Research On Ways Of Plusing WOB While Drilling

The proportion of Horizontal well, high angle well, small diameter well, deep well, old well side drilling well in the drilling is more and more big along with the increase of the difficult of oil production. Many problems will be created if people still use the conventional way of plusing drilling pressure by drill collar, such as low drilling speed, drilling pressure distortion, drilling pressure fluctuations, drilling pressure cannot meet the design weight on bit, high drilling cost, it is difficult to achieve high efficiency drilling. Hydraulic thruster changes fundamentally the method to adding weight on bit, it don’t depend drill string’s own gravity, but by high pressure drilling fluid, it will creat a pressure drop in the hydraulic thruster’s piston top and bottom face and creat weight on bit. Hydraulic thruster separates the mechanical connection between upper drill string and bit it applys weight on bit through the high pressure drilling fluid, so it possess the basic characteristic of the hydraulic and flexible.The main content is divided into three parts, the first part summary that domestic and foreign study how to plus weight on bit by drill collar and hydraulic thruster. Article introduces difficultys nowadays in various special drilling.The second part is the research of related characteristics about drill collar plus weight on bit. Article analyze the disadvantages when plus weight on bit by drilling collar in some special drilling. Last conclusion is the way of plusing weight on bit by drill collar simply makes a series of problems, such as the vibration of weight on bit, the difficulies to show the weight on bit, drilling tools’s fatigue failure, bending of the drill string, these problems will effect well quality. Method of plusing weight on bit by drill collar is suitable for vertical well, small Angle well, shallow Wells and average formation. Over-commiting drill collar also brings some negative effects, such as bending of the drill string, curvature of the drill, increasing friction, reduce drilling safety and efficiency, increase energy consumption. Comparing hydraulic thruster, the method of plusing weight on bit by drill collar is suitable for vertical well, small Angle well, shallow Wells and average formation, it isn’t suitable for high Angle well, horizontal well and large displacement well, deep well, ultra deep well and non-average formation, also not suitable for offshore floating drilling, slim-hole drilling, casing drilling and continuous tube drilling. Reducing speed to reduce the tool’s wave, high speed will increase the vibration of drilling tools when dilling collar is applied, increasing wob is helpful to reduce the vibration of drilling tools When speed is constant.The third part is the research of related characteristics when hydraulic thruster plus wob. The study show that hydraulic thruster can reduce the fluctuation of wob greatly compared with the drill collar wob fluctuation, the wob fluctuation is very small. When using the hydraulic thruster to plus wob, we can increase the quality of BHA under telescopic rod properly within the scope of the process, it can increase the damping cycle value to improve the effect of vibration reductio. Whether vertical Wells and horizontal Wells or slimhole Wells, no matter the formation is or isn’t average, hydraulic thruster reduce wob distortion degree greatly, avoiding"false wob","steal wob"when plus wob with drill collar, it can improve the drilling speed. Force analysis show the drilling tools that can produce pressure drop will make a effection to the calculating of theory wob when use hydraulic thruster and other drilling tools at same time. When we plus wob with hydraulic thruster,"neutral point"still exist at the top of the piston, the"neutral point"is due to the effect of the step reaction and buoyancy, neutral point position is reduced greatly after using hydraulic thruster, drill string above the piston will not bend. Proper number of drill collars are connected among hydraulic thruster and bit, so it is beneficial to break rock, but also can make wob display easy when piston movement to limit position.optimize the signal device make the display of limit position of the piston more accurate, it can warn the operator to control drill string at any time,the signal device not extra consump water power and the sidewall erosion, it improve the quality of the borehole. Finally, article reaserch the economy and effect hydraulic thruster when used in oil field, result shows that cost is reduced greatly and reduce deviation degree and improve the rate of drilling.In a word, when plus wob use by drill collar in in the vertical wells, small angle well, Asakai drilling,wob can be adjusted steplessly and accuratly, wob fluctuation is small, almost no distortion, wob display intuitivly and accuratly, but it exists some limitations in special wells. Hydraulic thruster is used in highly deviated wells, horizontal wells, large displacement well, deep well, ultra deep well and in non-average formations, at this time the advantage is more significant, it is suitable for floating drilling,casing drilling and coiled tubing drilling, hydraulic thruster avoid a series of problems in a larger extent when use singlely drill collar, such as drilling string vibration and bend of lower part of drilling string.