Enhanced Rig Classification System: Impact and Limitations of Torque and Drag, Buckling, and Hydraulics on the Drilling Envelope

Research output: ResearchMaster's Thesis


With the constant development of new generations of drilling rigs, the market for available types of rigs becomes more varied. Additionally, after a severe oil price drop—as is experienced now—many, especially smaller-sized, land-based rigs, are free to be rented. As these rigs have no sophisticated universal classification, it is nearly impossible to select the correct rig for the specific job. Further, decisions which are solely based on hookload or horsepower often result in selecting (costly) over-sized rigs. As part of the theoretical background, the conventional and additional use of drilling envelopes is discussed. Further, various physical concepts and models are reviewed within the topics of torque and drag (including buckling) and drilling hydraulics. Furthermore, drilling problems related to both topics are examined. In order to determine the drilling envelope of a specific drilling rig—described by true vertical depth (TVD) and departure—simulation software is used. The application is written in MATLAB and is designed to easily enter input data. Moreover, the code is optimized to give accurate results, using the models stated in the theoretical background, and at the same time, be most time-effective. In addition, a new and enhanced rig classification is presented. Similar to bit and pumpjack classifications, it consists of a four-character code. A symbol, thereby, denotes rig’s constructional design, while stand capacity, and TVD and departure ratings are expressed as three digits. True vertical depth and departure ratings are derived from simulations using the created software and a set of fixed input parameters known as the standard case. Lastly, several case studies exemplify the application’s workflow and derivation of the rig code. Additionally, these case studies illustrate further purposes of the software.


Original languageEnglish
Award date18 Dec 2015
StatePublished - 2015