Problem of well deviation control
Well deviation control is the primary problem in casing drilling, and the deviation directly affects the vertical depth of the drilling hole. That is to say, whether the buried depth of oil layer can be stabilized with the actual depth of drilling depends on well deviation. The drilling pressure is controlled within a reasonable range of 10-30KN. During casing drilling, there is no drill collar and centralizer in the casing string. During the compression process, the casing string is easily compressed, leading to deviation. Therefore, drilling pressure must be strictly controlled in the process of drilling. From this point of view, the choice of PDC bit is more suitable for casing drilling. Rotary speed control is low speed, generally controlled within 60-120r/min, low speed drilling process is conducive to stability of casing string, and is conducive to well deviation control. The derrick base is installed flat, to ensure the vertical of the drilling hole, and to strengthen the monitoring of the midway inclinometer. On the one hand, it is easy to understand and control the lower well slanting control, and on the other hand it is easy to calculate the vertical depth.
After casing drilling and completion, the casing string stays in the well directly, so it is very important for casing protection. Use casing buckle. Casing is sealed by thread. During casing drilling, casing special adhesive should be used to ensure reliable sealing and reliable connection. Casing anticorrosion problem. When the casing is drilled, the outer wall is worn out due to rotation, and the outer coating is easy to fall off. The inner wall is eroded by drilling fluid, and the inner anticorrosive coating is also eroded. The first is to use the casing for the drilling to do the internal and external coating anticorrosion; two is to use low speed small drilling pressure drilling in drilling to reduce the wear of the outer wall of the casing. The three is to increase the size of the drill hole, to reduce the pressure in the tube and to reduce the erosion of the drilling fluid on the inner wall of the casing.