Advanced Well Modeling and Diagnostics to Manage Annulus Pressure

Abstract

In order to monitor and diagnose B annulus pressure in the recently drilled extended reach drilling (ERD) and maximum reservoir contact (MRC) 30,000-35,000 feet-long wells a systematic study was conducted to understand causes of this pressure and to develop pressure management guidelines that will allow safe operation of these wells. Newly-drilled wells were monitored from the construction phase to the well completion, handover, clean-up and then production phase with the focus on the following: Monitoring well parameters on daily basisBleed-off analyses (volumes and sample analysis)Review of the cementing job and the logs for 9-5/8" casing and 13-3/8" casingDiagnostic analyses including modeling and logs if necessaryMaximum allowable wellhead operating pressure (MAWOP) calculations Detailed descriptions have been provided on how the annular fluid expansion volume due to a thermal effect was estimated using a computer modeling calibrated and history-matched to the field data. Results of modeling along with diagnostics using tools like spectral noise log (SNL), high precision temperature log combined with distributed temperature sensing have provided conclusive evidence that the wells are integral and safe to operate. This unique combination of modeling and diagnostic tools allowed to optimize logging duration, minimize well shut-in time and improve fidelity of diagnostics through more detailed logging in the areas of interest. It was concluded that the main factors contributing to the B annulus pressure are the thermal effect seen during the well start up, the quality of cement job for the production casing, the volume of fluid in the annulus and the connectivity to the formation, if any. The study demonstrated that the wells are safe to operate with pressures below MAWOP and that B annulus is not in communication with the reservoir.