Pressure Losses Calibration in Managed Pressure Drilling

Abstract

Managed Pressure Drilling (MPD) usage is in increasing demand in both offshore and onshore market – especially for wells with narrow drilling pressure margins. Maintaining desired constant Bottom-Hole Pressure (BHP) within given range during MPD operation requires accurate hydraulic modeling for frictional pressure losses. Surface BackPressure (SBP) and StandPipe Pressure (SPP) data, measured in real-time, allows the calibration of frictional pressure losses and an estimation of BHP more accurately. An estimation of SPP is calculated based on integration from the measured SBP back to the inlet in the hydraulics model. The pressure loss increment in the hydraulics model is calculated based on a difference between the measured and estimated SPP value. The system parameters are monitored during drilling and could be adjusted based on the hydraulics model corrected for the pressure loss. The frictional pressure loss due to the drilling pipe rotation could be calibrated by analyzing a difference between the measured and estimated SPP for two operations: without rotation and with rotation. This work underscores the development and usage of advanced hydraulics modeling to accurately calculate BHP during MPD operations. In current hydraulics, mathematical models have been developed to account for various operating parameters, wellbore geometry and fluid properties. This is an enabler to estimate pressure, density, rheology, temperature, and cuttings distributions within the wellbore, drill string and surface equipment more precisely. The frictional pressure loss model includes rotational pressure losses, local pressure losses at special tools and tool joints. This model is based on empirical sub-models which require experimental verification for accuracy. The results of the BHP, calculated with a calibrated hydraulic model, are compared with corresponding results calculated with the uncalibrated model. The use of the pressure calibration for the hydraulics model allows estimating BHP with less error. Recommendations are presented for the accurate mathematical modeling and their applicability and limitations for successful MPD operations.