BAKER HUGHES - Drilling Fluids Reference Manual

Water Based Drilling Fluids
However, the costs associated with the use of environmentally acceptable, invert emulsions
drilling fluid systems limit the application of such systems.
Water-based muds (WBM) are attractive replacements from both cost and environmental
perspectives. However, conventional WBM systems have failed to meet key performance criteria
obtained with OBM in terms of rate of penetration, bit and stabilizer balling, lubricity, filter cake
quality, and thermal stability. Past efforts to develop improved WBM for shale drilling have been
hampered by a limited understanding of the drilling fluid/shale interaction phenomenon. Recent
studies of fluid-shale interactions, however, have produced fresh insights into the underlying
causes of borehole instability. Experimental evidence reported by many researchers has shown
that the chemical potential driving force, created from the activity difference between the drilling
fluid and shale, can counteract the hydraulic driving force (the difference between the mud
weight and pore pressure). A theoretical relationship, based on fundamental thermodynamic
principles, has been postulated to support the experimental observations that osmotic pressure
acts as a negative hydraulic pressure in its influence on water movement.
Overview of the PERFORMAX System
PERFORMAX is Baker Hughes Drilling Fluid’s
3 rd generation high-performance water-base
drilling fluid that is designed to emulate
performance characteristics previously achieved
only with emulsion based drilling fluids. These
attributes include shale inhibition (reduced pore
pressure transmission), cuttings integrity, high
rates-of-penetration, and reduced torque and drag.
Two features of PERFORMAXthat contribute to
wellbore stability are: 1) ultra-fine, deformable
sealing polymer particles in MAX-SHIELD
(diameter: ~ 0.2 µ) that mechanically seal shale
micro-fractures, which physically block further
intrusion of drilling fluid filtrate into the shale
matrix; and 2) the resin and aluminum complexes
in MAX-PLEX, in combination with MAX-
SHIELD, produce a semi-permeable membrane at
the shale surface and chemically improve the
osmotic efficiency, and reduce pressure
transmission into shales.
Pore pressure transmission tests clearly show that
MAX-SHIELD effectively works in combination
with MAX-PLEX to achieve pore pressure
transmission characteristics previously achieved only with emulsion-based drilling fluids (oilbased
or synthetic-based).
Reference Manual
Baker Hughes Drilling Fluids
3-94 Revised 2006