Designed for a range of works completion and workover, including perforation, stimulation and jamming, as well as for the conservation of wells and temporary blocking of the bottomhole formation zone. Salt and a polymer-salt systems are salt solutions of varying density, which may be thickened with polymeric additives.
Thickening polymers salt solutions allows to obtain systems without washing the solid phase with controlled rheological and filtration characteristics.
SALT FLUSHING SYSTEMS
- RGS-132: density from 1100 to 1320 kg/m3;
- RGS-145 density from 1320 to 1450 kg/m3;
- RGS-155: density from 1450 to 1600 kg/m3.
POLYMER-SALT FLUSHING SYSTEMS
Flushing system of this type is prepared by dissolving the polymers in salt solutions at a certain ratio of temperature and density. Such technology allows for directional regulation filtration and rheological properties without reducing solutions while their density.
The polymer-salt systems can be prepared on the basis of brines produced in the territory of Ukraine or on the basis of dry salt produced by industry and delivered in standard packaging.
The polymer-salt systems may be prepared directly in the well and the special stationary node. For this washing system requires a stirring device - clay mixer or agitators. It is also possible to produce a solution in the hopper cementing machine or directly into a wellbore.
TECHNOLOGICAL PROPERTIES
- The density of the polymer-salt wash systems can vary from 1100 to 1550 kg/m3.
- Thermal stability of the polymer-salt systems is within 120-140oC.
- Reduction factor reservoir permeability after exposure to polymer-salt washing systems, higher than that provided under the influence of drilling mud filtrate hlorkalievogo and close to a level that ensures the application of OBM.
- To provide a technologically acceptable level of fluid loss, the concentration of polymer in the system does not exceed 3-4% of dry product.
Depending on the polymer concentration may change in the rheological properties of the system within wide limits. The values of the constants rheological fluids are shown in the table below:
| Polymer concentration | The index of consistency - К, dPa. сn | The index of non-linearity of the system - n | ||
|---|---|---|---|---|
| % | at 20°С | at 80°С | at 20°С | at 80°С |
| 2 | 4.4 | 1.2 | 0.77 | 0.86 |
| 3 | 16.3 | 4.3 | 0.69 | 0.855 |
| 4 | 42.2 | 9.1 | 0.68 | 0.85 |
| 5 | 85.3 | 16 | 0.652 | 0.847 |
| 6 | 99.7 | 18.4 | 0.647 | 0.819 |
| 7 | 164 | 32.5 | 0.624 | 0.793 |
| 8 | 244.8 | 69.4 | 0.604 | 0.704 |
| 9 | 390 | 93.9 | 0.532 | 0.670 |
| 10 | 459 | 135.5 | 0.528 | 0.623 |
ADVANTAGES
The polymer-salt flushing systems are characterised by:
- high density;
- high salinity;
- high inhibiting properties.
Compared with conventional brines, polymer-salt systems have
- low filtration;
- higher rheology;
The combination of technological properties provides a significantly higher coefficient recovery reservoir permeability than using traditional brines.
THE POLYMER-SALT FLUSHING SYSTEMS ARE CHARACTERIZED BY
- resistance to biodegradation;
- low freezing point (for solutions with the density of 1280 kg/m3 - below -50°C);
- ecological safety.
LIMITATIONS
With the increase in the density of salt and a polymer-salt compositions increases the risk of crystallization of the salt brine at low temperatures. The temperature of crystallization for the polymer-salt solution with the density of 1550 kg/m3 of -18 ÷ -20 ° C.
