Constant Bottom Hole Pressure (CBHP) Flashcards
Pressure Relationships in MPD: Static vs Dynamic
Static condition:
-pump off, fluid is not moving
-BHP=Hydrostatic Pressure
=0.052 x MW (ppg) x TVD (ft)
Dynamic condition:
-pump switch on, fluid in flowing
-have added pressure due to friction
-BHP=Hydrostatic pressure + Annular Friction Pressure
Where, annular friction pressure=MD (ft) x constant
How does the PRESSURES in MPD look graphically vs DEPTH.
Individually and combined.
What happens to BHP when we start moving the fluid?
As we move the fluid, we need more force, extra pressure to move the fluid against the annular friction, hence, the BHP increased.
What is Equivalent Mud Weight (EMW)?
EMW is an alternative way of expressing PRESSURE at a CERTAIN POINT in a well
It is a MW that would give the EQUIVALENT PRESSURE AT THAT POINT in the well
EMW (ppg) = Pressure (psi) / (Depth (ft) x 0.052)
What is EMW equation?
EMW (ppg) = Hydrostatic Pressure (psi) / (TVD ft x 0.052)
What is Equivalent Circulating Density (ECD)?
It is the pressure when the pump is switch on.
It is the term to express P.hydrostatic & P.AFP as an EMW
EXTRA INFO:
ECD is the combined weight of the drilling mud and any other fluids that are circulating in the wellbore during drilling divide by the cross sectional area of the well bore.
ECD takes into account the frictional pressure drop that occurs as the drilling mud circulates.
What is ECD equation?
ECD= HP + AFP / (TVD ft x 0.052)
It is calculated to determine the pressure that is being exerted on the formation being drilled and to ensure the well is being drilled safely and efficiently
What term do we use to express P.hydrostatic as an EMW?
Equivalent Static Density (ESD)
What term do we use to express Phydrostatic + Pannular friction as an EMW?
Equivalent Circulating Density (ECD)
If we want to plot ECD & ESD using EMW on the x-axis, instead of pressure, how would it look?
If taking drilling fluid returns across an MPD choke (closed system) what happens to the pressure drop across the choke when we stop circulation to make a connection?
How can we do to solve this problem to keep constant BHP?
Draw Flow Routing — Drilling ahead in MPD
Standpipe - Mud Pump - Mud Tank - Flowmeter - MPD Choke - RCD
Draw Flow Routing —Connection during MPD -Pascal’s Law
Explain this graph:
Applying 443psi SBP will replace AFP that will be loss during connection.
How would these lines be plotted as pressure gradients, or EMW?
What is the effect of EMW at different depths?
Explain Drilling Window (or Pressure Window).
ECD modeling will depend on what factors?
Draw ESD & ECD in conventional drilling.
What is Anchor Point?
What is Surge & Swab?
Surge:
When running in BHA/casing in to the hole, the pressure increase below the BHA/casing
Swab:
When pulling out BHA/casing from the hole, the pressure decrease below the BHA/casing