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This thesis intends to evaluate, theoretically and quantitatively, existing studies related to the absorptive capacity of the Saudi Arabian economy. In our study, we put forward a new approach to understand the concept of absorptive capacity _ one which takes into account the special characteristics of oil-based economies in building a macro-economic model. We define absorptive capacity as "the ability of the economy to absorb, and utilize oil-revenues effectively, within a given period." Such utilization will be for consumption, investment and trade. Our approach is quite comprehensive since it considers all sectors in the economy. The Saudi economy with its unique feature represents an interesting development pattern, where the problem is not capital scarcity but capital abundance and its effective utilization. We believe that this criterion alone mandates a new development model, a task that we have tried to fulfill in this study. Our study aims to examine the success of the Saudi economy in utilizing oil revenues to expand its absorptive capacity and in accelerating the process of diversification of the economy. Accordingly, an econometric model has been formulated and the statistical results have been presented. The simulations exercises are designed to test the validity and stability of the model. The study also provides a forecast for the absorptive capacity of the Saudi economy until 2000. A comparison between our projection and the government's estimation for the Fourth Plan (1985-1990) is also presented. On the basis of the available statistical criteria, the performance of our model could be regarded as very satisfactory. We hope that the policy implications derived from this empirical investigation will be helpfull as guidelines in formulating future policies for providing sound and stable growth of the economy.

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Improved oil recovery (lOR) techniques target the 60% of oil left behind by primary and secondary methods (those that utilise the natural energy of an oil reservoir). Air injection in situ combustion (lSC) is a thermal lOR technique used in general to increase the temperature in a reservoir and in turn reduce the viscosity of the oil. This increases the mobility of the oil and can lead to significant improvement in recovery factors. The process is complex and much work is needed to improve modeling capabilities essential for reservoir management. To investigate high pressure air injection a combustion tube facility has been commissioned and four in situ combustion tube tests completed. This involved the development of data acquisition and control software (lsc View) to fully automate the air injection facility. The ISC tests were carried out with a West Shetland Clair crude oil of 19.7°API and air injection fluxes between 12 and 70m3/m2hr and pressures between 50 and 100 bar. Post-mortem analysis of the burned cores showed 100% oil displacement in areas of core swept by the combustion front. In these areas the amount fuel burned varied between 4.6 and 15.3 %OOIP (original oil in place). The combustion front temperatures varied between 450°C and 730°C. It was found that combustion front temperature increased with air injection flux. The combustion front velocity varied between 10.4 and 22.2cmlhr. The combustion front velocity was observed to increase with pressure thus the combustion front velocity and hence propagation of the combustion front was shown to be reaction rate dependent. History matching of the ISC tests was completed using the STARS simulator (Computer Modeling Group) a fully implicit non isothermal reservoir simulator. The simulations showed that when the grid size approached that of the actual reaction zone then the kinetics at different pressures did not change. Therefore, at this grid scale, the kinetic parameters used for a pseudo component representation of the oil can be applied as if it were a pure component, independent of pressure.

In-situ combustion is an oil recovery technique in which air, or oxygen enriched air is injected into a reservoir in order to displace the oil. Under suitable conditions the oxygen will burn with part of the oil, raising the temperature of the reservoir and reducing the viscosity of the oil, hence allowing it to flow more easily. A serious problem with mathematical modelling of in-situ combustion is that of flame extinction due to grid block size effects. When modelling a field scale process using finite difference techniques the grid block size will be far larger than the flame length. Since parameters such as temperature and saturations are averaged over a grid block they will be misrepresented in the Arrhenius reaction rate equation, and the flame may die out. The approach taken to overcome the problem is to decouple the flame from a conventional finite difference simulator and solve separately for the reaction rate and flame velocity. This is achieved using a steady state analysis that applies a reduced set of the conservation equations in a moving frame over the flame region, and solves the resulting eigenvalue problem using a shooting method. The reaction rate and flame velocity determined by the steady state analysis are then used to apply the 'thin flame' technique to the conventional simulator. This treats the flame as a moving heat source and displacing pump, travelling through the domain with the velocity obtained by the steady state analysis. The steady - state analysis is compared with experimental results glvmg good agreement for the flame parameters. The thin flame method produces excellent agreement with the conventional simulator on laboratory scale simulations, and on field scale simulations it greatly reduces the problems associated with grid block size effects.

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