Interfacial tension measurements of the binary systems (N2 + H2O), (Ar + H2O), and (H2 + H2O), and ternary systems (CO2 + N2 + H2O), (CO2 + Ar + H2O) and (CO2 + H2 + H2O), are reported at pressures of (0.5 to 50.0) MPa, and temperatures of (298.15 to 473.15) K. The design of a custom-built Interfacial Properties Rig was detailed. The pendant drop method was used. The expanded uncertainties at 95% confidence are 0.05 K for temperature; 0.07 MPa for pressure; 0.019·γ for interfacial tension in the (N2 + H2O) system; 0.016·γ for interfacial tension in the (Ar + H2O) system; 0.017·γ for interfacial tension in the (H2 + H2O) system; 0.032·γ for interfacial tension in the (CO2 + N2 + H2O) system; 0.018·γ for interfacial tension in the (CO2 + Ar + H2O) system; and 0.017·γ for interfacial tension in the (CO2 + H2 + H2O) system. The interfacial tensions of all systems were found to decrease with increasing pressure. The use of SGT + SAFT-VR Mie to model interfacial tensions of the binary and ternary systems was reported, for systems involving CO2, N2 and Ar. The binary systems (N2 + H2O) and (Ar + H2O), and ternary systems (CO2 + N2 + H2O) and (CO2 + Ar + H2O), were modelled with average absolute relative deviations of 1.5 %, 1.8 %, 3.6 % and 7.9 % respectively. For the (CO2 + Ar + H2O) system, the agreement is satisfactory at the higher temperatures, but differs significantly at the lower temperatures. Contact angles of (CO2 + brine) and (CO2 + N2 + brine) systems on calcite surfaces have also been measured, at 333 K and 7 pressures, from (2 to 50) MPa, for a 1 mol·kg-1 NaHCO3 brine solution, using the static method on captive bubbles.

The onshore tank farm operations has become more useful and handy, as a result of increased international sea-borne trade, particularly, the unprecedented higher volume of petroleum products and hazardous chemicals traffic globally. The onshore tank farm is a facility used for safe discharge, loading and storage of petroleum products and other hazardous chemicals at the ports. It has become an important element in the supply chain system because of the increased universal energy demand and the fact that large number of modern tanker vessel is busy and efficiently moving cargo to different destinations around the world. The tank farm serves as a back-up facility to the ports. However, it has high degree of system-wide challenges of potential major incidents/accidents, as evidenced in various tank farm recorded accidents, which occurred at different times with estimated losses valued in millions of US dollars. The accidents could be catastrophic, leading to deaths, extensive damages and adverse impact on environment. To eliminate or minimize the risk of major incident/accidents, as well as minimize the magnitude and severity, it is acutely urgent to uncover and assess all potential hazards, with a view to adopt the best preventive/mitigative policy direction in the management of this strategic facility. This thesis presents multiple safety/risk assessment approaches, uncertainties treatments and decision making techniques that are capable of finding optimal solutions that will ensure safety of tank farm operations. The standard tools of analysis employed in this tank farm operational risk assessment are Failure Mode Effect Analysis (FMEA), Faulty Tree Analysis (FTA), fuzzy logic, Analytic Hierarchy Process (AHP) and Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS). Firstly, the FMEA-Fuzzy Rule Based (FRB) is applied in Hazard Identification (HAZID) and risk evaluation of tank farm operations. The methodology is utilized to discover five possible causes of catastrophic accidents in tank farm operations. The causes/hazards are described as the automatic shut-down oil safety valve failure, pipe corrosion protection system failure, automatic tank gauge system failure, leak detection device system failure, and secondary containment monitoring system failure. In the risk assessment conducted, the leak detection system failure was identified as the riskiest hazard using the Expected Utility Theory. Consequent upon the need for further investigation, another technique, Fuzzy Fault Tree (FFT), as novel model is used successfully to investigate and understand the causes of the leak detection system failure. The main aim of these two exercises is to assess risks and facilitate proper manage of these risks in tank farm operations, in order to forestall accidents that could cause damage to the facility, workers and the port environment. Nevertheless, the tank farm operations need to be optimized by ensuring the efficiency and safety of all systems and sub-systems through the adoption of best safety management decisions, which is achieved by employing AHP-TOPSIS model. This method is used to solve a complex multi-criteria decision-making problem such as selection of best Safety Control Design (SCD) among various SCDs identified. Finally, the results produced from the developed models and frameworks are summarized and other areas where they can effectively make impacts in HAZID, risk assessment and safety improvement are defined.

