The "Golden Three Checks" Before Equipment Startup
Operating a full-hydraulic drilling rig is akin to driving an off-road vehicle: the greater the power, the greater the need for caution. Before every startup, you must complete the following steps:
Hydraulic System Inspection: Check that the oil level in the reservoir is aligned with the centerline of the sight glass, and inspect all pipeline connections for any signs of leakage.
Power Unit Test: Run the unit under no-load conditions for 3 minutes, observing the pressure gauge to ensure it remains stable within the 1.5–2 MPa range.
Drill String Verification: Apply specialized lubricant to all threaded connections, and verify that the verticality deviation of the drive rod is less than 0.5°.
The Nuances of Drilling Control
The essence of operating a wireline coring rig lies in a technique best described as "gentle yet firm":
Initial Penetration: When first entering the rock formation, employ a "light pressure, slow rotation" mode, applying a thrust of 5–8 kN with a rotational speed controlled between 150–200 rpm.
Stable Drilling Phase: Adjust parameters according to the rock lithology; for granite, apply 15 kN of thrust at 400 rpm, whereas for shale, reduce the thrust to 10 kN.
Detecting Formation Changes: Sudden fluctuations in the pressure gauge readings or abnormal rotational speeds often serve as critical indicators that the drill bit is transitioning into a different rock layer.
The Art of Core Extraction
The core extraction process demands the precision and finesse of a surgical procedure-it must be executed cleanly and decisively:
Determining Core-Up Point: When the drilling depth reaches 90% of the length of a single drill rod, halt the feed mechanism and rotate the drill string backward (counter-clockwise) for 2–3 turns.
Deploying the Core Lifter: Slowly lower the core lifter through the inner bore of the drill string, taking care to avoid contact with the borehole walls, which could lead to the drill string becoming stuck.
Core Separation: When hoisting the drill string, maintain a steady upward speed of 0.5 m/s; immediately halt the hoisting motion upon hearing a distinct "click" sound to prevent the rock core from fracturing.
