Sohrab Zendehboudi

Evaluating the unloading gradient pressure in continuous gas-lift systems during petroleum production operations

Evaluating the performance, applicability, and field testing of various artificial lift methods, in particular continued gas-lift, can be time consuming and costly. To overcome these drawbacks, it is needed to propose a reliable model to estimate gas-lift applicability in advance of the installation under specific well operational conditions such as tubing size and design oil rate. In this study, the robust least square modification of support vector machine (LSSVM) methodology is implemented to propose a computer program, by which the unloading pressure gradient region can be determined in various design oil production rates and also tubing sizes. The developed LSSVM model results indicate 1.084% average absolute relative deviation from the corresponding unloading pressure gradient literature values, and squared correlation coefficient of 0.9994.

Estimation of the effect of biomass moisture content on the direct combustion of sugarcane bagasse in boilers

Many of the large-scale biomass combustion systems for producing heat, hot water, or steam accept biomass fuels containing relatively large amounts of moisture. Dry biomass burns at higher temperatures and thermal efficiencies than wet biomass. Flame temperature is directly related to the amount of heat necessary to evaporate the moisture contained in the biomass, the lower the moisture content, the lower the amount of energy needed to remove the water and the higher the boiler efficiency. In this article, a simple predictive tool is developed to estimate boiler efficiency as a function of stack gas temperature and sugarcane bagasse moisture content. The method quantitatively illustrates the effect of moisture content on the performance of a thermochemical process, for the direct combustion of sugarcane bagasse in a conventional boiler. The results are found to be in excellent agreement with reported data in the literature with average absolute deviation being around 1%. The tool developed in this study can be of immense practical value for engineers to have a quick check on biomass moisture content on the boiler performance at various conditions without opting for any experimental trials. In particular, engineers would find the approach to be user-friendly with transparent calculations involving no complex expressions.

A new method estimates TEG purity versus reconcentrator temperature at different levels of pressure in gas dehydration systems

There are several processes and principles for obtaining high triethylene glycol (TEG) purity in gas dehydration process. All methods are based on the principle of reducing the effective partial pressure of water in the vapour space of the glycol reboiler, and hence obtaining a higher glycol concentration at the same temperature. One of the most common methods for enhancement of the glycol concentration has been by means of pressure reduction in the reboiler. In this article a simple method is developed to estimate TEG purity as a function of reconcentrator (reboiler) temperature and pressure. The results are found to be in excellent agreement with reported data in the literature with average absolute deviation being around 0.05%. The tool developed in this study can be of immense practical value for engineers to have a quick check on TEG purity as a function of reconcentrator (reboiler) temperature and pressure at various conditions without opting for any experimental trials. In particular, engineers would find the approach to be user-friendly with transparent calculations involving no complex expressions.

CALCULATING PSEUDO-STEADY-STATE HORIZONTAL OIL WELL PRODUCTIVITY IN RECTANGULAR DRAINAGE AREAS USING A SIMPLE METHOD

To determine the economical feasibility of drilling a horizontal well, engineers need reliable methods to estimate its productivity. In this work, a simple-to-use method is developed to rapidly estimate a pseudo-steady-state horizontal wells productivity. Estimations are found to be in excellent agreement with the reliable data in the literature, with average absolute deviation being less than 1%. The tool developed in this study can be of immense practical value for petroleum engineers to make a quick check on a pseudo-steady-state horizontal wells productivity at various conditions without opting for any field trials. The predictive tool is simple and straightforward, and it can be readily implemented in a standard spreadsheet program. The prime application of the method is as a quick-and-easy evaluation tool in conceptual development and scoping studies where horizontal wells are being considered. The method may also serve as a benchmark in numerical reservoir simulation studies.

Investigation of Gravity Drainage in Fractured Porous Media Using Rectangular Macromodels

The oil production from well fractured carbonate reservoirs is a considerable part of the total oil production in the world. The petroleum resource base in naturally fractured reservoirs is estimated to be in the range of billions of barrels in the U.S and in addition, a multibillionbarrel international oil resource base exists in naturally fractured reservoirs. Gravity drainage is important in some of oil recovery processes, either acting as the driving force in processes using horizontal wells or altering the displacement patterns during water-flooding, chemical flooding, CO2 flooding and other EOR methods. The gravity drainage process has a major effect on oil recovery from oil reservoirs. Gravity drainage driven oil production in naturally fractured and other complex reservoirs falls into two regimes: the balk flow regime and the film flow regime. Oil recovery by gravity drainage in a fractured reservoir strongly depends on the capillary height of the porous medium. Capillarity and gravity forces are usually the major driving forces in fractured reservoirs. This PhD thesis consists of two main parts namely: 1) Experimental works on gravity drainage, and 2) Modeling and simulation of the gravity drainage processes using COMSOL® software. An appropriate design of experiment (DOE) method was selected to find the most important parameters contributing in gravity drainage and then conduct the experiments in a useful as well as economic manner. A two-dimensional experimental setup was employed to investigate free fall gravity drainage (FFGD) and controlled gravity drainage (CGD) using unconsolidated glass beads fractured porous media having various fractures configurations. Flow visualization measurements were carried out. Following the flow visualization experiments, parametric sensitivity analysis was performed considering the effects of different system parameters such as fracture aperture, matrix height, permeability, and fluid properties on the dependent variables including drainage rate, critical pumping rate, maximum drainage rate, recovery factor and so on. These experiments enabled us to capture some aspects of the recovery mechanism and the flow communication between matrix block and fracture during gravity drainage. After analyzing the experimental data for the FFGD test runs, it was found that the rate of liquid flowing from matrix to fracture is proportional to the difference of liquid levels in the matrix and in the fracture. In addition, the characteristic rate and the maximum liquid drainage rate from the fractured models were determined for such a stable gravity-dominated process. The experiments showed that the presence of fracture is more influential in lower matrix permeability systems. For a given fracture-matrix system with different initial liquid saturation conditions, it was seen that the production history can be correlated by plotting the fraction of recoverable liquid as a function of time. Furthermore, the recovery factor can be correlated using dimensionless numbers such as the Bond number and the dimensionless time. For the controlled gravity drainage (CGD) test runs conducted, the experimental results indicated that higher pumping rates cause a higher difference between the liquid levels in the fracture and