No description available.

A range of methods which allow quantitative integration of 4D seismic and reservoir simulation are developed. These methods are designed to work with thin reservoirs, where the seismic response is normally treated in a map-based sense due to the limited vertical resolution of seismic. The first group of methods are fast-track procedures for prediction of future saturation fronts, and reservoir permeability estimation. The input to these methods is pressure and saturation maps which are intended to be derived from time-lapse seismic attributes. The procedures employ a streamline representation of the fluid flow, and finite difference discretisation of the flow equations. The underlying ideas are drawn from the literature and merged with some innovative new ideas, particularly for the implementation and use. However my conclusions on the applicability of the methods are different from their literature counterparts, and are more conservative. The fast-track procedures are advantageous in terms of speed compared to history matching techniques, but are lacking coupling between the quantities which describe the reservoir fluid flow: permeabilities, pressures, and saturations. For this reason, these methods are very sensitive to the input noise, and currently cannot be applied to the real dataset with a robust outcome. Seismic history matching is the second major method considered here for integrating 4D seismic data with the reservoir simulation model. Although more computationally demanding, history matching is capable of tolerating high levels of the input noise, and is more readily applicable to the real datasets. The proposed implementation for seismic modelling within the history matching loop is based on a linear regression between the time-lapse seismic attribute maps and the reservoir dynamic parameter maps, thus avoiding the petro-elastic and seismic trace modelling. The idea for such regression is developed from a pressure/saturation inversion approach found in the literature. Testing of the seismic history matching workflow with the associated uncertainty estimation is performed for a synthetic model. A reduction of the forecast uncertainties is observed after addition of the 4D seismic information to the history matching process. It is found that a proper formulation of the covariance matrices for the seismic errors is essential to obtain favourable forecasts which have small levels of bias. Finally, the procedure is applied to a North Sea field dataset where a marginal reduction in the prediction uncertainties is observed for the wells located close to the major seismic anomalies. Overall, it is demonstrated that the proposed seismic history matching technique is capable of integrating 4D seismic data with the simulation model and increasing confidence in the latter.

