The Multilayer Transient Test is a well-testing technique designed to determine formation properties in multiple layers, and it has been proved effective during the past two decades. To apply the Multilayer Transient Test, a combination of rate profiles from production logs and transient rate and pressure measurements are required at multiple surface rates. Therefore, this method can be time consuming and may involve significant errors due to inaccurate transient flow rate measurements. A new testing approach is proposed after realizing the limitations of the Multilayer Transient Test. The new testing approach replaces the transient flow rate measurement with transient temperature measurement by using multiple temperature sensors. This research shows that formation properties can be quantified in multiple layers by analyzing measured transient temperature and pressure data. A single-phase wellbore/reservoir coupled thermal model is developed as the forward model. The forward model is used to simulate the temperature and pressure response along the wellbore during the transient test. With the forward model, this work proves that the transient temperature and pressure are sufficiently sensitive to formation properties and can be used for multilayer reservoir characterization. The inverse model is formulated by incorporating the forward model to solve formation properties using nonlinear least-square regression. For the hypothetical cases, the proposed new multilayer testing method has successfully been applied for investigating formation properties in commingled multilayer reservoirs. Layer permeability, damaged permeability, and damaged radius can be uniquely determined using single-point transient pressure data and multipoint transient temperature data at appropriate locations. Due to the proposed data acquisition scheme, only one surface flow rate change is needed to implement this testing approach, which significantly reduces the test duration compared to the standard multilayer transient testing approach using a series of flow rate changes. Of special interest, this is the first test design that shows promise for determination of the damaged radius, which can be useful for well stimulation design. In addition, temperature resolution, data noise, and data rate impacts have been studied along with a data filtering approach that enable selection of suitable pressure and temperature sensor technologies for applying the new testing method.

Reservoir fluids are rarely found in homogeneous structures having homogeneous properties. The various elements and processes of the petroleum system result in complex fluid distributions and compositions. A sound understanding of these complexities can avoid disappointing results and costly mistakes when designing the completion and production of the reservoir. The earlier these complexities are understood in the exploration phase, the better are the chances of a successful decision making process in the design phase of the project. Assessing reservoir compartment connectivity is of paramount importance for a optimal field development. Recent technological advances in wireline formation testing and sampling provide asset teams with a new methodology to evaluate in situ fluid properties and reservoir connectivity. After a review of the technology of downhole fluid analysis (DFA), the currently available methods of modeling equilibrated fluid gradients are presented. Fluid composition equilibrium is a stationary state where all components have reached zero mass flux. A reservoir model is designed to simulate numerically equilibration processes over geologic timescales at isothermal conditions where diffusion and gravity are the active mechanisms. A variety of initial conditions and reservoir fluid types is considered. Non-equilibrium fluid gradients and their transient behavior as they evolve towards fluid composition equilibrium are the main interest of this study. The results are compared in case studies, that are available in published literature. The modeling methods allow modeling of vertical and lateral fluid gradients. After a discussion of the cases, this thesis gives recommendations on 1) what fluid properties should be assessed and 2) how many data points are needed to reduce the chance of misinterpretation of non-equilibrium gradients in the presence of faults. To make best use DFA data, the property that exhibits the largest gradient needs to be investigated, as it yields the greatest potential to assess connectivity. The shape of the distribution of fluid composition within a compartment is found to be an important part in investigating reservoir connectivity. During data acquisition efforts should be made to acquire enough data points to reveal this shape. In combination with the presented techniques to identify non-equilibrium conditions, this will optimize DFA data acquisition and maximize the value of the data.

