It is generally not possible to drill a well through all of the formations from surface to the target depth in one hole section. The well is therefore drilled in sections, with each section of the well being sealed of by lining the inside of the borehole with steel pipes, known as casing and filling the annular space between this casing string and the borehole with cement, before drilling the subsequent hole section.
Lead in
Make comments about reasons for casing off formations.
unstable formation high pore pressure zones
well formation lost circulation zone
selective access structural support
Pay special attention to the pronunciation and stress of the following words.
con duit [΄kondjuıt, ΄konduıt] thr ea ded a n ti ci pat ed li ner
sub se que nt [΄sλbsıkwənt] hyd r au lically
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