Production Forecasting, Performance Analyses and Behavior of Shale Volatile Oil Reservoirs
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Due to the continual depletion of non-renewable conventional oil and gas resources and a corresponding rise in the global demand for energy, there are needs for alternative sources of energy. Unconventional resources like shale can provide a possible panacea to this critical energy issue for decades to come. Worldwide, shale resources are vast with several countries having enormous reserves of shale oil and gas. According to Rystad Energy, more than 50% of the United States’ oil reserves come in the form of unconventional shale oil, with Texas alone containing approximately 60 million barrels (Matthews, 2016). The combination of horizontal well drilling and hydraulic fracturing has enabled us to produce economic volumes of shale oil and gas in recent years. Therefore, shale oil and gas research is very important to the energy industry as a whole. The oil and gas industry requires accurate assessment and valuation of unconventional resources. With proper assessment of unconventional reserves, appropriate economic and organizational decisions can be made by companies, investors and other stakeholders. Production forecasting and reserves estimation are vital for correct assessment and valuation of unconventional resources like shale. A good understanding of the behavior and production mechanisms of shale volatile oil reservoirs enable better reservoir performance analyses and production forecasting. The major focus of this dissertation is to find and explore reliable, easy-to-use ways of forecasting production, estimating reserves as accurately as possible, and in the process increasing our understanding of how shale volatile oil reservoirs behave. This study covers different approaches to production forecasting using reservoir simulation, empirical and statistical methods. Several reservoir simulation models were compared. Improvements and suggestions for improvement of existing empirical decline curve analysis forecasting methods were thoroughly investigated. Six critical stages in the gas-oil ratio history of shale volatile oil reservoirs were identified and several factors impacting production performance were examined. A new approach to forecasting production and gas-oil ratios from shale volatile oil reservoirs called the Principal Components Methodology was also developed. The work done in this dissertation will be a valuable contribution to the enhancement of petroleum production and reservoir engineering as well as the growth of the oil and gas industry.