An investigation of the stress-strain behaviour of a GRE cylindrical structure used for a drilling-with-casing application and its influence on torsional vibrations

An investigation of the stress-strain behaviour of a GRE cylindrical structure used for a drilling-with-casing application and its influence on torsional vibrations

Van der Poll, J.W.

Bakker, T. (mentor)
Nagelhout, A. (mentor)
Fernandez Villegas, I. (mentor)
Burnaby Lautier, E. (mentor)

Civil Engineering and Geosciences

Section Petroleum Engineering

2010-07-09

For the geothermal wells of the Delft Aardwarmte Project it has been chosen to drill with glass-reinforced epoxy (GRE) composite casing in a drilling-with-casing setup. This MSc thesis report describes the results of experimental work to assess the stress-strain behaviour of GRE casing, in particular under axial, torsional and combined axial-torsional loading. These properties have subsequently been used to assess the effects of using GRE casing on standard drilling properties such as the stretch and twist of the drilling tubulars, and the effect on torsional vibrations. The following conclusions can be drawn: 1. For axial loads (in tension) up to 33% of the expected maximum drilling loads: a. No evidence was found of non-linear behavior. b. The measured elasticity modulus is 1.91*1010 N/m², which corresponds closely to the manufacturer’s data. c. The maximum expected elongation of a GRE casing string of 3300 m used for drilling-with-casing is 1.66 m, which is 0.06 m more than that of a steel drill pipe under similar drilling conditions.. 2. For torsional loads up to 98 % of the expected maximum drilling loads: a. The stress-strain behaviour in the tangential direction remains linear. b. The shear modulus measured is deemed incorrect due to the mechanical properties of the test bench. The shear modulus as reported by the manufacturer is 6.78*109N/m2. c. The maximum expected twist in a GRE casing string of 3300 m used for drilling-with-casing is 9.25 turns which is 6.3 turns more than that of a steel drill pipe under similar drilling conditions. d. The natural frequency in torsional vibration of a GRE casing is much lower than that of a steel casing in a comparable drilling setup due to its much lower torsional stiffness. However the large diameter of casing, as compared to conventional drill pipe, results in an increase in torsional stiffness. The combined effect is an increased natural frequency of GRE casing compared to steel drill pipe. e. As a result, the critical rotary speed, i.e the rotary speed below which one can expect the occurrence of stick-slip torsional vibrations, is lower for GRE casing than for steel drilling pipe under similar drilling conditions, i.e. the effect is beneficial. 3. Under increasing axial tension the torsional stress-strain behaviour displays an increasing hysteresis. a. The torsional dampening, expressed as energy loss per loading/unloading cycle ranges from xx% to xx%. This is much higher than the typical internal torsional damping in steel drill pipe. b. The typical external torsional dampening caused by fluid drag and borehole friction while drilling is in the order of 50%. The effect of internal damping caused by hysteresis during torsional loading of GRE casing is therefore noticeable, and results in a further beneficial decrease in the critical rotary speed for stick-slip torsional vibrations.

Composite Drilling Torsional Vibrations

http://resolver.tudelft.nl/uuid:65ab1a5e-1d5c-440c-ba45-dd291799a31d

2010-09-17

Student theses

master thesis

(c) 2010 Van der Poll, J.W.