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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
311

Characteristics and removal of filter cake formed by formate-based drilling mud

Alotaibi, Mohammed Badri 15 May 2009 (has links)
Formate-based mud has been used to drill deep gas wells in Saudi Arabia since 2004. This mud typically contains XC-polymer, starch, polyanionic cellulose, and a relatively small amount of calcium carbonate particles, and is used to drill a deep sandstone reservoir (310°F). Calcium carbonate particles are frequently used as weighting material to maintain the pressure that is required for well control and minimize the leak-off. Such solids become consolidated and trapped in the polymeric material and this makes the filter cake a strong permeability barrier. Various cleaning fluids were proposed to remove drilling mud filter cake; including: solid-free formate brine and formate brine doped with organic acids (acetic, formic, and citric acids), esters, and enzymes. The main objective of this research is to assess the effectiveness of these cleaning fluids in removing drilling mud filter cake. A dynamic high-pressure/high-temperature (HPHT) cell was used to determine characteristics of the drilling mud filter cake. Drilling mud and completion fluids were obtained from the field. Compatibility tests between potassium formate brine, cleaning fluids, and formation brine were performed at 300ºF and 200 psi using HPHT visual cells. Surface tensions of various cleaning fluids were also measured at high temperatures. The conventional method for cleaning the filter cake is by circulating solid-free formate brines at a high flow rate. This mechanical technique removes only the external drilling fluid damage. Citric acid at 10 wt%, formic acid, and lactic acid were found to be incompatible with formate brine at room temperature. However, these acids were compatible with formate brine at temperatures greater than 122°F. Only acetic acid was compatible with formate brine. A formula was developed that is compatible at room and reservoir temperature. This formula was effective in removing filter cake. A corrosion inhibitor was added to protect downhole tubulars. In general detail, this research will discuss the development of this formula and all tests that led to its development.
312

Electro-optically tunable polarization independent add drop filter with relaxed beam splitter in linbo3

Shin, Yong-Wook 15 May 2009 (has links)
A polarization-independent electro-optically tunable add/drop filter utilizing non-polarizing novel relaxed beam splitters has been developed in LiNbO3 at the 1.55μm wavelength regime. The operation of this filter is based on passive directional coupler type beam splitters and strain-induced phase-matched TE↔TM polarization mode converters on an asymmetric Mach-Zehnder interferometer waveguide configuration. Fabrication parameters for channel waveguides, relaxed beam splitters and polarization mode converters were optimized individually then integrated to produce the final device. Single mode channel waveguides for both TE and TM polarizations were realized by the diffusion of 7μm wide Ti strips into LiNbO3 substrate. Relaxed beam splitters were produced using Ti diffused waveguides in a directional coupler configuration with 3.5mm long coupling region, 0.6º bending angle, and separation gap of 11μm and 13μm between waveguides. Tunable TE↔TM polarization mode converters with 99.8%
313

Development of an infrared absorption spectroscope based on linear variable filters

Nogueira, Felipe Guimaraes 15 May 2009 (has links)
The objective of this thesis is to develop a low-cost infrared absorption spectroscope based on linear variable filter (LVF) technology for the automated detection of gases and vapors, and the semi-automated detection of liquids. This instrument represents an alternative to electronic-nose instruments based on cross-selective gas sensor arrays. Instead, the proposed instrument uses the idea of computational “pseudo-sensors”, whereby spectral lines in an analytical instrument are clustered into groups and used as independent variables. We characterize the system on a number of performance metrics, uncovering its detection limits and resolving power. We present calibration methods to estimate the concentration of analytes in a matrix of absorbing species, as well as signal processing techniques for spectral classification. Specifically, we validate the instrument on a mixture calibration problem with simple and complex chemicals, and compare the efficiency of different calibration methods to estimate the concentration of one analyte in the matrix. Moreover, we demonstrate the use of the instrument on two real-world applications in the foodstuffs domain: oil adulteration and trans fatty acid (TFA) detection. The instrument, combined with signal processing techniques, is able to fully discriminate oils, as well as classify margarine and spreads onto high-TFA and low-TFA groups. Despite operating at a low spectral resolution, our results show that the LVF based spectroscope is a promising alternative to traditional analytical techniques for selected niche applications.
314

Non-Adjoint Surfactant Flood Optimization of Net Present Value and Incorporation of Optimal Solution Under Geological and Economic Uncertainty

