Real-Time Drill Bit Wear Prediction by Combining Rock Energy and Drilling Strength Concepts


A central element to reduce drilling cost is to improve drilling operation by analyzing real-time data. Developing advanced real-time analysis tools is one way to improve the drilling operation. Two approaches which currently are used for optimizing the actual rotary drilling process are mechanical specific energy and inverted rate of penetration models. The mechanical specific energy method is defined as the work needed to destroy a given volume of the rock. It can act as a tool during the drilling operation to detect changes in drilling efficiency thus providing a method to optimize the drilling parameters to enhance instatanious rate of penetration. Rate of penetration models, on the other hand, can be used to calculate formation drillability considering the effects of drilling parameters, bits design and bit wear. Drilling optimization using rate of penetration models is done by changing the drilling parameters and/or bit design to find the optimum drilling scenario for an entire bit run. The mechanical specific energy log and the drillability ratio differ when mud weight is changed and when bits are worn. These two differences are due the fact that mechanical specific energy does not include bit wear as well as the effect of changing mud weight. By combining these methods and modifying the mechanical specific energy equations to incorporate these effects and the mechanical specific energy can be used as a real-time trending tool for bit wear estimations. In this analysis, wells from offshore Middle East and onshore North America are analyzed. The field results are very encouraging in that the bit wear for both roller cone and PDC bits can be predicted. The field validation of this new approach shows that the supplementary information on the bit wear status can in some cases benefit in the decision of when to pull the bit while it still is in the hole and thereby possibly improve overall economics of the drilling operation.

Meeting Name

13th Abu Dhabi International Petroleum Exhibition and Conference (2008: Nov. 3-6, Abu Dhabi, United Arab Emirates)


Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Drillability; Drilling Cost; Drilling Efficiency; Drilling Operation; Drilling Optimization; Drilling Parameters; Field Validation; Formation Drillability; Mechanical Specific Energies; Middle East; Mud Weights; New Approaches; PDC Bit; Rate Of Penetration; Real-Time Analysis Tools; Real-Time Data; Rotary Drilling; Supplementary Information; Wear Estimation; Wear Prediction; Bits; Offshore Oil Wells; Optimization; Superconducting Tapes; Rock Drilling

International Standard Book Number (ISBN)


Document Type

Article - Conference proceedings

Document Version


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© 2008 Society of Petroleum Engineers (SPE), All rights reserved.

Publication Date

01 Nov 2008