In recent years, production in unconventional reservoirs has increased exponentially due to technological breakthroughs in horizontal well completions. However, even with new technology, ultimate recovery after primary production in these reservoirs is extremely low (5-10% of original oil in place). The huff n’ puff process is considered to be a strong candidate for enhancing these notoriously-low recovery factors in unconventional reservoirs, especially those that are liquid-rich, in a cost-effective manner. Huff n’ puff is an enhanced oil recovery method in which one well alternates between injection, soaking, and production. Gas injection is often used in this scenario because of its high injectivity compared to water and its ability to develop miscibility with the reservoir oil. In this work, a recycled hydrocarbon gas was used due to its ease of accessibility within the target reservoir. In this work, the application of huff n’ puff to a liquid-rich shale reservoir with nanodarcy-range permeability was investigated both experimentally and numerically. A completely unique experimental setup was fabricated in order to execute oil recovery experiments on preserved core plugs taken from the target reservoir. In these experiments, it was shown that significant amounts of oil could be recovered after two huff n’ puff cycles lasting approximately one day each. Using propane as the injection gas resulted in higher recoveries when compared to the recycled gas due to enhanced miscibility with the oil. It was also shown that the ratio between soaking pressure and production pressure is a significant factor in recovering oil via huff n’ puff. An additional cycle was run with a longer soaking time, but no additional oil was recovered. A set of numerical reservoir models was also created to further investigate the recovery mechanisms in the huff n’ puff process. Lab-scale models were created in an attempt to replicate the experimental findings. The results showed that the recoveries seen in the experiments and simulations were very similar. Also, as long as injection took place above MMP, it was shown that the gas and oil mixed similarly in all cases regardless of pressure. Furthermore, lower production pressures allowed for more gas expansion and therefore better recovery, proving that production pressure alone may be an important parameter rather than the ratio between production and injection pressures. Field-scale models were also created. These models also showed that gas expansion plays a significant role in recovering oil. However, there were several key differences associated with sweep efficiency and the use of live oil versus dead oil.

Enhanced Oil Recovery (EOR) in tight and shale oil reservoirs has been a difficult problem due to their high degree of heterogeneity and low to ultralow matrix permeability. Primary recovery factor from these reservoirs is generally lower than 10% of original oil in place (OOIP), which leads to the need for non-conventional technologies for EOR in these reservoirs. A thorough understanding of mass transfer processes in ultralow permeability porous media is required for successful designs of EOR projects in tight oil formations and shales. In this study, two advanced EOR methods that involve the reinjection of field gas into shale and tight oil reservoirs are investigated. In the first part of this dissertation, field gas huff-n-puff process as an EOR method for shales is systematically investigated using an optimal experimental design. For a better understanding of the mass transfer mechanisms in nano-sized pores, the effect of pressure program (i.e., pressure buildup and drawdown during a huff-n-puff cycle), reservoir and crude oil properties, solvent selection, and huff-n-puff cycle duration on oil recovery were investigated. The results show that thermodynamic phase behavior, molecular diffusion, and convection could be related to oil recovery factor, production rate, and produced oil composition, forming a conceptual model for natural gas huff-n-puff in shale reservoirs. The second part of this dissertation presents the investigation of a novel EOR method targeting water-sensitive tight formations with sub-10-mD permeability. Mobility control is crucial for high recovery efficiency in these tight oil reservoirs with high heterogeneity. Preferential flow in high permeability zones (or "thief zones") results in poor sweep efficiency. Conventional conformance control techniques such as polymer gels or even aqueous foam may not be suitable for water-sensitive, low-permeability reservoirs. Therefore, a novel concept of non-aqueous foam for improving field gas miscible displacement has been developed. This foam process involves the injection of a raw mixture of natural gas liquids (MNGLs) with non-condensable gas and a foaming agent, which could improve the sweep efficiency by the generation of non-aqueous foam and maximize the displacement efficiency due to the solubility between the crude oil and MNGLs. A specialty surfactant has been developed which could stabilize non-aqueous foam in MNGLs-crude oil mixture for in-situ foam generation. A pore-scale study of this foam process has been conducted using microfluidics to relate oil displacement to foaming mechanisms. The findings from this microscopic study have been validated using core flooding experiments on tight rocks. It can be concluded from both pore- and core-scale studies that the in-situ propagation of non-aqueous foam could be achieved for the first time and delay the injectant breakthrough, resulting in significant improvement of sweep efficiency

