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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Oil-rich developing economies have in their oil a valuable asset which could enable them to achieve a transformation to economic maturity largely unhindered by the constraints of foreign exchange and/or domestic savings. Yet the existence of such an asset creates tendencies that would lead to 'too-fast' depletion rates and structural distortions which, together, threaten the viability of these economies in the long run. The question of optimal growth with exhaustible resources is, therefore, of considerable relevance to such economies. This thesis attempts to assess the past impact of oil on the Iraqi economy and to study its future optimal growth. The former issue is dealt with through an analysis of the structure and the general trends in the development of the Iraqi economy during the period 1953-1974. The study reveals a growing structural imbalance manifested by the growth of Services at the expense of Commodity sectors, a failure to diversify exports, and an increase in dependence on oil revenues. The problem of optimal growth is examined using a linear programming input-output type model, the two main features of which are (1) an explicit recognition of Iraq's dependence on an exhaustible resource (oil) as a source of foreign exchange and savings, (2) the use of optimal oil pricing trajectories for the Organisation of Petroleum Exporting Countries as a group for the valuation of Iraq's oil exports. Apart from determining Iraq's optimal oil depletion path, the model also throws some light on the way Iraq's optimal growth path is affected by such factors as OPEC's pricing strategies, Iraq's absorptive capacity as well as by the requirements of some important economic development objectives, such as achieving self sufficiency in foreign exchange after oil is completely exhausted.

The material presented in this thesis falls into two main sections: 1. The determination of barium, strontium and calcium in oil-well waters (i) Determination of barium It is revealed that the addition of magnesium (5 g l-1) to samples for the determination of barium by d.c. plasma atomic emission spectrometry enhances the sensitivity of the analysis and dramatically reduces interference from calcium and strontium at both atomic and ionic emission wavelengths. (ii) Determination of strontium The determination of strontium in waters, was also subject to the interference of the concomitant elements like calcium, barium and magnesium. However, the addition of 3 g l-1 sodium with or without 5 g l-1 of magnesium eliminated all the interferences in the d.c. plasma and in the dinitrogen oxide-acetylene flame. (iii) Determination of calcium The determination of calcium in oil-well waters encountered some interference arising from the presence of sulfate. However, the effects of phosphate and sodium were also investigated in both air-acetylene and dinitrogen oxide-acetylene flames and in the direct current plasma. It was shown that the interference was reduced in the cool flame when 2 g l-1 of lanthanum was added. The absorbance of calcium was depressed by the presence of 2 g l-1 of sodium. The interferences from both sulfate and phosphate were eliminated when the hot flame or the d.c. plasma were used. 2. Slurry nebulization for soil, sediment and fertilizer samples A slurry atomisation direct current plasma (DCP) emission and flame atomic absorption and emission (FAAS and FAES) for the determination of alkaline earth elements and also of other minor and major elements in soils, marine sediments and fertilizer is reported. The results obtained by slurry nebulization, with lithium added as ionisation buffer, were compared with results obtained following fusion with LiBO2 at 950o for 10 minutes and dissolution of the residues in 4&'37 HNO3.

Investigation of forward in situ combustion have been carried out in a 7.3 cm diameter tube having a length of 0.869 m. Experiments at pressures up to 50 psig were made to study combustion characteristics and enhanced oil recovery of three different crude oils, namely North Sea Forties (36.6 °API), Maya Isthmus (32.4 °API) and Maya (22.1 °API). Sand packs were prepared with oil saturations in the range 38-44.32%. Close adiabatic control of the combustion tube was achieved for both dry and wet combustion modes. Detailed production history and overall mass balances are presented. Correlation in both graphical and tabular form is given for air-fuel ratio, oxygen utilisation and normalised combustion velocity. In this respect, the results of the present work show good agreement with those of other workers. Normal wet, partial quenched modes of combustion were produced using WARs up to 3.75 m3/Mm3 (STP). The combustion front temperature was not significantly affected by the cooling effect of the injected water. Under partially quenched conditions, high combustion-steam zone temperatures were achieved. For wet combustion, the oxygen utilisation generally improved slightly. Air requirement, air-oil ratio and fuel consumption all decreased with increased water-air ratio and increased with increased clay content. The velocity of the combustion front (normalised with respect to the air flux) increased in a linear manner as the WAR increased. Increasing the clay content, however, gave rise to a decrease in the combustion front velocity. High oil recovery, at 79.37%, was achieved during normal wet combustion of Forties oil. In sand mixtures containing amorphous silica powder, the combustion exhibited virtually 100% oxygen utilisation, with higher carbon burning rates compared with runs using clay addition. These effects are attributed to the nature and magnitude of the surface area of solid additives, which play an important role in the oxidation mechanisms.

