摘要：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 altera-tion 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 prop-erties at HTHPconditions by using an OFITE HTHP rheometer. A formulated ultra-HTHP WBDF with the mud weight of 2.46 g/cm3 which can be used in deep and ultra-deep well drilling was chosen to carry out a matrix of experiments. The experimental re-sults showed that the rheological behavior of ultra-HTHP WBDF was significantly influenced by tem-perature and pressure. The temperature was the larg-est influenced factors on the HTHP rheological prop-erties for ultra-HTHP WBDF and the effect of pres-sure on rheological parameters, however, was more apparent at a lower shear rate range. The combined effect of temperature and pressure on HTHP rheo-logicalbehavior 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 tem-perature, pressure and shear rates.
关键词：Waterbased drilling fluid;rheological properties;rheology;deep and ultra-deep well drilling;high temperature and high pressure
