Horizontal Directional Drilling Company Asia

With the data provided by the surveyors, the locator operator or drilling manager will make a bore plan and profile using the Atlas bore planning computer software. The bore plan will establish the entrance and exit angles and the radius of the pipe curvature, to achieve the depth and length of the drill. The bore plan will also show any utilities that were found by the survey team and will allow for the necessary deviation of the pipeline to avoid contact with the utility.

When the bore plan is completed it will be presented to the client or his representative for approval. Upon approval of the bore plan the HDD operations can proceed.

2. PREPARATION OF SITE
An all weather access to the entrance and exit sites for the HDD operations must be constructed and a level hard standing area for the drilling equipment prepared at each of these sites as follows:

a) Exit or rig side
A rectangular area has to be prepared that is approximately 10 metres long by approximately 5 metres wide.

Access to the entrance should be an all weather road capable of withstanding heavily loaded transporters. The hard stand should be either clay filling with a cover of laterite, wooden mats or steel plates.

The clean water (not salt-water) requirements should be met by either a reliable pumped supply or by water trucks. If it is determined that the water supply is not sufficient to meet the needs of a crossing, water storage tanks will be used to store enough water to meet the requirement.

Pits will be excavated at the pipeline exit and entry points. The pits are to contain the borehole slurry. They must be of sufficient capacity to accommodate the used slurry/cuttings mixture. Further disposal of the used bentonite during the operation must be possible using other means and should be arrange for together with the client

b) Entrance side
The hard stand should be constructed in a similar manner to the exit. A similar access, as constructed for the exit should be provided. A slurry pit will be constructed to collect any bentonite/slurry discharged from the drill hole.

3. HDD DRILLING OPERATION
The survey team will place stakes at the pipeline exit and entry points. The directional drilling unit is placed at the exit where the drill will enter at exactly the correct location. The drill unit is then elevated at the rear so that the entrance angle conforms to the drill profile drawing. The rig is then anchored in position. If necessary a 20 tonne excavator will also be used as an anchor for the drill rig.

The drilling operation begins by drilling a pilot hole using the drill bit, the drill head and the pressure injection of drilling fluid. The drilling is carried out continuously in intervals of 4.5 metres, equivalent to one length of drill pipe. Location of the drill bit is monitored using the DCI locating system. An electronic transmitter in the drill head sends information to the locator operator’s receiver. As each drill rod is drilled into the ground the locator operator takes a reading from his equipment and informs the drill operator of the location, pitch and roll of the drill head. From this information the operator knows the location of the drill head at all times. The operator uses the information to maintain the preplanned path of the bore. The accuracy of the drilling is verified by comparing the coordinates of the actual location of the drill bit against the planned drill profile. If there is a major difference between the actual and planned location of the drill bit, the operator is able to correct the actual profile by pulling back to a correct position of the planned profile and begin re-drilling.

Once the drill bit exits the other end of the drill hole, the drill head is removed and a reamer is attached to the drill string. Depending on the diameter of the pipe to be installed, several reamings with progressively larger diameter reamers may be necessary (i.e. with a 24 inch diameter pipe, the first reaming could be with an 16 inch reamer, the second reaming with a 24 inch reamer and the third reaming with a 32 inch reamer). During the reaming process, drilling fluid is pumped under pressure through the drill string to the reamer. As the drill rig pulls the reamer back, drill pipe is attached continuously behind the reamer for the subsequent reaming and pipe pulling operations.

When the bore hole has been reamed out to the correct diameter the back reamer is sent back down the bore one or two more times to ensure that the hole is clear of any large objects and that the slurry in the hole is well mixed.

This prepares the hole for the pipe to be pulled in. Once the driller is satisfied that the hole is clear and ready for the pipe, the pull head is connected to the drill string via a swivel. The swivel prevents the client’s pipe from rotation during the pullback.

Prior to the pull back, the client’s pipe, which has had a pull head welded on to it, has been prepared and hydrostatically tested by the client in a single length. The length being equivalent to or greater than the length of the drilled hole.

The client’s pipe is then pull back toward the exit area by the drill rig.

4. LEAVING THE SITE
The site will be left clean and tidy and basically in a similar condition as it was prior to the drilling commencing.

5. DOCUMENTATION
Upon completions of the HDD crossing Strega will produce an as built drawing using CAD, which will be presented to the client.

For additional information, comments, or questions, please contact Strega