Method of Optimizing Motor and Bit Performance for Maximum ROP


Downhole motors are widely used to drill vertical, directional and horizontal wells in conjunction with Polycrystalline Diamond Compact (PDC) bits. When a bent housing Positive Displacement Motor (PDM) is oriented for slide drilling to manipulate a well's trajectory, the drill string does not rotate. Consequently, the rate of penetration (ROP) typically decreases. It is therefore important to optimize bottomhole assembly (BHA) performance in conjunction with PDC drill bits. This paper discusses how motor performance data, coupled with an ROP model, can predict the optimal weight-on-bit (WOB) required to derive maximum ROP for a given section of a hole to be drilled. This approach solves the ROP model and determines the ideal WOB with respect to any restrictions that PDM performance equations apply on it. Bit wear is included in the ROP model and an analysis is performed to optimize a given interval of wellbore. The optimization approach is illustrated with two examples for different formation types and one field case comparing the performance of two motors with PDC bits. The optimum WOB, maximum average ROP and differential pressure values are the outputs from the analysis. This analytical approach can be used to determine the optimum PDM/PDC bit combination to achieve maximum ROP through a wide range of operational conditions.


Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Analytical Approach; Bottomhole Assembly; Differential Pressures; Downhole; Drill Strings; Motor Performance; Operational Conditions; Optimal Weight; Optimization Approach; PDC Bit; Polycrystalline Diamond Compact Bits; Positive Displacement Motors; Rate Of Penetration; Two-Motor; Wellbore; Bits; Diamond Drilling; Horizontal Wells; Oil Wells; Respirators; Well Drilling; Motors

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version


File Type





© 2009 Canadian Institute of Mining, All rights reserved.

Publication Date

01 Jun 2009