:All depths should be referenced to what is termed a ''base log''. The base log is selected from a logging tool where strong or forceful tool positioning is not used. Free-moving tools travel through the borehole more smoothly than tools that are pushed with great force against the borehole wall, such as the [[Basic open hole tools#Density|density log]]. For this reason, strongly centralized tools are not selected as the base log. A [[Basic open hole tools#Resistivity|resistivity log]] ([[Basic open hole tools#Induction|induction]] or [[Basic open hole tools#Laterologs|laterolog]]) is usually selected as the base log. For example, if [[Basic open hole tools#Gamma ray|gamma ray]] logs are available from both the density tool and induction tool strings, it is wise to select the gamma ray from the induction tool as the base log. The gamma ray from the density curve and all curves recorded with the density are then shifted to match the induction log depths. The base curve should also be selected based upon its expected strong correlation with the curves to be depth matched. | :All depths should be referenced to what is termed a ''base log''. The base log is selected from a logging tool where strong or forceful tool positioning is not used. Free-moving tools travel through the borehole more smoothly than tools that are pushed with great force against the borehole wall, such as the [[Basic open hole tools#Density|density log]]. For this reason, strongly centralized tools are not selected as the base log. A [[Basic open hole tools#Resistivity|resistivity log]] ([[Basic open hole tools#Induction|induction]] or [[Basic open hole tools#Laterologs|laterolog]]) is usually selected as the base log. For example, if [[Basic open hole tools#Gamma ray|gamma ray]] logs are available from both the density tool and induction tool strings, it is wise to select the gamma ray from the induction tool as the base log. The gamma ray from the density curve and all curves recorded with the density are then shifted to match the induction log depths. The base curve should also be selected based upon its expected strong correlation with the curves to be depth matched. |