Study On Hydraulic Pressure Loss Of Geological Drilling With Small Annular Gap

With the development of deep drilling,the technical demand for deep hole drilling is also increased.The high annular pressure consumption caused by the small annular gap of deep geological hole makes the accurate prediction of annulus pressure consumption is particularly important.The eccentric drilling string and high speed rotation of the drilling string have obvious influence on the annulus pressure consumption.The conventional hydraulic pressure consumption calculation model cannot be fully applied to the small ring space gap drilling.The existing hydraulic pressure consumption calculation model of deep geological holes has insufficient consideration on these factors.Therefore,it is necessary to study the hydraulic pressure consumption calculation model suitable for the small annular gap geological drilling.The main contents of this paper are as follows:(1)Based on the Hydraulic Research of small hole drilling at home and abroad,according to the characteristics of small annular gap geological drilling,the hydraulic pressure consumption of different flow states(laminar flow and turbulence)is studied.The influence of eccentric and rotating of drill pipe on annulus pressure consumption under different flow conditions is considered.(2)The results show that the eccentricity of drill pipe will lead to the decrease of annular pressure loss and increase with the increase of eccentricity.When considering the rotation of drill pipe,the influence of the rotation of the drill pipe on the pressure loss is small under the concentric annulus flow,while the rotation of the drill pipe increases the pressure loss of the annulus with the increase of the rotating speed.(3)Based on the core drilling program,the overall annulus pressure loss is calculated and analyzed.The results show that: when the drilling hole size is small,the reduction of annular pressure loss caused by drill pipe eccentricity is more obvious,and the reduction can reach more than 10 MPa in some drilling structures;when the drill pipe and eccentricity are considered at the same time,the influence of drill pipe eccentricity on reducing pressure loss and the influence of drill rod rotation on increasing pressure loss should be considered comprehensively.