Page 208 - Petrophysics

PERMEABILITY-POROSITY RELATIONSHIPS 181

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0.01 0.1 1 5 10 20 50 80 90 95 99 99.9 99.99
Percent samples with larger permeability
Figure 3.53. Llykstru-Parsons coeflcdent for u heterogeneous reservoir.

The recovery of fluids obtained is primarily dependent upon the
permeability and porosity of the formation tested and the viscosity of the
fluids contained in the zone. Various techniques have been developed for
analyzing the fluid recovery and recorded pressure curves to determine
whether or not a formation test has indicated that commercial production
can be attained.
To utilize these pressure curves, some knowledge of the response
of the curve to a given formation conditions is necessary. Basic to this
knowledge is an understanding of various analytical equations describing
the flow of fluids through porous media. These equations, which
are solutions of diffusivity equations for different boundary conditions,
express the relationship between characteristics of the porous rock, such
as porosity and permeability, and properties of the fluids (oil, gas, and
water) moving through the rock.
The basic well testing technique is to create a pressure drop in the
bottom-hole pressure, which causes reservoir fluids to flow at a certain
rate from the rock to the wellbore, followed by a shut-in period. The
production period is generally referred to as the “pressure drawdown”
whereas the shut-in period is called the “pressure buildup.”