A.30° B.60° C.90° D.180°
A.实现“软关井” B.降低井口套压 C.灌注重泥浆 D.泄掉井内泥浆
A.开启度变小并关闭 B.开启度变小并趋于关闭 C.开启度变大并全开 D.开启度变大并趋于全开