Dynamics of Drilling Systems With an Antistall Tool: Effect on Rate of Penetration and Mechanical Specific Energy

Abstract

Summary This paper considers the effect of an antistall tool on the dynamics of deep drilling systems. Field results show that the antistall tool increased the rate of penetration (ROP) of drilling systems when compared with ROP in offset wells drilled without this tool. We developed a model–based approach to investigate the effect of this downhole tool on the ROP and on the mechanical specific energy. Toward this, a drillstring model including the antistall tool was constructed; it describes the coupled axial/torsional dynamics in the form of delay differential equations. Simulation results and a dynamic analysis based on averaging the obtained steady–state response show that an increased drilling efficiency was obtained using the antistall tool, resulting in a higher ROP.

Predictive Model of a Mole-Type Burrowing Robot for Lunar Subsurface Exploration

“…The autonomous burrowing robot is assumed to be a rigid cylindrical rod, because it is relatively stiffer than the lunar regolith. This type of assumption is widely accepted in the geotechnical field [33,44,45]. The fundamental problem is actually simplified as the dynamic interaction of the rigid rod with the elastic response of lunar regolith.…”

Internal mechanics of anti stick–slip tool

“…The parameters are used to model the ASST are taken from [19], which are close to the working range values. The parameters values used for the numerical simulations are given in the Table 2.…”

“…So far only limited attempts have been made to describe such systems (see e.g. [19]) and a further work is needed to attain fundamental and practical insights. In this study, the background to ASSTs is given and the new mathematical model is proposed.…”

“…A couple of attempts have been made to model a downhole drilling with an ASST in [19,48], where a torsional pendulum model with a motion constraint converting rotational displacement into axial displacement were used. These studies considered an ASST incorporated into a drill-string without a detailed modelling of an ASST itself, which has very nonlinear nature.…”

Feedback control method to suppress stick-slip in drill-strings featuring delay and actuation constraints

“…A number of strategies aimed at mitigating stickslip oscillations have been reported in the literature. The company Tomax patented their unique AST (Anti-Stall Tool) [25,26] which tackles the stick-slip problem from that of a mechanical design perspective. The control input to the drill-string itself, whether it be toptorque, WOB or top-drive rpm, acts as other potential control parameters for the prevention of stick-slip.…”