ULZhG ultra light killing fluids for the wells with abnormally low formation pressure 

Well-killing, even within the same area, requires an individual approach to the selection of killing fluid parameters. Well-killing fluids with low densities, which are able to prevent fluid loss, well productivity decreasing after maintenance and long period of resumption of stable output of the wells after maintenance, must be used for killing of the wells with abnormally low formation pressure.

Ultra light killing fluids of ULZhG brand with densities from 0.7 to 0.99 g/cm3 were designed in Polyex for killing of the wells with abnormally low formation pressure for performing maintenance and repair works.

The product is hydrocarbon-free water-based liquid with addition of viscoelastic surfactant SURFOGEL® grade D and inert filler EXTELIGHT®, which allows the well-killing fluid density to be decreased substantially and to be varied within wide range.

Application area

  • Killing of the wells with abnormally low formation pressure.
  • Cleanout of horizontal wellbore from residual proppant in the wells with hydrofracs.

Appearance Viscous suspension with the color varying
from milky to light-grey or Indianapolis red 
Density, g/сm3   0.7g/сm3  0.75g/сm3
0.8g/сm3  0.85g/сm3
0.9g/сm3  0.99g/сm3   
Brookfield viscosity at 20 s-1
at 30˚С, not more than    
500 mPa·s 
SURFOGEL® grade D type 70-100
SURFOGEL® grade D type 100-150   

Up to 80°С
Up to 120°C
Freezing point, not higher than   0°С
Aggregative stability of ultra light
well-killing fluid checked
in laboratory conditions  
14 days  
Aggregative stability of ultra light
well-killing fluid checked
in laboratory conditions 
90 days  

* Thermostability of ready-to-use ultra light killing fluid depends on the type of VES base used in the fluid, i.e. SURFOGEL® grade D (Surfactant base) type 70-100 or SURFOGEL® grade D (Surfactant base)type 100-150.

Customer Benefits

  • Nonflammable fluid.Hydrocarbon-free and polymer-free composition.
  • Depending on the base of VES may be applied at the temperatures up to 120 °C. 
  • Inert to the formation rocks.
  • Liquid circulation and bottom-hole zone cleanout is possible.
  • No colmatation of formation pay zone is observed due to the spherical shape of the filler and it’s optimal fraction selection.
  • Well-killing fluid density 0.7 g/cm3 can be achieved, it provides the possibility of gas-lift wells completion with no coil tubing technology application.   
  • Low plastic viscosity of gelling base (7.87 mPa•s at 30°С) provides low injection resistance.
  • Thixotropy  of ultra light killing fluid ULZhG prevents gas-outs and facilitates killing of high gas-oil ratio wells for maintenance works.
  • Substantially reduced period of resumption of stable output of the wells after maintenance (average well resumption period after killing with ULZhG makes 3 days).

Process Technique

Ultra light killing fluid ULZhG is normally supplied component-wise and is mixed right before the application at site at brine preparation unit. ULZhG is a solution of the SURFOGEL® grade D system components Surfactant Base and Activator in fresh process water. Further some amount of inert filler EXTELIGHT® is added which allows lowering of killing fluid density to 0.7 g/cm3.

The choice of the type of SURFOGEL® grade D Surfactant Base depends on the application temperature. The amount of EXTELIGHT® depends on the required fluid density. Total content of SURFOGEL® grade D complex components in the fluid makes  4-10%.

Depending on the grade ultra light filler EXTELIGHT® is either polymer microsphere filler or microsphere filler made of silicates of different nature. Depending on the nature of silicates  EXTELIGHT®varies in its thermal resistance and mechanical damage strength. 

To obtain more information and to select the optimal design of application and consumption of ultra light killing fluid of ULZhG brand it is recommended to contact the specialists of Polyex company. 

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