A new Horizontal Directional Drill (HDD) under river crossing record has been set in terms of pipe diameter, pipe weight and length of crossing in India.
In October 2014, Trenchless Engineering Services Private Ltd (TESPL) of Delhi, India was awarded the project for Installation of Pipeline across Yamuna River near Yamuna Nagar, Haryana. GAIL (INDIA) Limited is the owner of this project. GAIL (INDIA) Limited has appointed Engineers India Limited (EIL) as their Project ManagementConsultant (PMC) for implementation of the Project
TESPLhas largest number ofHDD Rigs in Indiai.e. 14 numbers including Maxi Rigs ranging from 100 Ton to 400 Ton pulling capacity. TESPL has successfully installed in total of 85700 meters of Pipeline by HDD in India as well as overseas. TESPL is the only company in India which has installed 2000 meters plus HDD crossings 10 times since year 2012. The Yamuna River crossing under Bawana-Nangal Pipeline Project as a replacement pipeline under the O&M Department of GAIL India Ltd was a big challenge for the company in terms of Planning and Execution.
OVERVIEW OF PROJECT
GAIL is operating BawanaNangal Pipeline (BNPL) since 2012 for transportation and distribution of natural gas to various consumers en-route from Bawana (Delhi) to Nangal(Punjab).
Earlier 36”x 650 Meterspipelinewas laid across Yamuna River(near Yamuna Nagar) by HDD got exposed due to meandering of the river.Therefore, new HDD was required to be carried out parallel to the existing pipeline atthe location. The project came under competitive bidding in August 2014 and the same was awarded to TESPL in October 2014.
- Installation of 36” x 2000 Meters Pipeline.
- Installation of 6” x 2000 Meters Conduit pipeline with HDPE and OFC sub-ducted.
- Hook up with Existing pipeline on both ends of crossing and Commissioning
Kick Off meeting for the project was held in October 2014 at GAIL (INDIA) Office in Noida to discuss various points and issues regarding implementation and execution of project. It was decided and agreed to lay and Install 6” Conduit pipeline prior to Installation of 36” pipeline because of several advantages. Drilling of pilot hole for 6” pipeline gave a good knowledge and understanding of ground and soil conditions. Also 6” pipeline shall act a Return line for transportation of Bentonite from Pipe side to Rig side during Reaming and Pulling stages of 36” pipeline installation.
Installing large diameter pipelines with HDD requires an annular space with approximately 12-inches larger hole to reduce friction during pullback. In soft soils, such as Yamuna River crossing, a large HDD bore diameter can collapse and cause delays in construction, increased costs, and possible settlement damage.
Large and long HDD Project requires High capacity HDD Rig, high grade drill pipes and high pressure Mud pump to circulate bentonite in hole. Keeping all these requirements, parameters and challenges in mind, TESPL decided to deploy
- HDD Rig - HDD Rig having 350 Ton pulling capacity.
- Drill Pipes - S-135 grade 6-5/8” drill pipes.
- 2 nos. Mud Pump - High Pressure 600 GPM capacity.
- 2 nos.Recycling Systems - 1000 GPM Capacity.
- Steering System - Paratrack.
- Slurry Pumps - Sykes/Godwin.
- Reamers - Ranging 24”, 30”, 36” 42”,48”,54”
Width of Yamuna River along the alignment is 570 Meters. After reviewing the Geotech Soil report which indicates soil strata under river bed consist of greyish fine sand with SPT field ‘N’ value ranging between 55 to 70 and soil erosion in river, Bore hole profile was designed to lay 36” pipeline at a depth of approximately 22 Meters below the Lowest Bed Level (LBL) of river.
PROFILE DESIGNING AND EXECUTION
Pilot Hole profile was designed to ensure minimum stresses on 36” pipeline and to minimize pull load as less as possible.
- Entry angle at Rig side 11.00 degree
- Exit angle at Pipe side 7.00 degree
- Radius of Curvature 1000.00 Meters
- Depth below river bed level 22.00 Meters
A smooth exit angle of 7 degree was designed to feed 36” pipeline gently into 48” reamed hole. Less exit angle also help in holding and handling of 36” pipeline easily.
All equipment and heavy machines, as required, were deployed on work site to start. Site setup was completed on 8.01.2015 and TESPL was ready to start pilot hole drilling. Unfortunately Work was stopped by landowners on 11.01.2015 demanding their previous dues and compensation from OWNER. The access road to Rig side was also blocked by landowners. After timely intervention and regular meetings of OWNER’s representative with Landowners, TESPL was able to start pilot drilling for 6” conduit pipeline on 08.10.2016.
