The application of enhanced oil recovery (EOR) for a Saudi Arabian carbonate reservoir was the subject of this study. Initial process screening revealed that miscible displacement was the only viable EOR process for recovering the relatively heavy oil (28 ° API). The use of separator gas, separator gas enriched with liquefied petroleum gas (LPG), pure LPG, CO2, and CO2 enriched with LPG as displacing fluids was explored. Some of the experimental results were presented in the 1987 Middle East Oil Technical Conference (see ref. 1). Further results obtained from a continuation of the study are described in this paper. The minimum miscible pressure of pure CO2 with oil was found to be higher than the reservoir pressure. CO2 enriched with 15 percent LPG gave optimal multiple-contact miscibility conditions. An unconventional apparatus consisting of a slim tube and a core holder joined in series was designed to study multiple-contact displacement. It was found to be very useful for investigating the effectiveness of enriched CO2 as a displacing fluid. The conclusions of this experimental study for the carbonate cores were:Oil displacement efficiencies by LPG and enriched CO2 were comparable, although the displacement mechanisms were different.The optimal size of LPG and enriched CO2 was 5 and 25 percent, respectively.Water alternating with gas (WAG) gave similar results when used in place of continuous CO2 as driving fluid.CO2 acted as an excellent buffer for separating the displacing fluid from the driving fluid.The amount of oil recovered by the miscible process was twice as much as that recovered by waterflooding. INTRODUCTION Several researchers have demonstrated that multiple-contact miscibility (MCM) tests require certain length or travel distance before the miscibility develops. Their reports2,3,4,5 showed that short cores could not be used in MCM displacement experiments to estimate the recovery from large scale systems. In this study, an improved linear model, called combined slim-tube coreflood apparatus, was employed to perform MCM enriched CO2 tests. This unconventional model consisting of a 41 foot (12.5 m) long slim-tube connected in series with a core holder, allows the miscible bank to develop in the slim-tube and then miscibly displace the crude out of a 12 inch (30.5 cm) composite core. Holm6 and Ehrlich et al7 have used similar experimental models for achieving the same purpose.

Wire Wrapped Screens (WWS) have received more attention from Steam assisted Gravity Drainage (SAGD) operators. A WWS is commonly fabricated with a wedge-shaped wire that is spiral-wound around a perforated base pipe to form a Wire wound Mesh (WWM). This produces a single, continuous, keystone-shaped helical slot with a large open flow area to enable for fluid flow while maintaining the structural rigidity of the base pipe and providing sand control to the wellbore.The structural integrity of a WWS with dual ring Wrap-On-Pipe (WOP) WWM and gap opening and closing within the WWM during thermally-induced loading were assessed through a full-scale thermal test program and Finite Element Analysis (FEA), during which the WWS was subjected to thermal cycle loading between 20°C (68°F) (room temperature) and 280°C (536°F), simulating the target temperature of a relatively high-temperature SAGD project in northern Alberta. The loading condition selected as the worst-case scenario from a service limit state perspective for the testing and FEA was to enable the WWS specimens to freely expand during the initial heating phase and then axially constrain them for the subsequent thermal cycle loading. This loading condition was selected because it was the scenario most likely to cause gap width opening between the wire wraps to an extent where the WWS could no longer provide suitable sand exclusion.The FEA was used to determine the peak plastic strains within the base pipe and the effect that the residual stresses, introduced by the welding process, have on the structural integrity of the WWS. The frictional conditions between the spiral-wound wire and base pipe were found to have a significant impact on limiting axial movement between the WWM and base pipe, and the axial strains developed in the screen. In addition, an analytical model is presented that estimates the gap opening of the WWM because of thermal strains, which compared well to the results obtained through FEA.The testing was conducted to assess the structural capacity of the WWS design and monitor change in gap widths during thermal cycling at key structural locations of the WWS design. The strain monitoring results from the full-scale test program were found to be consistent with the predicted strains from the FEA assessment. This paper presents testing and FEA results for a WWS with WOP WWM, and investigates the potential of a WWS to provide long-term and reliable sand control for SAGD wells.