HDD Execution method

Before starting the executive operation, the activities of the engineering department should be carried out as follows:

1. Visiting the project site and mapping the site
2. Carrying out geotechnical work by drilling 4 boreholes and presenting the final report
3. Carrying out depth measurement operations and reporting
4. Preparation of plan and transverse profile for pipeline crossing
5. Designing and preparation of pipeline crossing operations maps and workshop equipment maps and equipment placement
6. Carrying out engineering and design studies, calculation of forces, stress analysis and buoyancy control
7. Preparation of executive documents, including technical specifications, executive manuals for pipe welding, hydrostatic testing and pipe coating
8. Preparation of project schedule and weighted analysis of activities
9. Examining and approving the executive proposal to start executive operations

The process of horizontal directional drilling operation (H.D.D.):

The set of drilling operations is carried out on two sides of the river, called Rig Side and Pipe Side, so that the drilling machine, power supply system or Power Pack, power generator, drilling mud production and pumping system and storage and control ponds, cabin or steering room and a set From the drilling rods (pipes with a length of approximately 9.5 meters that are threaded on both sides and are twisted behind each other to send the drill into the soil and guide the drill in the drilling path.) all on the Rig side or the Rig Side area and It is installed with a suitable placement and on the other side, the main pipes of the water supply plan are welded on the roller as long as the length of the route. This area is called the Pipe Side area.
The welded pipe in the mentioned project for a length of 500 or 600 meters is radiographed after installation, and the welds are insulated with polyurethane. Also, before starting the pipe pulling operation, it is necessary to perform a hydrostatic test to detect leakage and an electrical coating test to confirm the correctness of the insulation done.

Directional horizontal drilling method or HDD:

1. pilot hole drilling operation
2. Widening operation or reaming (Back Reaming)
3. Pulling operation

First step: pilot drilling or guide hole (Pilot Drilling)

In the first stage of the drilling operation, the drill bit is placed in the ground from the predetermined entry point, this point is close to the drilling machine and in the Rig Side area, and the exit point is in the Pipe Side area. be These points have already been determined by mapping and aligned, so in this way, by starting the drilling machine, the drilling operation of the guide hole has started and will continue until reaching the exit point.
The power supply for the operation of the drilling machine is done by the Power Pack and the pressure force created by the Rig is transferred to the drill head through the pipes of the drilling machine or rods. (to identify the position and coordinates of the drilling drill), with the standard angle and curve that was previously determined during the mapping operation and approved by the consultant, is driven into the ground by the rig of the drilling machine from the specified entry point, which during In this operation, drilling fluid or a mixture of bentonite mud and water with percentages appropriate to the drilling conditions and soil type is injected into the channel through hollow drilling pipes with the help of a high pressure pump and through the nozzles of the drill head. This operation is performed for several purposes. becomes:
A) Creating fluidity in the drilling path and simplifying drilling and reaming operations
b) Construction and strength of the wall of the guide hole to maintain it until the start of the next operation
c) Preventing the rapid wear and destruction of the drill bit and increasing the working power by moving the drill forward and in the drilling path, non-magnetic pipes are screwed one by one to the previous pipe and this process is continuous until the drill head exits the exit point. or Exit Point continues.
The position and coordinates of the drill head are always measured by a sensor installed at the back of it through a cable extending along the path and by creating a magnetic field and scaling this field with the natural magnetic field of the earth and then sending the information to the control and processing cabin. The information sent is determined by computer, so that it is always clear at what depth, length and width the drill head is located, and in case of deviation from the determined path, it is possible to compensate and guide the drill to the correct position through special engineering techniques.

Drilling drill head with the help of a knee installed behind it has the possibility to change the angle to the left and right, which can lead the drill to new positions by applying a small twist in the guide tube (Rod) to achieve the initial path.
It is obvious that during the course correction operation, the rotational movement of the drilling pipes and the application of torque have been stopped.

Second stage: widening operation with reaming (Back Reaming)
After drilling the guide hole and the corrections made in the drilling path and exiting the drill from the Exit Point, the reaming operation begins, so that the drill head and elbow are opened and the reamer or widening tool with the appropriate diameter is closed. The widening or reaming operation takes place in one or more stages, which depends on the diameter of the final pipe, the material of the ground and the strength of the initially created hole.
The tools used in this stage are chosen by the operator and according to the type of ground and are installed instead of a drill, such that in soft ground, conical or barrel reamers, in medium and slightly hard ground, butterfly reamers or Fly Cutter, and in Hole Opener tool is used for stony fields.
At the same time as drilling mud is injected through the rotating pipes and reamer, the assembly is drawn towards the Rig and for each pipe branch that opens from the Rig or Rig Side, one pipe from the Pipe Side is added to the back of the reamer. With this work, if needed, the reaming can be repeated up to several stages depending on the type of ground. Also, this action, the presence of Rods on both sides of the reamer, creates more safety than if the reamer stops and gets stuck. The fly cutter can be pulled or pushed or Torque from both sides to get rid of the tool. continued the operation. Sometimes, in case of bigger problems and the tool is locked, the connected bulldozer is used for pulling or pushing.

The third stage: Pulling operation or stretching of the main pipe

After finishing reaming and making the diameter of the hole 30 to 50% larger than the diameter of the main pipe (in order to create a buoyancy space and facilitate the stretching of the pipe and achieve minimum friction and wear between the pipe and the body of the hole), the head of the main pipe, which is cap and has a pull head through the swivel tool (it is a device that can rotate from both sides and it is possible to remove annoying twists in the pipe stretching stage and prevent them from being transferred to the pipe and prevent various damages and causing ruptures in the welding and cutting areas of the pipe). It is connected to the back of the reamer and by applying the pulling force by the rig device, the main pipe is gradually guided from the pipe side into the channel and pulled to the rig side, as soon as the pipe head leaves the entry point, the pulling operation is completed and the operation is completed. it stops.

It should be noted that despite all the measures taken to maintain the health of the pipe being pulled and to prevent damage to the pipe, after the completion of the Pulling operation, the main pipe is again subjected to the electrical insulation test. Also, in order to prevent the spread of bentonite mud into the river or dry areas and damage to the environment, by installing the drilling mud recycling cycle system, all the bentonites coming out of the system can be collected again and after purification and removal of impurities, used again.
In the end, it should be mentioned that the extraordinary superiority of horizontal directional drilling method has been proven in today’s industrial world, and the increasing number of ongoing projects shows the advantages of this method compared to traditional methods, for example, pipe crossing. Gas or oil from the river even in terms of security and preventing potential dangers such as explosions, explosions, etc. clears the river path from the existence of similar obstacles that prevent the traffic of ships and barges. In this way, it is possible to cross the river by commercial, recreational ships, etc., and it also creates great advantages from an environmental point of view. Currently, Iranian specialists and experts in terms of having this special expertise in the neighboring countries and the Persian Gulf region are managing and leading HDD projects, while by advertising and informing the main employers (water and sewage companies, National Gas of Iran, National Iranian Oil Company, Telecommunication Company, etc.) can increase the scope of application of this industry as in other parts of the world and save millions of dollars to increase the importance and safety of pipelines in crossing riverbeds and similar obstacles and It provides great environmental benefits.