Self-sustaining smouldering combustion of coal tar for the remediation of contaminated sand:Two-dimensional experiments and computational simulations

This study presents the development and validation of a computational model which simulates the propagation of a smouldering front through a porous medium against unique experiments in coal tar and sand. The model couples a multiphase flow solver in porous media with a perimeter expansion module based on Huygens principle to predict the spread. A suite of two-dimensional experiments using coal tar- contaminated sand were conducted to explore the time-dependent vertical and lateral smouldering front 6 propagation rates and final extent of remediation as a function of air injection rate. A thermal severity analysis revealed, for the first time, the temperature-time relationship indicative of coal tar combustion. The model, calibrated to the base case experiment, then correctly predicts the remaining experiments. This work provides further confidence in a model for predicting smouldering, which eventually is expected to be useful for designing soil remediation schemes for a novel technology based upon smouldering destruction of organic contaminants in soil

Varyans bileşenlerinin kestirim yöntemlerinin incelenmesi

TEZ1910Tez (Yüksek Lisans) -- Çukurova Üniversitesi, Adana, 1995.Kaynakça (s. ix-xviii) var.xx, 70 s. ; 30 cm.

The Effect of Heterogeneity on In-situ Combustion: The Propagation of Combustion Fronts in Layered Porous Media

This report extend the approach to heterogeneous systems, by considering the simpler case of in-situ combustion in layered porous media (and particularly to a two-layer model). Analytical models were developed to delineate the combined elects of fluid flow, reaction and heat transfer on the dynamics of combustion fronts in layered porous media, using as parameters the thermal coupling between the layers, the heat transfer to the surroundings and the permeability contrast

Non-Adiabatic Effects on Combustion Front Propagation in Porous Media: Multiplicity of Steady States

The sustained propagation of combustion fronts in porous media is a necessary condition for the success of an in situ combustion project for oil recovery. Compared to other recovery methods, in situ combustion involves the added complexity of exothermic reactions and temperature-dependent chemical kinetics. In the presence of heat losses, the possibility of ignition and extinction (quenching) exists. In this report, we address the properties of combustion fronts propagating at a constant velocity in the presence of heat losses

The Dynamics of Combustion Fronts in Porous Media

In this report, a method for solving this problem by treating the reaction region as a place of discontinuities in the appropriate variables, which include, for example, fluxes of heat and mass was proposed. Using a rigorous perturbation approach, similar to that used in the propagation of flames and smoldering combustion, appropriate jump conditions that relate the change in these variables across the front was derived. These conditions account for the kinetics of the reaction between the oxidant and the fuel, the changes in the morphology of the pore space and the heat and mass transfer in the reaction zone. The modeling of the problem reduces to the modeling of the dynamics of a combustion front, on the regions of either side of which transport of momentum (fluids), heat and mass, but not chemical reactions, must be considered. Properties of the two regions are coupled using the derived jump conditions. This methodology allows one to explicitly incorporate permeability heterogeneity effects in the process description, without the undue complexity of the coupled chemical reactions

Numerical Simulation of Hydraulic Fracturing Water Effects on Shale Gas Permeability Alteration

Hydraulic fracturing has been recognized as the necessary well completion technique to achieve economic production from shale gas formation. However, following the fracturing, fluid–wall interactions can form a damaged zone nearby the fracture characterized by strong capillarity and osmosis effects. Here, we present a new reservoir multi-phase flow model which includes these mechanisms to predict formation damage in the aftermath of the fracturing during shut-in and production periods. In the model, the shale matrix is treated as a multi-scale porosity medium including interconnected organic, inorganic slit-shaped, and clay porosity fields. Prior to the fracturing, the matrix holds gas in the organic and the inorganic slit-shaped pores, water with dissolved salt in the inorganic slit-shaped pores and the clay pores. During and after fracturing, imbibition causes water invasion into the matrix, and then, the injected water–clay interaction may lead to clay-swelling pressure development due to osmosis. The swelling pressure gives additional stress to slit-shaped pores and cause permeability reduction in the inorganic matrix. We develop a simulator describing a system of three pores, two phases (aqueous and gaseous phases), and three components (H 2O , CH 4, and salt), including osmosis and clay-swelling effect on the permeability. The simulation of aqueous-phase transport through clay shows that high swelling pressure can occur in clays as function of salt type, salt concentration difference, and clay-membrane efficiency. The new model is used to demonstrate the damage zone characteristics. The simulation of two-phase flow through the shale formation shows that, although fracturing is a rapid process, fluid–wall interactions continue to occur after the fracturing due to imbibition mechanism, which allows water to penetrate into the inorganic pore network and displace the gas in-place near the fracture. This water invasion leads to osmosis effect in the formation, which cause clay swelling and the subsequent permeability reduction. Continuing shale–water interactions during the production period can expand the damage zone further