Sometime 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. The decision shall be based 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 permeable 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 can be modified with chemicals (cement additives).
b) The higher the injectivity rate, the higher the volume of cement filtrate the permeable media will be able to receive. Previous to the squeeze cementing operation an injectivity test is always performed, this injectivity is directly proportional to 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. Margin for squeeze pressure
- Medium/High fluid loss + Medium/Low injectivity = rate of filtration controlled by the permeable media. 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.