The Combined Effect of Near-Critical Relative Permeability and Non-Darcy Flow on Well Impairment by Condensate Drop-Out

1998 ◽  
Author(s):  
S.M.P. Blom ◽  
J. Hagoort
Keyword(s):  
Relative Permeability ◽  
Combined Effect ◽  
Drop Out ◽  
Darcy Flow

The Combined Effect of Near-Critical Relative Permeability and Non-Darcy Flow on Well Impairment by Condensate Drop Out

1998 ◽  
Vol 1 (05) ◽  
pp. 421-429 ◽  
Author(s):  
Saskia M.P. Blom ◽  
Jacques Hagoort
Keyword(s):  
Steady State ◽  
Gas Phase ◽  
Relative Permeability ◽  
Capillary Number ◽  
Radial Flow ◽  
Drop Out ◽  
Darcy Flow ◽  
Gas Reservoirs ◽  
Strongly Coupled ◽  
Original Manuscript

This paper (SPE 51367) was revised for publication from paper SPE 39976, first presented at the 1998 SPE Gas Technology Symposium, Calgary, 15-18 March. Original manuscript received for review 19 March 1998. Revised manuscript received 8 July 1998. Paper peer approved 13 July 1998. Summary We present a comprehensive numerical method to calculate well impairment based on steady-state radial flow. The method incorporate near-critical relative permeability and saturation-dependent inertial resistance. Example calculations show that near-critical relative permeability, which depends on the capillary number, and non-Darcy flow are strongly coupled. Inertial resistance gives rise to a higher capillary number. In its turn, the improved mobility of the gas phase caused by a higher capillary number enhances the importance of the inertial resistance. The effect of non-Darcy flow is much more pronounced in gas condensate reservoirs than in dry gas reservoirs. Well impairment may be grossly overestimated if the dependence of relative permeability on the capillary number is ignored. P. 421

Effect of Non-Darcy Flow on Well Productivity of a Hydraulically Fractured Gas-Condensate Well

2009 ◽  
Vol 12 (04) ◽  
pp. 576-585 ◽  
Author(s):  
Jitendra Mohan ◽  
Gary A. Pope ◽  
Mukul M. Sharma
Keyword(s):  
Hydraulic Fracturing ◽  
Relative Permeability ◽  
Gas Condensate ◽  
Darcy Flow ◽  
Productivity Improvement ◽  
Well Productivity ◽  
Fracture Width ◽  
Gas Condensate Reservoirs ◽  
The Impact ◽  
Actual Fracture

Summary Hydraulic fracturing is a common way to improve productivity of gas-condensate wells. Previous simulation studies have predicted much larger increases in well productivity than have been actually observed in the field. This paper shows the large impact of non-Darcy flow and condensate accumulation on the productivity of a hydraulically fractured gas-condensate well. Two-level local-grid refinement was used so that very small gridblocks corresponding to actual fracture width could be simulated. The actual fracture width must be used to accurately model non-Darcy flow. An unrealistically large fracture width in the simulations underestimates the effect of non-Darcy flow in hydraulic fractures. Various other factors governing the productivity improvement such as fracture length, fracture conductivity, well flow rates, and reservoir parameters have been analyzed. Productivity improvements were found to be overestimated by a factor as high as three, if non-Darcy flow was neglected. Results are presented that show the impact of condensate buildup on long-term productivity of wells in both rich and lean gas-condensate reservoirs. Introduction A significant decline in productivity of gas-condensate wells has been observed, resulting from a phenomenon called condensate blocking. Pressure gradients caused by fluid flow in the reservoir are greatest near the production well. As the pressure drops below the dewpoint pressure, liquid drops out and condensate accumulates near the well. This buildup of condensate is referred to as a condensate bank. The condensate continues to accumulate until a steady-state two-phase flow of condensate and gas is achieved. This condensate buildup decreases the relative permeability to gas, thereby causing a decline in the well productivity. Afidick et al. (1994) studied the Arun field in Indonesia, which is one of the largest gas-condensate reservoirs in the world. They concluded that a significant loss in productivity of the reservoir after 10 years of production was caused by condensate blockage. They found that condensate accumulation caused well productivity to decline by approximately 50%, even for this very lean gas. Boom et al. (1996) showed that even for a lean gas (e.g., less than 1% liquid dropout) a relatively high liquid saturation can build up in the near-wellbore region. Liquid saturations near the well can reach 50 to 60% under pseudosteady-state flow of gas and condensate (Cable et al. 2000; Henderson et al. 1998). Hydraulic fracturing of wells is a common practice to improve productivity of gas-condensate reservoirs. Modeling of gas-condensate wells with a hydraulic fracture requires taking into account non-Darcy flow. Gas velocity inside the fracture is three to four orders of magnitude higher than that in the matrix. Use of Darcy's law to model this flow can overestimate the productivity improvement. Therefore, it is necessary to use Forchheimer's equation to model this flow with an appropriate non-Darcy coefficient that takes into account the gas-relative permeability and water saturation.

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