Thesis (M.S.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains x, 71 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 64-68).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 150-164).

M.Ing. / In the drilling process, the majority of hole inaccuracies can be corrected with the use of secondary hole operations. Hole location errors cannot be corrected as their magnitude is determined at the beginning of penetration of the drill point into the material. This thesis investigates the influence of the drill bending stiffness on the hole location error when drilling with ordinary twist drills. Infrared sensors were developed for the drill point location measurements, the initial wandering of the drill and the final hole location error. Also investigations were made into the on-line monitoring of the drilling process using acoustic emission in the audio range. The acoustic signal was transformed to the frequency domain and related to the torque and the thrust magnitudes. The relationships in the acoustic emission, torque and thrust and chip formation between drilling low carbon steel and aluminium were determined.

This thesis has been motivated by the need to construct reliable, experimentally callibrated models of the drill-string assembly, that capture important phenomena associated with the drilling process, such as torsional oscillations, stick-slip and whirling. This can be achieved using a continuous finite element model, as well as low-dimensional torsional pendulum models in limited cases. The importance of this work lies in the fact, that the experimental rig utilizes real industrial drillbits and rock samples, which after careful identification of TOB speed curves, allows to use an equivalent friction model to accommodate for both frictional and cutting components of the bit-rock interactions. As a first step, a preliminary calibration of the FE model for a straight configuration of the drill-string is carried out, that allows to utilize the low-dimensional model to replicate behaviour of the system. In both of these cases, the agreement between experiments and modelling is achieved. Based on these preliminary studies, it is possible to verify the model in a prebuckled drill-string configuration, for which case a qualitative as well as quantitative agreement with the experiment is obtained. This allows to identify regions where the most dangerous phenomenon of stick-slip is present in parameter space of WOB and top angular speed. Next, the analysis is focused on the whirling phenomenon and calibration of the reduced order rotor model to replicate the motion of the BHA in the bore-hole. A qualitative agreement with the experiments is obtained. An interesting phenomenon of co-existing forward and backward periodic whirling solutions are observed both experimentally and numerically. The influence of the initial conditions and the friction between the BHA and the borehole are investigated, what revealed that there is a threshold value of friction coefficient for which the whirling direction changes from forward to backward.

published_or_final_version / abstract / Civil Engineering / Doctoral / Doctor of Philosophy

No description available.

Air drilling is limited to competent formations that are essentially dry. In these circumstances large shale fragments are often observed and it is believed that these large shale fragments are not from the cutting action of drill bit at the bottom of the hole but from caving in, or sloughing of the wellbore wall. This type of wellbore instability problems may occur when drilling formations have significant amounts of water-sensitive clays. Change in shale water content due to water dehydration induces additional rock stresses near the wellbore, which can destabilize the borehole. The primary cause of this problem may well relate to moisture movement. Because as air is often used as the drilling fluid, the water in exposed pores will start to evaporate into the borehole, so that the water content is reduced. This results in the development of different stress patterns and the shale fractures and falls into the wellbore. The work of this thesis simulates the shrinkage and the consequent cracking pattern. A model of a bonded granular material is created and its properties confirm it to be that of a brittle, isotropic elastic solid. Crack growth is simulated by sequentially removing the most highly stressed bond in turn. A number of different geometries are simulated and the influence of stochastic bond strength on the cracking pattern is investigated. The model results show that cracking pattern produced in the simulations is consistent with the ‘blocky’ debris sometimes seen during air drilling and so the recommendation is made that air used for drilling should be sufficiently humid to avoid the dehydration of the shale.

M.Ing. / Please refer to full text to view abstract

M.Ing. / This dissertation provides a review of the most notable papers published with regard to the specific performance characteristics of Tunnel Boring Machines (TBM's) during the past twenty years. It is a literature study of a Bibliography of 57 publications, which were screened from an original list of 970 documents ...

A Thesis Submitted to the Faculty of Engineering University of Witwatersrand, Johannesburg for the Degree of Doctor of Philosophy. Johannesburg 1977 / No abstract