Determination of Drilling Rate Index Based on Rock Strength Using Regression Analysis

Abstract

Drillability is influenced by many factors, including machine parameters and rock properties. The main machine parameters for drilling include rotational speed, thrust force, torque and flush pressure. The specific rock characteristics that affect penetration rate comprise uniaxial compressive strength (UCS), tensile strength, Young's modulus, hardness and brittleness. In this study, drilling rate index (DrI) is attempted to predict based on UCS and Brazilian tensile strength (BTS) of rocks. Simple and multiple regression analyses have been carried out to determine the best measure of the relation between DrI and two geomechanical properties. The DRI value is strongly related to the uniaxial compressive strength and indirect tensile strength. However, when the uniaxial compressive strength and tensile strength of rock are jointly considered, the correlation coefficient increases. The relationship between the geomechanical properties (UCS, BTS) and the DRI were determined using multiple regression analysis. Strong relationships were obtained from these analyses for the rock strength (UCS) above and below 100 MPa with the correlation coefficients 0.81 and 0.88 respectively.The results of the regression analyses show that for more precise prediction of DRI, rocks should be classified according to their strength.

Thermal Effects on the Drilling Performance of a Limestone: Relationships with Physical and Mechanical Properties

“…In other words, since DRI and UCS tests are destructive, for each temperature they are performed using different fragments (whose values are averaged and then correlated). Thus, regression curves are calculated using the mean values of each property determined at each temperature in line with other authors [10,27,50] since the pairs of correlated values of each sample that define the scatter cannot be considered for adjusting such functions. Different correlation functions exist between SJ, S 20 , and other physicomechanical parameters of the intact rock, but they do not refer to thermally treated samples.…”

“…Capik et al [9] used 43 samples from different types of rocks and determined that DRI decreased with increasing UCS, PLT, BTS, and SH, and that DRI increased with apparent porosity and void ratios. More recently, Yenice [10] found better predictions of DRI from UCS and BTS for hard rocks (UCS > 100 MPa) than for soft rocks.…”

A New SJ* Value Based on Sievers’ J-Miniature Drill Tests to Determine the Drillability of Limestones

“…Thus, the efficiency of a rockcutting tool and its durability are important factors to consider [3]. Modern research shows that the mechanical and physical properties of rocks strongly condition drilling performance, such is the case for surface hardness, point hardness, porosity, uniaxial compressive strength and tensile strength [4,5].…”