Feasibility analysis of pipeline directional drilling technology directional drilling is technically feasible. The key is to form a stable tunnel in the underground area to ensure that the pipeline can be smoothly dragged back, or the underground soil layer has become a fluid so that the pipeline can follow these fluids. The external force can be dragged back.
However, the situation that the entire traversing section is ideal fluid is relatively rare, and localized foreign matter may cause damage to the pipeline anti-corrosion layer. Therefore, it is required to have a forming tunnel before the pipeline is towed, and to inject a suitable mud into the tunnel. If the tunnel can be kept clear during the dragging process, the maximum stress acting on the pipeline, the drill pipe and the load on the rig equipment are within the allowable range, and directional drilling is feasible.
Because the crossing project varies, there is no clear standard to indicate whether directional drilling is feasible, but also depends on the technical equipment and experience of the construction unit.
For the sake of simplicity, the technical feasibility of the analysis can be compared with the basic parameters of the previous project, namely the formation condition, the length of the crossing, and the diameter. These three factors will greatly determine the feasibility of directional drilling. .
The primary consideration is the formation condition, where the two formations are the most unfavorable for crossing, ie gravel formations with high gravel content, rocks of particularly high strength and hardness. When the stratum contains too much gravel component, it is difficult to form a hole. Because of poor stability, it is not easy to be drilled into a hole or partially collapsed after hole formation, and it is not easily carried away by the mud in the hole, becoming a drill bit, reamer drilling and pipeline. Obstacle when dragging back. Rocks with high strength and hardness are also obstacles to crossing. The drilling and reaming speeds are particularly slow. The requirements for drill pipe and drilling tools are high, and the drilling direction is difficult to control. On the contrary, the rock that is particularly easy to be broken is like gravel. Bringing instability. See Table 1 for the relationship between formation conditions and crossing feasibility.
The routing geological conditions of pipeline crossing may be quite complicated. Different sections contain different components. Although the optimization design of the crossing curve will sometimes pass through the stratum which is not conducive to crossing, whether the crossing can be determined by the length, continuity and integrity of the stratum crossing The position of the strip crossing the curve, such as changing the order of several types of strata, will completely change the crossing situation. In addition, the understanding of the formation conditions is based on the analysis of the properties of the drilling core. Since the drilling survey is carried out discontinuously, and the pipeline crossing is continuously carried out along the design curve, unexpected formations may be encountered during actual crossing, before construction. Various factors need to be fully considered.
The length of the crossing and the diameter of the pipe are mainly limited by the capacity of the drilling rig and the drilling tool, because during the drilling of the guiding hole, the flexibility of the drill pipe makes the crossing length not extend indefinitely, and the drilling direction of the drill bit is controlled as the crossing length increases. The ability is gradually weakened, and the guide holes are difficult to complete according to the designed crossing curve.
To achieve the return of the finished pipeline, the hole diameter needs to be expanded to 1.2 to 1.5 times the diameter of the pipe. Thus, for large-diameter pipeline crossing, the torque is very large when reaming the hard stratum, and the strength of the drill pipe sometimes fails to meet the requirements; In the case of drilling gravel and sandy strata with the largest length and diameter, the larger the diameter of the tunnel, the more difficult it is to maintain a stable state and the landslide is easy to occur. These factors limit the passage of large diameter pipelines. Table 2 lists the maximum records of the length and diameter of the crossings that have been completed so far, and can be compared when analyzing the feasibility of directional drilling.
This article is reproduced from Bazhou Lutong Engineering Co., Ltd.: http://
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