EXPERIMENTAL STUDY ON RHEOLOGICAL PROPERTIES OF ULTRA-HIGH TEMPERATURE WATER BASED DRILLING FLUID FOR GEOTHERMAL WELL DRILLING APPLICATIONS

Designing proper ultra-high temperature water based drilling fluid that can function properly under the conditions of geothermal well drilling operations are very challenging. One of these challenging is the alteration of the rheological properties of WBDF due to the high temperature and high pressure conditions under bottom-hole. With the goal of increasing understanding of rheological behavior of ultra-HT WBDF during the geothermal well drilling operations and for providing a HTHP theological database of drilling fluid, an experimental study based on a rheological evaluation of a formulated ultra-HT WBDF with the mud weight of 1.04 g/cm(3) which can be used in geothermal well drilling operations was carried out with a matrix of experiments by using an OFITE HTHP rheometer. The results showed that the rheological behavior of ultra-HT WBDF was significantly influenced by temperature and pressure. Temperature was the largest influenced factors on the rheological properties. The combined effect of temperature and pressure on rheology of ultra-HT WBDF was complex and the rheological properties showed different laws at a lower shear rate range and a high shear rate range. Besides, Herschel-Bulkley model can accurately fit the ultra-HT WBDF over a wide range of temperature, pressure and shear rates.

Automated summary

Designing proper ultra-high temperature water based drilling fluid for geothermal well drilling operations is challenging due to the alteration of rheological properties under high temperature and pressure conditions. Temperature is the primary factor influencing rheological properties, with a complex combined effect of temperature and pressure on rheology. The Herschel-Bulkley model is accurate in fitting the ultra-HT WBDF over a wide range of conditions.