Inorganic scale may precipitate in oilfield systems, down hole in the reservoir, in the production flow tubing, and in surface facilities, as a consequence of thermodynamic changes that affect the flowing brines. These changes may be induced by temperature or pressure changes, or by mixing of incompatible brines. While much work has been performed to study the effect of thermodynamic changes such as pressure decrease or temperature increase on scale precipitation, it is only recently that a body of work has been developed on the impact that the dynamics of brine mixing in the reservoir has on scale precipitation in situ. Much of this work has been conducted using finite difference simulators, which are handicapped with regard to these calculations in that numerical dispersion effects can be orders of magnitude greater than physical dispersion. The introduction of chemical reaction calculations into streamline simulation models presents a very significant opportunity for improving the accuracy of such calculations. While numerical dispersion effects for immiscible calculations (eg water displacing oil) can be countered by pseudoisation of the relative permeability functions, in finite difference models it is difficult to control numerical dispersion for miscible displacements e.g. seawater (with a Sulphate concentration) displacing formation water (with a Barium concentration), which may lead to scaling in the reservoir (Barium Sulphate precipitation). Streamline simulation reduces the numerical errors for both miscible and immiscible displacement, thus making the scaling calculations much more accurate. The objective of this PhD project was to study the application of a streamline simulator, which has the appropriate chemistry modeling capabilities, to realistic reservoir scenarios. The project consisted of two stages: 1) Study of synthetic systems to identify the impact of brine mixing in simple scenarios (eg single layer and multi-layer quarter five spot patterns) 2) Application of the technique to full field reservoir systems to improve the capability of making scale management decision during the project Front End Engineering and Design (FEED) phase. The calculations performed demonstrate where, and under what conditions, scale precipitation takes place in situ in the reservoir, and what the resulting impact on the chemical composition of the produced brine will be. This information is key in the planning of the management of oilfield scale.

Cell migration is a fundamental biological phenomenon that is critical to the development and maintenance of tissues in multi-cellular organisms. This thesis presents a series of discrete mathematical models designed to study the migratory response of such cells when exposed to a variety of environmental stimuli. By applying these models to pertinent biological scenarios and benchmarking results against experimental data, novel insights are gained into the underlying cell behaviour. The process of angiogenesis is investigated first and models are developed for simulating capillary plexus expansion during both wound healing and retinal vascular development. The simulated cell migration is coupled to a detailed model of blood perfusion that allows prediction of dynamic flow-induced evolution of the nascent vascular architectures – the network topologies generated in each case are found to successfully reproduce a number of longitudinal experimental metrics. Moreover, in the case of retinal development, the resultant distributions of haematocrit and oxygen are found to be essential in generating vasculatures that resemble those observed in vivo. An alternative cell migration model is then derived that is capable of more accurately describing both individual and collective cell movement. The general model framework, which allows for biophysical cell-cell interactions and adaptive cell morphologies, is seen to have the potential for a range of applications. The value of the modelling approach is well demonstrated by benchmarking in silico cell movement against experimental data from an in vitro fibroblast scrape wound assay. The results subsequently reveal an unexplained discrepancy that provides an intriguing challenge for future studies.

Fluvial reservoirs are amongst the most prominent hydrocarbon bearing deposits in the world. Complexity in channel networks, spatial pattern and internal heterogeneities are of the main challenges in characterising these types of reservoir. In this thesis, a novel geoengineering approach is implemented to integrate the multidomain information (e.g. outcrop and time-lapse seismic interpretation) and to describe the well-test response of certain fluvial deposits. Comprehensive modelling and numerical well-test simulations have then been employed to study the dynamic behaviour of such systems. These resulted in diagnosing a well-testing family that includes a new generalised "Ramp Effect" model that is presented for the first time. Using systematic geostatistical modelling, the ramp effect is elaborated in terms of spatial statistics. The ramp model has been demonstrated by a few real-life well-test examples in a variety of channelised environments. Sophisticated multi-point statistics modelling are utilized to capture the facies transitions producing the lateral crossflow transients that result in the ramp effect and to demonstrate how the response can be generated in a meandering and anastomosing fluvial environments. Internal cross-flow can be confused with external layer cross-flow and with other linear flow responses (e.g., parallel faults, natural or artificial fractures). The non-uniqueness in interpretation of the ramp effect is addressed by employing time-lapse seismic data, which help in detecting the spatial geological heterogeneities and constraining the welltest interpretations. The illuminating power of the time-lapse seismic data is illustrated by synthetic seismic modelling examples. The implications of a complex fluid (i.e. gas-condensate liquid drop-out) on altering the well-test and seismic responses are also discoursed. A compositional reservoir simulator is employed to mimic the complex fluid behaviour of the fluvial reservoirs showing the ramp effect. Application of compositional simulations highlights the limitations in current petro-elastic modelling that are unable to take the compositional changes into account. Therefore, a novel approach is also developed to improve the petro-elastic modelling which facilitates the synthetic seismic generation in the presence of continuous composition changes of the fluid. This leads towards a better description of the reservoirs under simultaneous effect of geological and fluid heterogeneities.

