What is worse, sand particles may even flow back into the formation to cause damage.

更为严重的是，井底砂粒可能随冲砂液重新返入油层，并对油层造成伤害。

youdao

What is worse, sand particles may even flow back into the formation to cause damage.

更为严重的是，井底砂粒可能随冲砂液重新返入油层，并对油层造成伤害。

youdao