The penetration of a tool into solid rock is fundamental to all mechanical rock cutting processes. Rock in place in the Earth's Crust, can be considered as a semi-infinite solid since initially it presents only one free face for attack. Only by developing a second free face in the rock, however small, can excavation proceed. Man seems to have been aware of this, perhaps only subconsciously, since he first started trying to excavate a shelter for himself out of solid rock. The problems associated with rock excavation today are basically the same as those confronting the early cave-dwellers. We are still attempting to improve the design of tools, using materials that are readily available, economical to use, and resist breakage and wear. We continue to seek more efficient methods of attacking the rock thereby excavating a greater volume of rock for a given expenditure of effort resulting in increased rates of advance. Compared to developments in other scientific fields, however, rock excavation technology has seen few revolutionary innovations in its long history. The situation is such that rock excavation remains an art rather than a science.

The aim of this study is to combine petrophysical and geochemical data in order to reconstruct the migration history and pathways of mixed microbial-thermogenic gases drilled on the Nile Delta fan, offshore Egypt. While general interest lies in understanding migration routes, rates and mechanisms special attention is dedicated to understanding (1) the origin of gas in both reservoir and non-reservoir units using chemical and isotopic fingerprints and (2) whether a free gas phase supports relatively rapid leakage via bulk flow in non-reservoir units, both above and below commercial accumulations. The Pilocene section in this study is a classic slope environment comprising channels, mud-rich turbidites, mass transport complexes and hemipelagites. Data from seismic and drilled wells suggest that the channel and levee reservoirs are rarely full to spill, implying either a lack of charge and leakage rates which precludes complete filling of the structures. The provided data set enables a quantitative assessment of gas distribution and its genetic fingerprint in the context of both stratigraphic position and lithology. Data is reported from 25 wells, each provided with a conventional wireline log suite and some with borehole images and high-quality core images. Gas concentration data, plus compositional and isotope data are available for isotubes and headspace gas for both reservoir and non-reservoir units. Small-to-medium scale linear and non-linear depth shifts between different techniques (core recovery, core logging, wireline logging) in conjunction with scale and resolution issues demanded logical/stochastic depth synchronisation and well as harmonisation of signal resolution (typically up-scaling). Accordingly, great care was taken to depth-match core, log and gas data. In general, there is evidence of leaking thermogenic and partly biodegraded gas from the reservoirs under investigation, while some microbial methane appears to be retained in the cap rock. Careful assessment of the maturity of the thermogenic gas charge suggests that in a given structure, maturities are similar throughout the sampled section of underseal, reservoir and top seal. Furthermore, compositional temperature stratification suggests a balance between influx of fresh gas and microbial metabolism rates, supporting the concept of a dynamic charge-leak scenario that is sustaining hydrocarbon fermenting microbial communities in the deep biosphere. It was found that microbial recycling of hydrocarbons at depth enables the identification of diffusive gas mixing pathways in the combined analysis of methane and ethane compositional and isotopic data. The proposed diffusion pattern supports the idea of a widely present coupling between both methanogenic and biodegrading microbial communities that exhibit strong carbon isotopic dis-balances at gas-water contacts (GWC) where nutrient supply is in favour of the biodegrading metabolism. Although the hypothesis of coupled diffusive/microbial gas overprints complies with (1) various literature reports that microbial attack on free gas phases is hindered by restricted physical access and (2) segregative isotope fractionation as a consequence of differences on methane and ethane diffusivity, it is conditional to the nature of gas mixing patterns along borehole trajectories in the context of lithology and pore fluid saturations. Undoubtedly, the ubiquitous presence of microbial gas has consequences for vertical net leakage. As classic empirical wireline models for hydrocarbon saturation (i.e. free gas phase volumetrics) are not suited for clay-dominated cap rock sections, an alternative approach presented in this study is based on total gas (TG) modelling from nuclear logs and its solubility in the formation of brine. The calibrated saturation model is scale-independent and implies that free gas occurs on the most of the clay-dominated non-reservoir sections. However, model resolution is not sufficient to capture the suspected filamentary network of free gas phase within the mudrock pore space that enables relatively rapid leakage via Darcy flow. In an unique attempt to validate manual and thereby subjective lithofacies allocations to core images a subset of rock sample properties such as grain size fractions and porosity were successfully modelled using quantitative core image properties. However, model validity appears to be restricted to clay-rich lithofacies due to both an absence of calibration data for sands and occurrence of abnormally dark sandstone units. Further, an artificial neural network (ANN) was trained to propagate the calibrated core fancies along the entire wireline logged borehole section to set the lithological context for a detailed fluid flow analysis. Reproducibility of input (core) facies by output (wireline) facies is similar to the reproducibility by fellow geoscientists but could not be significantly improved to 60-80% of reliability by reduction of facies types. The study shows that a combination of geochemical data with lithological and petro-physical information generates detailed insights into rates, mechanisms, and pathways of two phase flow through the deep biosphere of gas-charged basins. Vertical, geologically rapid flow through mud-rich sequences is a viable migration route for gas if the influence of cap rock bypass systems (permeable faults, sandstone intrusions, mud volcanoes etc.) is restricted. It was found that an adequate quantification of both thermogenic gas fraction and diffusive gas mixing fingerprints is crucial to identity stratigraphic intervals that are not dominated by advective leakage through the pore space and are consequently bypassed.

