in the preferred embodiment it specifically does not consider the affects of parameters that are not represented in wire line log data or are not generally known before the well is drilled but in alternative embodiments such parameters as shown in fig2 may be considered problems with bit balling center for the most part around shale drilling shale is encountered in approximately 75 of the drilling done for oil and gas steiger and leung 1992 and can be among the most difficult formations to drill shale is defined as a fine grained detrital sedimentary rock formed by the consolidation of clay silt or mud and characterized by their finally laminated structure bates and jackson 1987 further properties include low permeability and high sensitivity to water because transport mechanisms are slow and their structure is water sensitive mechanical and physical properties change with exposure to fluids most problems become worse the longer the shale is exposed gault et al 1988 identified the type and quantity of clay in the shale as an important variable determining drillability specifically he identified cation exchange capacity cec potential as measured by methyl blue absorption testing young smectite clays found in u2018 gumbo u2019 shale which are highly water sensitive score high and signal bit balling until the introduction of aggressive pdc drill bits and improved hydraulics bit balling and unacceptability slow drilling occurred often in these environments drilling below 10 000 feet with dense drilling muds generally higher than 12 lbm gallon mud presented new problems due to high hydrostatic mud pressures here too unacceptable penetration rates were observed however in the beginning it was not.