Estimation of the depth of frost penetration in both uniform and layered soils in frost-affected regions

One of the most important factors affecting pavement performance is climate, including frost action and precipitation. The performance of pavements in frost-affected regions depends to a large degree on the depth of frost penetration. In this paper, a simple predictive tool is developed to calculate a new correction coefficient depending upon the thermal ratio and fusion parameter. The new correction coefficient can be used in follow-up calculations to estimate the depth of frost penetration for both uniform and layered soils in frost-affected regions to evaluate the performance of pavement. The results of the proposed method are found to be in excellent agreement with reported data in the literature with average absolute deviation being less than 0.8%. The predictive tool is simple, straightforward and can be readily implemented in any standard spreadsheet programme leading to accurate, smooth and non-oscillatory data points. The prime application of the method is as a quick-and-easy evaluation tool in conceptual development and scoping studies in which the depth of frost penetration for both uniform and layered soils in frost-affected regions is being considered. The method may also serve as a benchmark in numerical and rigorous simulation studies.

A novel method to estimate the specific gravity and refractive index of seawater

AbstractSeawater is described by a number of physical and chemical parameters that are useful in measurement and analysis of materiel effects. The material dissolved in seawater will not only affect its specific gravity, but also its optical properties, or rather, the degree to which light is refracted as it passes through the sample of water. The specific gravity and refractive index of seawater are related directly to salinity and temperature. In this work, an attempt has been made to develop simple predictive tools to estimate specific gravity and refractive index of seawater as a function of salinity and temperature. Estimations are found to be in excellent agreement with reported data in the literature with average absolute deviation being less than 0.2%.The predictive tool developed in this study can be of immense practical value for engineers to have a quick estimate on the specific gravity and refractive index of seawater without opting for any experimental trials. In particular, process and water...

Hybrid connectionist model determines CO2–oil swelling factor

In-depth understanding of interactions between crude oil and CO2 provides insight into the CO2-based enhanced oil recovery (EOR) process design and simulation. When CO2 contacts crude oil, the dissolution process takes place. This phenomenon results in the oil swelling, which depends on the temperature, pressure, and composition of the oil. The residual oil saturation in a CO2-based EOR process is inversely proportional to the oil swelling factor. Hence, it is important to estimate this influential parameter with high precision. The current study suggests the predictive model based on the least-squares support vector machine (LS-SVM) to calculate the CO2–oil swelling factor. A genetic algorithm is used to optimize hyperparameters (γ and σ2) of the LS-SVM model. This model showed a high coefficient of determination (R2 = 0.9953) and a low value for the mean-squared error (MSE = 0.0003) based on the available experimental data while estimating the CO2–oil swelling factor. It was found that LS-SVM is a straightforward and accurate method to determine the CO2–oil swelling factor with negligible uncertainty. This method can be incorporated in commercial reservoir simulators to include the effect of the CO2–oil swelling factor when adequate experimental data are not available.

Validation of CFD model of multiphase flow through pipeline and annular geometries

Accuracy of prediction of pressure losses plays a vital role in the design of multiphase flow systems. The present study focused on the development of a computational fluid dynamics model to predic...

A comprehensive study on multiphase flow through annular pipe using CFD approach

The objective of the study is to analyze three-dimensional fluid flow through annular pipeline with multiphase fluids using Computational Fluid Dynamics (CFD) simulation. ANSYS Fluent version 16 platform is used to perform the simulation. Eulerian model with Reynolds Stress Model (RSM) turbulence closure is adopted to analyze multiphase fluid flow in annular flow line. The results are validated with existing experimental data and empirical correlations. A robust simulation model is developed that can be used further for different applied cases. Geometry and boundary conditions of flow are adopted from experimental works to validate the simulation. The sensitivity analysis is also conducted to observe the flow characteristics. Fluid inlet velocity of distinct phases, inner pipe rotation and eccentricity are used as input or independent parameter and pressure gradient (pressure loss per unit length) and local concentration profile at different sections of geometry are the primary output parameter to analyze. The key results show that changing inner pipe rotation and eccentricity have a significant impact on output pressure and local particle distribution which eventually help to find way out from particle blockage. The outcome of this study will help oil and gas industry in designing the pipeline.