Bottomhole Scroll Design Of Experimental And Theoretical Study

The domestic and international research express that the well bottom pressure is the main factor to affect the machine's drilling velocity, along with pressure increasing, the penetration rate present the index number regulation to descend soon and almost. For lowering effect of the well bottom pressure-drop to the penetration rate, the underbanlanced drilling technique the worker put forward the (near equilibrium artesian well) technique; In order to cancel well bottom pressure-drop's influence to the penetration rate, and then put forward to underbanlanced drilling and near balance drilling, these techniques not only raises the machine to drill availably soon, but also is advantageous to discover and protect the reservoir. In regard to the exaltation machine drill soon , underbanlanced drilling apply in the complicated region still unsafe , it is applied and the nearby and partial pressure of the well bottom can be lowed, but a pressure of the wellbore be placed in the near equilibrium, thus can guaranteed the well's safety, and then can lower the well bottom pressure, enhance the penetration rate and discover the reservoir soon and in time .With the help from the vortex theories of the modern hydrodynamics, this text puts forward to, vortex machine design way of thinking of lower the well bottom pressure of the nearby and partial pressure. This kind of vortex machine installs on the bit, under the drill string 'motivation, spray the shoot of the nozzle to flow through its top to produce the vortex to flow in the annulus, make the drilling fluid column pressure in the annulus above the vortex machine cant deliver to the well bottom completely, causing the part of the well bottom pressure lower. After putting forward physics model of the whirlpool machine design, this text built up the fluid mechanics model of the description whirlpool machine work condition, the model includes the bit to spray the influence that the mouth shoots to flow to flow the field to flow the field to the vortex machine outputly.Adopt the standard k-e turbulent model, deduces and builds up the turbulent flow model adopt with it by time average method, to this mode, solving the method have the following characteristics:1. Can directly perceived through the senses of drown to shoot to flow the field to carry on three dimension digital simulation in the well bottom, keep the view ground see the well bottom nearby well face pressure of variety circumstance.2. Consider the drill stem and bit to revolve the influence that flows the field to the well bottom neighborhood, adjust the structure parameter and the water power parameters of the whirlpool machines, can control the variety circumstance that the well bottom neighborhood flows the field, the pressure field.The theory calculation studies the enunciation:1. When flow rate is 0.024m3/s,0.026 m3/s, 0.028 m3/s, 0.030 m3/s and 0.032 m3/s, thegreater the flow rate is, the greater the pressure loss on the bit is, which increases linearly; the pressure differential between bottom hole and top of vortex device tends to increase linearly as flow rate rises; the increase of rotating speed of the annular eddying flow generated by the high velocity jet is resulted from the increase of flow rate, at the same time, partial bottom hole flow field is also involved in the rotation, eventually leading to reduction of bottom hole pressure.2. When the inclination angle of a side nozzle is 0, 30,45 and 60 degrees, the eddying flow of the bottom hole vortex device will cause rotation at the bottom hole, affecting on the jet from bit nozzles. As a result, a minimum pressure drop is reached at an inclination angle of 45 degrees, obvious positive pressure is created at 0 degree while obvious negative pressure is created at 30 - 60 degrees, including a maximum negative pressure differential occurred at about 45 degrees. From this fact, it can be shown that it is better not to select 0 degree nozzle and 45 degree nozzle is preferred.3. Among four sizes of side nozzle: 5, 6, 7 & 8 mm, the smaller the nozzle diameter is, the greater the pressure loss is; the smaller the diameter is, the higher the velocity of the drilling fluid jetted from the nozzle is and the greater the rotation energy is, leading to reduction of the hydrostatic pressure of liquid column at bottom hole.In order to confirm that the well bottom vortex machine can lower the pressure of the well bottom neighborhood availably, the exaltation drilling speed, designed the theories design to make two kinds of wells of specification bottom vortex machine according to the vortex machine, open the exhibition the experiment test and the research work that the spot experiment, experiment the research enunciation well bottom whirlpool machine and can lower the pressure of the well bottom neighborhood availably .At ZhongYuan oil filed new text of 72-189 well and 269-6 well carry on experiment, the penetration rate raise by 15% in average.This text sets out from the basic theories of the hydrodynamics, put forward the well bottom whirlpool machine design, and the digital simulation, the indoor experiment tests to system research .The research confirmed that the well bottom vortex machine can lower partial pressure of the well bottom neighborhood.