Directional drilling technology discussion

When are directional drills generally used? It is generally used when crossing rivers, roads, railways, etc. that are not suitable for large-scale excavation. How much does directional drilling cost per meter? The cost per meter is not necessarily certain. It depends on the size of the pipe diameter, the difficulty of crossing, etc. to determine the issues that should be paid attention to when crossing with a directional drill? There are many issues that should be paid attention to when directional drilling crosses. Generally, attention should be paid to the geological conditions of the crossing site, the impact of the crossing on the crossing site, the impact of the crossing geology on the crossing pipeline, the impact of the crossing location and length, etc.

I am currently constructing a long-distance oil pipeline project. What is the difference between directional drilling and pipe jacking? What should I pay attention to during construction?

The following is an excerpt from Huang Chunfang's "Prohibited Content, Please Delete", published by Sinopec Press in 2008. Please see the original book for specific details. Chapter 12 Construction of long-distance oil and gas pipelines using trenchless methods to cross obstacles. Long-distance pipelines stretch for hundreds of kilometers or even thousands of kilometers. They inevitably have to pass through artificial and natural obstacles, such as mountains, valleys, rivers, lakes, ponds, roads, railways, etc. They can pass through or across them. At present, pipeline crossing methods include directional drilling, tunnel excavation, pipe jacking and large excavation. ； The tunnel excavation method is divided into two types: manual drilling and blasting method and shield tunnel excavation method. There are more than ten types of pipe bridges including simply supported beams, arch spans, cable-stayed bridges, suspension cables and suspension cables. Due to length, this chapter only introduces the directional drilling method, pipe jacking method and shield tunneling method among the trenchless methods. Section 1 Directional Drilling Pipe Crossing Construction 1. Overview Directional drilling is mainly used to cross rivers, lakes, railways, highways, mountains or buildings (structures) and other obstacles to lay large-diameter, long-distance oil and natural gas pipelines. During directional drilling, according to the designed drilling trajectory, directional drilling technology is used to first open a pilot hole, and then connect a large-diameter reaming bit at the end of the drill pipe and a pipeline to be laid with a diameter smaller than the reaming bit for reaming and pipe back-drag. While expanding the hole and pulling back, pull the pipeline to be laid into the guide hole to complete the pipe laying operation. Sometimes, depending on the model of the drilling rig and the diameter of the pipeline to be laid, the hole can be expanded one or more times before dragging back the pipe section that has passed the pressure test and leak detection. During the directional drilling process, most of the work is done by rotating the drill pipe. Choosing the torque of the drilling rig is equally important as the axial feed force and back drag force. The directional drilling method is an economical and practical pipe laying method that can achieve safe and reliable pipeline burial depth. It should be the first preferred method for pipeline crossing. The advantages of directional drilling are: Less disturbance to the surface ； Fast construction speed ； The direction of pipe laying can be controlled and the construction accuracy is high. The disadvantages of directional drilling are that it has high requirements on the construction site, it is difficult to construct in the gravel layer, and it is generally not suitable for strata where it is difficult to form holes. 2. Horizontal Directional Drilling Crossing Construction Technology: The use of horizontal directional drilling rigs for pipeline crossing construction is generally divided into two stages.: The first stage is to drill a pilot hole as accurately as possible according to the design curve ； The second stage is to expand the guide hole and drag the product pipeline (usually PE pipe, optical cable casing, steel pipe) back into the enlarged guide hole to complete the pipeline crossing work. Directional drilling pipeline crossing construction procedures 1. Drill pilot holes:

3# The directional drilling in the economic zone is mainly a rotary drill, and the pipe jacking is driven by jacks and dug manually.

The length of directional stations is relatively long. Now in China, it can be about 1.5km, or at least several hundred meters. If it is too short, it cannot be opened. Pipe jacking generally does not exceed 100m.

Directional drilling and pipe jacking are both trenchless crossing methods. The construction process of pipe jacking is simple, but the crossing length is generally not large. Because the radius of curvature of the pipeline is taken into account for directional drilling, the penetration length cannot be too small, and the minimum should be more than 1000D. The current maximum penetration angle should be about 15°. If you pass through villages or densely populated areas, directional drills are very suitable. The cost of directional drilling is actually very low. Of course, it has a lot to do with the pipe diameter and geological conditions. Generally speaking, 3,000 yuan/meter is enough (even for 1016 pipelines).

I have a question. Due to geological conditions in the long-distance transmission project currently under construction, part of the pipe jacking project has become a directional drilling project. There are a total of three pipes passing through, one with a diameter of 400, two with a diameter of 200, and one optical cable. When I checked the budget with the owner, according to the quota, I took out 400 drilling tools, 300 drilling tools and 200 drilling tools respectively (the optical cable and a 200 pipe were in the same hole). Pre-reaming is multiplied by 3 times the penetration length. However, the owner said that if the drilling rig is in an operating pit, the drilling tool can only be removed once, and it can be taken according to 300. Pre-reaming medium-sized drilling rigs below 300 do not expand holes, so pre-reaming can only take the length of one diameter 400. I don’t know much about the budget of directional drills, and there is no explanation in the quota. Please ask an expert on directional drill budgets to help analyze it. Is it the owner who is right?/