- by Safar Mohammad Khan, Deputy General Manager-HDD, Apollo Techno Industries
Horizontal Directional Drilling is a technology in pipe and utility installation that allows greater accuracy and flexibility in placement and ends the need for costly digging, large crews, road closures and other complications of traditional digging and pipe installation.
Horizontal Directional Drilling is a steerable guided method of Installing underground utilities (Viz, OFC, PC, Gas Pipe line, Water & Sewerage Pipe Line, etc) in a prescribed bore path using a surface launched HDD Machines (Apollo, Vermeer, Ditch Witch, XCMG, Drilto, Goodeng, Dilong, American Augur, herrenknecht, etc. Apollo has created good niche in small and mid-size machine and doing very rigorous & extensive work in the technical specification with the quality components in manufacturing of MAXI RIGS (>45 TON Rigs). Recently, Apollo has developed an outstanding Maxi Rig model A1200 which is getting popular specially to make drill in rock by using the Mud Motor. A prescribed boring is used when open trench or open excavation is not possible. The tools and technique used in the HDD method are high demanding technology in Gas Pipe Line Projects (viz LDLP-Long Distance Pipe Line Project, CCPLP-Cross Country Pipe Line Project, GPLDP-Gas Pipe Line Distribution Project. It is now common the HDD machine usage for laying OFC, Power cable, water and Sewerage Pile line of Telecommunication companies, SEB and City Municipals respectively.
Directional control of the HDD drill path is limited. An operator can adjust the direction of the bit by stopping the rotational movement and then thrusting the bit forward. The slanted face of the drill bit causes it to adjust its angle into the ground. HDD rigs allow for a transmitter to be installed just behind the drill bit. A person holding a receiver above the ground over the drill bits location will be able to determine the position and direction of the drill. This information is used by the operator to make minor adjustments to compensate for any deviation.
Drilling mud is pumped down the drill string and into the drilling bit, where it exits through holes in the bit. The purpose of the drilling mud is to keep the transmitter cool, stabilize the walls of the tunnel and remove the spoil. As it washes back up the hole to the surface, it removes the spoil from drilling along with it. Drilling mud is recycled by using screens and hydro cyclones to remove the spoil. It is processed back into a tank on the surface before being pumped into the drill string again. This is called reclaiming or recycling the mud.
Installation of a pipeline string by HDD is generally accomplished in following six stages:
- Soil Investigation
- Drill path design
- Drilling the Pilot Hole
- Pree-reaming the horizontal Boring or Reaming
- Pull back operation
- Installation of Conduits
Different types of drilling bits/drill heads (diamond bit/Tungsten bit/VCP bit/hard face bit) are used in the pilot-bore process. Selection of drill bit is depend on the type of soil strata. The purpose of the soil testing is not only to determine the feasibility of HDD crossing, but also to establish the most efficient way to accomplish it. If the strata becomes very hard (>90 MPA) then to use the rock cutting tools accordingly like Mud motor, Air Hammer, ARMOR, etc. On the geo-tech information governs the determination of best crossing route along with selection of drilling tools and execution methodology.
Following shall be investigated during the pedological survey:
Soil identification to locate rock, rock inclusions, gravelly soils, loose deposits, Hard Morum , Boulders, Brittle rock, black laterite, pebble stone, mountain blend, fast stak & bluff stone, etc.
Soil Strata investigation is performed by analyzing the soil sample extracted from bore-holes drilled along the pipeline route called as bore log data. For big crossings, bore logs are typically taken at 200 m intervals. For short crossings, ie, crossings which are less than 300 m length, as few as three bore log may be sufficient. The borings should be near the drill-path to give accurate soil data, but sufficiently far from the borehole to avoid pressurized mud from following natural ground fissures and rupturing to the ground surface through the soil-test bore hole. A thumb rule is to take borings at least 10m to either side of bore path. Although these are good general rules, the number, depth and location of boreholes is best determined by Engineer.
Drill path design
One of the key considerations in the design of the drill-path is creating as large a radius of curvature as possible within the limits of the right-of-way. Small radius of curvature induces bending stresses and increases the pullback load due to the capstan effect. The capstan effect is the increase in frictional drag while pulling a pipe around a curve due to a component of the pulling force acting normal to the curvature. Higher tensile stresses reduce the pipe’s collapse resistance. Curvature requirements are dependent on site geometry (crossing length, required depth to provide safe cover, staging site location, etc) But, the degree of curvature is limited by the bending radius of the drill rod and the minimum elastic bending radius of the pipe.
