The Design And Experimental Study Of Downhole Casing Slotting Tool

Hydrocarbons are essential national strategical resource,which lays an important foundation for national economy and its people's living.Therefore,it has been an assiduously seeking goal for the researchers in the petroleum industry to enhance the uttermost output of oil and gas wells,as well as the ultimate recovery of oil and gas field.As an emerging technique to increase the yield and efficiency of oil wells,radial horizontal well has drawn the attention of petroleum researchers,successfully.Currently,there exist two techniques to drill radial horizontal wells:the first one utilizes the traditional casing section milling and hole enlarging technique;the other one is casing sidetrack drilling technique.When casing sidetrack drilling technique is used to drill a radial horizontal well,instruments such as small-diameter positive displacement motor,cardan joint,opening bit are needed to make a window on the casing tube.Thereafter,small-displacement water jet is used to drill hole in the cement and reservoir.However,this radial horizontal well drilling technique is undermined by the potential accidents like window opening failure of casing tube and cement sheath.Besides,the diameter of the acquired horizontal well by this technique is quite small,which limit the enhancement of well output.For casing section milling and hole enlarging technique,the construction is complicated and difficult to be carried out,because the casing tube needs to be milled a long section and the wellbore needs to be enlarged,limiting its field application.Although faced with these construction difficulties,the diameter of the acquired horizontal well is relatively large,which leads to a significant improvement.Therefore,it is necessary to improve the casing section milling and hole enlarging technique.In this thesis,a new method,which applies abrasive water jet to drill radial horizontal wells,is put forward.Our research will have a positive influence on the field application of radial horizontal well.According to the requirement for casing slotting and wellbore enlarging in the process of radial horizontal well drilling,highly efficient nozzle for abrasive water jet was optimized.The nozzle is composed of two sections,including a straight section and a concentration section.The length of the straight section is 2.0?2.5d.The concentration section has an angel of 15°?25°and a length of more than2d.After the experiments taking four different factors and economy into consideration,we found out that the optimal nozzle arrangement is 6 nozzles in a single row.For casing slotting,with this nozzle arrangement,when the volume fraction of abrasives is 13.1%and the grain size of the abrasives is 0.4?0.8mm,the proper abrasive is garnet particles.The cutting efficiency for N80 casing tube reaches a peak when the cutting head moves at 5-10 mm/min,and the casing tube can be totally penetrated.The maximum width of the cutting window could reach up to 62mm.In this research,a set of downhole casing slotting equipment was designed and manufactured,which is composed of cutting head speed control system,water jet system,tools resetting system and cutting head with optimized nozzle arrangement.Its structures are designed reasonably and system running is reliable.