Slug sizes

Micellar/polymer (MP) chemical enhanced oil recovery systems have demonstrated the greatest potential of all of the recovery systems under study (170) and equivalent oil recovery for mahogany and first-intent petroleum sulfonates has been shown (171). Many somewhat different sulfonate, ie, slug, formulations, slug sizes (pore volumes), and recovery design systems were employed. Most of these field tests were deemed technically successful, but uneconomical based on prevailing oil market prices (172,173). 

Comparison of Retention Properties of Three Desorbents with an Increasing Degree of Ethoxylation The individual behavior of three nonionic desorbents (NP 14, 30 and 100 E.O) is compared in Figure 8. Slug size was 1.16 PV in those tests. The outflow of the tracer indicates the slug front of the additive injected. The concentration used was 5 g/1 in all tests. On a weighted basis, it was the NP 30 E.O., that led to the lowest final retention, i.e. 0.30 mg/g of rock (Table II). 

Crude Oil Slug Type Slug Size % PV Tertiary Recovery % oil in place... 

The results show that for a given slug size, a composite slug recovered more crude than a single slug of equivalent size. 

Figure 7. Effect of Micellar Slug Size on the Oil Recovery Efficiency of Micellar Slug B4...

Next, the proportions of oil-rich and water-rich slugs were varied for a given slug size (10% pv) and the tertiary recoveries were compared. As seen in Table V, oil-rich slugs were more effective... 

Small micellar slugs (2-5% pv) can recover 3 to 15 times their volume of waterflood residual oil. Final oil saturation was reduced to 0.02% pv for 2% pv slug size and,0.01% pv for 5% pv slug size. 

Table VIII. Tertiary Recovery with Smaller Slug Size...

Initial Oil Saturation - 31.94% PV Slug Size - 5% PV B4 Graded Buffer Size - 50% PV Frontal Velocity -1.39 m/day Tertiary Recovery - 97.94% OIP... 

Oil recovery increases with an increase in micellar slug size. But the process efficiency drops and the surfactant loss increases. 

Because the benzene derivative and nitric acid are immiscible, the impact of mixing/ distribution on slug formation was investigated. Uniform slugs of the aromatic compound/nitric acid were formed in a Y-piece [22]. The capillary attached has a stabilizing effect on the slug flow. The deviation of slug size distribution is very small (about 5%). Hence, interfacial area is nearly constant for this type of capillary flow. 

The surfactant adsorbs on water-wet glass beads. Experiments reported in Ref. 27 show that about 0.5 HCPV of surfactant solution is required to satisfy the adsorption capacity of the bead pack. Hence, when a slug size of 0.2 HCPV of carbon dioxide and an equal slug of surfactant solution are injected together, the surfactant is all adsorbed when about 40% of the volume of the bead pack has been contacted. This is apparently sufficient to obtain the benefits of... 

Based on Cases krl to kr4, we change the surfactant slug size from 0.1 PV to 0.2 PV, and the concentration from 3% to 1.5%. We also move 0.2 PV polymer into the surfactant slug. The resulting cases are II to 14. In these cases, we start... 

To investigate the effect of the amounts of polymer and surfactant injected, we use different concentrations and slug sizes and compare the incremental oil recovery factors and chemical costs (chemical Ib/bbl incremental oil) for different amounts of polymer and surfactant injection. The amount of surfactant injected is commonly presented in concentration (%) PV(%), and the amount of polymer is commonly presented in mg/L PV(fraction). Note that the unit PV is in fraction of pore volume. This section presents both polymer and surfactant in concentration (%) PV(%). The relationship between these two units is mg/L PV(fraction) = 100 concentration (%) PV(%). Figures 9.5 and 9.6 show the results. From these two figures, we can see that the more chemicals injected, the more incremental oil is recovered. However, in general, the chemical cost per barrel of incremental oil is also increased. Apparently, when a low load of chemicals is injected, the chemical cost per barrel of incremental oil is not sensitive to the amount of chemical injected. This observation is seen for both polymer and surfactant. 

ALKALINE CONCENTRATION AND SLUG SIZE IN FIELD PROJECTS... 

Alkaline Concentration and Slug Size in Field Projects... 

Figure 10.33 shows the cumulative percentage versus the total injected alkali, which is presented by the product of concentration (%) and slug size (% PV). At the 50% cumulative percentage, the product is 17. For most of the field projects, the incremental oil recovery factors were 1 to 2%. 

A UTCHEM chemical flood model was built based on history-matching core flood experiments. The chemical parameters were calibrated through matching experiments. The calibrated parameters were used to build a field sector model to simulate the ASP pilot test. In the model, detailed alkaline reactions were considered. It was probably the hrst time such an ASP model was applied in a real held scale. The model was used to optimize injection schemes. For example, the model showed that when the post-flush slug volume was in the range of 0.15 to 0.35 PV, the pilot performance was insensitive to the slug size. Therefore, 0.15 PV of post-flush slug was selected for the injection scheme. 

---