Retrograde condensation in natural porous media: An in situ experimental investigation

Abstract

Complex in situ behavior of fluids during a retrograde condensation process is experimentally investigated in a miniature sandstone core sample. Two depletion experiments were conducted with various pressure decline rates using a three-component synthetic gas mixture with a dew point of 3610 psi. A state-of-the-art miniature core-flooding system integrated with a high-resolution micro-computed tomography scanner was employed to acquire pore-scale evidence of condensate nucleation, growth, accumulation, and mobilization in a natural porous medium under different depletion conditions. Analysis of pore-scale fluid occupancy maps demonstrates the formation of discrete nuclei of the condensate in pore throats and crevices as the pressure drops slightly below the dew point. The in situ fluid configurations show that a greater pressure drawdown rate significantly increases the condensate growth and accumulation. The results also illustrate the occurrence of condensate-to-gas imbibition displacements, i.e., snap-off and piston-like events, and the consequent trapping of the gas phase in the pore space. As the pore pressure is reduced, the condensate droplets are found to connect to each other through wetting layers, whereas the large gas clusters are continuously fragmented into smaller globules with reduced hydraulic connectivities. This effect was more pronounced in the case of the high depletion rate experiment. Furthermore, the condensate banking was not completely eliminated (through evaporation) by re-injecting the gas phase. This implies that in the development of a gas condensate reservoir, condensate dropout and banking should be minimized in the first place by, for instance, producing at lower pressure drawdown rates.

Synergistic Effects of Aqueous Phase Viscoelasticity and Reduced Interfacial Tension on Nonwetting Phase Displacement Efficiency: An In Situ Experimental Investigation

“…The tomograms acquired during each experimental stage were then reconstructed to create a stack of two-dimensional (2D) slices. The 2D slices were analyzed using a histogram-based segmentation method in Avizo 9.4.0 software (Thermo Fisher Scientific) to generate pore-scale fluid occupancy maps 28 in which the aqueous, oil, and solid phases are distinguished from each other. These images were further processed to obtain in situ saturation and fluid occupancy data.…”

Microfluidic study of surfactant flooding of heavy oil in layered porous media containing fractures

“…It is well‐established that pore‐level visualizations using micromodel patterns deliver valuable information for a better understanding of the unrecognized processes, extend our knowledge of existing concepts, and contribute to the development of new perspectives. [ 34 ]…”

“…It is well-established that porelevel visualizations using micromodel patterns deliver valuable information for a better understanding of the unrecognized processes, extend our knowledge of existing concepts, and contribute to the development of new perspectives. [34] Researchers have found several main mechanisms for increased oil recovery through surfactant injection through experiments conducted by direct observation in microfluidics. Yadali Jamaloei and Kharrat [35] used an etched-glass micromodel to observe the two-phase flow of surfactant flooding into an oil-saturated porous medium.…”

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

“…Condensate gas reservoirs are widely distributed worldwide, accounting for 7.5% of the total recoverable resources of hydrocarbons; therefore, there are broad prospects for their exploration and development [1][2][3]. 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].…”