Simulation of Residual Oil Saturation in Near-Miscible Gasflooding Through Saturation-Dependent Tuning of the Equilibrium Constants

Abstract

Summary Conventional miscible or near-miscible gasflooding simulation often overestimates oil recovery, mostly because it does not capture a series of physical effects tending to limit interphase compositional exchanges. Those can include microscopic bypassing of oil situated in dead-end pores or blocked by water films, as well as macroscopic bypassing caused by subgrid-size heterogeneities or fingering. We here present a new engineering solution to this problem in the near-miscible case, relying on our in-house research reservoir simulator. The principle is, while using a black-oil or an equation-of-state description, to dynamically decrease the K-value of heavy components and possibly increase the K-value of light components as the oil saturation reaches the desired residual limit; this enables changing the phase boundaries when needed while preserving the original fluid behavior during the initial production stages. The benefits of the proposed solution are demonstrated on a reservoir-conditions tertiary-gas-injection experiment, performed in our laboratories, for which residual saturations as well as oil-phase and individual-component production rates have easily and successfully been history matched. Results are then compared with matches obtained by use of saturation exclusion and α-factors methods. As a proof of concept, the suitability of the new method to simulate incomplete revaporization of condensate during gas cycling is also illustrated, on the third SPE comparative-solution-project case.

Development of a Giant Carbonate Oil Field, Part 1: Fifty Years of Pressure Maintenance History

“…Despite such favorable conditions, residual oil is still expected in the pilot area (Patacchini, Duchenne, Bourgeois, Moncorgé, & Pallotta, 2015) Although the GIP's main purpose was not pressure maintenance, pressure increases of 600 to 800 psi were observed in the wells located in a 4 -5 km range; as soon as GIP ceased, pressures in the wells started to drop, as can be seen in Figure 8 where combined BHCIP of three wells located in the GIP area are shown. The pilot injection wells started in 2001 and were shut-in at the end of 2009 as a result of maturity in terms of operation and data acquisition.…”

Gas Injection EOR Screening by Laboratory Experiment and Sector Modeling in Carbonate Reservoir

“…Significant hysteresis occurs during WAG injection between imbibition and secondary drainage, and these effects, along with three-phase flow, must be correctly represented (Jerauld 1997). Laboratory experiments observed that bypassed oil occurs even after miscible flooding, and accurate computation of residual oil to miscible flood (S orm ) is crucial for correct recovery estimation (Hiraiwa et al, 2007;Bourgeois et al, 2011;Patacchini et al, 2015). Moreover, the timing of gas and WAG injection should be defined after robust screening, as early gas injection will result in poor volumetric sweep efficiency, whereas late injection will result in very low oil production rate (Jerauld et al, 2000).…”