Organoclay influence on high pressure-high temperature volumetric properties of oil-based drilling fluids

•Organoclay suspensions show density-temperature dependence similar to that of synthetic oil-based drilling fluids.•Tait equation is appropriate to estimate the density under downhole conditions.•The organoclay suspensions show an expansive volumetric behavior which is dampened by increasing pressure.

Two organoclays, commonly used in the formulation of drilling fluids, were dispersed in a mineral oil. Organoclay mass fraction ranged from 0.01 to 0.05. PVT data for the mineral oil and all the suspensions studied were obtained by using a high pressure vibrating tube densimeter, in a temperature range comprised between 40 and 140 °C and pressures up to 1200 bar. The main objective of this work was to study the influence of organoclay nature and concentration on the density of organoclay suspensions in a wide range of pressure and temperature. A Tait-like equation fitted the volumetric behavior of these suspensions fairly well. Organoclay addition to the liquid matrix yielded a significant increase in density values in the whole range of temperature and pressure tested. The expansive volumetric behavior of these suspensions is essentially influenced by organoclay nature and dampened by increasing pressure.