  High velocity outflows from supermassive black holes have been invoked to
explain the recent identification of strong absorption features in the hard
X-ray spectra of several quasars. Here, Monte Carlo radiative transfer
calculations are performed to synthesise X-ray spectra from models of such
flows. It is found that simple, parametric bi-conical outflow models with
plausible choices for the wind parameters predict spectra that are in good
qualitative agreement with observations in the 2 - 10 keV band. The influence
on the spectrum of both the mass-loss rate and opening angle of the flow are
considered: the latter is important since photon leakage plays a significant
role in establishing an ionization gradient within the flow, a useful
discriminant between spherical and conical outflow for this and other
applications. Particular attention is given to the bright quasar PG1211+143 for
which constraints on the outflow geometry and mass-loss rate are discussed
subject to the limitations of the currently available observational data.
