How does a drill rig work?

Constructing a pipeline using a gravity drill consists of two basic processes: pilot drilling and reaming with module insertion.

1.Pilot drilling with drilling rig assembly

Machine assembly

Before performing a pilot drill, its path must be marked, in accordance with existing construction documentation and the design of the installation being implemented. The planned drill path should be marked, which makes it easier to control the progress of the work through the receiver of the location system. After marking the drill direction, the drill depth should be marked on the inner wall of the well, taking into account the previously determined drill direction. Then, the drill rig mounting system should be installed in the starting well. The next step is to lower the drill rig and the spreader arms into the well. The drill rig should be lowered vertically, suspended by the dedicated rear transport eye. After the initial assembly, you can proceed to precise setting of the direction and slope of the drill. When the machine is mounted as in the drawing below, it is ready to be connected to the power supply and to perform a pilot drill. 

Pilot drilling

After connecting the hydraulic and flushing lines, the first step is to drill the well wall and deepen the stuffing box. The next step is to install the pilot rod, turn on a small flow of drilling fluid, and insert the head of the pilot rod behind the well wall.

The next step is to install the gland in the well wall. The first rod, together with the gland, should be connected to the drill string, the mud should be turned on and drilled until the gland is inserted into the recess and installed. The installation of subsequent rods increasing the length of the drill string should be repeated until the pilot fin has drilled through to the target well or chamber. This means that the pilot drilling has been completed. During the pilot drilling, it is worth continuously monitoring and, if necessary, correcting the slope and direction of the drilling.

The pilot drilling is a very rich source of information on both ground conditions, soil inclusions and the possibility of stabilizing the channel with mud. This information can be transferred to the later stage of reaming and pulling the pipe. Drilling through rocks or other obstacles can cause vibrations of the pilot rod and transfer to the entire drill string. Difficult ground conditions also affect the maximum feed rates or hydraulic pressure values. A change in ground conditions during the pilot drilling will be visible to the operator both in the pressure value and in the speed of the drilling. The above conditions occurring during the pilot drilling should be taken into account when selecting the type of reamer to be used at the stage of reaming and pulling the pipes. In addition, changes in ground conditions should be observed and, if necessary, the composition and amount of drilling mud supplied to each meter of the drilling should be changed.

2. Pulling in the pipe modules and dismantling the machine

Pipeline reaming and pulling

The first stage of the process of reaming and pulling pipe modules is to select the appropriate reamer. It must be well-matched to the ground conditions and the necessary parameters of the drilling. Information and experience gained during the pilot drilling should be taken into account. The purpose of using reamers during the insertion of the pipe is primarily to increase the diameter of the drill hole to a size that will allow the installation of the pipeline. In addition, the reamer's tasks include mixing the spoil with the drilling fluid, partially compacting it and introducing it into the resulting annular space between the pipeline and the resulting drill hole. This allows for the stabilization of the hole and protects it from blocking or sticking the pipe. The next stage is to mount the starting pipe together with the clamps placed inside it on the reamer swivel.  The reamer prepared in this way, with the starting pipe mounted on the swivel, is ready for installation in the final well.

Before installing the reamer in the drilling line in the final well, the appropriate diameter of the core drill for concrete should be matched to the reamer and a hole should be made in the final well with it. This will ensure that the reamer and starting pipe assembly can be freely inserted behind the well wall. After drilling the well wall, the bit should be withdrawn in the machine's working motion and the core drill should be dismantled. Then the bit should be removed from the working zone and the reamer and starting pipe assembly should be placed in the starting well. In the next step, the reamer should be inserted behind the well wall and the reaming process should be started. 

After pulling the reamer behind the wall, continue the reaming process by gradually adding additional pipe modules. connecting them with a power-driven compression tool dedicated to the pipe diameter, and also reduce the number of rods in the drill string in the starting well/chamber to gradually move the reamer closer to the starting well. When the reamer is directly in front of the starting well wall on its outside, unscrew the remaining, last rod in the drill string, dismantle the gland from the well wall and mount the core drill on the drilling rig connector in order to drill a hole to allow the pipeline to be inserted into the starting well.

After drilling, the crown should be dismantled from the nozzle, removed from the starting well and the final stage of pipe pulling, i.e. inserting the reamer together with the pipe from the pipe modules built on it into the starting well. The reamer together with the starting pipe should be gently pulled into the starting well so as to enable the reamer to be disconnected from the pipeline.

Finally, the pipeline ends need to be sealed, in accordance with the construction documentation. For this purpose, transition sleeves with seals, dedicated to the modular pipes supplied, and e.g. quick-setting mortar can be used. 

Dismantling the drilling rig

The final stage of the process is to dismantle the machine and its accessories. To do this, you need to go through the assembly process in reverse order, skipping the processes related to setting and adjusting.