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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

Development, Validation, and Utilization, of a Long-term Nearshore Synthetic Wave Record

Pena, Sergio A 01 January 2019 (has links)
The need for a consistent and accurate production of long-term nearshore wave record is discussed. With multiple decades of offshore hindcasts and long, continuous data sets available, it is possible to create a nearshore synthetic wave record. The Brevard County coastline offers an area with a high quality 62-year long offshore hindcast, as well as an 11-year long and nearly continuous high-resolution nearshore wave record to compare with model performance. This thesis presents the steps in the development and performance of the synthetic nearshore wave record produced. A novel approach was used to compare, validate and calibrate this type of data which included using quantile-quantile plots and bin-averaged scatter plots. In a comparison between two reputable deep-water hindcasts (MSC50 and Wavewatch III), it was found that Wavewatch III significantly underpredicts wave heights in the higher range (>8m). At the nearshore STWAVE proves to be a simple, robust and fast way to create a nearshore wave record. Root mean squared error (0.272m-0.317m) and modified index of agreement (0.697-0.646) values for significant wave height show promising results for overall model performance with the currently available hindcast. Possible future improvements could be made by modifying the offshore hindcast to have finer grid resolution and further studying different friction models for the nearshore wave transformation model. Overall, the use of the MSC50 hindcast, to drive STWAVE at the nearshore, exhibits good agreement with ADCP data and analysis for significant wave heights can be used with confidence. Currently, no long-term trends can be resolved with the available record at the location used herein, yet more years of data/hindcasts in the future could provide more evident trends in wave climate change.
2

Pressure Normalization of Production Rates Improves Forecasting Results

Lacayo Ortiz, Juan Manuel 16 December 2013 (has links)
New decline curve models have been developed to overcome the boundary-dominated flow assumption of the basic Arps’ models, which restricts their application in ultra-low permeability reservoirs exhibiting long-duration transient flow regimes. However, these new decline curve analysis (DCA) methods are still based only on production rate data, relying on the assumption of stable flowing pressure. Since this stabilized state is not reached rapidly in most cases, the applicability of these methods and the reliability of their solutions may be compromised. In addition, production performance predictions cannot be disassociated from the existing operation constraints under which production history was developed. On the other hand, DCA is often carried out without a proper identification of flow regimes. The arbitrary application of DCA models regardless of existing flow regimes may produce unrealistic production forecasts, because these models have been designed assuming specific flow regimes. The main purpose of this study was to evaluate the possible benefits provided by including flowing pressures in production decline analysis. As a result, it have been demonstrated that decline curve analysis based on pressure-normalized rates can be used as a reliable production forecasting technique suited to interpret unconventional wells in specific situations such as unstable operating conditions, limited availability of production data (short production history) and high-pressure, rate-restricted wells. In addition, pressure-normalized DCA techniques proved to have the special ability of dissociating the estimation of future production performance from the existing operation constraints under which production history was developed. On the other hand, it was also observed than more consistent and representative flow regime interpretations may be obtained as diagnostic plots are improved by including MBT, pseudovariables (for gas wells) and pressure-normalized rates. This means that misinterpretations may occur if diagnostic plots are not applied correctly. In general, an improved forecasting ability implies greater accuracy in the production performance forecasts and more reliable reserve estimations. The petroleum industry may become more confident in reserves estimates, which are the basis for the design of development plans, investment decisions, and valuation of companies’ assets.

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