Page 364 - Reservoir Formation Damage

344 Reservoir Formation Damage

the reaction and the slopes of the stability boundaries are temperature
dependent (Schneider, 1997).
For example, consider (Schneider, 1997):

+ 2e~ + 2H + H 2O
Hematite Magnetide (13-37)

Assigning unity for the activities of the water and solid mineral phases,
the equilibrium constant expression reads as (Schneider, 1997):

1
(13-38)

Hence, a logarithm of Eq. 13-38 yields the equation for the hematite-
magnetite boundary as:

= -logK eq-pH (13-39)

which can be used to construct a pe - pH chart (Schneider, 1997).

Geochemical Model Assisted Analysis of Solid Mineral—
Aqueus Phase Interactions and Construction of Charts

Because of the highly complicated nature of the interactions of solid
minerals and aqueus solution in geological porous media, it is most
convenient to facilitate appropriate geochemical models for the analysis
of the potential chemical interactions and formation damage affects. A
typical example of such studies has been carried out by Schneider (1997)
in an effort to quantify the potential formation damage problems, which
would result from the invasion of incompatible foreign water, such as by
drilling and workover fluids and water flooding, into the Lower Spraberry
sandstone reservoir formation of Texaco's Jo Mill Unit (JMU) field.

Mineral Characterization and Analyses

Based on the analyses using a scanning electron microscope, electron
microprobe, and x-ray diffraction, Schneider (1997) determined the
properties of the sandstone as: "Fine-grained, immature sandstones that