Application of Soft-Torque Rotary Table in Mobile Bay

Abstract

She1 1 Offshore Inc. (SOI) has successfully installed and operated the Soft Torque Rotary System (STRS) f o r the f i r s t time on two d r i l l i n g rigs operating in Mobile Bay. Application of the STRS has significantly reduced torque fluctuations (up t o 8O%), torsional d r i l l string vibrations, and b i t slip-stick conditions. The STRS attenuates and interrupts the torsional oscillations of the d r i l l string and t h u s prevents the buildup of energy i n torsional waves that are reflected back and forth between the b i t and the rotary table. I t can be installed on any r i g equipped with an independent electronically driven rotary table or top drive. The STRS i s inexpensive (about $25M f o r Shell group companies), easy t o i n s t a l l , and has been a factor in improved dri 11 ing penetration rates realized on the SL 531 No. 3, a complex directional well drilled in the Mobile Bay area. Additionally, the STRS has been instrumental in avoiding expensive ($5MM-$lOMM) d r i l l string failures on the SL 531 No. 3. Further work needs t o be done t o f u l l y quantify the impact of the STRS on reducing these types of failures.

The control of drilling vibrations: A coupled PDE-ODE modeling approach

“…This system was developed by the Shell company in the early 1990s (Javanmardi and Gaspard, 1992). The STRS is a PI-like speed controller which involves a pair of gains κ i (drive stiffness in Nm/rad) and κ p (drive damping in Nms rad −1 ) that must be calculated according to the drillstring and BHA configuration.…”

A Systematic Approach to Performance Drilling in Hard Rock Environments

“…As torsional waves propagate along the drillstring, the 'soft' operating characteristic absorbs the energy and prevents the development of stick-slip (Halsey, et al, 1988;Sananikone, et al, 1992;Jansen, et al, 1995). The first STRS systems were introduced decades ago, and while some notable successes were achieved (Javanmardi, et al, 1992), the advent of alternating current (AC) top drives made the original implementations less effective. The operator has worked diligently with top drive manufacturers over the past two years to remedy this, and upgraded systems were introduced in the Haynesville.…”