Numerical simulation of thermal and reaction waves for in situ combustion in hydrocarbon reservoirs

New in situ combustion (ISC) method variants hold much promise in the way of ultimate oil recovery and recovery rates. The interactions of thermal and reaction waves for ISC recovery of heavy oils are here investigated numerically. A set of dimensionless screening parameters is developed in order to investigate important ISC phenomena, i.e. ignition delay time, flame thickness and propagation, ultimate recovery, and recovery efficiency. Defining a heavy oil Damköhler number (DaO) allows the identification of three performance regions of ignition delay: thermal diffusion limited, chemistry limited, and oxygen supply limited. There exists also a coke Damköhler number (DaC) threshold for the combustion wave to propagate or else extinguish. The ISC process efficiency and recovery rate are observed to be functions mainly of the DaC number and less so of the DaO number. © 2013 Elsevier Ltd. All rights reserved

Simulations of thermal upgrading methods for oil shale reservoirs

This paper analyzes reaction and thermal front development in porous reservoirs with reacting flows, such as those encountered in shale oil extraction. A set of dimensionless parameters and a 3D code are developed in order to investigate the important physical and chemical variables of such reservoirs when heated by in situ methods. This contribution builds on a 1D model developed for the precursor study to this work. Theory necessary for this study is presented, namely shale decomposition chemical mechanisms, governing equations for multiphase flow in porous media and necessary closure models. Plotting the ratio of the thermal wave speed to the fluid speed allows one to infer that the reaction wave front ends where this ratio is at a minimum. The reaction front follows the thermal front closely, thus allowing assumptions to be made about the extent of decomposition solely by looking at thermal wave progression. Furthermore, this sensitivity analysis showed that a certain minimum permeability is required in order to ensure the formation of a traveling thermal wave. It was found that by studying the non-dimensional governing parameters of the system one can ascribe characteristic values for these parameters for given initial and boundary conditions. This allows one to roughly predict the performance of a particular method on a particular reservoir given approximate values for initial and boundary conditions. Channelling and flow blockage due to carbon residue buildup impeded each method's performance. Blockage was found to be a result of imbalanced heating. Copyright 2012, Society of Petroleum Engineers