GEOG 4891 Lecture Notes - Lecture 4: Polyethylene Terephthalate, Caving, Buoyancy
Document Summary
In practice, conductor casing diameters are from 95/8 to 30 inches, and lengths are from 20 to 1000 ft depending on consolidation of surface formations (collapse risk! Purposes: to avoid collapsing unconsolidated surface formations, to facilitate mud flow line to the pits. To provide diverting surface water or gas flows through a rotating head fitted above the flow line outlet. Intermediate (protective) casing string(s) takes place in between surface casing string and. To case the well bore section for safe drilling to final depth. To shut of subnormal formation zones against mud lost. To shut off abnormal formation pressure zones against formation fluids influx to the wellbore. To isolate troublesome zones such as shales and loose sections against swelling, caving, collapsing, etc. To provide a back-up for production casing string. When second intermediate casing string is required, usually drilling liner string is set.