This thesis dea1s with mode11ing of formation damage resu1ting from invading s01ids, particu1ar1y in re1ation to water injection schemes Where10wconcentration micron and sub-micron s01ids are concerned. Ear1ier investigations were considered inadequate for study of formation damagedue to partic1e invasion in manyrespects such as the nature of damage, depth of damage characteristics and the inf1uence of various parameters on the damagedata. A porosity mode1(in 1inear and radia1 forms) based on mass ba1ance of partic1es and a pore size distribution based 3Dcapi1lary network model are presented. The network model uses various particle capture criteria including a newprobability criteria to model particle retention. The resu1ts from rock core based f10wtests are presented and ana1yzed. The f10w tests were conducted on 00x25 •4na-dia. sandstone cores of permeabi1ity range of 250 to 1000 md using 1-15 ppm concentrations of O-3~ a1umina partic1es at flow-rates of 0.45-1.00 mils up to 150 hours equiva1ent to over 40000 core pore v01umes. The experimental invastigations showthe importance of depth of damageand 10ng duration experiments on formation damagedata studies. Experimental permeability shows si.mp1e semi-1og dec1ine with gross f10w ve1ocity. serious occurs even for the 10w concentration systems. The iBIporta.nce of core preparation is stressed, where the use of brok.en faced cores is shown to be more appropriate for conducting partic1e inv . . as1.onexperuaents as comparedto the conventiona1 sa.wn-facedcores. Both the porosity mode1and the network.mode1predictions are shownto agree reasonab1y we11with the experimenta1 data.

The Palaeocene and Eocene Forth Field is located in Quad. 9, Block 23/b, adjacent to the East Shetland Platform. The Fourth reservoir consists of a series of massive well sorted, medium to fine grained, turbidite sands which contain biodegraded oil and gas. The textural homogeneity of the Forth sands suggests that sedimentary facies was not a major diagenetic control. The timing of oil migration and the periodicity of oil leakage controlled the relative paragenesis in different sand units. Pervasive ferroan and non ferroan calcite cemented sand horizons dominate the Forth paragenetic sequence. Bitumen filled inclusions within these cements indicate oil emplacement and carbonate cementation occurred simultaneously. Calcite oxygen isotope results suggest East Shetland Platform meteoric water, flushed the reservoir, biodegrading the migrated oil and displacing the original seawater. Biodegradation of oil took place at the palaeo-oil water contact, producing a laterally extensive cementation zone. Frequent oil leakage may have produced a series of different palaeo-oil water contacts which became preferential cementation sites. The Palaeocene Balmoral Field is located approximately 100kms to the south of Forth in Quad. 16, Block 21. To a large extent, the distribution of non-carbonate diagenetic phases in the Balmoral Field is controlled by lithoclast composition and the relative abundance of interbedded shales. Non ferroan and ferroan calcite concretions preferentially precipitated where there were localised accumulations of organic matter. The concretions precipitated at < 500m burial depth, sourced by bacterial oxidation and sulphate reduction of organic matter in meteoric pore fluids. Meteoric water is thought to have been derived from the East Shetland Platform to the north of Balmoral. Oil migrated into Balmoral during the Oligocene, post-dating meteoric flushing. Laterally extensive carbonate cements, formed in association with oil biodegradation, have the potential to compartmentalise a reservoir. The distribution of these cements within Tertiary reservoirs adjacent to the East Shetland Platform is likely to be controlled by the relative timing of meteoric flushing and oil migration.

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