This is the first method to determine surge and swab pressure.
Learn more about Surge Pressure and Swab Pressure
Surge is additional pressure due to pipe movement downward and swab is reduction of pressure due to upward movement of drill string.
Bottom hole pressure is reduced due to swabbing effect.
Bottom hole pressure is increased due to surging effect.
This is another method to determine cutting slip velocity. The process of calculation is quite different from the first method however it is still straight forward calculation. It still gives you the following answers: annular velocity, cutting slip velocity and net velocity.
Let’s get started with this calculation method.
1. Determine n
Where;
n is the power law exponent.
Θ600 is a value at 600 viscometer dial reading.
Θ300 is a value at 300 viscometer dial reading.
Cutting slip velocity is velocity of cutting that naturally falls down due to its density. In order to effectively clean the hole, effect of mud flow upward direction and mud properties must be greater than cutting slip velocity (settling tendency of cuttings). Otherwise, cutting will fall down and create cutting bed.
You can learn more detail about it via this topic -> Cutting Slip Velocity
This calculation will show annular velocity, cutting slip velocity and net velocity so you can use as a reference for you hole cleaning indication.
There are 2 calculation methods and I will show the first method via this topic.
One function of cement is to support casing string and the shear strength of cement holds casing string once cement is set. You may think about other load supporting casing as compressive loading at coupling areas or thermal movement. They are the part of the supporting force as well but the most support is from the cement shear strength.
(Diagram above shows how shear strength of cement supports casing string)
We don’t normally measure shear strength of cement but we can apply knowledge from Civil engineer to estimate the shear strength from the compressive strength. Generally, cement has the shear strength approximately 1/12 of compressive strength. For instant, if the cement 1000 psi compressive strength, its shear strength is 83.3 (1000 x 1/12) psi.
For the previous topic, Hydraulicing Casing (pressure to lift the casing while cementing), you already know the concept. This topic will demonstrate you how to figure out if the casing will be hydraulically lifted while pumping cement.
Example:
Casing 9-5/8”, 40 ppf (pound per foot), ID of casing = 8.835”
Casing is set at 3,200’MD/3,000’TVD
Top of cement at 600’MD/550’TVD
Previous casing shoe (13-3/8”) = 1000’MD/900TVD
Cement weight = 14.0 ppg
Mud weight = 9.5 ppg
Displacement fluid weight (Brine) = 8.4 ppg
What is the condition at the static condition after cement in place?
What is the maximum pressure that we can apply before the casing is hydraulically pumped out of the well?
