Phase behavior of gas condensate in fractured-vuggy porous media based on microfluidic technology and real-time computed tomography scanning

Abstract

With the development of gas-condensate reservoirs, the phase behavior of gas condensate undergoes continuous changes. The phase behavior of gas condensate in PVT cylinders is different from that in fractured-vuggy gas-condensate reservoirs because multiscale pore structures can affect the phase behavior. By vuggy, we mean the formation of a reservoir contains cavity structures. To elucidate the influence of fractured-vuggy porous media on phase behavior of gas condensate, a microfluidic chip and a fractured-vuggy carbonate sample were prepared for pressure depletion experiments. The phase behavior of gas condensate in the chip during depressurization was observed via brightfield optical microscopy. The real-time computed tomography scanning was used to analyze pore structure of the sample and to obtain the phase behavior of gas condensate under different pressures. The results showed that the dew point pressure of the gas condensate was increased from 12.0 MPa in PVT cylinders to 14.8 MPa in nanochannels of the chip. The condensate liquid appeared in micropores at 14.4 MPa. The change of the average radius, coordination number, and tortuosity of condensate liquid ganglia were calculated and analyzed using pore network models. The shape factor and the Euler number were used to classify the condensate liquid into four types including clustered, branched, membranous, and droplets ganglia. The condensate liquid was generally distributed as clustered ganglia. This study provided evidence of the effect of fractured-vuggy porous media on phase behavior of gas condensate and clarified that the phase behavior of gas condensate varies in multi-scale pores.

A Novel Method for the Quantitative Evaluation of Retrograde Condensate Pollution in Condensate Gas Reservoirs

“…The retrograde phenomenon is common in the development of condensate gas reservoirs due to their special fluid properties, which results in the precipitation of condensate oil near wells and leads to a reduction in gas well production [4][5][6][7]. To study the retrograde phenomenon and assess its impact on the yield during the development of condensate gas reservoirs, substantial research has been conducted on condensate gas phase characteristics, the evaluation of retrograde pollution, and the impact of retrograde pollution on production, which has mainly been carried out through physical experiments and numerical simulation methods [8][9][10][11]. In relation to the phase characteristics of condensate gas reservoirs, Onoabhagbe et al [12] propose a novel approach for tracking the phase change based on simulating the formation of condensate blockage in tight as well as low-and high-permeability reservoirs; Wang et al [13] improve the Peng-Robinson model to simulate the phase change of condensate gas and calculate the Processes 2024, 12, 522 2 of 14 volume of condensate oil considering the effect of capillary forces; and Abbasov et al [14] analyze the influence of gas components on the retrograde condensation of condensate gas based on the results of retrograde condensation simulation experiments.…”