This handbook provides a comprehensive but concise reference resource for the vast field of petroleum technology. Built on the successful book "Practical Advances in Petroleum Processing" published in 2006, it has been extensively revised and expanded to include upstream technologies. The book is divided into four parts: The first part on petroleum characterization offers an in-depth review of the chemical composition and physical properties of petroleum, which determine the possible uses and the quality of the products. The second part provides a brief overview of petroleum geology and upstream practices. The third part exhaustively discusses established and emerging refining technologies from a practical perspective, while the final part describes the production of various refining products, including fuels and lubricants, as well as petrochemicals, such as olefins and polymers. It also covers process automation and real-time refinery-wide process optimization. Two key chapters provide an integrated view of petroleum technology, including environmental and safety issues.Written by international experts from academia, industry and research institutions, including integrated oil companies, catalyst suppliers, licensors, and consultants, it is an invaluable resource for researchers and graduate students as well as practitioners and professionals.

Enhanced Oil Recovery (EOR) methods could be considered as the future of oil production. Particularly, Huff-n-Puff (HnP) EOR is a very promising technique implemented in unconventional reservoirs. HnP efficiency strongly depends on injection gas properties and formation characteristics. The main goal of this thesis was to emphasize oil recovery mechanisms for different injection gases as well as successful HnP execution criteria. In addition, gas diffusion was modeled by two methods. The Eagle Ford formation was chosen as a simulation environment due to its reduced oil production over the last five years. Research process included four major steps. First, the Eagle Ford reservoir was modeled using its typical characteristics and production. Based on sensitivity analysis results, appropriate permeability values, water saturation, porosity, and wettability were selected for primary production case. Second, a series of numerical laboratory experiments were conducted in order to evaluate oil recovery mechanisms and static mixing behavior between reservoir fluid and injection gas. Third, the HnP simulations were performed considering multiple design realizations and gas diffusion correlations. According to the sensitivity analysis results, optimum HnP gas injection patterns were chosen for comparison purposes. Finally, the economic feasibility of the EOR projects was evaluated by deterministic and probabilistic models. Oil and gas price forecast, oil and gas production prognosis, and fiscal system were modeled during this assessment. The research results suggested that rich hydrocarbon gases possessed better mixing behavior with reservoir fluid independently of its gas-oil ratio compared to the CO2. However, the HnP process with CO2 injection outperformed lean hydrocarbon gas operation. As a consequence, it was concluded that condensing drive dominated during the HnP process with hydrocarbon gases and vaporizing drive in CO2 HnP. The effect of the other oil recovery mechanisms was less vital. Therefore, field gas composition was considered as a decisive HnP design variable. Economic evaluation contributed to the profitable HnP project identification. Eagle Ford’s black oil was founded as the only reservoir fluid in which it is profitable to implement gas injection. Ultimately, the research provided valuable models for the HnP process implementation

Oil Recovery in Shale and Tight Reservoirs delivers a current, state-of-the-art resource for engineers trying to manage unconventional hydrocarbon resources. Going beyond the traditional EOR methods, this book helps readers solve key challenges on the proper methods, technologies and options available. Engineers and researchers will find a systematic list of methods and applications, including gas and water injection, methods to improve liquid recovery, as well as spontaneous and forced imbibition. Rounding out with additional methods, such as air foam drive and energized fluids, this book gives engineers the knowledge they need to tackle the most complex oil and gas assets. Helps readers understand the methods and mechanisms for enhanced oil recovery technology, specifically for shale and tight oil reservoirs Includes available EOR methods, along with recent practical case studies that cover topics like fracturing fluid flow back Teaches additional methods, such as soaking after fracturing, thermal recovery and microbial EOR