04_2- Pressure Drop Hierarchy

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The Concept of Pressure The Concept of Pressure Drop HierarchyDrop HierarchyMinimization of Minimization of

Channeling TendenciesChanneling Tendencies

Beirute Consulting, L.L.C. 2

Minimization of Channeling Minimization of Channeling TendenciesTendencies

Centralization of the pipe. API 67% is not a recommendation! Consider 90% or more when possible

Channeling is still possible in annuli with Channeling is still possible in annuli with well centralized pipe, well centralized pipe, even with 100% even with 100% standoff!! standoff!!


Previous Concepts to Minimize Previous Concepts to Minimize ChannelingChanneling

Density increasing toward the bottom of the hole

Consistency (rheology) increasing toward the bottom of the hole

Plug flow


Better Concept to Minimize ChannelingBetter Concept to Minimize ChannelingPressure Drop HierarchyPressure Drop Hierarchy

Pressure drop depends on:

– rate

– density

– rheology

– well geometry: diameter, length

Pressure drop = f (Rate, Density, Rheology, Flow area, Length)

Pressure drop includes all the import Pressure drop includes all the import variables! It is a more general approach!!!variables! It is a more general approach!!!


Pressure Drop HierarchyPressure Drop Hierarchy We are talking here about friction pressure

(resistance to flow). NO hydrostatic pressure!!!!

Concept:Concept: – Low mobility (high pressure drop) fluids have

low tendency to channel through high mobility (low pressure drop) fluids

– High mobility (low pressure drop) fluids have high tendency to channel through low mobility (high pressure drop) fluids


Race of the Fat and the Skinny GuyRace of the Fat and the Skinny Guy

Who is more likely to win?????????????


Hierarchy of Pressure Drop to Hierarchy of Pressure Drop to Reduce Channeling Tendencies Reduce Channeling Tendencies To help with fluid displacement and to minimize potential minimize potential

for channeling,for channeling, use a pressure drop hierarchy of the mud, spacer, and cement slurry.

This means that each fluid (with the possible exception of the flush) should have a higher frictional pressure drophigher frictional pressure drop in the annulus at the given pump rate than the fluid above it.

The rheology/density of the fluids needs to be designed to accomplish this for the given openhole annular configuration and the pump rates to be used in the job.

In addition, whenever possible, each fluid density should be about 0.50 - 1.0 lb/gal greater than the density of the fluid it is displacing (density hierarchy)


Hierarchy of Pressure DropHierarchy of Pressure DropReduces tendencies to channelingReduces tendencies to channeling

Frictional Frictional PressurePressuredropdrop increasingincreasing

Mud Mud

SpacerSpacer

CementCement

Hole BottomHole Bottom


Using a Simulator - Cem-Job ExampleUsing a Simulator - Cem-Job Example

04_2- Pressure Drop Hierarchy

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