
Collar for Collar Cementing is applied for liner collar cementing with assembly for multistage hydraulic fracturing with isolation of horizontal sector into zones with hydro-mechanical packers.
While using an MMC-G-type collar the following process operations are performed:
• washing and washing ports opening through internal overpressure build-up after isolation
of tube space from outer annular space;
• washing with ball-drop;
• cementing ports opening when a ball is set into a collar seat;
• casing cementing with starting of a cementing plug after pumping in cement slurry;
• displacing of cement slurry to the outer casing annular space until receiving the “bump”
signal;
• collar ports closing by the internal overpressure build-up.