Odi, Uchenna O. 2009 December 1900 (has links)
The advent of smart well technology, which is the use of down hole sensors to adjust well controls (i.e. injection rate, bottomhole pressure, etc.), has allowed the possibility to control a field in all stages of the production. This possibility holds great promise in better managing enhanced oil recovery (EOR) processes, especially in terms of applying optimization techniques. However, some procedures for optimizing EOR processes are not based on the physics of the process, which may lead to erroneous results. In addition, optimization of EOR processes can be difficult, and limited, if there is no access to the simulator code for computation of the adjoints used for optimization. This research describes the development of a general procedure for designing an initial starting point for a surfactant flood optimization. The method does not rely on a simulator's adjoint computation or on external computing of adjoints for optimization. The reservoir simulator used for this research was Schlumberger's Eclipse 100, and optimization was accomplished through use of a program written in Matlab. Utility of the approach is demonstrated by using it to optimize the process net present value (NPV) of a 5-spot surfactant flood (320-acres) and incorporating the optimization solution into a probabilistic geological and economic setting. This thesis includes a general procedure for optimizing a surfactant flood and provides groundwork for optimizing other EOR techniques. This research is useful because it takes the optimal solution and calculates a probability of success for possible NPVs. This is very important when accessing risk in a business scenario, because projects that have unknown probability of success are most likely to be abandoned as uneconomic. This thesis also illustrates possible NPVs if the optimal solution was used.
315

Initial Member Selection and Covariance Localization Study of Ensemble Kalman Filter based Data Assimilation

Yip, Yeung 2011 May 1900 (has links)
Petroleum engineers generate reservoir simulation models to optimize production and maximize recovery. History matching is one of the methods used to calibrate the reservoir models. During traditional history matching, individual model variable parameters (permeability, relative permeability, initial water saturation, etc) are adjusted until the production history is matched using the updated reservoir model. However, this method of utilizing only one model does not help capture the full range of system uncertainty. Another drawback is that the entire model has to be matched from the initial time when matching for new observation data. Ensemble Kalman Filter (EnKF) is a data assimilation technique that has gained increasing interest in the application of petroleum history matching in recent years. The basic methodology of the EnKF consists of the forecast step and the update step. This data assimilation method utilizes a collection of state vectors, known as an ensemble, which are simulated forward in time. In other words, each ensemble member represents a reservoir model (realization). Subsequently, during the update step, the sample covariance is computed from the ensemble, while the collection of state vectors is updated using the formulations which involve this updated sample covariance. When a small ensemble size is used for a large, field-scale model, poor estimate of the covariance matrix could occur (Anderson and Anderson 1999; Devegowda and Arroyo 2006). To mitigate such problem, various covariance conditioning schemes have been proposed to improve the performance of EnKF, without the use of large ensemble sizes that require enormous computational resources. In this study, we implemented EnKF coupled with these various covariance localization schemes: Distance-based, Streamline trajectory-based, and Streamline sensitivity-based localization and Hierarchical EnKF on a synthetic reservoir field case study. We will describe the methodology of each of the covariance localization schemes with their characteristics and limitations.
316

Development of Self-destructing Filter Cake

Rostami, Ameneh 2010 August 1900 (has links)
The main goal of drilling a horizontal well is to enhance productivity or injectory by placing a long distance drain-hole within the pay-zone. Poor drilling fluid design results in difficulties such as poor hole cleaning, excessive torque or drag, wellbore instability, stuck drill string, loss of circulation, subsurface pressure control, poor cement jobs, and difficulties associated with running electric logs and formation damage can result. Neither of the conventional chemical cleaning methods can overcome problems for filter-cake removal in long horizontal and maximum reservoir contact wells because of limitations such as the complex geometry of wells, non-uniform chemical distribution, low contact between cleaning fluids/filter cake, and high chemical reaction rate, especially at high temperatures. This study describes a novel self-destructing drilling fluid system. Filter cakes are formed from a formula of drilling fluid that have a mixture of solid acid precursor and particulate solid acid-reactive materials. Then in the presence of water, the solid acid precursor (polylactic acid) hydrolyzes and dissolves, generating acids that then dissolve the solid acid-reactive materials (calcite). It effectively stimulates the horizontal section right after drilling and eliminates acidizing, resulting in significant cost savings, and improves filter-cake removal, thus enhancing the performance of the treated wells. A series of experiments have been run in the lab to determine the efficiency of this new system. Properties of this drilling fluid are measured. Experiments on solid acid particle size showed that the best size-distribution of solid acid precursor and solid reactive material to make a self-destructing filter cake is fine particles of calcium carbonate used as weighting material with 150 microns polylactic acid as solid acid precursor. By comparison of the results of the experiments at different temperatures, 230 degrees F has been chosen as the best temperature for running experiments. The self-destructing drilling fluid systems need enough time for the solid acid to be hydrolyzed and therefore remove the filter cake. After 20 hours of contact with the water as the only cleaning solution, about 80 percent of the filter cake was removed. Calcite is found to be the dominant compound in the sample of remained filter cake, which was proved by x-ray diffraction tests. Secondary electron microscopy (SEM) results show the morphology of the remained filter cake sample and confirm the crystalline area of calcite.
317

