For serious formation leakage, the working fluid can't carry sandcolumn to ground surface in the process of sand washing.
由于地层漏失严重,作业冲砂施工过程中工作液无法将井筒内的砂柱携出地面。
2
The group will change the depth of the sandcolumn, add rusty nails to several pails (in an effort to increase virus removal), and alter other parameters.