Downhole seismic testing and seismic cone penetration testing (SCPT) have shown little change since the 1990’s, with essentially the same sensors, sources, test procedures and analytical methods being used. In these tests, the time differences of first-arrivals or other reference points early in the time-domain signals have been used to calculate shear and compression wave velocities in soil and rock layers. This time-domain method requires an operator to pick the first arrival or other reference point of each seismic wave in the time record. Picking these reference points correctly is critical in calculating wave velocities. However, picking these points in time records is time consuming and is not always easy because of low signal-to-noise ratios, especially in the case of shear waves which arrive later in the time record. To avoid picking reference points, a cross-correlation method is sometimes applied to determine travel times of the seismic waves, especially in traditional downhole testing. One benefit of the cross-correlation method is that it can be automated. The cross-correlation method is not, however, appropriate for evaluation other body wave characteristics such as wave dispersion and material damping. An alternate approach is to use frequency-domain analysis methods which are well suited for evaluating time changes between all types of waveforms measured at spatially different points. In addition, frequency-domain methods can be automated and attenuation measurements can also be performed. Examples of such testing procedures with Rayleigh-type surface waves in geotechnical earthquake engineering are the Spectral-Analysis-of-Surface-Waves (SASW) and Multi-Channel-Analysis-of-Surface-Waves (MASW) methods. In this research, an automated procedure for calculating body wave velocities that is based on frequency-domain analysis is presented. The basis for and an automated procedure to calculated body wave dispersion is also presented. Example results showing shear wave velocity and material damping measurements in the SCPT are presented. The objective of this study is to improve downhole seismic tests with boreholes, cone penetrometers or flat-plate dilatometers by developing a frequency-domain analysis method which overcomes many of the disadvantages of time-domain analyses. The frequency-domain method is called the Spectral-Analysis-of-Body-Waves (SABW) method. The SABW method does not require an operator to pick the first-arrival or other reference times. As a result, the shear wave velocities and wave dispersion can be calculated in real time using the interpretation method with an automatic calculation procedure, thus reducing human subjectivity. Also, the SABW method can be used to determine additional information from the dispersion curves such as the material damping ratio and an estimate of soil type based on the dispersion relationship. In this research, field SCPT measurements are presented as an example to illustrate the potential of the SABW method. Measurements with shear waves are highlighted because these measurements are most often required in geotechnical earthquake engineering studies. / text

The current standard electrical downhole machine is the induction machine which is relatively inefficient. Permanent magnet (PM) machines, having higher efficiencies, higher torque densities and smaller volumes, have widely employed in industrial applications to replace conventional machines, but few have been developed for downhole applications due to the high ambient temperatures in deep wells and the low temperature stability of PM materials over time. Today, with the development of variable speed drives and the applications of high temperature magnet materials, it is increasingly interesting for oil and gas industries to develop PM machines for downhole applications. Recently, some PM machines applications have been presented for downhole applications, which are normally addressed on certain specific downhole case. In this thesis the focus has been put on the performance investigation of different PM machines for general downhole cases, in which the machine outer diameter is limited to be small by well size, while the machine axial length may be relatively long. The machine reliability is the most critical requirement while high torque density and high efficiency are also desirable. The purpose is to understand how the special constraints in downhole condition affect the performances of different machines.  First of all, three basic machine concepts, which are the radial, axial and transverse flux machines, are studied in details by analytical method. Their torque density, efficiency, power factor and power capability are investigated with respect to the machine axial length and pole number. The presented critical performance comparisons of the machines provide an indication of machines best suitable with respect to performance and size for downhole applications. Conventional radial flux permanent magnet (RFPM) machines with the PMs on the rotor can provide high torque density and high efficiency. This type of machine has been suggested for several different downhole applications. Flux-switching PM (FSPM) machines, which have the PMs located on the stator and are therefore more reliable, can theoretically also exhibit high torque density and relatively high efficiency. This thesis has put an emphasis on studying this type of machine. Two FSPM machines have been investigated in detail and compared by analytical method, FEM simulation and prototype measuremens. Their operating principle and important design parameters are also presented. A lumped parameter magnetic circuit model for designing a high-torque FSPM machine is newly introduced and the designed machine is verified by FEM simulations. A prototype machine with an outer diameter of 100 mm and an axial length of 200 mm is built in the laboratory and tested at room temperature. Based on that, the machine performance at an ambient temperature of 150°C is also predicted. The results show that the FSPM machine can provide a high torque density with slight compromise of efficiency and power factor. Choosing a proper machine type is significantly dependent on the application specifications. The presented results in this thesis can be used as a reference for selecting the best machine type for a specific downhole case.

