The existence of Hight Frequency Torsional Oscillations or HFTO in drilling operations have been revealed from faster sampling of shock and vibrations downhole. No drilling vibration mitigation technology has shown better ability to mitigate HFTO than the Tomax Anti Stick-Slip Tool.
Both testing and mathematical modelling show how the HFTO is triggered by the event where the drilling bit overcomes static torque and breaks free from standstill after a stall. (Illustration). The accumulated energy at this point is far beyond requirement to turn the string. The result is excessive vibration in the torsional direction, typically dictated by the torsional stiffness of the Bottom Hole Assembly (BHA).
The control algorithm of the Tomax Anti Stick-Slip Tool (AST) balances the force on the cutters to drill more rock using less energy. That means faster speed and less wear. The same algorithm prevents energetic torsional vibrations, known as stick-slip, with unparalleled efficiency. These are the same energetic stick-slip cycles that are now proven to be the driving force behind the recently discovered High Frequency Torsional Oscillations (HFTO).
HFTO is like no other vibration phenomena linked to downhole tool damage. Effective stick-slip prevention will choke the HFTO phenomenon and render it harmless. The AST’s inherent ability to remove the root cause of HFTO is probably the main reason for Tomax’ reputation for limiting tool damage.
Positive Displacement Motors have their elastomer stator life determined by the accumulative number of stalls, whether full stalls or hard-to-record micro-stalls resulting from HFTO. The AST provides effective prevention of all PDM stalls and, since its introduction, has proven capable of significantly extending PDM stator life and thus drilled footage.
The downhole regulator function of the AST delivers three sources of savings: faster ROP, less damage and more footage. This makes the AST a great choice for business improvement. The AST gains are visible to the driller as well as on the bottom line. These multiple sources of savings have given the Tomax AST a strong market position, with continuous growth.