural network (CNN) models have been widely used for fault
diagnosis of complex systems. However, traditional CNN models rely on small
kernel filters to obtain local features from images. Thus, an excessively deep
CNN is required to capture global features, which are critical for fault
diagnosis of dynamical systems. In this work, we present an improved CNN that
embeds global features (GF-CNN). Our method uses a multi-layer perceptron (MLP)
for dimension reduction to directly extract global features and integrate them
into the CNN. The advantage of this method is that both local and global
patterns in images can be captured by a simple model architecture instead of
establishing deep CNN models. The proposed method is applied to the fault
diagnosis of the Tennessee Eastman process. Simulation results show that the
GF-CNN can significantly improve the fault diagnosis performance compared to
traditional CNN. The proposed method can also be applied to other areas such as
computer vision and image processing.Comment: 6 pages, 5 figure
New analytical approximate solutions of Fifth-order KdV equation
In this paper, we have exposed a process of how to implement a new splitting Adomian decomposition homotopy perturbation method to solve fifth-order KdV equations. The new methodology is applied on two kinds of fifth-order KdV equations with initial data: The first is Sawada-Kotera equation and the second its Lax equation. The numerical results we obtained from solutions of two kinds of fifth-order KdV equations, have good convergent and high accuracy comparison with other methods in literature. The graphs and tables of the new analytical approximate solutions show the validity, usefulness, and necessity of the process. Keywords: Splitting scheme, Adomian decomposition, homotopy perturbation method, fifth-order KdV equation, convergence analysis. Mathematics Subject Classifications 2010 [MSC]: 76S05, 65N99, 35Q3
Splitting Decomposition Homotopy Perturbation Method To Solve One -Dimensional Navier -Stokes Equation
We have proposed in this research a new scheme to find analytical approximating solutions for Navier-Stokes equation of one dimension. The new methodology depends on combining Adomian decomposition and Homotopy perturbation methods with the splitting time scheme for differential operators . The new methodology is applied on two problems of the test: The first has an exact solution while the other one has no exact solution. The numerical results we obtained from solutions of two problems, have good convergent and high accuracy in comparison with the two traditional Adomian decomposition and Homotopy perturbationmethods . 
Numerical Solution of Mixed Volterra – Fredholm Integral Equation Using the Collocation Method
معادلات فولتيرا- فريدهولم التكاملية المختلط ((MVFIEs لديها اهتمام كبير من قبل الباحثين مؤخرا . الطريقة العددية الي اقترحت لحل هذا النوع من المعادلات تستعمل نقاط التجميع وتقريب الحل بواسطة الدالة اساس الشعاعي (radial basis function) و متعددة حدود من الدرجة الثانية واندراج النقطة من دون استخدام الشبكة, ولسهولة الحل تم استخدام اصفار متعددة حدود ليجندر كنقاط تجمع. الغرض الرئيسي من استخدام دالة أساس الشعاعي ومتعدد الحدود هو التغلب على التفرد الذي قد يرتبط بأساليب التجميع. علاوة على ذلك، فإن وظيفة الاستيفاء التي تم الحصول عليها تمر عبر كل النقاط المنتشرة في مجال ما ، وبالتالي فإن وظائف الشكل هي من خصائص خاصية دلتا. تمت مقارنة الحل الدقيق للحلول الانتقائية بالنتائج التي تم الحصول عليها من التجارب العددية من أجل التحقق من دقة وكفاءة طريقتنا.Volterra – Fredholm integral equations (VFIEs) have a massive interest from researchers recently. The current study suggests a collocation method for the mixed Volterra - Fredholm integral equations (MVFIEs)."A point interpolation collocation method is considered by combining the radial and polynomial basis functions using collocation points". The main purpose of the radial and polynomial basis functions is to overcome the singularity that could associate with the collocation methods. The obtained interpolation function passes through all Scattered Point in a domain and therefore, the Delta function property is the shape of the functions. The exact solution of selective solutions was compared with the results obtained from the numerical experiments in order to investigate the accuracy and the efficiency of scheme
Soft computing models for assessing bond performance of reinforcing bars in concrete at high temperatures
The bond between steel and concrete in reinforced concrete structures is a multifaceted and intricate phenomenon that plays a vital role in the design and overall performance of such structures. It refers to the adhesion and mechanical interlock between the steel reinforcement bars and the surrounding concrete matrix. Under elevated temperatures, the bond is more complex under higher temperatures, yet having an accurate estimate is an important factor in design. Therefore, this paper focuses on using data-driven models to explore the performance of the concrete-steel bond under high temperatures using a Gene Expression Programming (GEP) soft computing model. The GEP models are developed to simulate the bond performance in order to understand the effect of high temperatures on the concrete-steel bond. The results were compared to the multi-objective evolutionary polynomial regression analysis (MOGA-EPR) models for different input variables. The new model would help the designers with strength predictions of the bond in fire. The dataset used for the model was obtained from experiments conducted in a laboratory setting that gathered a 316-point database to investigate concrete bond strength at a range of temperatures and with different fibre contents. This study also investigates the impact of the different variables on the equation using sensitivity analysis. the results show that the GEP models are able to predict bond performance with different input variables accurately. This study provides a useful tool for engineers to better understand the concrete-steel bond behaviour under high temperatures and predict concrete-steel bond performance under high temperatures
An optimized prediction of FRP bars in concrete bond strength employing soft computing techniques
The precise estimation of the bonding strength between concrete and fiber-reinforced polymer (FRP) bars holds significant importance for reinforced concrete structures. This study introduces a new methodology that utilizes soft computing methods to enhance the prediction of FRP bars’ bonding strength. A significant compilation of experimental bond strength tests is assembled, covering various variables. Significant variables that affect bonding strength are found in the study of this database. The prediction process is optimized using soft computing methods, particularly Gene Expression Programming (GEP) and the Multi-Objective Genetic Algorithm Evolutionary Polynomial Regression (MOGA-EPR).The proposed soft computing approaches accommodate complex relationships and optimize prediction accuracy depending on the input variables. Results demonstrate its effectiveness in predicting bond strength and comparing it with existing codes and other models from the literature. The results have shown that the MOGA-EPR and the GEP models have high R2 values between 0.91 and 0.94. The proposed new models enhance the reliability and efficiency of designing and assessing FRP-reinforced concrete
Shear strength assessment of reinforced recycled aggregate concrete beams without stirrups using soft computing techniques
This paper presents a study to predict the shear strength of reinforced recycled aggregate concrete beams without stirrups using soft computing techniques. The methodology involves the development of a Multi-Objective Genetic Algorithm Evolutionary Polynomial Regression (MOGA-EPR) and Gene Expression Programming (GEP) models. The input variables considered are the longitudinal reinforcement ratio, recycled coarse aggregate ratio, beam cross-section dimensions, and concrete compressive strength. Data collected from the literature were used to train and validate the models. The results showed that the MOGA-EPR and GEP models can accurately predict the shear strength of beams without stirrups. The models also performed better than equations from the codes and literature. This study provides an alternative approach to accurately predict the shear strength of reinforced recycled aggregate concrete beams without stirrups
A New Technique for Simulation the Zakharov–Kuznetsov Equation
In this article, a new technique is proposed to simulated two-dimensional Zakharov–Kuznetsov equation with the initial condition. The idea of this technique is based on Taylors' series in its derivation. Two test problems are presented to illustrate the performance of the new scheme. Analytical approximate solutions that we obtain are compared with variational iteration method (VIM) and homotopy analysis method (HAM). The results show that the new scheme is efficient and better than the other methods in accuracy and convergence
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