Chaper 8 High Pressure High Temperature Wells

Question 1

Define the temperature and pressure characteristics of an HPHT well?

Answer 1

Formation temperature greater than 149*C… Either the max pressure gradient of any porous formation to be drilled exceeds 18.1kPa/m, or pressure control equipment with a rated working pressure in excess of 68.95MPa is required.

Question 2

How does the safety margin afforded by the mud hydrostatic differ in an HPHT well as compared to a standard well?

Answer 2

Because there is very little margin between formation pressure and facture pressure, the overbalance (safety margin) afforded by the mud hydrostatic is minimal in an HPHT well.

Question 3

How is it possible to have a well flowing at the surface but still be overbalanced downhole? What should be done?

Answer 3

Facture breathing is occurring. Shut-in the well and conduct diagnostics!

Question 4

Explain the mechanism by which supercharging occurs?

Answer 4

Circulating pressure force mud into fractures in the rock which increase in length as the pressure continues to be applied. When pressure is released or reduced then the fractures close up, forcing fluid back into the wellbore and causing an apparent ‘flow’ at surface.

Question 5

Which well control method should be used to circulate the well if flowback occurs?

Answer 5

The Drillers Method is proffered.