在四川地区,由于地层较硬,岩层的研磨性很强,在这种地层中钻进,严重存在着井眼尺寸不足问题,相应地,钻头外径磨损也很严重,一般钻头外径磨小10～50毫米,因此,新钻头往往下不到井底,有时距井底15～30米即遇阻,只得进行划眼。当钻头划眼到井底后,钻头外径又磨小10毫米以上,甚至无进尺起钻。为了解决这个问题,我们试制并使用了8 1/2″×7″三滚轮扩大器,起到了保证井跟足尺寸和避免钻头外径过多磨小的作用;同时还能扶正钻头, In Sichuan Province, due to the stratum is hard, strong abrasive formations, drilling in this formation, there is a serious lack of wellbore size, correspondingly, the drill bit diameter wear is also very serious, drill bit diameter is generally small 10 ~ 50 mm, therefore, the new drill is often under the bottom of the well, and sometimes 15 to 30 meters from the bottom of the well that is encountered resistance, had zoned. When the drill to the bottom of the well planted, drill bit diameter and grinding small 10 mm or more, and even no footage from the drill. In order to solve this problem, we tried out and used the 8 1/2 “× 7” triple-roller expander to ensure that the wells meet the required size and avoid too much grinding of the drill’s outer diameter. At the same time,