Gas-Condensate Pseudopressure in Layered Reservoirs

Abstract

This paper presents verification of the Fevang and Whitson (1996) gas-condensate pseudopressure method for layered reservoirs. Layers may be characterized by widely varying permeability and composition, and they may be communicating or noncommunicating. The pseudopressure method is used in well calculations for coarse-grid models with relatively large areal grid dimensions (>50 m), capturing near-well condensate blockage without local grid refinement, thereby reducing run time and model size.The paper presents examples from several field studies and from two synthetic systems using a commercial reservoir simulator. The field studies include rich-and lean-condensate reservoirs.The study was conducted using a commercial compositional reservoir simulator. Three-dimensional multilayer, fine-grid (radial and Cartesian) models and equivalent coarse-grid models were used. Both depletion and gas-injection cases were simulated for a wide range of reservoir fluids. Reservoir performance of fine-grid models and coarse-grid models was compared using the gas-condensate pseudopressure method and showed comparable results in all cases studied, including relative permeabilities with capillarynumber dependence and high-velocity (␤) flow treatment.The coarse-grid model with pseudopressure is somewhat dependent on coarse-grid size, generally requiring ⌬x=⌬y≈50-100 m for lean gas condensates and ⌬x=⌬y≈100-200 m for rich gas condensates.The paper verifies for the first time that the gas-condensate pseudopressure method as proposed by Fevang and Whitson (1996) is valid and accurate for layered systems with significant heterogeneity (permeability variation), with and without crossflow, with and without capillary-number modification of relative permeabilities, and for widely ranging fluid compositions in each layer. Fevang and Whitson (1996) show that the flow toward a gascondensate well producing from a reservoir can be divided into three main flow regions, extending from the wellbore outward: the near-well region, the condensate-buildup region, and the singlephase gas region. Flow Regimes and Flow Behavior in a Gas-Condensate Well Near-Well Region (Region 1).The near-well region is an inner near-wellbore region saturated with oil and gas with both fl owing simultaneously. The fl owing composition [i.e., the gas/oil ratio (GOR)] within this region is constant throughout, and equal to the composition of the produced wellstream mixture. Furthermore, the dewpoint of the producing wellstream mixture equals the reservoir pressure at the outer edge of this region, p*.The gas relative permeability in this region is mainly a function of liquid-saturation distribution. The steady-state saturation distribution in Region 1 is determined (as a function of pressure) specifically to ensure that all liquid condensing from the singlephase gas and entering Region 1 has sufficient mobility to flow through and out of Region 1 without any net accumulation. Condensate-Buildup Region (Region 2). This is a region of condensate buildup in which the liquid con...

A case study of gas-condensate reservoir performance under bottom water drive mechanism

“…Specifically, the calibrated radial model was found to converge in radial flow using gas-condensate fluid. Moreover, the calibrated grid was also found to be similar to that used previously by Singh and Whitson (2010) in a study on gas-condensate reservoirs. After successfully passing the convergence test in the radial direction, the calibrated grid was tested for convergence in the axial direction.…”

“…If the traditional method is used to calculate rate (mobilities evaluated at gridblock pressure), the loss in well deliverability will be under-predicted. Singh and Whitson (2010) also verified the validity and accuracy of the pseudopressure method for layered systems with significant heterogeneity in permeability and gas-condensate composition. Tran et al (2015) used both pseudopressure and local grid refinement to model condensate-banking phenomenon, and then applied to horizontal and hydraulic fracturing design.…”

“…Consequently, the radial model with 15 cells and grid-cell size of the innermost cell of 0.177 ft (≈ 0.054 m) is suitable to simulate Sand20 gas-condensate reservoir. For comparison, this model is comparable with that in Singh and Whitson (2010), as summarized in Table 3.…”

Development of inflow performance model in high temperature gas-condensate reservoirs

“…Fluid flow near well bore region in depleted gas condensate reservoir below the dew point is in the form of two phases "gas and condensate (light oil)" (Fevang and Whitson, 1996;Mott, 2003;Qasem et al, 2014;Rahimzadeh et al, 2016;Thomas and Bennion, 2009;Whitson et al, 1999). Furthermore, gas condensate PVT properties are different from natural gas and crude oil due to the compositional changes that occurs below the dew point (Elsharkawy, 2006;Rayes et al, 1992;Whitson et al, 2000;Yang et al, 2007).…”

Condensate Recovery from a Fractured Carbonate Field

“…Also, the well productivity can be substantially decreased by condensates accumulating around the wellbore, reducing the gas relative permeability (e.g. Singh and Whitson 2008).…”