Use of Two-Phase Pseudo-Pressure for Well Test Analysis of Gas Condensate And Volatile Oil Below Saturation Pressure

摘要

This study examines the benefits of using two-phase pseudo-pressure in three areas: (1) rate dependent skin analysis; (2) bottomhole backpressure deliverability forecasting; and (3) deconvolution of the pressure transient response of wells producing from gas condensate and volatile oil reservoirs flowing below saturation pressure. The study was carried out with compositional simulations whose results were compared with field data.udIt was shown that below saturation pressure, single-phase pseudo-pressure analysis of gas condensate and pressure analysis of volatile oil does not correctly estimate the mechanical skin and non-Darcy factor, whereas two-phase pseudo-pressure analysis does, provided that the gas or oil relative permeability which incorporates high capillary number and non-Darcy effects is used for the two-phase pseudo-pressure calculation. High capillary number reduces the effect of condensate or gas blockage at the wellbore due to enhanced mobility below saturation pressure.udIt was established that stabilised backpressure deliverability line can be quantified with two-phase pseudo-pressure backpressure plot calculated with the relative permeability curves which incorporate high capillary number and non-Darcy effects instead of single-phase pseudo-pressure or pressure backpressure plots.udFurthermore, deconvolution of pressure, single-phase and two-phase pseudo-pressure in gas condensate and volatile oil data below saturation pressure were studied to identify and mitigate non-linearities. The deconvolved derivatives obtained from two-phase pseudo-pressure, pressure (for volatile oil) and single-phase pseudo-pressure (for gas condensate) exhibit similar late time behaviours, thus, justifying the simpler pressure and single-phase pseudo-pressure approach.udWhilst it is shown that in theory the use of two-phase pseudo-pressure calculated with relative permeability curves which incorporate high capillary number and non-Darcy effects linearizes the pressure transient response of wells producing from gas condensate and volatile oil reservoirs flowing below saturation pressure, in practice, the uncertainty in the input data required to generate two-phase pseudo pressure is likely to be too great to achieve a reliable analysis.