Why do we run casing in the well?

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Simple question: “What are the reasons casing is run in the well?”

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There are several importance of casing as follow;

• To prevent collapse of the borehole

• To confine production to the wellbore

• To provide a flow path for drilling fluid

• To contain formation pressure and prevent fracturing of upper and weaker zones

• To provide an anchor for surface and sub surface equipment

• To provide a high strength flow conduit for drilling fluid to surface and ,with BOP , permit the safe control of formation pressure

• To prevent contamination of fluid in formations

• To exclude water zones from the producing formations

 

Any additional ideas are welcome.

Ref books: Cementing Technology Books

Pressure Loss and Equivalent Circulating Density Review – Reverse Circulation

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We still have the same question as the previous post, Pressure Loss and Equivalent Circulating Density Review, but this case we will do reverser circulation, circulating from annulus to tubing , and see how much pressure and equivalent circulating density at bottom hole.

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Pressure Loss and Equivalent Circulating Density Review

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This example that I got from my junior member is very simple but it helps you a lot to understand about how to determine pressure loss during normal circulation.

Information given is listed below;

Pressure Loss and Equivalent Circulating Density Review

Circulate at 3 bottom up through open end tubing (Down tubing and up annulus) with 12.7 ppg mud.

Pump pressure = 1000 psi

Annulus friction loss = 50 psi

Inside tubing friction loss = 925 psi

Surface line friction loss = 25 psi

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How much pressure will we see at cement head in case of float shoe fail?

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I still have the simple but interesting question about hydrostatic pressure which you can apply this calculation into drilling/cementing operation. The question I got about how much pressure we will see at cement head in case of float shoe fail.

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What are Lead and Tail Cement?

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In some cementing operation, operators will pump 2 cement slurries, normally called “Lead Cement” and “Tail Cement”.  Both lead and tail cement have pro and con as described below.

Lead cement: Lead cement is in the top section of cement, where has lower both pressure and temperature (see figure above). It has lower density and strength than Tail cement; however, it is also cheaper than Tail cement.

Tail cement: Tail is pumped after lead cement because it must be settled at the lower section of well bore, where needs high strength cement (see figure above) . It has higher strength than lead cement, but it is more expensive than lead cement.

Ref books: Cementing Technology Books