Abstract
In the present work, the potential of N2 huff and puff process to enhance the recovery of tight oil reservoir was evaluated. N2 huff and puff experiments were performed in micromodels and cores to investigate the flow behaviors of different cycles. The results showed that, in the first cycle, N2 was dispersed in the oil, forming the foamy oil flow. In the second cycle, the dispersed gas bubbles gradually coalesced into the continuous gas phase. In the third cycle, N2 was produced in the form of continuous gas phase. The results from the coreflood tests showed that, the primary recovery was only 5.32%, while the recoveries for the three N2 huff and puff cycles were 15.1%, 8.53% and 3.22%, respectively.The recovery and the pressure gradient in the first cycle were high. With the increase of huff and puff cycles, and the oil recovery and the pressure gradient rapidly decreased. The oil recovery of N2 huff and puff has been found to increase as the N2 injection pressure and the soaking time increased. These results showed that, the properly designed and controlled N2 huff and puff process can lead to enhanced recovery of tight oil reservoirs.
Highlights
The soaring global energy demand coupled with the declining conventional oil production has resulted in an increased emphasis on harnessing unconventional resources, such as the tight oil
The objective of this paper was to evaluate the potential of N2 huff and puff process to enhance the recovery of tight oil reservoirs
The interfacial tension (IFT) between the crude oil and the N2 was measured at 0.5–20.5 MPa and 60 °C
Summary
The soaring global energy demand coupled with the declining conventional oil production has resulted in an increased emphasis on harnessing unconventional resources, such as the tight oil. Sanchez-Rivera et al.[7] used a compositional reservoir simulator (CMG GEM) to study different design components of the huff and puff process to identify the parameters having the largest impact on the recovery of oil, and to understand the reservoir’s response to cyclical gas injection. Ma et al.[9] studied the viability of CO2 huff and puff process as the primary means to enhance oil recovery in low-pressure tight reservoirs, and thereby optimized the corresponding key operating parameters of the process. It is of fundamental and practical importance to study the interfacial tension (IFT) between the crude oil and the gas at high pressures and elevated temperatures.
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