The preparation and analysis of input and model data was carried out. The importance of the correct technique of data filtering was highlighted with particular focus being emphasised on the removal of outliers in raw data. An important process in the use of Artificial Neural Network (ANN) models was identified as being the selection of the right input variables.A comparison between using factor analysis and statistical analysis in the selection of inputs and it was observed that the former gave significantly better results. The training and testing phase of Artificial Neural Network (ANN) model development was shown to be an important step in Artificial Neural Network (ANN) model development. If this phase was wrongly done then the ANN model would not be accurate in its predictions. Optimisation of the ANN model architecture was carried out with the amount of hidden layers, amount of neurons in the hidden layers, the transfer function used and the learning rate identified as key elements in obtaining an Artificial Neural Network (ANN) architecture that gave fast and accurate predictions. Fresh water addition and demulsifier addition were identified as key parameters in the economic performance of the desalting process. Due to a scarcity of water and the high cost of the demulsifier chemical it was important to try and optimise these two input variables thus reducing the cost of operations.

Although common clathrates hydrates have long been considered as a method for gas storage, transportation and separation, some drawbacks including the need for very high pressures and/or very low subzero temperatures, and unfavourable formation kinetics have been a hurdle to their widespread use at industrial scale. During the last decade, after it was discovered that small gas molecules can be incorporated into the empty cages in semi-clathrate structures, semi-clathrate hydrates (SCH) attracted massive interest as an alternative means of gas storage and separation, taking into account the higher dissociation temperatures of these compounds. Despite the increasing number of publications on SCH, there is still a lack of data about these species of hydrates from both thermodynamic and kinetic points of view. In light of the emerging applications of SCH, this study examines the behaviour of semi-clathrates in ternary systems of ‘gas + SCH former + water’ using an experimental approach. After determining the phase diagram for tetra-n-butyl ammonium bromide (TBAB, as the most common SCH former) by differential thermal analysis, the stoichiometric concentration of TBAB is identified, its hydrate phase boundary under methane (as the rightful substitute of natural gas) pressure is measured and the stability of SCH at atmospheric conditions is monitored. Methane uptake capacity of TBAB and other SCH formers is measured and calculated both volumetrically and gravimetrically. In another part of the study, SCH are used to capture CO2 from syngas mixture in a process called pre-combustion capture in power plants. A unique glass micro model setup is utilized to visualize the SCH in a 2D porous medium. Moreover, the hydrate formation rate of SCH is studied by a kinetic model. Finally, the phase equilibria of hydrogen clathrates at high pressures are measured and compared with those of semi– clathrates formed in the system hydrogen + TBAB + water. The results of this work clarify some new features of SCH and enhance in-depth understanding of their behaviour which can ultimately lead to realizing the possible practical application of SCH in gas storage and separation.

The acidic constituents of petroleum are called naphthenic acids. The basic process for the isolation of these acids from petroleum involves extraction of the oil with an alkali and acidification of the aqueous extract with a mineral acid to liberate the organic acids. This product contains not only carboxyllc acids, but also significant amounts of phenols and hydrocarbons. The name "naphthenic acids" was suggested long ago by Markownikoff (2), because the early investigation of these acids indicated that they are a mixture of alicyclic acids. Subsequent work showed that these acids do not consists entirely of alicyclic acids but also contain straightchain and branched-chain acids, yet the name naphthenic acids is still in use for the total acidic constituents of petroleum The total acididy of crude oil varies from one field to another. for example, acidities as low as 0.03% have been reported for some crudes (Iraky oil) and as high as 3% for others (Southern California oil) . However, Schmitz (3) reported a very interesting observation. He found that although the acidity of crude oils varies from one o i l to the other, most of them have negligible amounts of acid in the gasoline and the heavy lubricating oil fractions;

