Timely treatment of photocoagulation and (or) cryotherapy for prethreshold type 1 and threshold disease of ROP may lead to famous prognosis.

对阈值前病变1型阈值期ROP进行及时激光（）冻治疗具有比较满疗效。

The deep formation has a high degree of hardness and abrasivity;the bit type selection is difficult and the ROP is low especially under the high density mud.

深部井段地度高、研磨性强，钻头选型困难，特别是在高密度条件下机械钻速低。