Development of laboratory rock breakage techniques to relate energy and surface area produced by slow compression, drop hammer and stamp mill. A detailed study of laboratory rotary-percussive drilling in a wide range of rocks under different conditions, with the collection of drill cuttings and measurement of the drill parameters. The correlation of drill parameters with rock indices by energy concepts and the developed empirical formula. Field rotary-percussive drilling studies and collection of drill cuttings on the basis of laboratory analysis.

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Upscaling procedures attempt to account for subgrid heterogeneity in such a way that coarse grid simulations produce flow scenarios similar to those that one would obtain by running simulations directly on fine grid geological models. The conventional single-phase upscaling approach leads to averaging of low and high permeability streaks. As a result, the underlying physics of th~ reservoir is ignored and the permeability variability decreases. Consequently, further adjustment to absolute permeability is required in the history matching stage. The essential issue is whether the ultimate permeability distribution of the history-matched model bears any semblance or relationship to that of the upscaled model. This dissertation investigates the link between upscaling and history matching. First, we introduced the Effective Permeability Ratio concept (EPR) to formulate the errors arising from upscaling. Later, by employing geostatistics and assisted history matching techniques, coarse history matched model was generated by adjusting absolute.permeability fields. The comparison of resulted coarse model with upscaled mo~el proved that the permeability variability, which plays a major role in the flow response of reservoir models, could be preserved using the proposed workflow. Furthermore, the capability of suggested workflow in generating multiple history matched models enabled us to investigate the uncertainty in prediction performance using the Bayesian framework. In the cases studied, the proposed workflow produced a comparable result to the truth case suggesting that, the geological knowledge at the fine scale can be preserved appropriately on the coarse scale and the uncertainty in the field prediction can be quantified.

Gas hydrates are ice-like crystalline compounds, which form through a combination of water and suitably sized' guest' molecules under low temperature and elevated pressure conditioiJ.s. The formation of gas hydrates in subsea pipelines can cause pipeline blockage, resulting in serious economic and safety issues. Gas hydrate formation is generally prevented by employment of so-called 'thermodynamic inhibitors', which include salts and organic compounds such as methanol and ethylene glycol. However, the use of thermodynamic inhibitors can 'become uneconomical when high concentrations are required and/or water cut is high. There are also important associated issues with respect to inhibitor recovery and environmental damage. In the light of this, other methods for hydrate prevention such as making use of natural hydrate inhibitors in oil systems and application of a new family of hydrate inhibitors, - . termed 'Low Dosage Hydrate Inhibitors' (LDHI), are becoming attractive options. In this work both methods have been addressed by investigating the primary mechanism and the parameters involved in hydrate inhibition by the mentioned methods, using novel experimental techniques, and an in-house hydrate model. It is known- that water/oil (W/O) emulsions can reduce gas hydrate blockage risks. Natural surfactants such as asphaltenes and resins in the oil are commonly identified as the agents responsible for stabilising W/O emulsions. In this work, it was shown that oil properties, mixing rate and mixing history, water content, and operational conditions ,- (e.g. pressure) play significant role in reducing hydrate blockage risks in oil/water _systems. The effect of mixing rate on the induction time before hydrate formation was shown to be a function of system mixing history (degree of emulsification of water in oil). Before formation of stable emulsion, the induction time increased with mixing rate. However after formation of stable water/oil emulsion induction time was not a strong function of the mixing rate. Water content found to be the most important factor in controlling the risk. It was shown that for the oils tested, water cuts up to 20% do not pose any risk of blockage in the system tested while at 30% water cut a low dosage hydrate inhibitor will be needed for preventing hydrate blockage. A novel experimental set up (Glass Micromodel set-up) was used to obtain visual information regarding the state of water oil emulsion, size of water droplets in the emulsion, hydrates particle size and morphology and distribution of