The designed drilling profile consists of a series of straight lines and curves. The straight lines are referred as tangents. The straight sections are those in which the drilling hole curvature is ideally zero. This implies that any pipe section can be considered as straight section if the curvature of that section is less than that necessary to make the pipe deviate beyond the walls of the hole, which is roughly 1.5 times larger in diameter than the pipe itself.
Drilling the Pilot hole
The steering tool is placed within the Bore Hole Assembly (BHA). Generally, the BHA is made up of non-magnetic drill collars. The “lead collar” of the BHA is placed on the alignment of the particular crossing. After the alignment, the steering probe is energized with electrical current (wire-line steering) and a bearing for the drill path is established and logged into the surface computer. The drilling rig is set precisely on line with a transit. The non-magnetic “lead collar” (with steering probe) and the directional deviation tool are started exactly at the designated entry point. In most cases, one Non-Magnetic Drill Collar (NMDC) is used behind the BHA. A 10 m non-magnetic collar shall serve as a buffer between the steering probe (in the “lead collar”) and the steel drill pipe. Drill pipe is often highly magnetized due to the continual making up and breaking out the tool joint connections and can affect the tool parameters.
Pilot hole drilling typically is considered the most challenging and time consuming step. As each piece of drill pipe is advanced, the next drill pipe is fitted with a wire inside. This wire is attached to the corresponding wire of the drill pipe previously drilled. This internal wire is the vehicle used for the signal to be sent from the steering probe located in the Bottom Hole Assembly (BHA) to the surface computer. This process is repeated until the bit is advanced along the predetermined path and comes out at predetermined exit location as per the designed drilling path.
Pre-Reaming the Horizontal Boring/Reaming operation
Once the drilling bit exits out (punch out) of the pilot hole, the lead pieces/ drill pipes are unscrewed. The hole opener/ reamer is then attached to the leading pipe to start reaming operation. The reaming operation consists of using an appropriate tool to open the pilot hole to a slightly larger diameter than the carrier pipeline. The percentage oversize depends on many variables including soil types, soil stability, depth, drilling mud, borehole hydrostatic pressure, etc. Normal over-sizing may be from 1.4 to 1.5 times the diameter of the carrier pipe. While the over-sizing is necessary for insertion, it means that the inserted pipe will have to sustain vertical earth pressures without significant side support from the surrounding soil.
Good grade of bentonite is continuously pumped through the reamers to flush the cuttings and stabilize the hole. Similar procedure is repeated for all stages of reaming.
Pipe pull back
The pullback operation involves pulling the entire pipeline string in one segment (usually) back through the drilling mud along the reamed-hole pathway. The pulling equipment is attached to the leading end of the drill pipes string, and the prepared pipe string is fed gently into the bored hole. Proper pipe handling, cradling, bending minimization need to be followed. Axial tension force readings, constant insertion velocity, mud flow circulation/exit rates, and footage length installed should be recorded. The pullback speed ranges usually between 1 to 2 feet per minute. Pipe line projects in India
There is lot of gas pipe line projects for the expansion of Gas , crude oil , CNG, LPG, water and sewerage pipe line are already going on and lot of them are still awaited and could not come in the execution phase due to covid 19. All the projects are delayed and many more are in the bidding & Tendering phase.
Gas Pipe line project
Share of Natural Gas in India’s energy basket is 6.2% as against 23.4% globally. In India, in the state of Gujarat itself, it is 25%. The country aims to achieve share of Natural Gas in our energy basket from 6.2% to 15. States of Gujarat, Goa and Haryana and UTs of Delhi, Chandigarh, Diu & Daman and Dadra Nagar Haveli are fully authorized for development of CGD Networks. 53% of India’s area and 70% of its population spread over 402 districts in 27 states/UTs would have access to CGD Networks for supply of natural gas. Following are the winning entities will be developing all the gas pipe line city gas distribution work in near future - Torrent Gas, Adani Gas, Gujarat Gas, Indian Oil-Adani Gas, Hindustan Petroleum Corporation, Bharat Gas Resource, IOCL, Gail Gas, Unison Enviro, Thinkgas, Assam Gas Company & OIL, Maharashtra Natural Gas, Torrent Gas, ESSEL Gas Company, Megha Engineering & Infrastructure, Tripura Natural Gas Company, Green Gas , IGL will be working on city gas distribution pipe line installation work with the help of HDD method & open trench as well depending on the circumstances. PNG & CNG pipes will be parallel laid beneath the soil depth upto the 1.65 Mtrs to 2.00 mtrs. Total distribution work will be probably for 1,12,696-Kms across India.