Marine controlled-source electromagnetics (CSEM) techniques can be used to detect subsurface resistivity anomalies to discriminate hydrocarbon filled reservoir from the water saturated sediments in pre-drill appraisal of seismic anomalies in hydrocarbon exploration. The governing physics of marine CSEM is electromagnetic induction/diffusion therefore it has poor structural resolution. Current time – lapse CSEM feasibility studies for reservoir monitoring assume that the intrinsic limitation of CSEM has little impact on the dynamic fluid discrimination, as more structural constraining information are available at a producing oilfield. However, basic resistivity model is used without rigorous rock physics model, and is thus lacking in dynamic reservoir characterisation. Recent efforts at utilising simulation models combined with rock physics for realistic water-flooding front did not include reservoir management issues. In this thesis, CSEM is presented from the perspective of a reservoir manager, the end – user of this technology. A review of various hydrocarbon production mechanisms and scenarios showed that water – related mechanisms are ideally suited for time lapse CSEM applications as a complimentary tool to seismic in reservoir monitoring because of the resistivity anomaly generated as water replaces hydrocarbon. Channelized turbidite system for the North Sea oilfield model is used, such that the laminar lithological arrangement of sand and shale indicates that a linear arithmetic summation of resistivities of shale and sand will be a good representative of electrical rock physics model. Using this electrical rock physics model, three hydrocarbon provinces are assessed for the technical risk of time lapse CSEM project, in similar manner as done in 4D seismic projects. The North Sea province has highest technical risk, followed by the Gulf of Mexico, while the West Africa province has the least technical risk. A simulation to electromagnetic (sim2EM) workflow is then incorporated into the simulation to seismic (sim2seis) workflow. The sim2EM workflow is used to first examine the impacts of overburden complexity and sea water resistivity stratification on CSEM data. It is observed that the structural impacts are more pronounced on the static CSEM images than on its dynamic images. Then, coupled forward modelling of inline CSEM data and seismic amplitude data from a 3D fluid flow reservoir simulator is performed. The simulator serves the dual purpose of common oilfield in which production is aided by water injection, and of an interpretational constraint involving correlation of CSEM and seismic anomalies with injection and production activities at well locations (here called dynamic well tie). The time-lapse in-line CSEM amplitude change, modelled using dipole 1D, shows linear correlations of 64 to 68% with the change in water saturation. It is more responsive and consistently more linearly related to the change in water saturation than the seismic, despite the possible detrimental effects of reservoir heterogeneity. This is not surprising as seismic is responsive to a combination of changes in saturation and pressure. Coupled interpretation of seismic and CSEM modelled data show that time – lapse CSEM is a definite indicator of water saturation changes. For instance, when seismic softening due to rise in pressure masks increase in water saturation, or when seismic hardening due to pressure drop gives false increase in water saturation. The importance of brine mixing on the acoustic and electrical properties, during secondary and tertiary oil recovery, is examined. The seismic and EM rock physics are adjusted to cater for effective mixed brine resistivity, bulk modulus and bulk density, as functions of temperature and salinity for the injected and formation brines. Modelling of three scenarios of different combinations of injected and formation brines around the world, calibrated with a reference model in which brine properties were kept constant, indicate that EM is more responsive than the seismic, to the brine chemistry. Fluid flow modelling of sea water injection in the North Sea field shows that temperature effect is restricted to the vicinity of injector; while salinity effect travels farther from the injector along the water flooding front. The time-lapse EM could theoretically distinguish extreme brines. For instance, low salinity water injected into oil-wet reservoir with saline formation water; or moderately saline subsurface aquifer water injected into very saline formations of the Middle Eastern carbonates produced between -15 and 7% change in inline CSEM amplitude. In this thesis, 1D dipole forward modelling has generally highlighted values of EM in reservoir monitoring and management. Finally, repeat 3D EM data modelling produced time-lapse amplitude change of 0.3%, which is too small to be detected by the current CSEM acquisition. Thus, high precision EM field sensor will be required for practical application of 4D CSEM to reservoir monitoring. Only about 46% of this small 4D signature is interpretable for the change in transverse resistance of between -800Ωm2 and -1050Ωm2 (equivalent to resistivity reduction of between 13Ωm to 18Ωm). Broad qualitative information about the water flooded areas is provided, but fine detailed information about bypassed oil and early warning of water breakthrough could not be properly imaged.

The need of exploiting the offshore oil reserves and reducing the equipment costs becomes the motivation for developing new compact separation techniques. In the past years, the development of compact separators has almost solely focused on the cyclonic type separators made of pipes, because of their simple construction, relatively low cost of manufacturing and being able to withstand high pressures. Considerable effort has been put into the separator test program and qualification, and consequently notable advances in the compact separation technique have been made. However the application has been held back due to lacking of reliable predicting and design tools. The objectives of this study were threefold. Firstly, an experimental study was carried out aiming at understanding the separation process and flow behaviours in a compact separator, named Pipe-SEP, operating at high inlet gas volume fraction (GVF). Secondly it is to gain insight of the gas and liquid droplet flow in the compact separator by means of Computational Fluid Dynamics (CFD) simulations. Last but not least, the understanding and insight gained above were used to develop a comprehensive performance predictive model, based on which, a reliable optimizing design procedure is suggested. An experimental study was carried out to test a 150-mm Pipe-SEP prototype with a water-air mixture. Three distinct flow regimes inside the Pipe-SEP were identified, namely swirled, agitated, and gas blow-by. The transition of the flow regimes was found to be affected by inlet flow characteristics, mixture properties, geometry of the separator, and downstream conditions. A predictive model capable of predicting the transition of flow regimes and the separation efficiency was developed. A comparison between the predicted result and experiment data demonstrated that the model could serve as a design tool to support decision-making in early design stages ... [cont.].

