Comparative investigations into dynamic rheological modeling of the water-based drilling fluid under HTHP conditions

An accurate HTHP rheological model is essential for safe and economical deep drilling. In this work, the water-based fluid applied in Southwest China Gas Fields is selected as a typical example to systematically explore rheological modeling at elevated temperature(up to 180 degrees C) and pressure(up to 100 MPa). The HTHP rheological behavior of water-based drilling fluid was firstly investigated. Then general rheological modeling approaches and specific HTHP modeling process have been employed to establish an accurate HTHP rheological model. The results showed that for general rheological models, the Bingham model appears to be more suitable to predict the transient rheology at constant conditions; under HTHP conditions, a dynamic rheological model has been established using the relative dial reading method modified by the direct fitting, whose prediction deviation was in the range of -7.13%similar to 10.63%, meeting in-field application requirements well. This research will be useful to direct a comprehensive rheological treatment, and will also enrich the modeling strategy of HTHP rheology for drilling fluids.