Design of Microwave Filter Using Band-Gap Structures

Wang, Yu-Tsai 04 August 2004 (has links)
Using compact structure to improve the defect of traditional transmission line filter which size is too big or transmission line is too long. Two special structures are used to implement the filter that is smaller or superior characteristic. One of the two structures is called DGS that etched defect in the ground plane. The etched lattice shape for the transmission line consists of narrow and wide etched areas in backside metallic ground, which give rise to increasing the effective capacitance and inductance of a transmission line, respectively. Thus, by using this character, the low-pass filters are designed and implemented easily. Another structure is coupled of microstrip square open-loop resonators. First, the coupling coefficients of the three basic coupling structures versus distance between adjacent resonators and different offset is established by means of three-dimensional field analysis methods. Then, the band-pass filter will be implemented by the combination of three basic coupling structures. Finally, two low-pass filter which have cutoff frequency 5.4GHz¡B2.26GHz and a four-pole band-pass filter are designed and fabricated. All theoretical and experimental performance is presented.
318

Ultra-thin Thin-film Filters and Their Applications on WDM Systems

Chou, Tzu-Hung 14 June 2005 (has links)
The subject of this dissertation is to use precision cutting and polishing techniques to fabricate thin-film filters(TFFs) with a thickness of less than 100 £gm, and to discuss their applications in Wavelength Division Multiplexing(WDM) systems. To demonstrate the feasibility of the proposed technology, Si benches with wet-etching V grooves for precision fiber positioning and saw-cutting U grooves for placing the TFFs were fabricated. The insertion loss of the bench at 1.55 £gm input lights is less than - 0.5 dB. In addition, the stress induced pass band variations of band-pass TFF for Coarse WDM(CWDM) applications were studied. The pass band width of the band-pass TFF is 20 nm. After reducing the thickness of the 1.5 mm ¡Ñ 1.5 mm BP TFF to a thickness of 50 £gm, the center wavelength shift and pass band reduction are 4.64 nm and 1.54 nm, respectively.
319

Mining Mobile Groups from Uncertain Location Databases

Chen, Chih-Chi 21 July 2005 (has links)
As the mobile communication devices become popular, getting the location data of various objects is more convenient than before. Mobile groups that exhibit spatial and temporal proximities can be used for marketing, criminal detection, and ecological studies, just to name a few. Although nowadays the most advanced position equipments are capable of achieving a high accuracy with the measurement error less than 10 meters, they are still expensive. Positioning equipments using different technologies incur different amount of measurement errors ranging from 10 meters to a few hundred meters. In this thesis, we examine the impact of measurement errors on the accuracy of identified valid mobile groups and apply Kalman Filter and RTS smoothing as the one-way and two-way correction to correct the measurement data. In most settings, the corrected location data yield more accurate valid mobile groups. However, when the measurement error is small and users do not make abrupt change in their speed, mining mobile groups directly on the measurement data, however, yield better results.
320

Applying Morphological Filter to Stereo Video Compression

Chen, Chi-Hung 05 September 2005 (has links)
The topic of stereo video is getting more attention among these days due to its high quality of visual effect. However, the large volume of data is the problem of its application. There is much similarity between the parallax videos. This similarity is obtained by a shape compensation technique. The topic of this thesis is to investigate a compression technique by on the shape compensation stereo video data. The shape transformation in this paper is coded by the kinds of morphological operations to be applied. This processing is a type of operation by which the spatial form or structure of objects within an image are modified. Morphological operation is usually applied to the binary images. There are two problems for the selection of the optimal morphological filter: the collection of the candidate filters and the sources of the voters. For the gray level images the mask operation is changed to be the more complex window weighting operation. By a strategy of slicing the image umbrella, our masked gray morphological operation is also more computation-efficient than the regular gray morphological operation. Experimental results in this thesis have demonstrated that shape compensation is more efficient than motion compensation for the secondary (right) video sequence.

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