Drilling Industry Glossary

cable tool CaCl₂ weight calcium, total hardness cap rock cased hole casing casing centralizer casing coupling (collar) casing hanger casing head casing point casing pressure casing shoe casing string casing wear cement cement additive cement bond cement bond survey cementing cementing pump chlorides chlorides whole mud choke choke line christmas tree circulate circulation sub close in coarse LCM coiled tubing collapse pressure complete a well completion completion fluid concentration condensate conductivity conductor pipe contract depth contractor core cratering critical rate critical velocity crooked hole crossover sub crude oil cuttings

Circulation Sub

Circulation Sub is a downhole tool to control flow between the pipe and annulus. Once opened, the downward flow through pipe will be split. Partial of the circulating fluid will flow through the sideway ports to the annulus between wellbore and pipe. This is especially useful in applications such as drilling in slim-hole wells, or wellbore cleanup operations, where different annular flow rates are required in different annular sections to reduce ECD or pipe pressure requirement.

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