煤田超大口径套管固井技术

煤田开采过程中为了保证安全，改善地下工作面环境，近年来不断进行钻大口径井用以抽排瓦斯、向地下送风降温。然而钻井使用的是小钻机，完井作业时由于钻机提升能力有限，大口径套管按照石油工程方法下入困难。套管内、外环空容积大，注水泥过程中易发生浆体混窜，作业时间长，固井质量难以保证。通过采用浮力塞减重、管柱充空气、优化水泥浆体系及浆柱结构设计和内插管固井工艺等技术，成功地解决了小钻机下大口径套管超负荷、大口径套管抗挤强度低、易被挤毁等一系列技术难题。现场进行了9口井应用，固井成功率100%，固井质量合格，为今后超大口径套管固井提供了可借鉴的经验。

Cementing technology by super diameter casing in coal field

In the exploiting process in Coal field, in order to guarantee the safety and improve the underground working environment, large diameter wells are being drilling for gas drainage and air blasting to cool the underground in recent years. However, the drilling rig is small with limited lifting capacity, so the large diameter casing is difficult to trip down in petroleum engineering method during well completion. The large outer and inner annular volumes make cementing slurry easily to channel during injection, resulting in long working time, so it is difficult to ensure the cementing quality. Through losing weight by buoyancy piston, flushing air in pipe column, optimizing slurry system and interpolated-pipe cementing technology, the difficulties were successfully resolved, which were tripping the large diameter casing by small drilling rigs, low squeezing strength of large diameter casing, etc. The on-site field applications on 9 wells showed the results of 100% cementing success rate, and good cementing quality. It provides experiences for the future cementing by super diameter casing.