跟管钻进下套管技术在大洋钻探中的应用

Application of casing-while-drilling technology in ocean drilling

摘要:

大洋钻探通常采用无隔水管开路钻进，在松散破碎地层常因孔壁失稳导致孔内事故，最理想的护壁方式是下套管将不稳定地层封隔开。传统下套管方法程序复杂，作业时间长，易发生缩径、塌孔，套管不能顺利下入到预定位置，施工风险大、成本高。本文介绍了一种跟管钻进下套管技术，利用套管下扩孔器、井下动力钻具、套管送入工具等配套设备，实现钻进和下套管工序“合二为一”，简化了施工程序，可显著节省施工时间，解决了深海无隔水管钻进复杂地层下套管作业困难、施工风险大、成本高等技术难题，为实现海洋深部钻探取心目标提供了技术支持。

Abstract:

Riserless drilling is usually used in ocean drilling where downhole incidents often happens in loose and brokenformations due to instability of the hole wall. The most ideal way to protect the wall is to seal the unstable formation with casing. With the traditional casing RIH method, the procedure is complicated with long operation time, susceptible borehole shrinkage and collapse, difficulty in running the casing to the predetermined position, high construction risk and high cost, etc. This article introduces a casing-while drilling technique by which drilling and casing is combined into one step through a complete set of equipment such as the underreamer, mud motor, and casing running tool. The technique simplifies the operation procedures, saves operation time significantly, and has solved the technical difficulties in casing operation in deep sea riserless drilling in complex formation, such high operationrisk, high cost, etc., providing technical support for deep sea core drilling.