Rheological Properties of Invert Emulsion Drilling Fluid under Extreme HPHT Conditions

Abstract

Abstract Limited amount of rheological data generated under extreme high-pressure, high-temperature, (HPHT) conditions (>500°F/30,000 psi) have been published due to lack of suitable viscometer and drilling fluid for such conditions. This paper compares the rheological properties of invert emulsion drilling fluid generated from four types of HPHT viscometers and provides a simple rheological model that can be used to predict the behavior of OBM under extreme-HPHT conditions. Previously most of the HPHT studies were limited to 20,000 psi and 500°F. Recently more than one extreme-HPHT rheometers have become commercially available, which can measure the rheological properties of drilling fluids at conditions up to 600°F and 40,000 psi. These viscometers have been used to test various invert emulsion drilling fluid samples to the maximum capacity of the equipment. Parts of the data generated from one particular instrument have been compared with data obtained from other rheometers that are operated at lower temperature and pressure. The data indicated several factors can critically affect the rheology measurements, including drilling fluid chemistry, instrument set up and test schedule. Rheological properties measured by various instruments differed slightly from each other perhaps due to design differences. Temperature and pressure not only affect the rheological properties of the test fluid but may also impact the performance of the critical mechanical parts used for rheology measurement. In addition, HSE experience gained from working with extreme-HPHT instruments is also included in this paper.