Analysis on the cause of casing return after cementing
After casing cementing, the phenomenon of casing return is occurring in cementing operations of many major oilfields. There are many factors that cause this phenomenon. The most common factors are mainly from the following points.
First, the mud treatment is not thorough
In well circulation before cementing, mud sealing valve spool scouring floating hoop shoe, at this time if the mud is not thorough, containing larger particles of sand or impurities, after a long time of erosion, damage will be on the spool of the rubber sealing ring mechanism, thus affecting the sealing effect. Filter with displacement and sand in front of the casing. If the particles are too large, the filter screen should be replaced in time.
Two. Inadequate mixing of cement slurry
When cement is cemented, cement and water are mixed to form cement slurry and then injected into casing. If cement slurry is not fully mixed, it contains large cement blocks or grains, which will also damage the floating shoe shoe spool mechanism. It is also possible that after the completion of the cementing operation, the blocky or granular cement can not be closed before the valve core is closed when the floating shoe core is closed, resulting in cracks, which will affect the sealing.
Three. Pressure pressure requirement
Generally speaking, there are detailed requirements for cementing operation manual before and after bumping and pressing operations. For example, displacement displacement is less than 0.8 square minutes per blow before displacement is pressed, so as to prevent damage to floating hoop.