Etude de la récupération de bruts lourds en réservoir carbonaté fracturé par le procédé de combustion in situ, Study of heavy oil recovery from a fractured carbonate reservoir using in situ combustion

Sous la direction de Michel Quintard
Thèse soutenue le 04 décembre 2009: INPT
Cette thèse présente l'étude du procédé de combustion in situ (CIS) dans un réservoir carbonaté fracturé. Afin de modéliser et de simuler les processus à grande échelle, deux axes principaux sont distinguées, qui correspondent aux petites et grandes échelles. Pour traiter les problèmes à petite échelle, un simulateur commercial de réservoir est utilisé afin d’étudier le processus à l'échelle de la carotte. Tout d'abord, le simulateur est validé pour des procédés simples pour lesquels des solutions analytiques sont disponibles. La validation plus poussée est effectuée en utilisant des résultats expérimentaux publiés dans la littérature. Puis, quelques simulations du système fracturé à l'échelle de la carotte sont effectuées. Le but de ces simulations est d'aborder, la faisabilité du processus CIS dans le système fracturé et de distinguer l'importance relative des divers mécanismes de production pétrolière. Dans l'étape suivante, les tests de tube de combustion et de cellule cinétique sont réalisés, afin de mieux comprendre la physique du processus mais aussi la cinétique de combustion dans un système carbonaté fracturé. Les simulations sont également menées à échelle d'un bloc métrique. Afin d'obtenir la connaissance nécessaire pour le changement d'échelle, des simulations sur plusieurs bloc sont menées et les moyenne des certains paramètres sont estimées. Dans la dernière partie, les conclusions sont présentées et la technique de prise de moyenne est utilisée sur un processus simple (combustion du solide-gaz) afin de donner quelques pistes quant aux enjeux futurs de ce genre de problème.
-Bruts lourds
-Réservoir carbonaté fracturé
-Combustion in situ
The aim of the present work is to study the in situ combustion (ISC) process at inter-well scale in a fractured reservoir. Due to the complexity associated with the ISC process, highly heterogeneous nature of the fractured reservoirs and some unsuccessful attempts in the past to put the process into practice, the subject of ISC in fractured systems has been receiving little interest and there are still many essential open questions in this area. It is very challenging to answer the question whether the ISC process could be applied in a heavy oil fractured reservoir or not. And if the answer is positive, what is (are) the dominant oil recovery mechanism(s) and finally, how can we model and simulate this process, at least, at inter-well scale. This work tries to give answers to some of these questions. In this regard, we followed a step by step procedure. In the first step, general literature concerning the combustion process in porous media and particularly that related to the combustion process in an oil reservoir was reviewed. Some other references about the modeling of fracture reservoirs were also reviewed. This led us to distinguish some of the main challenges in this area and define a methodology for the rest of the work. Based on this methodology, the first target was to understand and to characterize the behavior of a combustion front at small (Darcy) scale. The second target was to apply the knowledge of the first part to propose a suitable model for ISC at larger scale. To this end, a commercial thermal reservoir simulator (STARS) was used. The simulator was validated for both simple process for which an analytical solution is available and for a more complex process where the laboratory results are on hand. Then, after the validation part, the numerical tool has been used to widely investigate the conditions where a reaction front can propagate in a fractured core. This allowed us to understand some of the leading mechanisms (oxygen diffusion coefficient for extinction/ propagation of combustion front and matrix permeability for oil production). Some other numerical studies provided us with some understanding about the most important mechanism(s) of oil production. Thereafter, some single block simulations were done to investigate the two-dimensional behavior of the ISC process, based on which the underlying process was found to be diffusion dominated both for heat and mass transfers. These results also helped us to distinguish the characteristic length scale of some important parameters (temperature, coke concentration, combustion front, etc.) which can give useful information about the large scale model. After that, an experimental part has been performed to find propagation conditions of ISC at laboratory scale. This was done by varying both the operational conditions (flowrate, pressure and oxygen concentration) and the characteristics of the fractured system (aperture, surface area, permeability). This permitted us to find that in some suitable conditions there is a possibility to generate a combustion front in a fractured system containing heavy oil. To give an idea about the modeling of the process at larger scale, some fine grid simulations are also performed using a multi-block model. By analyzing the results of this model some guidelines are proposed for the large scale model. At the end, a short discussion about the upscaling of an easy system (solid-gas combustion using an Arrhenius law as a function for the mass sink term in a conductive system) is presented based on an upscaling using the volume averaging method.
-In situ combustion
-Fractured reservoir
-Heavy oil
Source: http://www.theses.fr/2009INPT064H/document