CCTEG Xi'an Research Institute Successfully Retrieved 650-meter Directional Drilling Tools at Zhujiawan Coal Mine of Zhenxiong Coal Industry

Recently, CCTEG Xi'an Research Institute successfully retrieved a 650-meter directional drilling tool at Zhujiawan Coal Mine of Zhenxiong Coal Industry in Yunnan Province. Both the depth and difficulty of the retrieval operation set new records in Southwest China, which were reported explicitly by the WeChat official platform of Yunnan State-owned Assets and Yunnan Coal Chemical Industry Group Co., Ltd. Meanwhile, CCTEG Xi'an Research Institute also received a letter of gratitude from Zhenxiong Zhujiawan Coal Industry Co., Ltd.

When conducting geological surveys in the directional borehole at Zhujiawan Coal Mine, hole collapse and drill pipe sticking occurred after coal was detected at the bottom of the hole. While pulling out the drill, the drill pipe in the hole broke, leaving the drilling tool "trapped" at a depth of 650 meters. In China, the depth for handling similar accidents is usually within 500 meters. The depth of 650 meters far exceeds the limit of conventional retrieval operations. The drilling tool was wrapped in sediment on the borehole wall, and the borehole contained multiple curved sections, making traditional retrieval tools and methods ineffective.

After receiving the retrieval assistance request from Zhujiawan Coal Mine of Zhenxiong Coal Industry, CCTEG Xi'an Research Institute took prompt action. It jointly formed a technical assault team with Zhujiawan Coal Mine. Facing this "underground maze", the team meticulously prepared equipment and supplies, thoroughly reviewed geological data, conducted a comprehensive analysis using the borehole trajectory, and accurately located the stuck-point position. In view of the drill pipe's bending strength and lithological characteristics, a composite retrieval plan was formulated, and a full-process milling and retrieval operation was carried out in the borehole, gradually "gnawing" through the blocked section. After 12 days of continuous operation, the 657-meter-deep directional drilling tool was finally retrieved without damage.

This successful operation has broken through the limitation of the traditional milling process, which was previously applicable only to deep holes within 500 meters. It not only helped the client salvage the dropped drilling tools worth nearly 2 million yuan, but also set a new record for the depth of handling drill-burying accidents. A breakthrough has been achieved in the rescue of underground coal mine drilling accidents, providing a new paradigm for the industry to address ultra-deep-hole drilling accidents.