The use of horizontal directional drilling rigs for pipeline through the construction is generally divided into two stages: the first stage is to drill a pilot hole as accurately as possible according to the design curves; the second stage is to ream out the pilot hole, and will be the product of the pipeline (generally PE pipe, fiber optic cable casing, steel pipe) along the enlarged pilot hole back to the pilot hole, complete the Pipeline through the work.
1.1 Drilling pilot hole:
According to the geological condition of the traverse, choose the appropriate drill bit and guide plate or underground mud motor, start the mud pump to align with the point of entry into the soil for drilling, the drill bit in the drilling machine under the action of the thrust of the drilling machine driven by the rotating drilling machine (or the use of a mud motor to bring
drive the rotating drill bit) cutting the strata, and keep moving forward, each drilling a drill pipe to measure the actual position, and the actual position of the drill bit is to be measured once. The actual position of the drill bit should be measured once after each rod is drilled, so that the drilling direction of the drill bit can be adjusted in time to ensure that the curve of the completed pilot hole is in accordance with the design requirements, and so on
repeatedly until the drill bit comes out of the ground at the predetermined position and completes the drilling operation of the entire pilot hole. See Diagram 1: Drilling the pilot hole.
The drilling rig is mounted on the side of the entry point, and from the entry point, a curve is drilled from the entry point to the exit point along the designed line, which serves as a guide curve for the pre-expansion hole and for the back hauling of the pipeline.
1.2 Pre-reaming and towing back the product line:
Generally speaking, when using small drilling rigs, when the diameter of the product line is greater than 200mm, it is necessary to carry out pre-reaming; when using large drilling rigs, when the diameter of the product line is greater than 350mm, it is necessary to carry out pre-reaming, and the diameter of the pre-reaming and the frequency of pre-reaming depend on the specific type of drilling rigs and the geological conditions.
Back dragging the product line, the first reaming tool and the line connected, and then, start back dragging the operation, and by the drilling rig turntable to drive the drill pipe rotating back, reaming back dragging the product line in the back dragging the process is not rotating, due to the reaming
good hole filled with mud, so the product line in the reaming hole is in a state of suspension, the wall around the hole and the hole lubricated by mud, so that reduces the drag resistance. This reduces the drag resistance and protects the anti-corrosion layer of the pipeline, and after many pre-expanded holes by the drilling rig, the final diameter of the hole is generally 200mm larger than the diameter of the pipe, so it will not damage the anti-corrosion layer. See Diagram 2: Pre-reaming and Diagram 3: Towing back the pipe.
At the stage of drilling pilot holes, the drilled holes are often smaller than the diameter of the back hauling line, in order to make the drilled holes reach 1.3 to 1.5 times of the diameter of the back hauling line, it is necessary to use a reamer to expand the pilot holes from the point of emergence to the point of entry into the ground to the required diameter.
After the underground hole has been pre-expanded to meet the requirements for back hauling, connect the drill pipe, reamer, back hauling live section and the installed pipeline, and start from the point of emergence while expanding the hole and back hauling the pipeline to the point of entry.
2, horizontal directional drilling construction features:
2.1 Directional drilling through the construction will not obstruct traffic, will not destroy the green space, vegetation, will not affect the stores, hospitals, schools and residents of the normal living and working order, to solve the traditional excavation construction of the residents of the interference of the life of the traffic, the environment, the destruction of the foundation of the surrounding buildings and the adverse effects.
2.2 Modern traversing equipment through the high precision, easy to adjust the laying direction and depth of burial, pipeline arc laying distance is long, can fully meet the design requirements of the depth of burial, and can make the pipeline bypass the obstacles in the ground.
2.3 Urban pipeline network depth generally reaches three meters below the river, crossing the river, the general depth of 9-18 meters below the riverbed, so the use of horizontal directional drilling rigs through the surrounding environment has no impact on the environment, does not damage the geomorphology and the environment, to adapt to the requirements of environmental protection.
