EXPERIMENTAL RESEARCH ON THE HTHP RHEOLOGICAL PROPERTIES OF ULTRA-HIGH TEMPERATURE AND ULTRA-HIGH PRESSURE WATER BASED DRILLING FLUID

Designing proper ultra-high temperature and ultra-high pressure water based drilling fluid (ultra-HTHP WBDF) that can function properly under the conditions of ultra-HTHP drilling operations such as deep and ultra-deep oil and gas well drilling is very challenging. One of these challenging is the alteration of the high temperature and high pressure (HTHP) rheological properties of ultra-HTHP WBDF due to the HTHP conditions under bottom hole. In this paper, the rheological behavior of ultra-HTHP WBDF was investigated with different properties at HTHP conditions by using an OFITE HTHP rheometer. A formulated ultra-HTHP WBDF with the mud weight of 2.46 g/cm(3) which can be used in deep and ultra-deep well drilling was chosen to carry out a matrix of experiments. The experimental results showed that the rheological behavior of ultra-HTHP WBDF was significantly influenced by temperature and pressure. The temperature was the largest influenced factors on the HTHP rheological properties for ultra-HTHP WBDF and the effect of pressure on rheological parameters. however, was more apparent at a lower shear rate range. The combined effect of temperature and pressure on HTHP rheological behavior of ultra-HTHP WBDF was complex and the rheological properties showed different laws at a lower shear rate range and a high shear rate range. Moreover, Herschel-Bulkley model can accurately fit the ultra-HTHP WBDF over a wide range of temperature, pressure and shear rates.