Capillary Pressure Effect on Hydrocarbon Phase Behavior in Unconventional Reservoirs

2016 ◽  
Author(s):  
Yuan Zhang ◽  
Hamid R. Lashgari ◽  
Yuan Di ◽  
Kamy Sepehrnoori
Keyword(s):  
Phase Behavior ◽  
Capillary Pressure ◽  
Pressure Effect ◽  
Unconventional Reservoirs

Capillary pressure effect on phase behavior of CO2/hydrocarbons in unconventional reservoirs

Fuel ◽  
2017 ◽  
Vol 197 ◽  
pp. 575-582 ◽  
Author(s):  
Yuan Zhang ◽  
Hamid R. Lashgari ◽  
Yuan Di ◽  
Kamy Sepehrnoori
Keyword(s):  
Phase Behavior ◽  
Capillary Pressure ◽  
Pressure Effect ◽  
Unconventional Reservoirs

Thermodynamic Analysis of Phase Behavior at High Capillary Pressure

SPE Journal ◽  
2018 ◽  
Vol 23 (06) ◽  
pp. 1977-1990 ◽  
Author(s):  
Mohsen Rezaveisi ◽  
Kamy Sepehrnoori ◽  
Gary A. Pope ◽  
Russell T. Johns
Keyword(s):  
Phase Behavior ◽  
Capillary Pressure ◽  
Thermodynamic Analysis ◽  
Phase Stability ◽  
Tangent Plane ◽  
General Purpose ◽  
Distance Method ◽  
Capillary Equilibrium ◽  
Production Behavior ◽  
Reservoir Simulator

Summary High capillary pressure has a significant effect on the phase behavior of fluid mixtures. The capillary pressure is high in unconventional reservoirs because of the small pores in the rock, so understanding the effect of capillary pressure on phase behavior is necessary for reliable modeling of unconventional shale-gas and tight-oil reservoirs. As the main finding of this paper, first we show that the tangent-plane-distance method cannot be used to determine phase stability and present a rigorous thermodynamic analysis of the problem of phase stability with capillary pressure. Second, we demonstrate that there is a maximum capillary pressure (Pcmax) where calculation of capillary equilibrium using bulk-phase thermodynamics is possible and derive the necessary equations to obtain this maximum capillary pressure. We also briefly discuss the implementation of the capillary equilibrium in a general-purpose compositional reservoir simulator. Two simulation case studies for synthetic gas condensate reservoirs were performed to illustrate the influence of capillary pressure on production behavior for the fluids studied.

Phase Behavior and Minimum Miscibility Pressure in Nanopores

2014 ◽  
Vol 17 (03) ◽  
pp. 396-403 ◽  
Author(s):  
Tadesse Weldu Teklu ◽  
Najeeb Alharthy ◽  
Hossein Kazemi ◽  
Xiaolong Yin ◽  
Ramona M. Graves ◽  
...  
Keyword(s):  
Phase Behavior ◽  
Electrostatic Interactions ◽  
Structural Changes ◽  
Unconventional Reservoirs ◽  
Gas Oil ◽  
Confined Space ◽  
Liquid Equilibrium ◽  
Minimum Miscibility Pressure ◽  
Multiple Mixing ◽  
Carbon Dioxide Co2

Summary Numerous studies indicate that the pressure/volume/temperature (PVT) phase behavior of fluids in large pores (designated “unconfined” space) deviates from phase behavior in nanopores (designated “confined” space). The deviation in confined space has been attributed to the increase in capillary force, electrostatic interactions, van der Waals forces, and fluid structural changes. In this paper, conventional vapor/liquid equilibrium (VLE) calculations are modified to account for the capillary pressure and the critical-pressure and -temperature shifts in nanopores. The modified VLE is used to study the phase behavior of reservoir fluids in unconventional reservoirs. The multiple-mixing-cell (MMC) algorithm and the modified VLE procedure were used to determine the minimal miscibility pressure (MMP) of a synthetic oil and Bakken oil with carbon dioxide (CO2) and mixtures of CO2 and methane gas. We show that the bubblepoint pressure, gas/oil interfacial tension (IFT), and MMP are decreased with confinement (nanopores), whereas the upper dewpoint pressure increases and the lower dewpoint pressure decreases.

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