different phases in the system. The results showed that heavier components in the oil phase are attracted on gas hydrate crystals formed in a water foil emulsion (the oil surrounding the hydrate particles became brighter and more transparent). Furthermore, it was demonstrated that at static condition the agglomeration of hydrate particles appears to be easier than in flowing conditions in the Micromodel set-up. That was in line with the results obtained from the kinetic rig tests (where long shut-in times resulted in stirrer blockage). The principal limitation to curren~ Kinetic Hydrate Inhibitor (KHI) design techniques is a lack of verified molecular mechanisms for LDHI activity. In the framework of a jo~nt project between Heriot-Watt and Warwick Universities, a new approach has been used in the design and testing of new LDHIs. Chemicals designed using molecular dynamic simulation were subsequently synthesised (Warwick University) and tested using novel experimental techniques under simulated offshore pipeline conditions to evaluate their potential for use in offshore operations and factors affecting their performance and to study primary mechanism of hydrate inhibition (Heriot-Watt University). The new KHIs showed mild hydrate inhjbition erfect. In natural gas-water system, their performance was not as good as conventional i<HIs (poly-vinylcaprolactam (PVCap) and poly vinyl pyrrolidone (PVP)), however in methane water system, one of them performed better than PVP. Furthermore, the new KHIs demonstrated good antiagglomeration characteristics (after failure and hydrate formation). Visual observation of hydrate formation and growth in the presence of new KHI showed that it prevents agglomeration of the hydrate particles and cause deformation of the hydrate crystals. In general the performance of the KHIs tested in this study including conventional KHIs were better in structure II hydrate systems compared to structure I hydrates. Identification of the parameters affecting the performance of Kinetic Hydrate Inhibitors (KHI) is crucial for effective design, screening and deployment of them in deepwater applications. in this work, some of the influential parameters on the performance of PVCap were experimentally studied by application of a kinetic rig and a visual rig. The effect of mixing, pressure, polymer molecular weight, the solvent, subzero conditions, and different gas hydrate structures on the performance of a KHI, PVCap were investigated. The negative effect of static conditions on the performance ofPVCap was shown in a visual kinetic rig. By the experiments in a kinetic rig, the negative effect of pressure at constant subcooling on the performance of PVCap was demonstrated. It was shown that the low molecular weight PVCap inhibit hydrate formation better than .high molecular weight PVCap. At constant subcooling, PVCap was shown to inI:tibit structure II hydrate more effectively than structure I hydrate. The negative impact of corrosion inhibitor on the performance of PVCap was shown. The results showed that ethylene glycol (as a carrier fluid) does not have any significant effect on the perfonnance of PVCap. Furthennore, it was shown that PVCap can inhibit hydrate fonnation at subzero conditions in the presence of ethylene glycol. Anti-Agglomerants (AA) are another class of LDHIs developed over the last decade, which prevent hydrates from agglomerating and depositing in pipelines. In this work, after a brief description and literature survey on the development and testing of AA chemicals, a new methodology for testing AAs using the Kinetic Rig and the Glass Micromodel set up was presented. The perfonnance of AAs was evaluated in kinetic rig by torque measurements in different conditions. Two different types of impellers were used for torque measurement and it was shown that the torque llleasurement was improved by using a helical tube instead of paddle-shape impeller.. It was shown that the infonnation obtained from torque measurement technique can be used for screening AAs, however it is not sufficient for selection of an AA for field application. The complementary infonnation such. as hydrate particles size, morphology and their . distribution in different phases can be obtained from Glass Micromodel set-up. Preliminary experiments, using a proven AA chemical in comparison with another similar compound and an un-inhibited system, showed that the techniques developed in this study are suitable and effective for the testing ofAAs. In studying the kinetics of hydrate fonnation and inhibition at different conditions, a thennodynamic hydrate model is essential for predicting hydrate phase boundary from which the driving force for hydrate fonnation can be calculated. In this work an inhouse hydrate model (Heriot-Watt Hydrate Model (HWHYD model) has been used for thennodynamic description of the phases and' prediction of hydrate phase boundary. As part of. the above model, a new approach in modelling phase equilibria and gas . solubility in saline solutions has been proposed. Salts were introduced as components in the EoS by calculating their EoS parameters from corresponding cation and anion parameters. A non-density dependent mixing rule was used for calculating a, b, and c �·,parameters of the EoS. The inclusion of salts in the EoS resulted in the omission of Debye-Huckel electrostatic contribution tenn in the fugacity coefficient calculations. 