Assessment of drilling performance during Casing Drilling and optimization of the process has been achieved using an existing computer simulator, which has not been tested before in Casing Drilling applications while its value has been proven in conventional drilling. The simulator allows prediction of ROP using standard drilling data of WOB, RPM, flow rate, and formation parameters. Use of simulator post drilling allows fine tuning it to match drilling performance so that future jobs in the same field could be more optimally designed.
Different lithologies along the wellbore were defined in terms the rock type, strength, and abrasivity from drilling data collected while Casing Drilling of a 2000 ft well in Haynesville shale, where ROP was high in the upper part but fairly low in the lower part. Rock strength data normally is not given and estimation was made from databases for similar rocks while they could be estimated from sonic data if available.
Running the simulator allows for re-drilling the well utilizing all basic data and trying to match the real drilling time curve and the measured ROP. Good matching was achieved for the drilling depth-time and also ROP values were matched well over the whole depth interval. Using the simulated model, WOB and RPM were optimized to increase the ROP at the lower part of the well. The results proved that the simulator can simulate Casing Drilling effectively as it has proved its value for conventional drilling.
This work shows that the simulator can help the driller to use historical data of Casing Drilling and then by applying different scenarios, e.g. increasing WOB or RPM and he can apply them while drilling a new well to obtain higher ROP. Using the simulation results, optimal drilling parameters can thus be found for drilling future wells in similar geologic environments.