Huff-n-Puff Technology for Enhanced Oil Recovery in Shale/Tight Oil Reservoirs: Progress, Gaps, and Perspectives

Abstract

In recent times, particularly in the 21st century, there has been an alarming increase in the demand for global energy, along with continuous depletion in conventional oil reservoirs. This necessity has incentivized interested scholars and operators worldwide to seek alternative oil resources. To secure such accelerating energy demand, considerable effort has been directed toward the development of previously unconventional oil formations that, in past decades, had remained sidelined. Although shale oil reservoirs have seen tremendous success over the past decade, the continued challenges of rapidly declining oil flow rates and oil retention in the pores continuously persist. Substantial attempts have been made to improve shale-bypassed oil recovery; however, there is little data about the accessibility on recovery mechanisms, especially in the oil field. Furthermore, approachesparticularly, Huff-n-Puff (H-n-P) experiments using conventional proceduresfail to properly represent field conditions and they generate deceptive findings, because the utilized cores are not simulated under realistic reservoir conditions, leaving the significance of critical factors unclear. Therefore, this review study comprehensively and specifically discusses the feasibility of enhanced oil recovery (EOR) methods in unconventional oil reservoirs. Beside addressing the validity of the currently applied H-n-P technology in shale/tight oil reservoirs and underlining some critical gaps regarding laboratory results, modified technology is proposed in this paper for a better field future performance. The study is divided into sections, and each section analyzes the role of one specific H-n-P portion in detail, such as preferable injected solvents, their mechanisms, and critical factors affecting H-n-P recovery. The exceptions to this are the first and second sections, which provide a brief introduction about shale and tight oil reservoirs, a history of applied technology, and the method’s current problem statement. In the Introduction section, the authors will justify why this Review fills a critical gap in the field. Within the assessment study, great focus is given to the H-n-P technique, its parameters, and effective processes. In the final sections, carefully chosen experimental results and tools are reviewed to highlight the controversy and state “the gap”.

Asphaltene Precipitation and Deposition during Nitrogen Gas Cyclic Miscible and Immiscible Injection in Eagle Ford Shale and Its Impact on Oil Recovery

“…Unconventional resources, like shale reservoirs, are widely recognized for their extremely low permeability and porosity . Despite the fact that multistage hydraulic fracturing and horizontal well drilling techniques are used to extract the remaining oil from such reservoirs, only 4–6% of the trapped oil can be extracted, and the oil production drops after a few months, attributing to the ultralow permeability. − Water injection is also one of the suitable strategies for increasing oil recovery from conventional reservoirs; nevertheless, due to weak injectivity, insufficient sweep potency, and clay swelling concerns, this approach is not the ideal solution for tight reservoirs. , Cyclic gas injection outperforms gas flooding methods in terms of enhancing oil recovery, mainly in ultratight reservoirs. , The total organic carbon (TOC) is the most important influencing parameter on gas injection in tight reservoirs because kerogen makes the surface of the pore oil-wet, making the oil inside challenging to extract . Due to the combination of multiphase fluids (i.e., gas, oil, condensate, and water) and scales, multiphase flow production can create a number of challenges including wax and asphaltene deposition, hydrate formation, slugging, and emulsions .…”

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

“…Although less common than CO 2 EOR, the injection of other gases such as CH 4 and nitrogen (N 2 ) is practiced in the industry, too. − Compared to CO 2 , CH 4 is highly compressible and often more readily available. , CH 4 huff-and-puff injection experiments in core samples confirmed that the huff-and-puff injection operation could improve condensate oil recovery by 6%. , N 2 is relatively difficult to dissolve in crude oil and has a higher MMP than CO 2 . Therefore, the effect of N 2 injection is generally not as good as CO 2 injection.…”

Study on Influencing Factors of Water Huff-n-Puff Oil Recovery in Matrix-Fracture Systems of the Tight Sedimentary Tuff Reservoirs

“…With the continuous depletion of conventional oil and gas resources and the huge demand for oil and gas resources due to rapid economic development, the exploration and development of unconventional oil and gas resources have become more and more important. − In recent years, the Tuha oilfield has conducted a lot of geological exploration and oil and gas testing in the Santanghu Basin in northeastern Xinjiang, China, and finally discovered a new type of tight oil reservoirs, called tight sedimentary tuff reservoirs (TSTRs). − The formation of TSTRs is closely related to volcanic eruption and lake-basin deposition of volcanic ash. The exploration and development results show that TSTRs are significantly different from conventional tight oil reservoirs in terms of the reservoir-forming model, lithology, physical properties, and fluid properties. − …”