Horizontal Directional Drilling (HDD)
Horizontal?drilling?is?a?widely?used?technology?since?reservoirs?can?be?stimulated?by?drilling?at?an?angle?other?than?vertically?to?gain?Knowledge?that?can?not?be achieved?vertically?by?drilling. The?interaction?between?the?reservoir?and?the?Wellbore?can?be?improved?by?horizontal?drilling.
Since the 1970s, this technology has been in use. It is currently a reliable, safe, and cost-effective process for highway bores and is the latest industry standard for bores between 2 and 48-inch in diameter trenchless technology.
Horizontal Directional Drilling (HDD) is a method of installing underground pipelines, cables, and service conduits through trenchless methods. It involves the use of a directional drilling machine, and associated attachments, to accurately drill along the chosen bore path and back ream the required pipe.
By oilfield convention, a horizontal well is defined as a well with an inclination angle of 90 degrees from the vertical.
Horizontal Directional Drilling (HDD) is also defined as “A steerable system for the installation of pipes, conduits, and cables in a shallow arc using a surfaced launched drilling rig. Traditionally HDD is applied to large scale crossings such as rivers in which a fluid-filled pilot hole is drilled without rotating the drill string, and this is then enlarged by a wash over the pipe and back rotating the drill string, and this is then enlarged by a wash over the pipe and back reamer to the size required by the product.”
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1.??For the job at hand, a directional drill rig is sized.
2.??Drill rods are threaded together to create a drill string to advance the drill bit and to pull back Scrapers and goods.
3.??A transmitter/receiver for monitoring the drill and product position and recording it.
4.??A tank for mixing drilling fluid and storing it.
5.??A pump for the drilling fluid to circulate.
?The types of wells have become known as:
1.??Short-Radius
●?????Short radius has approximately 60 feet of buildup section and from 100 feet to 800 feet of horizontal section.
●?????Small diameter holes can be drilled from the same wellbore.??
●?????The short radius is drilled with special deviating systems and unconventional tubular.
Advantages
Disadvantages
2.??Medium-Radius
●?????Medium radius is characterized by a buildup angle from 6° to 35°/ 100 feet with a buildup section from 200 to 700 ft.
●?????The horizontal section can be from 1000 to 3500 ft. It is applied when drilling through fractured reservoirs and potential water and gas coning reservoirs.
3.??Long radius
●?????Long radius deviates mainly in the open holes. The buildup rate can be from 1° to 06°/100ft. The horizontal section can reach the level of 5000 ft.
●?????It is used in offshore and inaccessible locations.
●?????They are characterized by larger hole sizes and susceptible to high torque and drag due to longer open-hole sections, also larger holes allow for using larger positive displacement motors with higher horsepower.
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1.??Pilot Hole?
The first step is the drilling of a pilot hole with a small diameter. Drilling fluid is pumped to the drill bit through the drill pipe where high-pressure jets and the bit can grind the soil in front of the drill stem. The drilling fluid will also take the cuttings back to the drill rig's entrance pit.
Depending on the size and complexity of the shot, monitoring of the pilot hole can be achieved in many ways. Smaller shots are conducted using a walkover guidance system, while the bigger, more complicated shots have a magnetic wire line style system.
There is a transmitter or steering tool near the drill head in both techniques that sends a signal to the position engineer giving the exact coordinates of the drill steam.
Readings are continuously taken to verify the depth, orientation, and percentage slope of the drill head. The operator and locator will make adjustments to maintain the pilot hole in the predetermined bore route.
The velocity of the pilot hole will vary according to current soil conditions and the amount of steering required. The beacon housing and bit are separated when the exit point is reached and?replaced with a reamer.
2.??Pre-reaming
The second stage is to pre-ream and widen the pilot hole to a size adequate to mount the product lines safely. During pumping drilling fluid, a reamer is pulled back and rotated to cut and remove solids to widen the cavity. Depending on current soil conditions and the number of cuttings that are removed from the pit, pre-reaming speeds can differ.
Bentonite and other additives will be used to ensure a clean and stable hole. Bentonite is used to create a “cake layer” around the outside of the hole during pre-reaming. This will help with the stability of the borehole and with fluid loss or infiltration. Additives such as polymers are used to help break up the clay soils. More evenly mixed drilling fluid will prevent any blockages inside of the borehole.
3.??Pipe pullback
The final step is the pullback of the pipe within the pre-reamed hole. The drill rod and reamer will be attached to a swivel, which is utilized between the product line and the reamer to prevent any torsional stress from the rotating drill string from being transferred to the product pipe.
As the product pipe is pulled into the drill hole, drilling fluid is pumped downhole to provide lubrication to the product pipe.
1.????Avoid obstacles to the surface such as rivers, railways, or highways.
2.????Save the time of completion of the well and it is safe.
3.????Directional drilling often requires less support equipment than other methods.
4.????Current HDD equipment can install pipes in large diameters.
5.????Today's HDD equipment can operate effectively in most soil conditions, including loose and solid rock.
6.????More secure than above ground or trenched installations.
7.????Ground disturbance of drilling and target areas.