1200 meters! XCMG horizontal directional drilling through Malaysia Gulf
XCMG once received a letter of thanks from the chairman of bras company in Malaysia: “this is one of the most important projects in the history of our company On behalf of bras, I would like to express my heartfelt thanks for your excellent work! ”
This letter of thanks is inseparable from XCMG XZ5000. XCMG XZ5000 has worked continuously for 500 hours without failure to complete the largest submarine cable crossing project in Malaysia.
The trenchless cable laying project in Malaysia crosses the mouth of Lumut Bay in Malaysia, laying a Φ 610mm pipeline, with a horizontal distance of 1250m and a crossing depth of 26m below sea level. Due to the disorderly distribution of sand and silt and complex geological conditions in this area, the construction company selected XCMG xz5000 horizontal directional drilling rig for construction.
2 Drilling tool configuration
168 and 140 drill rods and 172 mud motors are used for guiding drilling. When reaming, use the combination of Φ 450mm ~ Φ 900mm cutting type and barrel type reamer for construction.
Guiding: double casing is used for guiding drilling. Firstly, 16 inch casing is used to isolate weak formation and seawater penetration in the soil forming section. Then, the pilot drilling is conducted to the near horizontal position according to the design curve, and the 12 inch casing is pushed through the 16 inch casing along the drill pipe until it is close to the horizontal position. After the completion of casing running, continue to drill according to the designed trajectory until the bit is unearthed. Reaming: the combination of cutting type and barrel type reamer is adopted for reaming. The cutting type reamer is divided into four levels: Φ 450mm, Φ 600mm, Φ 750mm and Φ 900mm. The outer diameter of the combined barrel reamer is slightly smaller than 50mm.
Pull back: the front end of the pipe is connected with a Φ 700mm barrel reamer. Due to the limitation of pipeline layout site, the pipeline needs to be towed back in five sections, and four times of welding is required during the period.
4 key issues
Double casing auxiliary measures are used in guiding drilling in complex formation. The 16 inch casing is mainly used to isolate the complex stratum and sea water in the soil section. Small casing is mainly used to limit the bending space of drill pipe and prevent drill pipe fracture. High power drilling rigs such as xz5000 can usually use the power head to drive the casing to rotate.
At the same time, the combination of two specifications of drill pipe: 140 drill pipe in front, easy to improve the deviation efficiency; 168 drill pipe in the back, to ensure the strength of the bending section of the drill pipe, to prevent drill pipe fracture accident.
Mud preparation scheme for hdd drilling
Since the project is constructed by the sea, the formation contains a lot of calcium and magnesium plasma components, so the mud additive needs soda ash and caustic soda to remove calcium and magnesium ions from seawater; at the same time, due to the interlacing of sand layer and silt layer, the formation stability is poor, so the mud additive also needs positive electric glue and wall protection agent to facilitate hole formation and protect hole wall, and the viscosity of pumped mud is not less than 50s.
Pipeline section pull back in this trenchless project
When horizontal directional drilling is used in common engineering construction, the pipeline should be pulled back at one time as much as possible. If the pipeline is pulled back in sections, the construction risk will be increased, especially when the formation is complex and the mud performance is not ideal, it is easy to cause pipe collapse accident.
However, in the face of a river of more than 1200 meters, the construction company can only choose to pull back in sections, which has a very high requirement for equipment performance parameters and technology.
The pipeline backhauling is divided into five sections and needs to be welded for four times. In order to ensure the construction safety, during the welding period, the mud is pumped into the hole every 20 ~ 30 minutes, so that the drilling hole is always filled with mud with good performance, effectively preventing the occurrence of hole collapse.
5 case summary
(1) When combined with cutting reamer and barrel reamer, the diameter of barrel reamer is usually 50 ~ 150 mm smaller than that of cutting type.
(2) When mud motor is used in soil layer, it is recommended to use special motor with light weight and centralization, so as to obtain better deflecting performance.
(3) It is recommended to complete the pipeline pullback at one time. When it is necessary to pull back in sections, the hole should be filled with mud, and the mud performance should be reliable to prevent pipe collapse.