2.4 Horizontal directional drilling rig through the construction, there is no water, underwater operations, does not affect the navigation of the river, does not damage both sides of the river dams and riverbed structure, construction is not restricted by the season, with a short construction period of less personnel, high success rate of the construction of safe and reliable and so on.
2.5 Compared with other construction methods, in and out of the site quickly, the construction site can be flexibly adjusted, especially in the urban construction can fully demonstrate its superiority, and the construction of the construction of a small area of low cost of construction, construction speed.
2.6 large river crossing, due to the pipeline buried in the ground below 9-18mm, oxygen and other corrosive substances inside the ground is very little, so it plays a natural anticorrosive and thermal insulation function, you can ensure that the pipeline running time is longer.
3, horizontal directional drilling system introduction:
Various specifications of horizontal directional drilling rigs are composed of drilling rig system, power system, control system, mud system, drilling tools and auxiliary equipment, their structure and function are introduced as follows:
3.1 Drilling rig system: is the main body of the traversing equipment drilling operations and towing back to the main body of the work, which consists of drilling rig mainframe, the carousel and so on, the drilling rig mainframe placed in the drilling rig frame, the drilling rig is placed in the drilling rig frame, the drilling rig mainframe is placed in the drilling rig frame and the carousel and so on. The main rig is placed on the rig frame to complete the drilling and towing operations. The turntable is mounted on the front end of the drilling rig, connected to the drill pipe, and by changing the turntable steering and output speed and torque size, to achieve the requirements of different operating conditions.
3.2 Power system: composed of hydraulic power source and generator, the power source is to provide high-pressure hydraulic oil for the drilling system as the power of the drilling rig, and the generator is to provide power for the supporting electrical equipment and construction site lighting.
3.3 control system: the control system is a computerized monitoring and control of the specific position of the drill bit in the ground and other parameters, to guide the drill bit to correctly drill the direction of the tool, due to the control of the system, the drill bit can be drilled according to the design curve, is often used in the handheld wireless and wired two forms of the control system.
3.4 Mud system: the mud system consists of mud mixing tanks and mud pumps, and mud piping, for the drilling rig system to provide the mud suitable for drilling conditions.
3.5 Drilling Tools and Auxiliary Tools: These are the various tools used for drilling and reaming in the drilling rig. Drilling tools mainly include drilling rods, drill bits, mud motors, reamers, cutters and other tools suitable for various geological conditions. Auxiliary tools include rings, swivel joints, and drag heads for various pipe diameters.
Through the construction site layout
1. The entry point is the main place of directional drilling construction, the drilling rig is arranged on the side, so the construction of the area is relatively large, DD330 drilling rigs for a minimum area of 30 × 30M, of course, can be adjusted accordingly according to the actual situation of the site, the DD60, DD-5 occupies a much smaller area accordingly.
2. One side of the excavation point is mainly used as a pipeline welding site, there should be a 20×20M site at the excavation point as a pre-expanded holes, back to the towing of the drilling rod and installation of other equipment; there is a length of the pipeline after the excavation point is equal to the length of the crossing of the pipeline welding work belt.
Traversal Example
Dagusha Traversal Drilling Rig Site Arrangement
Between September and October 1998, our company completed the traversal of two Φ219×8 and one Φ426×9 pipelines with a length of 960 meters in only 45 days in the Dagusha Sea River, Tanggu, Tianjin.
Dagusha crossing welding site (only two pipes are shown)
Horizontal Directional Drilling Crossing Construction Process Flow Chart
The use of horizontal directional drilling technology to cross rivers and other obstacles is a widely used construction method around the world. The Horizontal Directional Drilling Contractors Association (HDDCA) believes that during the project bidding process, horizontal directional drilling contractors should seek to obtain as much information as possible in order to make a complete and competitive offer, and that contractors should be provided with the following information prior to the commencement of work in order to ensure that future work can be carried out smoothly and that the project can be completed under these conditions
At the same time, adequate information can also be obtained to ensure that the work is carried out in a timely manner. Pre-construction of various types of information can also ensure that the construction process is safer, reduce the damage to the surrounding environment, so that the project is carried out more smoothly.
