Nader Mahinpey

IN SITU COMBUSTION IN ENHANCED OIL RECOVERY (EOR): A REVIEW

Enhanced oil recovery (EOR) refers to the technologies developed to increase extraction of crude oil from reservoirs after primary production. In situ combustion (ISC) is one of the methods developed for EOR. This review examines studies done by researchers worldwide to improve our understanding of the mechanism of oil cracking kinetics, which is one of the fundamental mechanisms of in situ combustion. Good agreement between the laboratory and field results has encouraged further research in this field. Extensive research at the laboratory scale to understand the pyrolysis and oxidation behavior of coke formed from medium and light oil and also to propose more realistic models to mimic the true behavior of in situ combustion has been undertaken in recent years. Apart from the classical Arrhenius model, researchers have come up with other models (two-step oxidation model) based on the type of combustion activity observed from their samples, thus modeling the process more accurately. Research work showing optimization of the parameters of ISC and improving the economic viability of the entire process is been one of the main focuses of this article. The review also explains the nature of the various experiments, sheds light on some of the concepts that remain unexplained, and opens the way for fresh thinking in those areas. It also highlights the possibility of developing global solutions for numerical simulation of this EOR process.

A Simple Kinetic Model for Coke Combustion During an In-Situ Combustion (ISC) Process

Although coke combustion studies have long been conducted, the literature is still lacking an accurate understanding of reaction kinetics. To this end, the thermo-oxidative behaviours of Neilburg oil and its asphaltene fraction were examined in the presence of core sand. Thermogravimetric analysis (TGA) was performed in a flowing atmosphere at the heating rate of 10°C/min up to 750°C. Both nitrogen and air were used at a flow rate of 45 ml/ min in the experiments. As earlier researchers have observed, at least two main regions of reactions were identified by the thermogravimetric (TG) and derivative thermogravimetric (DTG) thermograms. Various effects, including distillation, low-temperature oxidation (LTO), thermal cracking, middle-temperature oxidation (MTO), high-temperature oxidation (HTO) or combustion, and even mineral decomposition, were observed. In this study, Neilburg oil and asphaltenes were completely cracked in a nitrogen atmosphere at 425°C to produce coke. Subsequently, the fresh coke was subjected to isothermal combustion at several temperatures from 374°C to 519°C. A two-step oxidation reaction model was applied to describe this combustion process. The chemical reactions were simplified into two oxidations occurring in series. In the first reaction, coke was partially oxidized to form an intermediate product, which was then burned in the second reaction. Based on the TGA data, kinetic parameters were estimated with the aid of custom written software. For comparison, the one-step oxidation reaction model was also employed to predict the combustion process. The two-step oxidation reaction model gave a better fit to the experimental data. It was also confirmed that the coke derived from the Neilburg asphaltenes is reasonably representative of the coke derived from the whole oil.

Experimental Study on Local Mass Transfer in a Simplified Bifurcation Model: Potential Role in Atherosclerosis

Local mass transfer coefficients and flow patterns were examined in an idealized human aortic bifurcation model. The objectives of this study are to gain further insights on the convective mass transfer process and its possible role in the localization of atherosclerotic lesions. The laser photochromic tracer method provided velocity and wall shear stress estimates in the plane of symmetry of a UV-transparent Plexiglas bifurcation model. Steady flow data were acquired at Reynolds numbers of 500, 600, and 750. A novel copper electrodeposition technique was used to obtain time-averaged convective local mass transfer coefficients in a model identical to that used in the flow experiments. The laminar flow mass transfer data for the trunk of the bifurcation are in good agreement with the analytical Levesque solution. At the bifurcation, higher mass transfer coefficients along the inner wall and lower ones along the outer wall were observed. Further, mass transfer and wall shear stress follow similar patterns both on the inner and outer walls in that StSc2/3 and Cf/2 demonstrate analogous behavior. Lower transfer rates of momentum and mass occurred along the outer wall of the branches where lesions tend to develop.

The Effects of Mass Transfer Parameters on the Modeling of A PEM Fuel Cell

A detailed steady-state isothermal two-dimensional model of a proton exchange membrane fuel cell has been developed. This multi-component transport model coupled with flow in porous medium, charge balance, electrochemical kinetics and water movement in the membrane was solved using a finite element method. The solution was able to show the movement of water in the membrane by electro osmotic drags, the effects of channel width and bipolar plate shoulder dimensions, porosity, and relative humidity of the inlet steam of the anode and dry air on the cathode side.