A barite plug is a slurry of barite in fresh water or diesel oil which is spotted in the hole to form a barite bridge that will seal the flow and allow control of the well to be re-established.

The plug is displaced through the drillstring and, if conditions allow, the string is pulled up to a safe point above the plug. The barite settles out rapidly to form an impermeable mass capable of shutting off high rates of flow.

The effectiveness of a barite plug derives from the high density and fine particle size of the barite and its ability to form a tough impermeable barrier.

A barite plug has the following advantages:

• The slurry has a high density (19.0 - 22.0 ppg)
• It can be pumped through the bit and offers a reasonable chance of recovering the drillstring
• The material required is normally available at the rig site.
• The plug can be drilled easily if required.

The main disadvantages the risk of settling and consequent plugging of the drill string if pumping is stopped before the slurry has been completely displaced.

Two types of barite slurries can be used:

• Barite fresh water slurry
• Barite diesel Oil slurry

Other materials can be used if a very high slurry density is required to stop the flow so that the slurry will settle. llmenite and galena have been used in the past and micaceous hematite is potentially useful All of these materials have a higher density than barite. Regardless of the materials used, all slurry formulations should be pilot tested before mixing to ensure settling and dehydration before mixing.

Barite Plug - Fresh Water Slurry

The amount of barite and fresh water required to formulate .1.0 bbl of slurry at various densities is shown in the following table:

Barite Plug Preparation

The mix water is prepared first and barite is added as needed to attain the required slurry density.

Equipment needed

cementing unit with high pressure jet in mixing hopper

sufficient clean tankage to store the mix water

Mixwater preparation

Settling Recipe:

• 1 bbl water (fresh or sea)
• 15 lb lignosulphate
• 2 lb/bbl caustic soda (pH = 10.5 to 11.5)

Non-settling Recipe:

• 1 bbl water (fresh or sea)
• 15 lb lignosulphate
• 1 lb XC polymer
• Defoamer
• 2 lb/bbl caustic soda (pH = 10.5 to 11.5)

Barite Addition

Barite is added to mixwater as required to prepare the final slurry. The quantity of barite added is dependent  on the final slurry density required.

Setting Barite Plug

The barite plug will be set and the pipe pulled out of plug following these guidelines:

• Mix and pump slurry with drillpipe as close to bottom as possible.
• Displace slurry with mud at the same rate
• Immediately begin pulling pipe
• Monitor the annulus
• Trip out of hole after verifying the well is dead.

The barite plug should be pumped and displaced at a rate higher than the kick rate. If the kick rate is unknown a reasonable 5 to 10 bbl/min should be used for the first attempt although very large blowouts can ultimately require kill mud placement at 50 bbls/min.

A minimum final plug length of 200 ft and not less than 10 bbls volume should be used to ensure a good seal and allow accurate displacement into the wellbore.