Overview
A, development and use
Horizontal directional drilling technology first appeared in the 70s, is the combination of traditional road drilling and oilfield directional drilling technology, which has become a popular method of construction, can be used for the transportation of oil, natural gas, petrochemicals,
water, sewage and other substances and electricity, fiber optic cable construction of various pipelines. . It is not only applied to the crossing of rivers and waterways, but also widely used in highways, railroads, airports, coasts, islands, and densely built buildings, pipelines and other dense areas
.
B, technical constraints
Directional drilling construction technology was first used in the United States coastal areas of the alluvium through, and now has been able to start in the coarse sand, cobble, moraine and rocky areas and other complex geological conditions for the construction of the crossing. The longest crossings have been up to 6,000 feet with 18-inch diameter pipes.
C. Advantages
Horizontal directional drilling has been proven to be the lowest environmental impact construction method. This technology also provides the most protective layer for the pipeline and reduces maintenance costs, does not interfere with river transportation and shortens the construction period, proving to be the most efficient and least expensive crossing construction method available.
D, construction process and technology
1, pilot holes: pilot holes are drilled horizontally at a predetermined angle and along a predetermined cross-section of the hole, including a section of the straight diagonal and a section of large radius arc. While drilling pilot holes, the contractor may select and use larger diameter
drill pipe (i.e., flushing pipe) to shield the pilot drill pipe. The flushing pipe acts like a conduit and facilitates the retrieval of the pilot pipe and the replacement of the drill bit. Direction control of the pilot hole is accomplished by a controller (called a curved housing) located in the drill pipe at the rear end of the bit. The drill pipe does not rotate during the drilling process, but when a change of direction is required, the drilling route follows a smooth curve to the right if the curved housing is positioned to the right. The drilling curve is measured by an electronic direction finder placed inside the drill pipe at the rear end of the drill bit and transmits the measurement results to a receiver on the ground, where the data are processed and calculated, and then shown in digital form on a display screen, which is used to monitor the relationship between the drill pipe and the earth's magnetic
field and the inclination angle (the three-dimensional coordinates of the drill bit in the ground). The measured data is compared with the designed data to determine the deviation of the actual position of the drill bit from the designed position, and the deviation is controlled within the allowable range
, and so on until the drill bit emerges from the ground at the predetermined position according to the predetermined pilot hole curve.
2, pre-expansion:
After the completion of the pilot hole, to expand the hole to the appropriate diameter to facilitate the installation of the finished pipe, this process is called pre-expansion, (depending on the final size of the hole to determine the number of times to expand the hole). For example, if a 36-inch line is to be installed, the hole must be enlarged to 48 inches or more. Typically, a reamer is attached to the drill pipe on the opposite side of the rig and then rotated by the rig and dragged back into the pilot hole to enlarge the pilot hole while pumping a large volume of mud into the hole to ensure the integrity of the hole and to keep it from collapsing and to bring the cuttings back to the surface.
3, back to drag the pipe: after the completion of the pre-borehole, the finished pipe can be dragged into the drill hole. Pipe prefabrication should be completed on the side opposite the drilling rig. One end of the reamer is connected to the drill pipe and the other end is connected to the finished pipe through a rotary joint. The swivel prevents the pipe from rotating with the reamer and ensures that the pipe is dragged smoothly into the hole. Pullback is accomplished by the drilling rig, which also requires a large amount of slurry, and is continuous until the reamer and the finished pipe break away from the side of the drill
.
Two, site layout and design
A, road
construction site on both sides of the need for heavy equipment, in order to minimize the cost of access to both sides of the construction site of the road should be used as far as possible to reduce the distance of the new road, or the use of pipeline route of the construction right-of-way, all the relevant road right-of-way agreement should be provided by the owner, in the bidding stage before discussing these issues. It is too late to discuss these issues at the bidding stage.
