Technical Information

Cement Glossary

Pressure
A force applied over a specific area, commonly reported in lbf/in2 (psi).

Density
The unit mass of a material per unit volume, commonly reported in lbm/gal (ppg).

Specific Gravity
The ratio of the density of a material or fluid to that of water. This is a unitless number.

Friction Pressure
The pressure generated when a fluid is put into motion, commonly reported in lbf/in2 (psi).

Hydrostatic Pressure
The pressure that a fluid of a specific density exerts vertically, commonly reported in lbf/in2 (psi).

Equivalent Circulating Pressure (ECD)
The frictional gradient plus the hydrostatic gradient at a specific location in the wellbore, commonly reported in lb/gal or psi/ft.

Equivalent Mud Weight (EMW)
The hydrostatic gradient of all fluids above a specific point in the wellbore, commonly reported in lb/gal.

Total Measured Depth
The total length of a well or tubular, commonly reported in feet (ft).

True Vertical Depth
The vertical length of a well or tubular, commonly reported in feet (ft).

Bottom Hole Circulating Temperature (BHCT)
This is the temperature at the bottom of the well while circulating mud or cement. This temperature can be obtained from downhole temperature sensors, API tables and calculations, or through temperature modeling software.

Temperature Gradient
Temperature gradient describes the degree of temperature increase per a specific unit of vertical depth, commonly reported in oF/100 ft.

Bottom Hole Static Temperature (BHST)
Formation temperature at the total true vertical depth of the well is considered BHST. This temperature is calculated using a surface temperature and a temperature gradient appropriate for the area. It can also be measured using downhole temperature sensors.

Rheological Hierarchy
In order to effectively displace the fluid ahead, and prevent channeling, the viscosity of the trailing fluid must be greater than the preceding fluid. In a multiple fluid system, each fluid should be more viscous than the fluids entering the wellbore prior to it.

Density Hierarchy
Each fluid should be denser than the fluid preceding it to provide a stable wellbore once pumping has been completed. This prevents gravitational fluid swapping.

Static Gel Strength (SGS) Hierarchy
Static Gel Strength hierarchy means that the fluids at the bottom of the well develop static gel strength faster than the fluids at the upper sections of the well. This reduces the risk associated with post placement formation fluid influx as the fluids across the higher pressure, deeper zones develop static gel strength while hydrostatic pressure is maintained.