The control of the pilot hole curve is very important. Choose the best combination of drilling tools according to the type of strata crossing. In the rock construction process, for the high strength of the rock layer, you can use: (tri-cone bit + power drilling tool + probe chamber + non-magnetic drill collar + weighted drill pipe + ordinary drill pipe) drill tool assembly summarized the following experiences during the construction process:
① When the directional drill crosses a long distance, the frictional resistance increases, and the thrust of the drilling rig is not easy to reach the drill bit. The casing technology and the use of weighted drill pipes can be used to coordinate drilling measures, which can effectively improve the drilling efficiency and prevent the that the parts of the wellhead and the clay layer are deformed and unstable because of the long distance of the drill pipe.
② Because the rock formation is relatively hard and difficult to drill when drilling pilot holes, we use a mud motor as a power drilling tool, and its operation is completely driven by mud.
Due to the high mud pressure and fast flow rate, the insulating shrink sleeve of the joint of the control line is constantly scoured, causing it to repeatedly rub against the inner wall of the drill pipe and rupture, forming a short circuit or open circuit, causing signal interruption. When drilling the pilot hole, a retaining ring is added to the mud drill pipe cavity to relieve the impact of the mud on the control line to protect the control line, which can effectively prevent the loss of signal due to the damage of the control line. This measure has a good effect.
③ Analyze the operation of ground equipment when drilling pilot holes.
The long pilot hole distance is complicated and the formation is complicated. Cuttings, weight on bit, torque, ROP, pressure and other surface instruments can directly reflect the downhole conditions. Pay close attention to when drilling pilot holes, especially torque, pump pressure, and ROP. And rock cuttings, record important data in the steering process, analyze and judge the changes in the formation.
④ Preparation of mud.
In addition to the functions of cleaning and cooling the drill bit, carrying cuttings and assisting rock breaking, the main purpose of the mud is to protect the well wall. The clean bottom of the well can not only increase the drilling speed, but also reduce the wear of the drill bit. We prepare the mud suitable for the formation according to different formations. When drilling the pilot hole, we strictly control the viscosity, specific gravity, displacement, and pressure of the mud. In order to assist the system, adjust the ratio of mud preparation, play the role of mud in direction control, and make the crossing curve "flat, smooth, round and gentle".
⑤ It is difficult to find the rules when the drilling pilot holes. During construction, adjust the drilling speed of each drill pipe in time within the range allowed by the construction specifications, control the direction control parameters of each drill pipe, and ensure that the deviation of each rod is the minimum value. Because if the deviation of the pilot hole is too large, it will be difficult for the drill to break away from the original hole to drill a new hole when part or all of the drill rod is pulled out to correct the deviation. A curve with a large angle is formed at the intersection of the original hole and the new hole, which cannot meet the requirements of the radius of curvature of the pipeline.