Lost Circulation

Lost Circulation

The Lost Circulation: means the loss of quantities of Drilling Fluid during the Drilling Operations and the invasion of the Formation.

Topics

1. Cases of Lost Circulation
2. Types of Loss and its Treatments
3. Types of Formations at which the Lost Circulation occurs
4. What are the consequences of loss?
5. How to avoid Lost Circulation?

1. Cases of Lost Circulatio

There are many reasons that cause the loss of the Drilling Fluid inside the Formations which include:

When Mud Hydrostatic Pressure exceeds Formation Fracture Pressure, the fractures are created and the Drilling Fluid invasion goes into the Formation.

The Formation contains natural fractions that help the Drilling Fluid to run into it with large amounts.

The Drilling inside the unconsolidated Formations. As the Drilling in such formations leads it to collapse and creates corridors or fissures that cause the Loss .

2. Types of Loss and its Treatments

There are 2 types of Loss

1. Partial Loss

It is a partial loss of the Drilling Fluid that occurs in the high porosity and high permeability zone.

✅ Treated by an increase in the Mud Density and Viscosity.

2. Complete Loss

It is a total loss of Drilling Fluid and it does not come out to the surface at shale shaker. This occurs within the caves and layers with very large pores.

✅ Treated by dropping a group of clay balls mixed with weeds to lining the hole, or Drilling by concrete plugs.

3. Types of Formations at which the Lost Circulation occurs

Rocks with high permeability such as coarse rocks and some types of limestone.

Caves and Open Folds, Joints and Fissures.

Natural Fractures.

4. What are the consequences of loss?

Decreased amount of Drilling Fluid in the well which results in a decrease in Hydrostatic Pressure that leads to underbalance Drilling, accompanied by Kick, then Blowout.

The Mud Invasion into Formation and damaging it.

Possibility of Stuck Pipe.

Increasing the time spent in the Drilling Operations and thus increasing the total cost.

5. How to avoid Lost Circulation

Reducing Mud Hydrostatic Pressure by decreasing Mud Density.

Using the cement or a Concrete Plug instead of Mud.