B. Work Site
1. Rig Side - The rig site needs to be at least 30M (100FT) wide and 45M (150FT) long. This area is calculated from the point of entry, the point of entry should be located in the specified area of at least
3M (10FT), and because many drilling rigs supporting equipment or accessories do not have a specified storage location, so the drilling rig side of the construction site can be made up of a number of irregular small pieces in order to save the footprint, the site as far as possible
To be flat, hard, clean, in order to facilitate the construction. Because the crossing construction requires a large amount of fresh water for mixing mud, so the construction site should be as close as possible to the water source or easy to connect to the water pipeline.
2, the pipeline side of ---- in order to facilitate the prefabricated pipeline, the pipeline side of the construction site should have a sufficient length, which is also a key consideration. The width of the site should meet the needs of pipeline construction (generally
12----18 meters). Similarly, a site width of 30 meters (100 FT) by 45 meters (150 FT) is required on the excavation side. (The total length of the site is usually the length of the crossing pipe plus 30 meters.) Before towing back, the pipe should be prefabricated, including welding, balling, pressure testing and corrosion protection, etc. During the towing back process, the pipeline can not be connected,
Because the towing back process is to be carried out continuously. may cause the collapse of the underground hole, most likely to cause the failure of the entire project construction.
C, construction site survey
Once the construction site is determined, the corresponding area should be surveyed and draw detailed and accurate geological and geomorphological drawings. The accuracy of the final construction depends on the accuracy of the results of this survey.
D. Construction Design Parameters
1. The thickness of the overburden layer ---- takes into account factors such as the flow characteristics of the river to be traversed, the depth of seasonal flooding, future widening and deepening of the river channel, and the location of existing pipelines and cables. Once the construction site has been identified and the geological survey completed, the thickness of the crossing layer is determined, and in general the overburden should be at least 6 meters (20FT) thick. The above is only for river crossing, for other obstacles crossing will have other
requirements.
2, drilling angle and radius of curvature ---- In most of the crossings, the angle of entry is usually chosen between 8 and 12 degrees, and most of the work should be drilled firstly in a straight diagonal line, and then drilled in a large radius curve. The curve's radius of curvature
is determined by the bending characteristics of the finished pipeline and increases with diameter. The thumb rule for the radius of curvature of a steel pipeline is 100 FT/IN (generally 1000-1200 times the diameter of the pipe). The slanting straight line will guide
The hole curve will be guided to the design depth according to the predetermined direction, followed by a long horizontal straight line at this depth, and then reach the upward bending point and then to the point of emergence. The angle of emergence should be controlled between 5 and 12 degrees to
facilitate the back hauling of the finished pipe.
E, drilling construction
All the direction control tools include underground measuring electronics and ground receiving equipment, which can measure the magnetic azimuth (for left/right control) and tilt angle (up/down control) of the drill bit location and the direction of drilling.
1. Accuracy: The accuracy of the traversing construction depends to a large extent on the variation of the magnetic field. For example, large steel structures (bridges, piles, other pipelines) and power lines can affect the magnetic field readings. And through the excavation point of the pilot hole target deviation value should be controlled in the left and right 3 meters (10FT), length - 3 meters to 10 meters (-10 ~ 30FT) within the range.
2, finished drawings: In general, the pilot hole measurement and control should be measured and calculated every time the pilot hole is drilled into a drill pipe or every 9 meters (30FT). The above measurements and calculations completed pilot hole construction drawings the contractor shall provide to the owner. Alternative methods such as gyroscopes, ground penetrating radar and intelligent pipe clearing balls are also used for positioning.
