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Dynamic Data Analysis – v5.12.01 - © KAPPA 1988-2017
Chapte
r 6 – W ell models -p191/743
The figure below illustrates the fourth root plot.
Fig. 6.E.6 – Fourth root plot
6.E.6
Adding wellbore storage
Wellbore storage will affect the early time data by masking both bi-linear and linear flow. The
storage effect does not need to be very high in order to mask the fracture flow completely. The
interpreter is faced with data that cannot prove that a fracture exists; only the very negative
skin associated with the fracture and a marked increase in productivity will give him some
arguments that the stimulation job was indeed successful or partly successful.
In fact, the analyst is often faced with this dilemma. From a design point of view the fracture
job may be judged successful as we know what we pumped and the proppant disappeared, so
the fracture must be in the ground. But often, the frac will propagate up or down, and parallel
short fractures maybe induced thus masking the very long fracture that was designed for. It is
just not manifesting itself in the bottom hole pressure data.
The figure below illustrates the effect of wellbore storage on the early time behavior.
Fig. 6.E.7 – Wellbore storage influence