Page 126 - Reservoir Formation Damage

108 Reservoir Formation Damage

in a sand-pack. Such images provide valuable insight and understanding
of the alteration of porous rock by various processes.

X-Ray Fluoroscopy (XRF)
The X-Ray fluoroscopy technique is used for determining the drilling
mud invasion profiles in unconsolidated and consolidated core samples
and it is especially convenient for testing unconsolidated, sleeved core
samples (Amaefule et al., 1988). Amaefule et al. (1988) show a typical
X-ray fluoroscopic image.

Scanning Electron Microscope (SEM)
The rock and fluid interactions causing formation damage is a result
of direct contact of the pore filling and pore lining minerals present
in the pore space of petroleum-bearing formations. The mineralogical
analysis, abundance, size, and topology and morphology of these minerals
can be observed by means of the scanning electron microscopy (SEM)
(Kersey, 1986; Amaefule et al., 1988). Braun and Boles (1992) caution
that, although the SEM can provide qualitative and quantitative chemical
analyses, it should be combined with other techniques, such as the
polarized light microscopy (PLM) and the X-ray diffraction (XRD) to
characterize the crystalline and noncrystalline phases, because amorphous
materials do not have distinct morphological properties. An energy
dispersive spectroscopy (EDS) attachment can be used during SEM
analysis to determine the iron-bearing minerals (Amaefule et al., 1988).
Various specific implementations of the SEM are evolving. For example,
the environmental SEM has been used to visualize the modification of
the pore structure by the retention of deposits in porous media (Ali and
Barrufet, 1995). The cryo-scanning electron microscopy has been used
to visualize the distribution of fluids in regard to the shape and spatial
distribution of the grains and clays in the pore space (Durand and
Rosenberg, 1998). The SEM has also been used for investigation of the
reservoir-rock wettability and its alteration (Robin and Cuiec, 1998;
Durand and Rosenberg, 1998).
The SEM operates based on the detection and analysis of the radiations
emitted by a sample when a beam of high energy electrons is focused
on the sample (Ali and Barrufet, 1995). It allows for determination of
various properties of the sample, including its composition and topography
(Ali and Barrufet, 1995).
Typical SEM photomicrographs are shown by Amaefule et al. (1988).
The environmental SEM images shown by Ali and Barrufet (1995)
illustrate the modification of the pore structure by polymer retention in