Produced water presents economical and environmental challenges to oil producers. Downhole separation technology is able to separate oil or gas from produced fluid in downhole environment and injects waste water into deeper formations, thus saving energy and reducing waste emission. More than 120 downhole separation systems have been installed worldwide, but only about 60% of the installations achieved success. Most of the failures were due to the injectivity decline under the invasion of impurities in the injected water, such as suspended particles and oil droplets. A reliable model is needed to predict the reaction of reservoir permeability under the invasion of such impurities and serves as a tool to screen appropriate formations for downhole separator installations. / Previous experimental studies on particle-induced permeability damage reveal that high particle concentration, low fluid velocity, large particle size lead to more severe damage. The damage mechanisms are attributed to surface interception, bridging and size exclusion of particles in porous media. While for droplets, the resultant permeability decline is mostly due to surface interception. Empirical correlations with key parameters determined by core flooding data are widely applied to the simulation of permeability decline under invasion of particles and droplets. These correlations are developed based on characteristics of certain rocks and fluids, thus their applications are very restricted. / A more scientific method is to model the flow and capture of particulates at pore level. Reservoir rocks are porous media composed of pores of various sizes. Pore network models employ certain assumptions to imitate real porous media, and have been proved realistic in simulating fluid flow in porous media. In this study, a 2-dimensional square network model is used to simulate capture of particles and droplets in porous media. Pore bodies are represented by globes and pore throats are imitated with capillary tubes. The flow rates in the network are obtained by simultaneously solving mass balance equations at each pore body. The network model is tuned to match the porosity and permeability of a certain rock and serves as the infrastructure where the capture process takes place. / Particles are categorized as Brownian and non-Brownian particles according to size. For Brownian particles, diffusion is dominant and Fick’s law is applied to each pore inside the network to obtain deposition rate. For non-Brownian particles, their trajectories are mainly governed by gravity and drag force acting on them. Besides, the size of each particle is compared with the size of the pore where it is captured to determine the damage mechanism. For particles much smaller than the pore size, surface deposition is dominant and the permeability decline is gradual. For particles with sizes comparable to pore size, bridging and clogging are dominant and the permeability decline is much more severe. / Unlike particles, droplets can not be captured on top of each other. Accordingly, a captureequilibrium theory is proposed. Once the pore surface is covered by droplets, equilibrium is reached and droplets flow freely through porous media without being captured. The simulation on capture of oil droplets reveals that the surface wettability has significant influence on the resultant permeability damage. Most natural reservoirs are neutrally or oil wet. It is thus recommended to apply these surface conditions to future simulations. / The proposed model is validated with test data and reasonably good agreements are obtained. This new mechanistic model provides more insights into the capture process and greatly reduces the dependence on core flooding data.

Slurry is the fluid within a drilled excavation that is introduced when an excavation is deeper than the water table or where additional stability is needed for loose sandy dry soils. Although construction practices vary greatly throughout the country and the world, slurry levels should be maintained above the existing ground water level by a suitable margin. The most widely used slurry type is mineral slurry formed by mixing dry clay powder with water; either bentonite or attapulgite powder may be used (attapulgite being used in saline water conditions). Regardless of whether the slurry material is mineral, polymer or natural, the construction practice must address the slurry properties to ensure the stability of the excavation is never compromised. Proper performance of slurries used to stabilize drilled shaft excavations is maintained by assuring the density, viscosity, pH, and sand content stay within specified limits. These limits have been set either by past experience, research findings and/or by manufacturer recommended values. However, field slurry testing is time consuming as all measurements are manually performed. With the overwhelming advances in digital down-hole devices, it is not unreasonable to assume that slurry property tests are equally applicable to this trend. This formed the basis of this project. The most commonly used test to indicate slurry viscosity is the Marsh Funnel Test which is essentially a timed flow for a fixed volume of slurry to exit a falling head funnel. Using a library of unique pressure versus flow rate responses for a wide range of slurry viscosities, an automated downhole device was designed and tested that incorporated this information to estimate viscosity in the excavation without the need to remove slurry in order to test. Direct measurement of slurry density was also incorporated into the device and the sand content was computed from density and the viscosity where the suspended solids that make up the density stems from both the slurry products and the soil cuttings.

