| 摘要 |
Assembly for pressure control when drilling underground to locate or prod uce hydrocarbons; whereby the drilling is done by means of a drill string wi th fluid circulation down through the drill string and up through an annulus between tlie drill string and the open hole or casing, as the underground i n the open hole may comprise one or both of: areas with formation strength w hich is unable to withstand the pressure from the fluid circulation without fracturing and areas with formation pressure which cannot be combined with e ach other or the fluid circulation pressure without the fluid unintentionall y leaking in or out from the above-mentioned areas. The assembly is distingu ished in that onto the drill string a bottomhole assembly is fitted, compris ing: a reversible and expandable packer fitted near to the lower end of the drill string to seal the annulus, controllable from the surface a measuring device for measuring the pressure inside the annulus both above and below th e packer, with means to simultaneously transfer the data to the surface, a c irculation valve fitted above the packer and controllable from the surface i n order to open or close off the communication of fluids between the inside of the drill string and the annulus, a control valve (closing valve) fitted below the circulation valve and controllable from the surface, to open and c lose off the communication of fluids through the drill string, and a connect ing sub located above the packer and controllable from the surface for conne cting and un-connecting the drill string.
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