The Application of a New Drilling Model for Evaluating Formation and Downhole Drilling Conditions

Abstract

Abstract A new drilling model has been developed for the interpretation of downhole drilling conditions using surface and downhole drilling data. This model is based on the analysis of the interaction of the drill bit (PDC or impact) and the formation under in situ pressure conditions. It combines downhole and surface drilling data with MWD formation measurements to provide detailed drilling analyses for real-time applications. An expression for Drilling Response developed from the model provides information on lithologic changes and allows interpretation of downhole drilling conditions. Drilling Response is a function of lithology, pore pressure, mud pressure and bit properties and is computed from the following drilling parameters: rate of penetration, bit revolutions, and downhole weight and torque on bit. Techniques and expressions allowing computation of formation porosity and pore pressure on a foot by foot basis have also been developed based on the Drilling Response. Another key feature of the model is the identification of inefficient drilling conditions. Inefficient drilling conditions are expressed in the form of Drilling Alerts for real-time applications, allowing the operator to take the necessary action to rectify the problem at the wellsite. Drilling Alerts also allow the operator to continuously monitor the effects of any remedial actions. Bit condition is evaluated using Drilling Response and torque analyses. This allows the operator to assess bearing and tooth wear conditions for impact bits and cutter wear for PDC bits. Field Examples from sedimentary basins illustrate the usefulness of the model and its applications at the wellsite and in post-drilling analysis.