Depleting oil reserves and fluctuating oil prices have necessitated to increase the efficiency of oil production process. This thesis is focused on developing low-cost sensors, which can increase oil production efficiency through real-time monitoring of oil wells and help in safe transport of oil products from the wells to the refineries. Produced fluid from an oil well is a complex mixture of oil, water and gases, which needs to be quantified for various strategic and operational decisions. For many years, test separators have been used to separate oil, water and gases into three separate streams and then to analyse them individually. However, test separators are being replaced by multiphase flow meters (MPFM) which can analyse the complex mixture of oil, water and gas without separating it. However, existing MPFMs are either intrusive or require fluid mixing before the sensing stage. In contrast to existing techniques, first part of this thesis presents a microwave sensor, which can measure water fraction in oil in a non-intrusive way without requiring it to be mixed. Gas fraction sensing can also be performed using the same microwave sensor, which is an on-going work. The sensor operates on dielectric measurement principles and comprises a microstrip T-resonator that has been optimized for a 3D pipe surface. Certain locations on an oil field have limited available space, for which we have also presented a compact version of the microwave water-fraction sensor in this thesis. In this version, metallic housing of the sensor has been used to function as a ground plane for the coaxially located spiral resonator. This housing also protects the sensor from environmental effects. In addition to the efficient production of oil, its safe transport is also a concern for the industry. It is physically impossible to inspect a network of thousands of kilometres of pipelines manually. The existing leak detectors suffer from low sensitivity, high false alarms and dependence on environmental effects. In the last part of this thesis, we present a flexible ringresonator based leak detector, which can be clamped at vulnerable locations along the pipeline for early leak detection.

No description available.

