ARMA 12-241 Title: New Approach in Mechanical Modeling of Inserts of the Rollercone Bits

摘要

It has been well understood that the inserts or cutters on the cones of a rollercone bit directly interact with the rock at the bottom of the hole. Therefore, mechanical modeling of inserts while interacting with the rock is important in simulating/predicting drilling rate of rollercone bits. This paper addresses the modeling of cutter-rock interaction in terms of the geometry of the generated craters as well as the applied operational and design parameters. The model is developed based on an experimental study which was conducted using different levels of loadings, rotational speed, cone offsets, inserts and rock types. It has also been well recognized that the mechanism of rock-cutter interaction is a complicated phenomenon which makes it difficult to establish an analytical model to simulate this behavior. The complexity can be either due to modeling of the forces while a single insert penetrates into the rock or due to the sophistication in modeling the generated craters' geometry. In this study, multivariables regression analysis method was implemented to analyze and process the available laboratory data. The introduced models/correlations reflect the interaction mechanism between a rollercone bit and the rock and are capable of estimating formation drillability of a specific bit type (IADC code) considering integrated effects of the existing parameters. Moreover, the implementation of the mechanical model makes the drilling simulator predict more accurate rate of penetration values which helps improve drilling performance of the rollercone bits. The comparison between the simulator result before and after implementing the new models are also conducted which validates the feasibility of the developed mechanical models in predicting the rate of penetration of rollercone bits utilizing field data.