Hydrocarbons exist in abundant quantity beneath the earth's surface. These hydrocarbons are generally classified as conventional and unconventional hydrocarbons depending upon their nature, geology, and exploitation procedure. Since the conventional hydrocarbons are under the depletion phase, the unconventional hydrocarbons have been a major candidate for current and future hydrocarbon production. Additionally, investment and research have increased significantly for its exploitation. Having the shift toward unconventional hydrocarbons, this study reviews in depth the technical aspects of unconventional hydrocarbons. This review brings together all the important aspects of unconventional reservoirs in single literature. This review at first highlights the worldwide unconventional hydrocarbon resources, their technical concept, distribution, and future supplies. A portion of this study also discusses the resources of progressive unconventional hydrocarbon candidates. Apart from this, this review also highlights the geological aspects of different unconventional hydrocarbon resources including tight, shale, and coalbed methane. The petrophysical behavior of such assists including the response to well logs and the discussion of improved correlation for petrophysical analysis is a significant part of this detailed study. The variation in geology and petrophysics of unconventional resources with conventional resources are also presented. In addition, the latest technologies for producing unconventional hydrocarbons ranging from fractured wells to different fluid injections are discussed in this study. In the end, the latest machine learning and optimization techniques have been discussed that aids in the optimized field development planning of unconventional reservoirs.

It is predicted that worldwide the demand of energy by 2030 will rise by 50% and in contrast, oil and gas resources are declining day by day. To fulfil the demand of energy, it has now become necessary to increase the production of hydrocarbons from producing reservoirs using new enhanced oil recovery technology. Nanoparticles (NPs) having dimensions of 1-100 nm has shown the capability to solve the problem of oil recovery. The capability of nanoparticles to change certain factors inside the reservoir can significantly help in enhancing the oil recoveries from the producing reservoir. This review study aims to facilitate and encourage the researchers who are interested in enhancing oil recovery using nanoparticles. This paper presents the oil displacement mechanisms and the potential of 4 different types of nanoparticles (SiO 2 , Al 2 O 3 , Fe 2 O 3 , TiO 2 ) in enhancing the oil recovery. Results of laboratory experiments have been presented in this paper. Finally, the review concludes by identifying the future study opportunities for researchers in the application of nanoparticles assisted EOR.

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Hydraulic fracturing is widely accepted technology to unlock unconventional reservoirs and produce the hydrocarbon fluids at feasible rates, but reaching these rates requires an optimal designing of the hydraulic fracturing treatment. This study presents an approach to design an appropriate hydraulic fracture with proper material selection and optimized fracture half-lengths. In this approach, initially, a hydraulic fracture model is selected for fracture design while considering formation stresses and fracture propagation. After that, the proppants and fracturing fluids are selected based on in-situ stresses, hydraulic fracture permeability and conductivity, the sensitivity of formation with water, pressure and temperature conditions of the reservoir. After the selection of the above materials, five hydraulic fractures with fracture half-lengths of 318 ft, 415 ft, 539 ft, 618 ft, and 724 ft are selected based on the amounts of proppants pumped, and their production responses are plotted. After comparing the selected fractures, the optimal fracture treatment is achieved at fracture half-length of 618 ft due to its high fluid recovery, along with the low amount of proppant pumped (127 klbs), which ultimately increases revenue and puts less burden on the economics of the project. The approach used in this study will, therefore, help design future hydraulic fracture treatment with an optimized hydraulic fracture, resulting in high hydrocarbon production rates, and reduce the overall cost by selecting the compatible fracturing fluids and adequate amounts of proppants.

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