Electronics are normally designed to operate at temperatures less than 125 oC. For high temperature applications, the use of those normal electronics becomes challenging and sometimes impractical. Conventionally, many industries tried to push the maximum operating temperature of electronics by either using passive/active cooling systems or tolerating degraded performance. Recently, there has been a demand for more robust electronics that can operate at higher temperature without sacrificing the performance or the use of any weighty, power hungry, complex cooling systems. One of the major industries that need electronics operating at high temperature is the oil and gas industry. Electronics have been used within the field in many areas, such as well logging downhole telemetry systems, power networks, sensors, and actuators. In the past, the industry has managed to use the existing electronics at temperatures up to 150 oC. However, declining reserves of easily accessible natural resources have motivated the oil and gas industry to drill deeper. The main challenge at deep wells for downhole electronics is the high temperatures as the pressures are handled mechanically. The temperature in deep basins can exceed 210 oC. In addition, existing well logging telemetry systems achieve low data transmission rates of less than 2.0 Mbps at depth of 7.0 Km which do not meet the growing demand for higher data rates due to higher resolution sensors, faster logging speeds, and additional tools available for a single wireline cable. The main issues limiting the speed of the systems are the bandwidth of multi-conductor copper cable and the low speed communication system connecting the tools with the telemetry modem. The next generation of the well logging telemetry system replaces the multi-conductor wireline between the surface and the downhole with an optical fiber cable and uses a coaxial cable to connect tools with the optical node in downhole to meet the growing needs for higher data rates. However, the downhole communication system between the tools and the optical modulator remains the bottleneck for the system. The downhole system is required to provide full duplex and simultaneous communications between multiple downhole tools and the surface with high data rates and able to operate reliably at temperatures up to 230 oC. In this dissertation, a downhole communication system based on radio frequency (RF) transmission is investigated. The major contributions of our research lie in five areas. First, we proposed and designed a downhole communication system that employs RF systems to provide high speed communications between the downhole tools and the surface. The system supports up to six tools and utilizes frequency division multiple access to provide full duplex and simultaneous communications between downhole tools and the surface data acquisition system. The system achieves 20 Mbps per tool for uplink and 6 Mbps per tool for downlink with bit error rate (BER) less than 10-6. Second, a RF front-end of transceiver operating at ambient temperatures up to 230 oC is designed and prototyped using Gallium Nitride (GaN) high electron mobility transistor (HEMT) devices. Measurement results of the transceiver's front end are reported in this dissertation. To our knowledge, this is the first RF transceiver that operates at this high temperature. Third, current-voltage and S-parameters characterizations of the GaN HEMT at ambient temperatures of 250 oC are conducted. An analytic model that accurately predicts the behavior of the drain-source resistor (RDS) of the GaN transistor at temperature up to 250 oC is developed based on these characterizations. The model is verified by the analysis and the performance of the resistive mixer. Fourth, a passive upconversion mixer operating at temperatures of 250 oC is designed and prototyped. The designed mixer has conversion loss (CL) of 6.5 dB at 25 oC under local oscillator (LO) power of 2.5 dBm and less than 0.75 dB CL variation at 250 oC under the optimum biasing condition. Fifth, an active downconversion mixer operating at temperatures up to 250 oC is designed and prototyped. The proposed mixer adopts a common source topology for a reliable thermal connection to the transistor source plate. The designed active mixer has conversion gain (CG) of 12 dB at 25 oC under LO power of 2.5 dBm and less than 3.0 dB CG variation at 250 oC. Finally, a novel high temperature negative adaptive bias voltage circuit for a GaN based RF block is proposed. The proposed design comprises an oscillator, voltage doubler, and temperature dependent bias controller. The voltage offset and temperature coefficient of the generated bias voltage can be adjusted by the bias controller to match the optimum biasing voltage required by a RF building block. The bias controller is designed using a Silicon Carbide (SiC) bipolar junction transistor. / PHD / A downhole communication system provides two-way communications for multiple tools located in a deep oil well. The main challenge for the downhole communication system as the oil wells get deeper is the high ambient temperatures as the pressures can be handled mechanically. The temperature in deep basins can exceed 210 °C. Cooling and heat extraction techniques with fans are impractical for downhole systems due to increased weight, power, and system complexity. In addition, the current downhole communication systems have low transmission speed, which do not meet the growing demand for higher data rates due to higher resolution sensors, faster logging speeds, and additional tools available for a single wireline cable. In this work, a downhole communication system based on radio frequency (RF) transmission is designed. The system supports up to six tools and provides high speed simultaneous communications which enable more sensors to be integrated in each tool. A high temperature RF front-end of the transceiver which will be connected to each tool is designed and prototyped using Gallium Nitride (GaN) semiconductor technology. GaN technology is selected due its ability to operate at harsh environment. The measurement results show a reliable performance for the RF front-end at temperatures up to 230 °C. To our knowledge, this is the first RF front-end that operates at 230 °C reported in the open literature. The proposed downhole communication system will enhance the speed and reliability of the oil and gas operations. This also will enable the industry to observe the wells and act in real time which in turns save operation time and bring a significant cost reduction in oil and gas operations. Most importantly, the proposed system will enable the industry to explore deeper untapped wells and add more features to the tools which were not possible before due to speed and high temperature limitations.

Natural resources are always collected from harsh environments, such as mines and deep wells. Currently, depleted oil wells force the gas and oil industry to drill deeper. As the industry drills deeper, temperatures of these wells can exceed 210 °C. Contemporary downhole systems have reached their depth and temperature limitations in deep basins and are no longer meet the high requirements in harsh environment industries. Therefore, robust electronic systems that can operate reliably in harsh environments are in high demand. This thesis presents a high temperature reference voltage generator that can operate reliably up to 250 °C for a downhole communication system. The proposed reference voltage generator is designed and prototyped using 4H-SiC bipolar transistors. Silicon carbide (SiC) is a semiconductor material that exhibits wide bandgap, high dielectric breakdown field strength, and high thermal conductivity. Due to these properties, it is suitable for high-frequency, high-power, and high-temperature applications. For bypassing the lack of high temperature p-type SiC transistors (pnp BJT, PMOS) and OpAmp inconvenience, an all npn voltage reference architecture has been developed based on Widlar bandgap reference concept. The proposed reference voltage generator demonstrates for the first time a functional high temperature discrete reference voltage generator that uses only five 4H-SiC transistors to achieve both temperature and supply independent. Measurement results show that the proposed voltage reference generator provides an almost constant negative reference voltage around -3.23 V from 25 °C to 250 °C regardless of any change in power supply with a low temperature coefficient (TC) of 42 ppm/°C. / Master of Science