APPLYING OF STEEL AND LIGHTWEIGHT DRILL PIPES IN COMBINED DRILL STRING ASSEMBLY FOR DRILLING HIGH DEVIATED HORIZONAL WELLS

The paper considers the problem of creating axial load on bit while drilling the horizontal wells. One of the most promising ways to solve this problem is the use of steel drill pipes in conjunction with light-weight drill pipes in the drill string assembly which will reduce the weight of the drill string and reduce the frictional forces during drill string movement in a horizontal wellbore. Such a combined drill string assembly has several advantages, since the load created by the string of steel drill pipes in a deviated section of well and the smaller load losses by the string of lightweight drill pipes in the horizontal section makes it possible to more effectively create and transfer the axial load to the bit. The ratio of the lengths of steel and light-weight drill pipes in the combined string assembly will determine efficiency of the creating load to the bit. As a result of the research, a method was developed for calculating the optimal ratio of light-weight drill pipes to steel drill pipes as part of a combined drill string assembly, in order to achieve optimal indicator for the load on the bit. A detailed phased implementation of the calculation method is presented using the example of a horizontal well profile. The results of calculations carried out according to the proposed method are presented on the example of three profiles, with different lengths of the horizontal section. The proposed method for calculating the ratio of alloy drill pipes to steel pipes as part of a combined drill string allows to increase the efficiency when drilling wells with a long horizontal section and to achieve optimal performance of the load on the bit.