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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.
1

A Systematic Study of Matrix Acidizing Treatments Using Skin Monitoring Method

Pandya, Nimish 2012 May 1900 (has links)
The goal of this work was to evaluate matrix acidizing treatments of vertical and horizontal wells in carbonate reservoirs. Twenty field cases for acidizing treatments were analyzed by evaluating the skin factor evolution from on-site rate/pressure data during the treatment. A skin monitoring method based on the concept of inverse injectivity (Hill and Zhu, 1996) was used to calculate the skin factor evolution. Viscous diversion techniques were analyzed by using the viscous diversion skin model that accounts for viscosity contrast between the reservoir fluid and the injected fluid. The estimated skin evolution during the treatment was validated using the post-treatment well performance. From the post-treatment analysis, it was observed that emulsified acid was not an efficient viscous diverter because only 27% of the wells treated with emulsified acid showed evidence of viscous diversion. Therefore, other viscous diversion techniques are needed to ensure uniform acid coverage. In addition, treatments that involved diversion techniques such as foam, associative-polymers, and viscoelastic surfactants were also evaluated. Thus, the post-treatment evaluation was used to improve and optimize the acid treatment designs. This study was beneficial to diagnose if excess acid volumes were used, or effective diversion was achieved during the acid treatment.
2

Arterial Perfusion Detection Method By Synchronous Detection

Prevot, Yohan 04 November 2005 (has links)
The pressure ulcer is a well-known clinical problem that has plagued many patients in acute-care hospitals and chronic-care facilities. The pressure ulcer has the potential to diminish the quality of a patient's life by hindering the person's physical and emotional well-being. In addition, pressure ulcers are a high-cost problem. Past studies have shown that costs related to the treatment of pressure ulcers have reached 1.335 billion dollars a year in the United States alone. A pressure ulcer is defined as a lesion created by unrelieved pressure, which causes tissue ischemia and subsequently damages the underlying tissue. This sequence of events is mainly centered on ischemia. Ischemia is a condition created by an insufficient flow of blood to an organ or part of an organ such as the skin. The outcome of ischemia is cell death at the tissue level, which is commonly termed necrosis. In the past, researchers employed several different non-invasive techniques in order to detect changes in the condition of human skin when blood flow was restricted. The two most commonly used practices were Laser Doppler Velocimetry and Continuous Wave Ultrasound. Laser Doppler Velocimeter is used to measure cutaneous blood flow in a study region. The moving red blood cells in blood vessels cause a Doppler shift of incident laser light, which correlates with the velocity of blood flow. Continuous Wave Ultrasound involves an ultrasound signal, which is transmitted into the skin. The change in frequency of the reflected signal with respect to the transmitted signal provides an indication of blow flow. The objective of this research was to examine a method for the detection of arterial blood flow, which utilized the 4-electrode sensor for the measurement of Tissue Impedance or the Bio-impedance method. The system developed, for the synchronous detection method, consisted of both analog hardware and software tools. The analog hardware utilized synchronous detection. The software monitored and performed mathematical operations on the retrieved data. The system developed during this research demonstrated the ability to measure the pulsatile impedance of the skin and present the results in a fashion useful to healthcare providers.

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