Comprehensive Outlook into Critical Roles of Pressure, Volume, and Temperature (PVT) and Phase Behavior on the Exploration and Development of Shale Oil

Abstract

Shale oil has received increasing attention as an essential replacement for conventional oil resources. Shale oil recovery is a complex process controlled by interactions of many factors whose impact could be significantly different from conventional reservoirs. This study hence aims to fill the gaps in the literature by studying various aspects of the phase behavior of shale oil and their significance in different aspects of the recovery from oil shale. In the first part of this study, the standard practices, including experimental and theoretical methods for calculating the pressure, volume, temperature (PVT), and phase behavior of shale oil, is discussed in detail. Next, the effects of factors such as the composition of fluids, pore structure, and capillary forces on the phase behavior of hydrocarbon fluids are explained. The third part focuses on applying phase behavior for oil shale development. Moreover, the geological and geochemical processes that lead to the maturity of kerogen, the formation of shale oil, and the experimental methods by which those processes are currently studied are scrutinized. By studying the thermal and burial history of the hydrocarbon-generating strata and hydrocarbon-generating kinetics, the shale formation's oil and gas phase distribution can be predicted. Consequently, the sweet spots for the recovery of light condensate oil can be more accurately determined. The application of enhanced oil recovery methods is an inevitable part of recovery from conventional and unconventional formations. Therefore, the last part of this study analyses the changes in the phase behavior of shale oil when an external component, i.e., CO 2 or CH 4 , is injected into the reservoir. Reviewing the literature revealed that a more accurate prediction of hydrocarbon phase behavior can be made by combining different disciplines of science to achieve optimized plans for efficient shale oil development, making shale oil a more economically viable energy resource.

Application of Alkali-Novel Green Extracted Surfactant (AS) for Sustainable Chemical Enhanced Oil Recovery (CEOR) in Carbonate Petroleum Reservoirs

“…This phenomenon mitigates the immiscibility forces between oil and water, culminating in the creation of stable emulsions, a critical factor in assessing the surfactant’s efficacy in effectively mobilizing oil. The emulsion droplets obstruct high-permeability pores within the reservoir, compelling the injected displacement fluid to traverse low-permeability pores, resulting in a more efficient recovery of excess oil. − Furthermore, foam can augment the apparent viscosity of the injection phase (both water and gas) and direct it toward previously untapped areas within the porous environment, thereby enhancing the efficiency of oil sweeping from these regions . Typically, surfactants are injected with salt, alkali, and polymer additives.…”

Heating-Assisted CO2 Huff-n-Puff for Improved CO2 Utilization: Further Discussion of the EOR Mechanism and Enhancing Carbon Sequestration in Shale Reservoirs

“…To summarize, the research on shale reservoirs with poor physical properties, high organic matter and viscosity, and high wax content is still inadequate. Most of the studies are mainly focused on the development effect and micromechanism of different gases by shale gas injection or the effect of temperature on the physical or mechanical properties of shale. − Research on the development of heating-assisted CO 2 HNP is relatively rare, it is unclear how the displacement mechanism of heating-assisted gas HNP works, and the current research lacks guidance for CO 2 sequestration.…”

Significant Control of Gas Invasion to the Phase Behavior of Deep-Seated Hydrocarbon Fluids in Western Junggar Basin, NW China

“…Gas invasion is a significant factor leading to the evolution of hydrocarbon phases, with numerous reports worldwide in oil and gas fields. , Due to the intrusion of gases, hydrocarbons undergo phase separation and physical fractionation of components, resulting in changes to the original composition of hydrocarbon fluids and ultimately leading to phase transitions . The invading gases can be hydrocarbon gases or inorganic gases such as CO 2.…”