The pressure distribution model of air reverse circulation drilling system with hollow-through DTH hammer

With the development and improvement of whole-hole reverse circulation drilling technique with hollow-through DTH hammer, the hollow-through DTH hammer is used wildly in different drilling fields. When it is used to drill wells for oil and gas exploration and development, the diameter and depth of the well is usually bigger compared with that of the borehole in other application fields, and the determination of drilling technique parameters is critical. On the basis of structure characteristics of dual-wall drilling tools, the pressure distribution models in center hole and annular channel were established, and the calculation method of pressure drop on reverse drilling bit was introduced. The pressure distribution models can be used for determination of the reasonable parameters of the compressed air source as a base, at the same time, it provides reference for the selection of high-pressure equipments. The research on the pressure distribution model of reverse circulation drilling system is meaningful to ensure good drilling effect.