'Water-salt binary interaction parameters were optimised using freezing point �· depression and boiling point elevation data of aqueous electrolyte solutions. Gas ��. solubility data in aqueous electrolyte solution were used for optimising salt-gas BIPs. �· The predictions of the model have been compared with independent experimental data, .demonstrating the reliability of the approach.-The degree of subcooling is usually used as the driving force for hydrate fonnation; however, it does not encompass the effect of pressure. In this work, by application of the two latest driving force expressions for hydrate fonnation, and an in-house hydrate model the relationships between subcooling and the calculated driving force at different conditions for pure gas-water and natural gas-water systems have been analysed. The relationship between the driving force and the degree of subcooling for methane, ethane and propane demonstrated that subcooling is a good representative of driving force for pure compounds over a wide pressure range.�· For natural gas systems at isothennal conditions, between 5 and 20 MPa, subcooling underestimates the calculated driving force for hydrate fonnation; however, above 20 MPa, subcooling is a�· good�· representative of real driving force. Constant degree of subcooling is an appropriate criterion for up-scaling the tests with pure gas and natural gas. For natural gas-water systems at constant driving Jorce/subcooling conditions, the induction time does not seem to be a function of pressure, while in the presence of PVCap, increasing- the system pressure had a negative effect on the induction time. This was attributed to the effect of KHI and pressure on the kinetic barriers for hydrate fonnation in a system. Therefore, testing KHls at similar field conditions is recommended.

Problems related to crystallisation and deposition of paraffin waxes on oil pipelines during production and transportation of crude oil caused huge operational and financial losses to petroleum industry. This study is focused on the fundamental understanding of the mechanisms of wax deposition and investigates the effect of several major parameters on such deposition in a batch oscillatory baffled column (OBC). The OBC is a relatively new mixing technology and offers more unifoml mixing and particle suspension than traditional reactors. It is the intention of this work to characterise the effect of oscillatory mixing on the wax deposition process perhaps as an alternative way for mitigation of wax deposition pro.blems. Experiments have be~n carried out to examine the effects of aBC's operational parameters, wax-oil volume, paraffin wax content, carbon number of the solvents, baffles materials and structure on the wax deposition. Analyses conducted to evaluate and characterise the wax deposition are: the percentage of waX deposition (8, wt.%); the Avrami exponent (n) which c0l!esponds to the type of wax crystals; and the half time of deposition (tl/2) which is associated with the rateof deposition. On the study ofthe effect of OBC's parameters, it was found that increasing the oscillation frequency and amplitude reduced the overall deposition; baffles oscillation altered the type of wax crystal formed from needle type to clustered plate-like shapes; and accelerated the rates of deposition. On the effect of wax-oil volume, it was observed that increasing the volume reduced the deposition, increased n values and tlfl hence reduced the deposition rates. The study on the effect of paraffin wax content revealed that increasing the wax content increased the deposition, reduced n values and caused higher crystallisation rates. On the effect of solvent carbon numbers, it was found that the higher the carbon numbers, the more the deposition, lower n and t1/2. Lastly on the study of baffles materials and structure, it can be deduced that using different baffles materials had no significant impact on the deposition in the OBC. In summary, oscillatory baffled flow can be an effective means of mitigation of wax deposition problems. This work may also lead to a screening test for wax deposition inhibitors. Since the deposition of viscous materials is common to other sectors of the process industries, the results of this study will provide essential information for understanding and perhaps later implementation of the OBC technology in the related fields