Page 19 - Reservoir Formation Damage

4 Reservoir Formation Damage

means of experimental testing of a variety of cores from geologi-
cal porous media are the challenges for formation damage research.
As expressed by Porter (1989) and Mungan (1989), formation dam-
age is not necessarily reversible. Thus, it is better to avoid forma-
tion damage than try to restore formation permeability using costly
methods with uncertain successes in many cases. When a verified
generalized formation damage model becomes available, it can be
used to develop strategies to avoid or minimize formation damage.

Finally, it should be recognized that formation damage studies involve
many interdisciplinary knowledge and expertise. An in-depth review of
the various aspects of the processes leading to formation damage may
require a large detailed presentation. Presentation of such encyclopedic
information makes learning of the most important information difficult
and, therefore, it is beyond the scope of this book. Instead, a summary
of the well proven, state-of-the-art knowledges by highlighting the impor-
tant features, are presented in a concise manner for instructional purposes.
The details can be found in the literature cited at the end of the chapters.

Common Formation Damage Problems, Factors,
and Mechanisms

Barkman and Davidson (1972), Piot and Lietard (1987), and Amaefule
et al. (1987, 1988) have described in detail the various problems encoun-
tered in the field, interfering with the oil and gas productivity.
Amaefule et al. (1988) listed the conditions affecting the formation
damage in four groups: (1) Type, morphology, and location of resident
minerals; (2) In-situ and extraneous fluids composition; (3) In-situ tem-
perature and stress conditions and properties of porous formation; and
(4) Well development and reservoir exploitation practices.
Amaefule et al. (1988) classified the various factors affecting forma-
tion damage as following: (1) Invasion of foreign fluids, such as water and
chemicals used for improved recovery, drilling mud invasion, and workover
fluids; (2) Invasion of foreign particles and mobilization of indigenous par-
ticles, such as sand, mud fines, bacteria, and debris; (3) Operation con-
ditions such as well flow rates and wellbore pressures and temperatures;
and (4) Properties of the formation fluids and porous matrix.
Figure 1-1 by Bennion (1999) delinates the common formation damage
mechanisms in the order of significance. Bishop (1997) summarized the
seven formation damage mechanisms described by Bennion and Thomas
(1991, 1994) as following:

1. Fluid-fluid incompatibilities, for example emulsions generated
between invading oil based mud filtrate and formation water.