Paratrack guidance system was used to check the bore hole profile. Surface coil was laid on ground to check the position of Bit. Since we have to drill in a very close proximity of existing and running 36” pipeline, special care was taken against magnetic interference from existing pipeline during pilot drilling. Even a small error in judging the position of bit mayhit live pipeline leading to huge damage of life and property.
Pilot hole drilling was completed on 27.10.2015 and 6” Conduit pipeline was successfully pulled and laid on 28.10.2015
EXECUTION FOR 36” PIPELINE
After successful pulling of 6” pipeline, HDD Rig was dismantled and repositioned in the alignment of 36” pipeline profile to start pilot hole drilling. Pilot hole drilling was started on 15.11.2015.
During the pilot hole drilling, the crew hit a zone of gravel and clay, but the majority of the bore was completed in sand as expected. The depth of the pilot bore reached 21.78 Meters as it passed under the river bed in order to maintain the required cover required by OWNER. One of the main concerns was keeping the bore hole open in the sandy soil. To help overcome this challenge TESPL worked with high performance high viscosity bentonite - drilling fluid that helped to keep the hole open
Since the length of crossing was long, it was decided to run casing pipes of app. 200m -12.75” OD over drill string to provide enough push force on bit to penetrate further.
Pilot hole drilling was successfully completed in 22 days on 6.12.2015
After Successful completion of Pilot Hole, lead pieces are taken off. The reaming will be done in 5 stages.
Pullback load and pipe stress analyses were performed for this alignment using the ASME B31.8 Pipelines Guidelines (ASCE, 2005). Based on the analysis of pullback loads and pipe stresses, 16” HDPE and 6” MS Pipe were determined to be suitable for the project for anti-buoyancy.
For Anti Buoyancy TESPL inserted 16”x 30mm Thickness of HDPE Pipes in 36” product pipes. 6” MS pipe was used for waterfilling in 36” Product Pipe. Inserting the HDPE pipe for anti-buoyancy helps in reducing the upward force on the pipeline while pulling and also minimizes the coating damage on the pipeline to be installed. The water was filled in annulus to bring the pulling loads to within 150 tons.
As a contingency measure TESPL mobilized its own designed, engineered & fabricated Pipe Thruster having 500 tons push force. A FIRST IN INDIA. The Pipe Thruster was mobilized at site keeping in view of the local hindrances from the landowners which we had faced during the entire execution of the HDD Crossing. The Pipe Thruster plays a key role in this installation of the pipeline where ever there is a hold during the pulling operation where initial additional force is required to move the pipe during the pulling operation.
After completion of reaming operations and readiness of product pipe in all respect pipe string was aligned with reamed hole and placed on the rollers to minimize pulling load during pull back operation. At pipe side pulling head was connected to the pulling assembly, comprising a barrel reamer, rotating swivel, Knuckle Joint and drill string.The product pipe had been laid out and welded into to a single length equal to the length of the crossing.
Once all connections were made, the pulling commenced. Pipeline coating was checked by Holiday detector before the pipeline enter into hole. Any damages on coating were attended immediately. As drill pipes were pulled and removed at the rig, the pipeline was advanced through the drilled hole.
TESPL had deployed experienced man power to lay the pipeline successfully and to overcome any huddle during pulling phase.
Due to problems in rig hydraulics the pulling was suspended for a period of 30hrs. 1600m of 36” OD pipe was already pulled at that time. After rig was repaired pulling commenced again but loa had increased than rig capacity. TESPL’s immediately started thrusting pipe from pipe side and gave a simultaneous push. The pipe started moving at a load of 220 tons from thruster and 200 tons from rig. After about 100m of pull the loads came within rig capacity and thruster operation was suspended. TESPL successfully installed 36”x2000 Meter Pipeline on 23.04.2016.
Apart from the 36” of large diameter pipeline and 2000 meters length of the pipeline, we have faced continuous ROW hindrances and the main challenge was to continue the pulling operation without any hindrance for the ROW issues for which GAIL India Limited has taken help of the local administration also during that period.
TESPL Progressively mobilized 350T Rig Spread with all Accessories as a standby rig. At Rig side rig setup works has come to complete halt. Local farmers have come to site in large groups and asked us not to do any activity on site and threatened us with dare consequences. They have permanently setup a tent on site and are sitting on Dharna and same had been covered by media also in the local newspapers. GAIL India reached an agreement with the land owners in June 2015 for their unpaid previous dues of year 2010 when the pipeline was installed and because of the monsoon the work could not be started in July and was planned to start in October after the monsoon.