Determination of drilling fluid rheology under downhole conditions by using real-time distributed pressure data

摘要

One the most important tasks during any drilling operation is to measure rheological properties of drilling fluids to allow for optimum maintenance and wellbore hydraulics management. In current drilling practice, such measurement is routinely carried out by a mud engineer at the rig site using test protocols and equipment that quantify the relationship between the fluid's shear stress and shear rate, as standardized by the American Petroleum Institute (API). Usually, measurements are conducted at atmospheric pressure and standardized temperature and are therefore generally not representative of actual downhole pressure and temperature conditions. High Pressure High Temperature (HPHT) viscometers can of course be used at the drilling fluid design stage to determine its rheological properties under downhole condition. However, these properties are subjected to change during drilling operations due to variation in mud maintenance and the introduction of drilling solids and contaminations. In addition, installation of a HPHT viscometer at the rig site is highly impractical due to its cost, maintenance, calibration difficulties, and lack of dedicated personnel to run the equipment.