Horizontal directional drilling (HDD) becomes as a favorite crossing method in many situations for the installation of oil and gas pipelines as well as other utilities and transposition of obstacles. In all cases it is necessary to ensure the quality of pipeline design and construction/installation. The quality level of HDD section should required using the same criteria involving the entire pipeline project or other segment of the pipeline standard.
Horizontal Directional Drilling equipment, for shore approach crossing, furnished by Drilling Company shall include the following components:
- Horizontal Drilling Rig Unit with tensile and torque capacity adequate to crossing length (minimum 200ton), geotechnical conditions and pipe size.
- Control Cab Power Unit.
- Water Pump.
- Slurry Pump.
- Slurry Mixing Tank.
- Mud Recycling System (capacity in pressure and volume).
- Drill Pipe.
- Bentonite Storage.
- Water Storage.
- Clean Mud Storage.
- Dirt Mud Storage.
- Power Generators.
- Downhole survey system.
- Downhole drilling tools.
- Instrumentation sufficient to accurately locate the pilot hole, measure drilling fluid discharge rate and pressure, and measure drill string axial and torsional loads.
- Tanks, cranes and all ancillary support systems.
HDD Operational Procedures
Prior to start of work the Drilling Company shall prepare a written installation procedure for the owner review and approval. The crossing installation procedure shall consider possible interference with the prelaid pipelines installed by others. The Drilling Company shall install proper buoys to define the real pre-laid pipeline and structures position. The crossing installation procedures shall include the following:
- Site plan including location, general layout (equipment, material, support services), in scale and with dimensions.
- Description of HDD rig and ancillary equipment including model, date of manufacture, and specification with capacities and ratings.
- Proposed drill path showing the different soil layers with radius of curvature along the entire path.
- Coordinates and angles of the entry and the exit points.
- Type and amount of drilling mud and additives with the mud pressures anticipated during the installation.
- Drilling process including the pilot hole, surveying, reaming, swabbing, pullback, borehole maintenance, downhole tools, drilling and reaming rates, torque, etc.
- Contingency procedures in case of failure/mistake of one operation.
- Procedure for calibrating the surveys equipment in accordance to the owner references.
- Pre-survey of the subsea area required for pulling operations to assess potential interference of the pipeline to all potential subsea hazards.
- Description of the vessel and equipment required to pull back operations.
- Layout of the vessel-mooring anchors showing the actions taken to avoid interference with the existing seabed structures and pipelines.
- Buoyancy control during pull back operation.
- Detail procedure for the connection pipeline/drill pipe operation.
- Pulling forces and pulling rate during pullback.
- Downhole survey system to determine the horizontal and vertical coordinates along the drilling hole.
- Environmental protection plan, including soil erosion and sediment control devices, water and drilling fluid treatment equipment, waste disposal, and work site restoration.
- Safety and Quality Assurance plan.