Some time ago I put together a short paper about the principles of squeeze cementing. Below is an extract of this document.
Successful squeeze cementing relies mostly on selecting the correct cement slurry to form an effective cement cake or node. We base the decision shall on the injectivity test performed before the squeeze operation.
There are two main controlling variables during squeeze cementing that affect the rate of filtration. These are the fluid loss of the cement slurry and the permeability of the formation or porous media.
a) The higher the cement slurry fluid loss, the higher the amount of cement filtrate available for filtration. The fluid loss of the cement slurry is a property of the slurry that we can modify with chemicals (cement additives).
b) The higher the injectivity rate, the higher the volume of cement filtrate that the permeable media will be able to receive. Before every squeeze cementing operation, we always perform an injectivity test. This injectivity is directly proportional to the effective permeability from Darcy’s Law.
If we combine (a) and (b):
- High fluid loss + High Injectivity = very high rate of filtration = premature plugging. Not recommended.
- Medium/Low fluid loss + Medium/High Injectivity = rate of filtration controlled by cement slurry fluid loss. A margin for squeeze pressure.
- Medium/High fluid loss + Medium/Low injectivity = rate of filtration controlled by the permeable media. A margin for squeeze pressure.
- Low fluid loss + Low injectivity = very low rate of filtration = long operation. Not recommended.
2. and 3. are common scenarios for squeeze cementing with conventional slurries system, while 1. and 4. may require non-conventional slurries types or additional chemicals/materials.
More details in following posts.