State-owned gas utility GAIL India will invest over Rs. 45,000 crore over the next five years to expand the National Gas Grid and city gas distribution network.
GAIL currently operates 11,000-km of pipeline network and markets two-thirds of all-natural gas sold in the country. Out of Rs 45,000 cr investments, Rs 32,000 cr would go into pipeline laying and another Rs. 12,000 cr in city gas distribution (CGD) networks for retailing of CNG to automobiles and piped natural gas to household kitchens.
Adani Gas will invest up to Rs 9,000 crore in setting up city gas distribution network over the next 10 years to retail CNG to automobiles and piped cooking gas to households Adani Gas (AGL) on its own and in a joint venture with state-owned Indian Oil Corp (IOC) has won city gas licence for 38 geographical areas spread over 71 districts in 15 states.
GAIL is looking to put up 400 CNG stations and give out a record 10 lakh piped natural gas (PNG) connections to household kitchens in the next 3-5 years
Cross Country Pipe Line Projects- Some of the Major Players in India who are making cross country pipeline installation through HDD Method by their technology Innovations- ONGC, IOCL, OIL, GSPL, IGL, GSPC, Adani, Avantika, are the major pipeline developer in India.
Some Recent HDD Projects ( Cross Country) executed or under execution by Apollo A1200 HDD Machines IOCL-ADANI of gas pipe line project executed by M/s Guru Construction Company.
Gas Pipe line Dia-20”+6” bundle pulling, Location-Bhadreshwar at Sakra River/Ch.No-37860,Driller Name-BibhutiKr.Mandal, HDD Machine used-A1200.
GIGL(Gujarat State Petronet Limited) of Gas Pipe line Project, Executed by SNS Trechless Engineering, Bharuch ;Dia-30” CS, Location-Talwandi, Bhatinda, HDD Machine used-Apollo A1200, Shot Length-294 Metres, Soil –Normal soil with sand Impression.
Project status-Ongoing; Challenges Faced- None except the site management.
Apollo’s A1200 a powerful made in India HDD Machine equipped with world class specification which makes machine fast and reliable even capable to make drilling in black rock bed at Sakra River beneath the 14 Metres; 800 LPM big Mud Pump makes the water flow high, Joystick control systems & 6000 PSI operated hydraulic pumps along with the 6000 PSI rotation is found in A1200. This all makes this shot successful with excellent performance. All the HDD processes have been observed very effective and fast due to higher side in specification. A quality HDD Machine with the trained driller are must to make your pipe line installation successful. It was not found any challenges except the site management and its preparation. A quality mud motor along with all the site preparations are required ( viz Mud mixing systems, Mud Recycling systems, Rock Cutting reamers, Diesel etc).Some Interference was found in the locating systems due to salty nature of rock which was found in the rock.
Benefits of Directional drilling-
- Reduced soil disturbance.
- A single location area can be used to install different pipes.
- Reduces the fractures to existing rock formations.
- Reduces the contamination of groundwater pollution.
- Protects the ecosystem and adjacent areas.
- The directional drill produces twice the amount of oil or gas being extracted.
- Reduces the excavation and shoring costs.
- It is a safer operation than open cut.
- Weather will not impact directly on the process.
- Limited traffic and landscape disruption. Ideal for sites sensitive to surface disruption such as heavy roadways, airport runways, golf courses, etc.
- Ability to drill beneath surface obstructions or ongoing site operations.
Some of the factors such as increasing growth of telecommunication and oil & gas industries, high underground water extraction and growing awareness about minimally invasive techniques are boosting the market growth.
Horizontal directional drilling is one of the most specialized methods for installing underground conduits with minimal damages to the surrounding ecosystem 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. It is ideal for installing cables, conduits, and pipes for short-distance as well as long-distance projects and even at deeper depths.
Amongst Machines Parts, rigs segment accounted held significant market share during the forecast period. Rising demand for well-organized rigs in HDD projects for distant pipeline installations is propelling the growth of this segment. Midi HDD rigs are mostly used for laying of power and telecommunication lines and in installing heavy pipes for gas distribution. By geography, North America region has dominated the market during the forecast period due to factors, such as the increasing number of oil & gas industries and infrastructure development projects in this region.
Lot of infrastructure needs to be developed in India under the urban development programme for the smart cities where the LPG will be supplied through the gas pipe line to houses.5G network distribution is all well prepared by all the telecom companies ( airtel&Reliencejio) where the OFC duct will be well installed by using HDD machines.Power cable giants under the state electricity board will be expanded by using HDD Machines in India. Now, Municipals are also well knowledgeable to install water and sewerage pipe lines through non-disruptive technology.