Browsing by Subject "sensitivity study"
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Item An experimental investigation of the sensitivity of a buried fiber optic intrusion sensor(Texas A&M University, 2006-04-12) Kuppuswamy, HariniA distributed fiber optic sensor with the ability of detecting and locating intruders on foot and vehicles over long perimeters (>10 km) was studied. The response of the sensor to people walking over or near it and to vehicles driving nearby was observed and analyzed. The sensor works on the principle of phase sensitive optical time domain re ectometry, making use of interferometric effects of Rayleigh backscattered light along a single mode fiber. Light pulses from a highly stable Er:doped fiber laser emitting single longitudinal mode light and exhibiting low frequency drift are passed through one end of the buried fiber. The backscattered light emerging from the same fiber end was monitored using a photodetector. The phase changes produced in the light pulse due to the pressure of the intruder walking directly above or near the sensor or from the seismic disturbances created by vehicles moving in the vicinity of the sensor are detected using the phase sensitive Optical Time Domain Re ectometer (OTDR). Field tests were conducted with the sensing element as a single mode fiber in a 3-mm diameter cable buried at depths ranging from 8 to 18 inches in clay soil. It was observed that the sensor could detect intruders walking transverse to the cable line at a distance of 40 ft from it. A car moving at a speed of 30 mph on a rough road could be consistently detected up to a distance of 480 ft from the sensor, while a car driven on a smooth road 200 ft from the sensor could be detected only when passing through rough patches on the road. Tests were also performed with an intruder walking near the sensor while a car was driven at a speed of 30 mph on a rough road. The effect on the signal due to the intruder on foot could be distinguished clearly only when the car was at least 200 ft away from the sensor. The results in this thesis represent the first quantitative study of the sensitivity of the sensor under varied test conditions. It is expected that these findings will be helpful in the practical implementation of the long perimeter intrusion sensor along high security domains like national borders, military bases and government buildings.Item The Optimization of Well Spacing in a Coalbed Methane Reservoir(2012-02-14) Sinurat, Pahala DominicusNumerical reservoir simulation has been used to describe mechanism of methane gas desorption process, diffusion process, and fluid flow in a coalbed methane reservoir. The reservoir simulation model reflects the response of a reservoir system and the relationship among coalbed methane reservoir properties, operation procedures, and gas production. This work presents a procedure to select the optimum well spacing scenario by using a reservoir simulation. This work uses a two-phase compositional simulator with a dual porosity model to investigate well-spacing effects on coalbed methane production performance and methane recovery. Because of reservoir parameters uncertainty, a sensitivity and parametric study are required to investigate the effects of parameter variability on coalbed methane reservoir production performance and methane recovery. This thesis includes a reservoir parameter screening procedures based on a sensitivity and parametric study. Considering the tremendous amounts of simulation runs required, this work uses a regression analysis to replace the numerical simulation model for each wellspacing scenario. A Monte Carlo simulation has been applied to present the probability function. Incorporated with the Monte Carlo simulation approach, this thesis proposes a well-spacing study procedure to determine the optimum coalbed methane development scenario. The study workflow is applied in a North America basin resulting in distinct Net Present Value predictions between each well-spacing design and an optimum range of well-spacing for a particular basin area.