XuGong XZ5000 Works Non-Stop for 500 Hours to Complete Malaysia’s Largest Subsea Cable Crossing Project
1. Project Overview
The Malaysian cable non-excavation laying project crosses the Lumut Bay estuary in Malaysia, laying a Φ610mm pipe with a construction horizontal distance of 1250m and a crossing depth of 26m below sea level. Due to the chaotic distribution of sand and silt in the area and the complex geological conditions, the construction party chose the XuGong XZ5000 horizontal directional drilling rig for construction.
2. Drilling Equipment Configuration
The project uses 168, 140 drilling rods, equipped with a 172 mud motor for directional drilling. For hole expansion, a combination of Φ450mm to Φ900mm cutting and bucket-type hole expanders is used for construction.
3. Construction Technology
Directional Drilling: Directional drilling is assisted by double casing. Primero, a 16-inch casing is used to isolate the weak strata and seawater seepage of the soil entry inclination section. Then, according to the designed curve, directional drilling is carried out to approach the horizontal position, pushing the 12-inch casing along the drilling rod through the 16-inch casing, and continuing until close to the horizontal position. After the casing is lowered, continue drilling according to the designed trajectory until the drill bit emerges from the ground.
Hole Expansion: Hole expansion is carried out using a combination of cutting and bucket-type hole expanders. The cutting-type hole expanders are divided into four levels: Φ450mm, Φ600mm, Φ750mm, Φ900mm, with the outer diameter of the bucket-type hole expanders used in combination being slightly smaller by 50mm.
Pipe Pulling: During pipe pulling, the front end of the pipe is connected to a Φ700mm bucket-type hole expander. Due to the limited layout of the pipe, the pipe needs to be pulled back in five sections, requiring four weldings.
4. Directional Drilling in Complex Formations
The double casing assistance measures, where the 16-inch large casing is mainly used to isolate the complex strata and seawater at the soil entry section, and the small casing is mainly used to limit the bending space of the drilling rod to prevent the drilling rod from breaking. Large drilling rigs can usually use the power head to drive the casing to rotate and advance.
Al mismo tiempo, two specifications of drilling rods are used in combination: 140 drilling rods in front to improve the inclination efficiency; 168 drilling rods behind to ensure the strength of the bending section of the drilling rod and prevent accidents of drilling rod breakage.
Mud Preparation Plan
Since the project is constructed by the sea, the strata contain more calcium, magnesium, and other ionic components, so the mud additives require pure alkali and caustic soda to remove calcium and magnesium ions from seawater. Al mismo tiempo, because the strata are interlaced with sand layers and silt layers, the strata stability is poor, so the mud additives also need positive electrostatic glue and wall protection agents to facilitate hole formation and protect the hole wall, with the pumped mud viscosity not less than 50S.
Pipe Segmented Pulling
In ordinary engineering construction, the pipe is尽可能 completed in one pull back. If the pipe is pulled back in segments, it will increase the risk of construction, especially when the strata are complex and the mud performance is not ideal, it is easy to cause hole collapse and pipe clamping accidents.
Sin embargo, facing more than 1200 meters of rivers, the construction party can only choose to pull back in segments, which requires very high requirements for equipment performance parameters and technological methods.
This pipe pulling is divided into five sections, requiring four weldings. To ensure construction safety, during welding, mud is pumped into the hole every 20-30 minutes to keep the drill hole always full of high-quality mud, effectively preventing the occurrence of hole collapse accidents.