3. Geological Survey
A. Number of Pilot Holes
The number of pilot holes will depend on the stratigraphy of the planned traverse site and the length of the traverse. If the length of the crossing is 300 meters (1000FT), one borehole on each side of the crossing site will be sufficient, and if the results of the boreholes indicate that the geological conditions of the
area are relatively homogeneous, no further drilling and sampling will be necessary. If the exploration report shows that the geological conditions of the area are complicated, or the presence of rocks or coarse sand layer is found, then it is necessary to do further detailed
geological investigation. During long-distance and large-diameter traverses, coarse sand, pebbles, weathered rock or hard rock should be sampled every 180m----240m (600-800FT), and if there are clear indications that the geology is unusually complex, then more holes need to be drilled for additional sampling. All sampling holes should be in the direction of the traverse section, and the sampling depth should be based on the planned traverse depth. If possible, sampling holes should be located approximately 8 meters (25FT) to the side of the traverse centerline. Upon completion of the survey, the hole must be sealed to prevent mud leakage during construction.
B. Hole Depth
All holes should be at least 12 meters (40 FT) below the crossing point or 6 meters (20 FT) below the intended crossing depth, whichever is greater. In some cases, it may be beneficial to the contractor or the owner to set a deeper crossing depth or to actually cross the
curve deeper than the designed location. The key is to locate the crossing in a stratigraphically consistent formation that is conducive to hole formation, which is conducive to the success of the crossing.
C. Standard Classification of Soils
A qualified geotechnician or geologist should be able to classify materials according to the Unified Soil Classification System or ASTM Design Notes D-2487 and D2488. It is beneficial to have a field boring log provided by the field technician or drilling company
that includes a visual classification of the material as well as an interpretation and evaluation of the stratigraphic structure by the drilling company based on the results of the sampling.
D. Standard Puncture Test
SPT In order to better determine the density of the granular material, geologists usually do a standard puncture test SPT in accordance with ASTM specification D1586. This is a field test method that utilizes a standard-weight weighted weighted hammer to drive a spoon
shaped sampler into the soil at a certain depth, and the number of strokes is recorded up to a depth of 12 inches. Record the number of strokes at 12 inches of depth. The data obtained is a standard penetration resistance value and can be used to estimate the relative density of the non-polymerized soil at the test site. Some drillers choose to perform this test on a small scale in areas of consolidated soil or rock to confirm the consistency of the compacted soil and the hardness of the rock.
E. Core Sampling Methods
Most geological exploration companies prefer to use core samplers to obtain samples from subsurface cores, and these tests are generally conducted in accordance with ASTM Specification D-1587. These tests are similar to the standard penetration test described above, except that the sampler is a hydraulically driven, thin-walled, non-tempered steel cylinder with a sharp cutting edge. The required hydraulic values can be found in the field records, and this method allows relatively complete samples to be obtained for more detailed laboratory analysis. The samples can be analyzed in the field using a hand-held penetrometer, and for directional traverses, the cut-scoop sampler described above is usually sufficient for construction purposes.
F. Granulometric analysis
Granulometric screen analysis of samples is a mechanical test of granular material obtained at the construction site by means of a cut-scoop sampler. These samples are sent to a laboratory where they are passed through a series of screens to obtain the percentage of different sizes according to the size and weight of the particles, which is one of the most important tests.
G. Rock conditions
If the presence of rock formations is detected during a soil survey, the type of rock formation, relative hardness and unconfined compressive strength must be determined. Sampling is carried out by a professional exploration company using a diamond drill core bucket, with a typical core sample of
50 mm (2 inches) in diameter. Rock types are classified by geologists based on the quality of the core in relation to the total length of the core, rock hardness is based on a comparison of the rock with ten materials of known hardness, and compressive strength is obtained by precise measurement of the core followed by compression tests. These data are the physical parameters of the rock that allow the use of the type of drilling equipment and drill bits to be determined, and the traversing footage to be estimated.
Traversing companies can be found online. I'm working on a big project right now with a lot of crossings. I don't know what you do exactly, but if you're interested, let's talk and learn from each other.