Our freeze plugging system consists of injecting a thick slurry of water-based bentonite gel and applying a refrigerant to the target area to freeze the gel to form an ice plug.
The gel that is injected is of similar viscosity to peanut butter.
The bentonite slurry is sticky enough to bond to tubulars and wellhead components and viscose enough to hold the medium in place until frozen. The bentonite clay also adds structure to the ice plug in that the particles interrupt the fracture paths that would be found in pure water ice that is inherently brittle. We routinely pressure test the ice plugs to full working pressure of the equipment that we are working on and commonly install ice plugs to contain well pressures exceeding 40Mpa.The methods used depend on what the area to be frozen contains or has contained or whether there is a leak to atmosphere from the area to be frozen. Pressure testing is performed to 1 ½ times the surface pressure of the well, or to the maximum well head pressure rating.
Bentonite viscosifier is used in most cement slurries to decrease slurry weight and increase slurry volume. In bentonite-cement diesel-oil (BCDO) and bentonite diesel-oil (BDO) slurries, bentonite forms a thick, paste-like material that helps prevent lost circulation.
Bentonite is compatible with slurries containing fibrous, granular, and flake-type lost-circulation materials.
Bentonite can provide the following benefits:
- It is easily obtained and can be an effective lost- circulation material when mixed with other common oilfield materials.
- The overall cost for treatment can be less than that of other lost-circulation methods.
- This material can be effective in regular and cavernous lost-circulation zones and where drilling with fibrous, granular, or flake materials has been ineffective