High concentrations of H2S in petroleum gas and oil fields are attributed to Thermochemical Sulphate Reduction (TSR) reactions. H2S is toxic, Corrosive towards production steels, commonly associated with high carbon dioxide concentrations and consequently low hydrocarbon concentrations. High H2S concentrations may affect the economic viability of a gas or oil field. In this thesis, the reaction kinetics and mechanism of TSR are determined in laboratory simulations at formation water pH. In addition, high-resolution electron-optical techniques have been used to characterise TSR textures in natural, anhydrite-bearing rock samples. TSR experiments have been performed in the sodium sulphate - acetic acid - sodium acetate - elemental sulphur system, at temperatures between 100 and 350"C. Sodium sulphate was used as an appropriate experimental analogue for anhydrite. Reactions have also been performed using sodium bisulphate, dextrose, oxalic acid and hydrogen. Fluid-sampling hydrothermal pressure vessels were used, with which pressure and temperature could be controlled independently up to 50 MPa (500 bars; 7500 psi) and 350'C. The reactants were held within a gold reaction cell, with titanium closure and exit tube which leads to an external titanium sampling valve. Fluid samples were taken periodically to monitor reaction progress without quenching the reaction vessel to room conditions. The rate law for the temperature dependence of the TSR reaction rate (min") between sodium sulphate, acetic acid and sodium acetate, in the presence of elemental sulphur is: Log k= -7.42 (103 /T) + 8.46 Kinetic data suggest that TSR occurs rapidly on a geological time-scale at relatively low temperatures( 150'C). Sulphate half-lives are 15 days at 300"C, and 1650 years at 150'C. The activation energy of the reaction is 142 W/mol. TSR is a first order reaction with respect to sodium sulphate, acetic acid and hydrogen ion activity. Fluid pH increases by 1/2-1 unit during these reactions. Minimal sulphate reduction is observed when catalytic elemental sulphur concentrations (2-3% of ∑S) are used in the reaction. TSR occurs readily in experiments with an elemental sulphur concentration in excess of 22% of ∑S. Periodic sampling of reaction fluids has enabled time-variant isotopic determinations to be produced for the first time. Elemental sulphur undergoes hydrolysis (disproportionation) to generate hydrogen sulphide and sulphate. At in situ pH (5.23-6.05), bisulphate is the dominant oxidised sulphur species. However, a low equilibrium concentration of fully protonated sulphate is present. Neutrally charged H2SO4 undergoes reaction with hydrogen sulphide to form a thiosulphate reactive intermediate and water. This reaction is reversible and decomposition of thiosulphate to sulphate and H2S allows for sulphur isotope exchange between sulphate and hydrogen sulphide and exchange of oxygen between sulphate and water. Sulphur fractionation factors of 1.019-1.020 have been determined for the reduction of aqueous sulphate by acetic acid and sodium acetate, in the presence of elemental sulphur. Equilibrium oxygen isotopic exchange is attained in approximately I hour at 300'C. In acid conditions, thiosulphate decomposes to form nascent (monatornic) sulphur and sulphite. This reaction maintains a low concentration of nascent sulphur, which is the species that probably undergoes further reactions with organic species to form H2S and C02- Petrographically altered anhydrite from the Permo-Triassic Khuff Formation (offshore Abu Dhabi) has been investigated using optical microscopy, SEM and TEM. A framework of reaction textures that are indicative of varying degrees of TSR is presented. TEM analysis of apparently unreacted samples has identified the presence of small calcite crystals at the interfaces between nodular anhydrite and matrix dolomite. This is interpreted to represent fine-scale replacement of anhydrite by calcite and raises the possibility of using core material as a petrographic indicator of TSR. No orientation relationship was found between TSR calcite and any other reservoir phase.

No description available.

