Abstract: The invention relates to the measurement of the rheology of drilling fluid down a hydrocarbon well in real time during operations. A sensor device comprising a pipe rheometer with multiple diameters is installed in a bottom hole assembly tool, such that a portion of the total flow of drilling fluid passes through it. In this way the rheological properties of the drilling fluid can be determined under the high pressures and elevated temperatures encountered downhole.

Abstract: The invention relates to the drilling of wells in rock and hydrocarbon formations. Drilling is performed with a drill string having a bottom hole assembly (BHA) and drill bit. Drilling mud is circulated during drilling. A valved inlet port is provided in the BHA which, in the event of a pack-off, opens and allows drilling mud to enter an internal space in the BHA to relieve pressure. An outlet port at the proximal end of the BHA may be provided to allow he mud to flow back into the annulus around the drill string. In this way, rapid build-up of pressure is avoided and the driller has more time to respond to the pack-off.

Abstract: The invention relates to the measurement of the rheology of drilling fluid down a hydrocarbon well in real time during operations. A sensor device comprising a pipe rheometer with multiple diameters is installed in a bottom hole assembly tool, such that a portion of the total flow of drilling fluid passes through it. In this way the rheological properties of the drilling fluid can be determined under the high pressures and elevated temperatures encountered downhole.