The Development of ϕ228.6 mm Hydro-Efflux Hammer andROP Increase Test in Hard Formations

The Longtan- Maokou Formations in the ϕ311.1 mm vertical section of Fuling Shale Gas Field are characterized by high hardness and poor drillability, resulting in short service life of drill bit, and low ROP. In order to improve the ROP in this interval, a ϕ228.6 mm hydro-efflux hammer was developed, and the bench test was conducted. The results of bench test showed that the performance parameters of ϕ228.6 mm hydro-efflux hammer were adjustable in a wide range. While stroke, hammer mass and flowrate were variable, and other conditions remained unchanged, the impact force, single impact work and impact frequency exhibited a nearly linear change correspondingly. On the basis of bench tests, the structure and performance parameters of ϕ228.6 mm hydro-efflux hammer were properly selected, BHA and rotary percussion drilling parameters were optimized, and a field test was carried out in Well Jiaoye 109-1HF. The results of field test suggested that the ϕ228.6 mm hydro-efflux hammer had a significant drilling speed-up effect, which was 104.9% higher than the average ROP in the second interval of the adjacent wells. The successful development of ϕ228.6 mm hydro-efflux hammer could provide an effective solution for drilling speed-up in the hard formation of the second vertical section in Fuling Shale Gas Field.