Petroleum refining has entered a significant transition period as the industry moves into the 21st century and the demands for petroleum and petroleum products continue to show a sharp growth in recent years. Refinery operations have evolved to include a range of next-generation processes as the demand for transportation fuels and fuel oil has shown steady growth. The research described in this thesis has been focused on an investigation of hydrothermal processing of hydrocarbons, mainly heavy oils. Experiments were carried out at temperatures from 300 to 380 °C and at a pressure of 220 ± 10 bar in both batch and flow systems separately by using 1/4-inch stainless steel tubing. The experiments were performed by using different reaction systems: toluene/H2O, toluene/H2O2, toluene/H2O/air, and toluene/H2O2/air. A comparative study of these reaction systems spiked with sulphur and metals (nickel, vanadium) were also conducted at the same conditions. Toluene conversion was investigated in a batch reactor at supercritical conditions in the presence of water. The conversion of toluene increases with temperature and steam/carbon (S/C) molar ratio (i.e. H2O to toluene ratio), conditions that provide favourable operating conditions for toluene conversion order to get high content products (gases and liquids). The toluene conversion yields multiple desirable lighter (liquid) hydrocarbons. The major liquid products include benzaldehyde, ethylbenzene, cresols (opm-cresols), styrene, benzyl alcohol and benzoic acid. Progressively larger quantities of these products are possible at higher temperatures and at higher H2O/toluene ratios. The efficiency of toluene conversion into products reaches almost 91% at 380 °C at a H2O/toluene ratio of 3 to 1. The yields improve monotonically as longer reaction times are allowed. Furthermore, when adding H2O2, the yield of the major liquid products benzaldehyde, ethylbenzene, cresols (opm-cresols), styrene, benzyl alcohol, benzoic acid increases with temperature and at higher H2O2/toluene ratios. The efficiency of toluene conversion into products reaches almost 40% at 380 °C at H2O2/toluene ratio equals to 3:1 with 5% H2O2 in 5 min of residence time. The yields improve at longer residence times. In the gas phase, H2 increases with an increasing H2O2 concentration while again, the yield of CH4 is small. The CO content increases up to 40% when between 6% and 8% H2O2 is used at temperatures around 380 °C whereas the CO2 content decreases. The conversion efficiency of toluene converted into liquid and gas products increases with temperature. This increase is accentuated with an increase in the H2O2/toluene ratio. Toluene conversion is slightly higher in the water/toluene mixture (90%) than the H2O2/toluene mixture (just below 90%). This is important, since along with the increased cost associated with the need for H2O2 and hence the increased overall cost of operation, it suggests that the water/toluene system is the more desirable one to consider further. Experimental results also revealed that a maximum of about 90% of the Ni-TPP was converted to intermediate and final Ni-based products at a temperature of 380 °C and after a reaction time of 90 min. Under the same conditions, around 67% of the Ni was removed by the action of supercritical water, proving that supercritical water is capable of removing Ni from Ni-TPP. The same batch reactor system was also used to study vanadium removal. V-TTP (a vanadium-containing compound which was added to the toluene) also reacted with SCW suggestions a pathway for vanadium removal. The effects of reaction time and temperature were investigated, showing that approximately 91% of V-TPP was converted to intermediate and final products at a temperature of 380 °C and reaction time of 100 min. Under the same conditions, approximately 82% of the vanadium was removed. This process was deemed successful since it did not use a catalyst. Finally, the removal of unwanted/undesirable sulphur from the oil was also considered. A gradual increase in the % DBT conversion was found at higher temperatures. The maximum DBT conversion was achieved at the highest investigated temperature, i.e. 380 °C. A maximum DBT conversion of ~ 97% was recorded after 30 min of reaction time. Importantly, and contrary to the findings concerning the conversion of toluene, the introduction of H2O2 lead to a considerable improvement in the metal removal potential.

The value added by intelligent wells (I-wells) derives from real-time, reservoir and production performance monitoring together with zonal, downhole flow control. Unfortunately, downhole sensors that can directly measure the zonal flow rates and phase cuts required for optimal control of the well’s producing zones are not normally installed. Instead, the zonal, Multi-phase Flow Rates (MPFRs) are calculated from indirect measurements (e.g. from zonal pressures, temperatures and the total well flow rate), an approach known as soft-sensing. To-date all published techniques for zonal flow rate allocation in multi-zone I-wells are “passive” in that they calculate the required parameters to estimate MPFRs for a fixed given configuration of the completion. These techniques are subject to model error, but also to errors stemming from measurement noise when there is insufficient data duplication for accurate parameter estimation. This thesis describes an “active” soft-sensing technique consisting of two sequential optimisation steps. First step calculates MPFRs while the second one uses a direct search method based on Deformed Configurations to optimise the sequence of Interval Control Valve positions during a routine multi-rate test in an I-well. This novel approach maximises the accuracy of the calculated reservoir properties and MPFRs. Four “active monitoring” levels are discussed. Each one uses a particular combination of available indirect measurements from well performance monitoring systems. Level one is the simplest, requiring a minimal amount of well data. The higher levels require more data; but provide, in return, a greater understanding of produced fluids volumes and the reservoir’s properties at both a well and a zonal level. Such estimation of the reservoir parameters and MPFRs in I-wells is essential for effective well control strategies to optimise the production volumes. An integrated, control and monitoring (ICM) workflow is proposed which employs the active soft-sensing algorithm modified to maximise I-well oil production via real-time zonal production control based on estimates of zonal reservoir properties and their updates. Analysis of convergence rate of ICM workflow to optimise different objective functions shows that very accurate zonal properties are not required to optimise the oil production. The proposed reservoir monitoring and MPFR allocation workflow may also be used for designing in-well monitoring systems i.e. to predict which combination of sensors along with their measurement quality is required for effective well and reservoir monitoring.