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Among the many types of downhole vibrations, lateral vibration, axial vibration, stick-slip vibration, and high-frequency vibration are known as the 'four major types' most prone to causing failures. They either occur individually or in combination - lateral vibration wears out drilling tools, axial vibration cracks drill bits, high-frequency vibration accelerates equipment aging, and stick-slip vibration directly slows down drilling efficiency.
1.Lateral Vibration (Radial Vibration): The 'Swaying' Crisis of Drill String
Key Features: The drill string reciprocates in the direction perpendicular to its axis, similar to 'the shaking of a skipping rope'. The vibration direction is mostly horizontal or inclined, often accompanied by collision sounds between the drill string and the wellbore wall.
Main Causes:
★Uneven clearance between drill pipe and wellbore wall, leading to unbalanced bit force during hard formation drilling;
★ Insufficient rigidity of the bottom hole assembly (BHA), causing excessive flexibility of drill pipes in deep wells and prone to lateral bending;
★ Unreasonable stabilizer spacing, failing to effectively constrain the radial displacement of the drill string.
★Typical Risks: Drill pipe thread wear, joint fracture, wellbore wall enlargement due to collision, and in severe cases, 'keyseat sticking' (grooves worn on the wellbore wall due to long-term drill string swaying).
2.Axial Vibration: The 'Up-Down Bounce' Impact of Drill String
Key Features: The drill string reciprocates axially, similar to 'the extension and contraction of a spring'. The vibration amplitude ranges from a few millimeters to tens of millimeters, often accompanied by sudden fluctuations in weight-on-bit (WOB).
Main Causes:
★ Sudden force change when the bit cuts through hard interlayers, generating upward reaction impact force;
★ Unstable mud pulse pressure, causing periodic axial impact on the drill string;
★ Excessive WOB setting, leading to repeated bouncing when the bit fails to cut through the rock.
Typical Risks: Roller cone bit gear ring cracking, PDC bit cutting element loss, drill collar fatigue fracture, and even borehole trajectory deviation.
At present, Liuhe has integrated downhole lateral and axial vibration monitoring as a key function into core products such as engineering parameter tools and near-bit azimuth gamma tools. It enables real-time transmission of downhole vibration data. Referring to vibration standards of foreign counterparts, the lateral vibration peak shall not exceed 30g, and the axial vibration peak shall not exceed 15g. If monitored data exceeds this safety threshold, immediate intervention (e.g., optimizing WOB and rotational speed) shall be taken to effectively reduce vibration levels, avoid premature failure of downhole tools and drilling risks, and ensure operational safety and efficiency.
3.Slip-Stick Vibration: The 'Stall-Surge' Vicious Cycle of the Bit
Key Features: The bit periodically 'stalls→suddenly surges', similar to 'the rotation of a rusty hinge'. Torque and rotational speed show 'serrated fluctuations', which is common in directional and horizontal wells.
Main Causes:
☆ Static friction between bit and rock exceeds dynamic friction: when cutting resistance suddenly increases, the bit stalls, and torque is released instantaneously once reaching the critical point;
☆ Excessive WOB and low rotational speed, causing the bit to 'penetrate too deeply' in hard formations and fail to cut continuously;
☆ Poor mud lubricity, leading to cumulative frictional resistance between drill string and wellbore wall.
Typical Risks: 'Cracking wear' of bit cutting elements, drill pipe fracture due to instantaneous torque overload, significant reduction in rate of penetration (ROP) (up to over 50% in some cases), and even helical wellbore enlargement.
Liuhe’s downhole slip-stick and vibration sub, developed for MWD (Measurement While Drilling) systems, has been officially put into market application. This tool can accurately measure, analyze, and record key parameters such as downhole vibration and slip-stick levels, and achieve real-time data transmission. It effectively evaluates drilling safety and provides real-time alerts for conditions that may damage MWD and other downhole tools. By timely adjusting drilling parameters, it ensures downhole safety while maximizing drilling efficiency. In the next step, we plan to integrate slip-stick vibration monitoring into near-bit products to further enhance drill string safety and overall drilling efficiency.
4.High-frequency Vibration: The 'Invisible Accelerator of Equipment Aging'
Core Features: Vibration frequency exceeds 100Hz, invisible to the naked eye but accurately captured by instruments, similar to the 'high-frequency tremor of a mobile phone's vibration mode'. It features long duration and concentrated energy.
Main Causes:
☆ High-frequency friction between bit cutters and hard rock, such as when drilling through chert nodules;
☆ Fluid pulsation caused by wear of mud pump valves, with frequency related to pump speed multiples;
☆ Dynamic balance failure of rotating components (e.g., downhole positive displacement motors, bit bearings), leading to resonance with the wellbore during high-speed operation.
Typical Risks: Sensor malfunction, damage to electronic logging tools, 'accelerated fatigue' of drilling tool materials (high-frequency vibration causes micro-cracks inside metals), and equipment lifespan reduced by over 30%.
Currently, Liuhe's Pangolin Cross-screw Rotary Steerable System is equipped with a high-frequency torsional vibration measurement function. Relying on intelligent closed-loop control technology, this function can actively suppress issues such as stick-slip during drilling. It not only reduces drilling tool wear and avoids safety risks but also effectively improves the rate of penetration (ROP), providing critical support for the efficiency and safety of drilling operations.
High-frequency torsional vibration; the 'Four Key Challenges' of downhole vibration are critical obstacles to drilling safety, efficiency, and cost. Liuhe has successfully deployed monitoring product lines for lateral, longitudinal, and stick-slip vibrations, and has prioritized high-frequency vibration measurement as the R&D focus of next-generation technology. By building a complete technology chain from precise sensing, real-time warning to intelligent control, the company is committed to providing comprehensive vibration solutions for customers, continuously supporting cost reduction and efficiency improvement in drilling operations through innovative technologies.
