| 摘要 |
A circulation tool 128 for use in a borehole comprising a housing with an axially extending delivery bore 222, with a rotatable valve member 268 disposed within the bore. The valve member is preferably a ball valve and features a throughbore, which allows drilling mud to pass straight through the tool, and several curved circulation channels 328, which divert the drilling mud through a curved path to flow port passageways 220 where the drilling mud is discharged into the annulus. The throughbore and circulation channels do not intersect. The tool is activated by a drop ball or other actuation element, which lands on a seat and depresses a piston 240. The actuation element comprises phyllosilicate and disintegrates under pressure. Ideally, the actuation element constitutes between 5% and 60% bentonite by volume, and an additional salt, which constitutes between 25% and 90% by volume. |
