Application of air hammer drilling technology in the igneous strata of Well Hashen 201

The igneous strata in the Junggar Basin is competent with strong abrasivity and poor drillability, so it is usually suffered from well deviation, low rate of penetration (ROP) and long drilling cycle in the process of drilling. And consequently, the exploration and development progress in the target of igneous strata is impacted. In this paper, the technical difficulties of cone-bit gas drilling were investigated, and the rock breaking mechanisms of air hammer and its adaptability in igneous rocks were analyzed by means of igneous rock mechanics experiment. Then, based on the main structures and technical characteristics of KQC air hammer, the rock breaking mode of air hammer drilling with low weight on bit and rotation speed and high frequency percussion was put forward to prevent effectively the drilling tools from abrading and fatigue fracturing while achieving the deviation control and fast drilling of igneous rocks in piedmont zones. It was for the first time, applied on site in the igneous rocks of Well Hashen 201 in the Junggar Basin. Compared with cone-bite gas drilling, its average ROP and single-trip drilling footage are 2.45 times and 6.42 times higher when the well deviation is controlled below 2°. In Hashan block, remarkable deviation control and fast drilling is achieved with the single-trip drilling ROP of 14.29 m/h in the hole of Ø444.5 mm and the single-trip drilling footage of 470.62 m in the hole of Ø311.2 mm. It provides one effective technology for the optimized fast drilling in igneous strata.