Page 17 - Reservoir Formation Damage

2 Reservoir Formation Damage

under stress and fluid shear. These processes are triggered during the
drilling, production, workover, and hydraulic fracturing operations. For-
mation damage indicators include permeability impairment, skin damage,
and decrease of well performance. As stated by Porter (1989), "Forma-
tion damage is not necessarily reversible" and "What gets into porous
media does not necessarily come out." Porter (1989) called this phenom-
enon "the reverse funnel effect." Therefore, it is better to avoid forma-
tion damage than to try to restore it. A verified formation damage model
and carefully planned laboratory and field tests can provide scientific
guidance and help develop strategies to avoid or minimize formation
damage. Properly designed experimental and analytical techniques, and
the modeling and simulation approaches can help understanding, diagno-
sis, evaluation, prevention, remediation, and controlling of formation
damage in oil and gas reservoirs.
The consequences of formation damage are the reduction of the oil and
gas productivity of reservoirs and noneconomic operation. Therefore, it
is essential to develop experimental and analytical methods for under-
standing and preventing and/or controlling formation damage in oil and
gas bearing formations (Energy Highlights, 1990). The laboratory experi-
ments are important steps in reaching understanding of the physical
basis of formation damage phenomena. "From this experimental basis,
realistic models which allow extrapolation outside the scaleable range may
be constructed" (Energy Highlights, 1990). These efforts are necessary
to develop and verify accurate mathematical models and computer simu-
lators that can be used for predicting and determining strategies to avoid
and/or mitigate formation damage in petroleum reservoirs (Civan, 1994).
Confidence in formation damage prediction using phenomenological
models cannot be gained without field testing. Planning and designing
field test procedures for verification of the mathematical models are
important. Once a model has been validated, it can be used for accurate
simulation of the reservoir formation damage. Current techniques for
reservoir characterization by history matching do not consider the alter-
ation of the characteristics of reservoir formation during petroleum pro-
duction. In reality, formation characteristics vary and a formation damage
model can help to incorporate this variation into the history matching
process for accurate characterization of reservoir systems and, hence, an
accurate prediction of future performance. Formation damage is an ex-
citing, challenging, and evolving field of research. Eventually, the research
efforts will lead to a better understanding and simulation tools that can
be used for model-assisted analysis of rock, fluid, and particle interac-
tions and the processes caused by rock deformation and scientific guid-
ance for development of production strategies for formation damage
control in petroleum reservoirs.