Objective
The objective of this project is to improve the physical modelling and numerical simulation of oil recovery supported by in situ combustion. For this purpose, the influence exerted by the oil composition (especially the resin and asphaltene contents) on the generation of fuel during in situ combustion is to be investigated. The reaction kinetic data are to be determined as functions of the oil composition under isothermal conditions. With the aid of the data thus ascertained, a physically more exact description of the in situ combution process is envisaged on the basis of numerical models (at IFP, Paris). The results concerning reaction kinetics are to be employed in the investigations of the relationship between the oil composition and propagation velocity of the combustion front. For this purpose, combustion tests are to be conducted in a linear combustion cell under largely adiabatic conditions.
PHASE 1
Appropriate crude oil was enriched with its own asphaltenes or its own wax-resin complex in order to prepare oil mixtures of different colloidal composition. High-pressure differential thermal reactors were developed and employed for the experiments. The relationship between the oil composition and fuel formation was investigated with different pyrolytic media (nitrogen, carbon dioxide, steam) under isobaric (8 MPa) and isothermal (623, 723, 823 and 923 K) conditions. Both the total quantities of colloidal components in the oil and the pyrolytic medium thereby exert a quantitative effect on the fuel formation. Steam has proved to be the most effective pyrolytic medium, since it decidedly decreases the residue of pyrolysis, as compared with nitrogen and carbon dioxide. The quantity of fuel is directly proportional to the quantity of resins, waxes and asphaltenes.
Furthermore, the relationship between the oil composition and reaction kinetics of fuel oxidation has been investigated at constant pressure under isothermal and nonisothermal conditions. The kinetic parameters thus determined(K, KO, EA) indicate that the reactivity of the fuel toward oxygen at 623 and 723 K increases with augmenting wax-resin content in the oil. At higher temperature (823 and 923 K), however, the fuel from the mixture which is richest in asphaltenes is more reactive than that from the mixture richest in wax and resin. The same trend has also been observed for the combustion of the pyrolytic residue from pure asphaltenes or waxes and resins.
A linear combustion cell has been developed for investigating the propagation velocity of the combustion front with different composition of the oil employed. With this cell, experiments can be performed under quasiadiabatic conditions at a pressure of 8 MPa. This feature was achieved by means of a transportable, external heater which moves with the combustion front and thus largely compensates for the heat losses.
The propagation velocity of the combustion front can be measured by means of thermocouples arranged axially, and the variation of the pressure gradient can be recorded with the use of differential pressure transducers arranged radially. The efficiency of the combustion and the fuel balance can be calculated from the analysis of the product gases for oxygen, carbon dioxide, and carbon monoxide.
The same sock oil and mixture enriched with asphaltenes was employed for the combustion as for the kinetic investigations. Under identical conditions (air throughput : 93 sm3. m-1.
h-1, pressure : 8 MPa, residual oil saturation : about 40 %, the same values of the propagation velocity were measured; the higher fuel concentration in the mixture thereby decreases the velocity, but the higher reactivity counteracts this drawback.
PHASE 2
One- and two-dimensional models have been realized for simulating forward in sity combustion in the laboratory or in the reservoir.
The research project has been subdivided into two phases..
PHASE 1
This phase comprises three stages for investigation the combustion process. During the first stage, the relationship between the oil composition and generation of fuel is to be investigated. During the second stage, the effect of the oil composition on the reaction kenetics during combustion is to be examined. During the third stage, the influence of the oil composition on the propagation velocity of the combustion front is to be investigated with the use of the results from stages 1 and 2..
PHASE 2
During this phase, numerical models for in situ combustion are to be elaborated in two stages. Stage 1 comprises the development of a model without considering the fluid transport. In stage 2, a model is constructed with the fluid transport taken into account..
TECHNICAL DESCRIPTION
An appropriate crude oil is enriched with its own asphaltenes and resins for obtaining three types of model oil differing mutually in colloidal-chemical composition. The pyrolysis of the different model oil types is performed under inert gas, and the quantity of fuel thereby generated is determined. A differential reactor is being constructed for the purpose. An attempt will be made to derive a satisfactory correlation between the quantity of fuel thus formed and the oil composition. The combustion of the coke is to be investigated under isothermal conditions in the presence of air in a temperature range between 623 K and 923 K. The quantitative and qualitative analyses of the reaction gases, as well as the combustion temperature and pressure constitute the basis for the determination of the reaction rate constant for the oxidation.
By means of linear combustion tests, the effect of the oil composition on the propagation velocity of the combustion front is to be investigated.
The construction of the numerical models begins with a simplified radial model without considering kinetics and transport processes.
Heat exchange, reaction kinetics, and fluid transport are then taken into account, thus resulting in a two-dimensional model. The block size for the process description is thereby matched to the reservoir scale. The models are to be tested by the laboratory results of phase 1 and by means of field conduted experiments conducted in the classical manner.
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DEM - Demonstration contractsCoordinator
3392 CLAUSTHAL-ZELLERFELD
Germany