Accurate reservoir depletion or pressure change patterns are of great value when planning infill drilling programs for field development, as well as when monitoring injection wells and swept/unswept areas. In addition, a precise dynamic geomechanical description of the reservoir and overburden stress state could prevent costly undesired effects on the production infrastructure such as sea floor subsidence, casing shear and well failure. Dynamic characterization of reservoirs, until recently, had only well data to rely on, which apart from the inherent uncertainties (e.g. due to formation damage), provides no direct information on what is taking place between the wells. The advent of time-lapse seismic at the end of the 1990s meant that this gap could be bridged, providing measurements of the changes taking place in the subsurface. In its origins, time-lapse seismic was conceived as a tool to image intra-reservoir fluid movements via the dependency of reflection amplitudes on acoustic impedance, which is affected by fluid saturation changes in the porous reservoir rocks. However, depletion induced velocity changes are also non negligible. Furthermore, the reflectors may undergo deformation and displacement where compaction and subsidence are involved. As a consequence, analysis of amplitude changes is not straightforward, since in most cases, amplitudes have been shifted by a non negligible time difference or time-shift, presenting not only challenges, but also new possibilities. It is in the possibilities of these time-shifts that the present study is based. This research presents a novel method which numerically solves the static field problem in a multilayered heterogeneous media, relating overburden strain to reservoir depletion. It builds up on previous works based on Geertsma type solutions requiring a homogeneous half-space. This technique makes it possible to estimate the reservoir’s stress state, strain and pressure changes from measured overburden strain by considering the earth as a linear filter with reservoir compaction and overburden strain as parameters. However, some a priori knowledge is needed in the form of a rough subsurface model and a preliminary geomechanics simulation in order to approximate the transfer functions as Wiener filters. In this thesis, the Wiener filter concept has been applied to three real North Sea fields. First, to the Elgin field, an HP/HT shallow marine Upper Jurassic sandstone reservoir located in the UK sector of the North Sea. Then, to the Ekofisk and South Arne fields, both compacting chalk reservoirs in the Norwegian and Danish sector of the North Sea respectively. Additionally, by using a synthetic example the method has been validated and compared with a linear inversion approach using a Geertsma type Green’s function achieving higher accuracy. The project involved not only the development and application of the method itself, but the calculation of time-strains from the measured seismic and the construction and implementation of full field geomechanical models.

The introduction of synthetic fuels produced from various alternative approaches has led to the concern over their compatibility with elastomeric seals used in current aircraft engines. The aim of this research is to investigate into this compatibility issue of alternative aviation fuels with typical elastomeric sealing materials. Experimental methodologies employed were the stress relaxation test (under both isothermal and temperature cycling conditions) and the Fourier Transform Infrared (FTIR) spectroscopy. A wide range of valuable data was collected and detailed analysis was carried out using statistical method and the Hansen Solubility Parameters (HSPs). The outcome of this research establishes the fundamental stress relaxation characteristics of typical sealing materials in jet fuels produced via various sources. It demonstrates different impacts that individual fuel species may have on seals. A correlation has been found between the stress relaxation and the molecular structure changes of the O-rings. The HSP analysis suggests a good non-linear correlation between the equilibrium compression force and the RED number generated from the ‘triangle’ test data. It is proved that temperature is an influential factor in terms of the sealing performance of an O-ring. Generally, the stress relaxation process slows down (accelerates) as the temperature decreases (increases). At extremely low temperatures, seals become very inert and the relaxation process would stop. Temperature cycling tests show the relationship between seals’ ability to recovery from thermal contraction and the aromatic content in the fuel. Based on the knowledge gained here, recommendations have been given on the potential future work related to this topic.

No description available.

