One of the most significant aspects in the drilling operation is to reduce the non-productive time and to avoid borehole instability issues. In order to cater to these occurrences, one has to understand the formation properties, fluid hydraulics, and the basic mechanics behind drilling a well. In previous research, the factors that were widely discussed and results obtained were related to formation properties. However, while considering the stresses in the wellbore, mechanical factors such as the RPM and contact of casing at different positions in wellbore have been usually neglected. In furtherance to this study, the importance of thermal condition cannot be out ruled. This work presents the numerical analysis of influence of casing contact and down hole thermal conditions using FEA.
The classical equations used to obtain the wellbore stresses include very few parameters like the far-field stresses and wellbore geometry. They do not consider the influence of casing contact while drilling, mud-cake permeability, elastic, and inelastic properties of the formation. To take into account the effects of these parameters, FEA is carried out considering the above mentioned parameters in various scenarios. The main objective of these simulations is to investigate the hypothesis of the increase in hoop stress when the casing contact with regard to formation stresses orientations. The study of different cases shows the variation of a few hundred psi of hoop stress. To see the thermal effect, a thermo-elastic model is developed and it was found that there is a decrease in radial stress and hoop stress in near wellbore region with time. This reduction will have a considerable effect on fracture initiation in the vicinity of borehole wall. Also, smearing effect will be influenced by stress changes due to change in temperature. Combining both phenomena will give a better picture for smearing effect.
|Commitee:||Boukadi, Fathi, Guo, Boyun|
|School:||University of Louisiana at Lafayette|
|School Location:||United States -- Louisiana|
|Source:||MAI 55/03M(E), Masters Abstracts International|
|Subjects:||Engineering, Petroleum engineering|
|Keywords:||Casing drilling, Contact forces, Filter cake, Smearing effect|
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