Dynamic Fluid-Loss Measurement of Oil-Mud Additives

Abstract

Summary The objective of this laboratory study was to correlate the dynamic fluid loss (DFL) with the static [API high-temperature/high-pressure (HTHP)] fluid loss, the sticking coefficient, and the fluid-loss-control-agent (FLCA) concentration in oil muds. This was done as a continuing effort to use oil-mud FLCA's more efficiently in the field and to reduce pipe-sticking problems associated with deviated holes. Data were obtained with 13-lbm/gal [1558-kg/m3] inverted-emulsion muds by use of four different types of FLCA's over wide concentration ranges, but within the limits of reasonable field usage. The DFL data (at 250°F [121 °C] and 500-psi [3447-kPa] differential pressure) were obtained with newly developed cells in which filtration occurs in an annulus around a central permeable core. An asymmetric buildup of mud solids and fluid channeling in the annulus suggest a mechanism that would greatly increase pipe-sticking tendencies in deviated wellbores. The DFL decreased with decreasing static fluid loss. The laboratory-measured sticking coefficient, which should correlate with differential-pressure sticking in the field, was reduced as fluid loss decreased. The fluid loss generally decreased with increasing FLCA concentrations, with the major reductions occurring at concentrations of about 4 lbm/bbl [11.4 kg/m3].