Understanding the displacement and trapping of a displaced phase in porous media is important for applications in improved oil recovery (IOR) and carbon capture and storage (CCS). In IOR, we design the process to leave as little residual oil behind as possible, while for CCS, we do the opposite: we wish to maximise the amount of CO2 trapped by the host brine. Reservoir rocks display a range of wettability, from being preferentially water-wet they spontaneously imbibe water to oil-wet, or water repellent. Many rocks are mixed-wet, with both water-wet and oil-wet pores. The other wettability state is more intermediate-wet where, as we show, the rock appears to be largely non-wetting to both oil and water. Carbonate reservoirs, which house the majority of the world's remaining conventional oil, and which offer potential storage locations for carbon dioxide, have an altered wettability after contact with crude oil. In this thesis we study spontaneous displacement and trapping in carbonate rocks for different wettability conditions. The rate of spontaneous imbibition governs the rate with which oil, or carbon dioxide is trapped, while the residual saturation quantifies how much trapped. This is particularly important in carbonate reservoirs, which are almost extensively fractured. In these reservoirs, the principal mechanism for displacement is spontaneous imbibition of water to displace oil (or carbon dioxide) in the water-wet portions of the pore space. Pore structure and wettability are two of the main factors affecting displacement and capillary trapping. Experimental and pore-scale modelling studies have found a monotonic increase of residual non-wetting phase saturation, Snwr, with the initial non-wetting phase saturation, Snwi in a water-wet medium. However, altered-wettability systems have received relatively little attention, particularly those which are intermediate-wet. We first present the three carbonates we study in this thesis: Estaillades, Ketton and Portland. These are three quarry limestones that have very different pore structures and span a wide range of permeability. We present standard core analysis results including mercury injection capillary pressure and nuclear magnetic resonance response. We also study three-dimensional X-ray images of these samples, obtained at a resolution of a few microns. We use these experiments to assess the pore size distribution; we show that all the samples have micro-porosity and use the results to interpret the trapping and displacement experiments performed later. We then perform spontaneous imbibition experiments in these three carbonates under strongly water-wet conditions. We use scaling equations and recently published analytical solutions to assess the recovery of these rocks. We perform two sets of experiments. In the first, we measure the mass of water imbibed as a function of time. We show that the amount imbibed scales as the square root of time. In the second series of experiments, we measure saturation profiles as a function of distance and time using X-ray CT scanning. We demonstrate that the saturation profiles are functions of distance divided by the square root of time. We also demonstrate that the profiles are consistent with the analytical theory and, using reasonable estimates of relative permeability and capillary pressure, we can match the experimental results with the analytical solutions. We discuss how, in combination with conventional measurements of relative permeability (steady-state or using Buckley-Leverett theory in an unsteady-state experiment) these measurements could be used to measure capillary pressure and relative permeability. In the next phase of the study, we use organic acid (cyclohexanepentanoic acid) to alter the wettability of our samples and observe the relationship between the initial oil saturation and the residual saturation. We take cores containing oil and a specified initial water saturation and waterflood until 10 pore volumes have been injected. We record the remaining oil saturation as a function of the amount of water injected. In the water-wet case, with no wettability alteration, we observe, as expected, a monotonic increase between the initial and the remaining oil saturation. However, when the wettability is altered, we observe an increase, then a decrease, and finally an increase in the trapping curve for Estaillades limestone with a small, but continued, decrease in the remaining saturation as more water is injected. This behaviour is indicative of mixed-wet or intermediate-wet conditions as there is no spontaneous imbibition of oil and water. However, Ketton did not show indications of a significant wettability alteration with a similar observed trapping profile to that observed in the water-wet case. Portland limestone also showed a monotonic increasing trend in residual saturation with initial saturation but with a higher recovery, less trapping, than the water-wet case. Again, this is intermediate-wet behaviour with no spontaneous imbibition of either oil or water, and slow production of oil after water breakthrough. Finally, we repeat the same experiments but instead we age the three carbonates with a high asphaltenic content and high viscosity crude oil at 70C mimicking reservoir conditions. The results show a monotonic increase in residual saturation as a function of initial saturation but with higher recovery than the water-wet cases for Estaillades and Portland, with again no indication of wettability alteration for Ketton. We discuss the results in terms of pore-scale recovery process and contact angle hysteresis. We observe recovery behaviour that lies between the water-wet and mixed-wet conditions previously studied in the literature. Overall, the thesis demonstrates that recovery rate and the amount of trapping are sensitive to pore structure and wettability. Very different recovery trends were observed for three rocks with similar chemical composition. The work serves as a benchmark for further modelling and experimental studies. The recommendation is to reproduce, in the laboratory, conditions close to those observed in the reservoir, and to use imbibition and displacement measurements to quantify and constrain multiphase flow properties.