This paper will discuss the engineering process used to redesign the polycrystalline diamond cutter (PDC) and roller cone cutting structures of a Hybrid Bit in the challenging Foothills application of Colombia. The primary challenge to drill 14 3/4" section in Colombia foothills is high torque values its oscillations and vibration that produce premature damage of the PDC bits; specially while drilling Carbonera C5 formation, which has a very high abrasiveness and compressive strength (25 Ksi UCS). In addition to the traditional post-drilling analysis of the bit design, the use of an advanced polygonal mesh drilling simulation software in combination with laboratory test will be described as a key element to maximize the durability of the bit. This step of the process allows for the first-time an integrated analysis of the PDC/roller cone cutting structures all together. Analysis of the engagement balance along with the calculation of forces applied to the various cutting structure components, ultimately resulting in an improved optimization of bit performance beyond the common scenario considering the use of 4-5 PDC bits for the whole section.

A computational model, using a polygonal mesh simulation was developed for getting a deeper understanding of the PDC and roller cone interaction in the cutting structure of a hybrid drill bit; afterwards, this simulation software was calibrated with data from pressurized tests obtained in a drilling lab. Improvements of the bit cutting structure started with the ability to correlate the dull condition of the bit under several conditions of torque on bit (TOB), weight on bit (WOB) distribution and Depth of Cut (DOC). This, in turn, guided the bit design changes which were then validated by running the new design through the same simulation and achieving desirable results.

The optimized hybrid drill bit sets a footage record in the Foothills area drilling 50% further than standard PDC bits and achieving 39% more ROP than the previous hybrid bit design in offset wells. In addition to ROP and durability improvements, the original bearing – seal life was improved from 50% to 100% of effectiveness with the new design for this application in this hole size. The new design features optimized the depth of cut (DOC), the weight distribution across the cutting structure and increased stability and efficiency as well. Thus, overcoming the challenge to drill further and more efficiently through these challenging formations.

A specialized team has for the first-time optimized Roller cone structure and PDC structure together improving bottomhole drilling dynamics, performance and bit reliability for this application through the combination of robust polygonal mesh simulations of the drilling process and pressurized rock drilling tests in a drilling lab.

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