Evaluation of Commonly Used Fluid Rheological Models Using Developed Drilling Hydraulic Simulator

摘要

An interactive computer based drilling fluid hydraulic program was developed which takes into account the rheological models of Bingham, Power law and Herschel-Bulkley. The software developed in visual basic adds a new dimension to drilling hydraulics by including pipe roughness correction, eccentricity and the use of the Fann viscometer 6- dial readings in the hydraulic model. Field data of a well drilled with a water-based and oil-based mud in Oklahoma was used to validate the software. The measured frictional pressure losses for two (2) hole sections were matched with those obtained using the three models. It was observed that a single rheological model is not adequate as rheological behavior changes. That is, a drilling fluid rheology might match the power law model behavior at the surface and acts like a Hershel-Bulkley fluid at total depth. From the results, the Herschel-Bulkley model including pipe roughness correction gave an excellent prediction for pressure loss inside the drill string (96 percent accuracy) and the power law model gave good results (93 percent accuracy) for the annular pressure loss calculated.