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Effects of the formation to the orientation of the directional wells in the Adıyaman region

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2020
Ünlü, Ahmet
Directional drilling is controlling the inclination and azimuth of a wellbore to reach a predetermined underground target and is a method used widely nowadays. There are various methods for directional drilling operations such as; Mud Motor & Measurement While Drilling System (MWD) or Rotary Steerable System to reach the targets. Within the scope of this study, Mud Motor and MWD were used to change orientation of the hole. While drilling with mud motor, directional drillers (DD) make sliding drilling which means that DD drill with a mud motor rotating the bit downhole without rotating the drill string from the surface with using Tool-face which is taken from MWD system. Controlling hole orientation is important to drill smooth wells, to follow the plan with low tortuosity, to hit the target and to finish the well early. Several studies have been performed to investigate the parameters that affects the hole orientations. The factors affecting the orientation of the hole are weight on bit (WOB), bottom hole assembly (BHA), hole size, rotary speed (RPM), flow rate (GPM), stabilizers position on the drill string, drilling bit and stabilizers gauge. In addition to all of these parameters, orientation of the wells is also affected from the formation properties. This study detailed the effects of the formations to the orientation of the directional wells in the Adıyaman Region with the help of the field data. Even if the same parameters (WOB: 10-11 tones, flow rate: 450 gpm, RPM:40) are applied and the same equipments (8-3/8” of outer diameter sleeve stabilizer, 7-3/4” of outer diameter integral blade stabilizer, equal length of drill collars, roller cone drilling bit) are used in seven different wells to drill 8.5” (0.216 m) hole in diameter, theoretical expectations with respect to the orientation may not be obtained due to the formation effects. To see this effect, North/South and East/West deviations were calculated according to the wellhead location with the real and the calculated survey data. Real survey data were taken from the wells for every 30 m interval with the help of the MWD system. Moreover, data used for theoretical deviation calculation were obtained with using the output dog-leg of the Mud Motor. The differences between real and calculated results show the effect of the formation to the orientation and this gives us a chance to see if there is a trend or not between the wells when respective results are compared. As a result of this study, it was observed that there is a trend in the effect of the formation on the orientation in the Adıyaman Region. The direction and the deviation of the wells change for different wells although the formation has the same lithology. Moreover, the results show that when a well is drilled in a certain wellhead location in this region, the direction does not change from top to the bottom of the section.