Abstract
ABSTRACT In this paper the optimal gas flow rate in a retrograde gas condensate reservoir has been calculated in order to minimize retrograde condensation, maximizing the slip velocity, due to the positive coupling effect; and minimizing the pressure drawdown, due to the Forchheimer effect (non-Darcy effect, inertial effect). Non-Darcy behavior has been thoroughly described because of its importance for describing additional pressure drawdown (more than expected by Darcy equation) in fluid flow in porous media, in situations where high velocity occurs. The coupling effect explains the increment of the gas-condensate relative permeability with increasing velocity and decreasing the interfacial tension. The Forchheimer equation has been used to calculate the bottom-hole flowing pressure for different gas flow rates. Because of the second term in the Forchheimer equation, which is function of the square of the superficial velocity of the fluid, this obtained value is less than the bottom-hole flowing pressure obtained from Darcy equation. This is important because a higher quantity of condensate liquids is obtained, which reduces the relative permeability, and as a result, the gas flow rate decreases due to this effect. For those different gas flow rates, the optimal gas flow rate, where the bottom-hole flowing pressure is acceptable, has been found. The novelty of the present work, is to present the optimal point where the gas flow rate is maximum, in which the non-Darcy effect is negligible. Keywords: Forchheimer effect, Coupling effect, Gas Condensate Reservoir
Highlights
Gas condensate reservoirs have been classified between volatile oil and wet gas reservoirs
The behavior of gas condensate reservoirs is not fully understood, because of their complexity owing to the presence of a two fluid system, gas-phase and liquid-phase (Economides et al, 1987; Bloom, 1998; Yu, 1996; Gondouin, 1967) and they are becoming more common as the exploration for oil and gas are being targeted on deeper depths, higher pressures, and higher temperatures
The one-dimensional Darcy equation can be written as: where μ is the fluid viscosity, k is the permeability and v is the superficial velocity of the fluid, as defined by the following equation: This paper presents a methodology to analyze the Forchheimer effect and to observe the competition between inertial and coupling effects in the Pagoreni Field, which is a lean gas condensate field
Summary
Gas condensate reservoirs have been classified between volatile oil and wet gas reservoirs. The behavior of gas condensate reservoirs is not fully understood, because of their complexity owing to the presence of a two fluid system, gas-phase and liquid-phase (Economides et al, 1987; Bloom, 1998; Yu, 1996; Gondouin, 1967) and they are becoming more common as the exploration for oil and gas are being targeted on deeper depths, higher pressures, and higher temperatures. The behaviors of such systems are complex, especially in the near-wellbore region, where a high-velocity occurs (Gringarten et al, 2006). It is important to get a better understanding that leads us to accurate predictions of well deliverability for selecting the best development plan (Mott et al, 2000), and to avoid problems like non-reversible reduction in well productivity, having a less marketable gas, and not to meeting contractual obligations of gas sales
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