American Oil and Gas Reporter - February 2015 - 87

SpecialReport: Improved Oil Recovery
and other components toward the producing well's hydraulic fractures without
suffering from large viscosity contact between the injected CO2 and reservoir
fluids, which makes it impossible for
CO2 to channel or break through to the
producing well and bypass most of the
oil. After 4,000 days of continuous CO2
injection from the top of the reservoir,
most of the C1 and other components
have been swept uniformly to the producing well's hydraulic fractures.
It is well known that well deliverability
will be compromised by condensate accumulating near the wellbore. However,
the presence of hydraulic fractures also
can contribute to permeability and well
productivity. Figure 7 shows that as pressure declines rapidly along the fracture
block (1,10,2), condensate saturation
builds near (2,11,2) and on the fracture,
which results in the relative permeability
of the gas decreasing.
In our model, the grids near the wellbore and hydraulic fractures are not fine
enough to capture the condensate dropout and rapid pressure variations. It is

beyond the scope of this article to investigate the loss in well productivity index
caused by gas condensate blockage.
Conclusions
The objective of this work is to propose
a new approach utilizing the modified
zipper-frac technique to stimulate a pair
of horizontal wells. This requires perforating a staggered pattern of effective entrance holes through the pipe and cement.
Once the perforation and staging design
are completed for one lateral, the perforation scheme for successive laterals is
based on a staggered design for adjacent
wells.
Gas-injection EOR was performed in
this modified zipper-fractured horizontal
well. Unit fracture-controlled volume
simulation was able to represent the entire
horizontal well recovery on the basis of
symmetry. The phase behavior of CO2
mixed with reservoir fluids proved to be
efficient for enhanced recovery.
Our compositional modeling of gas
injection in a fractured horizontal well
pair demonstrates that CO2 from the in-

jection well fractures uniformly pushes
the reservoir fluids to the producing well
and its fractures, which increases cumulative gas recovery more than twofold.
The well's production performance is the
sum of all fracture network segments,
which strongly depends on fracture spacing.
Although loss in the well's productivity
index caused by condensate drop-out induced by the large drawdown in the fracture was not considered, condensate saturation builds in and near the fracture,
and gas relative permeability reduction
results were presented. The main goal of
this article is to examine the EOR potential
from gas injection in a modified zipperfractured horizontal well pair, which tends
to produce promising results.
Ì

Coming In March
AOGR casts the spotlight on several independents' pioneering strategies to treat and recycle water
recovered during well operations.

FEBRUARY 2015 87

American Oil and Gas Reporter - February 2015

Table of Contents for the Digital Edition of American Oil and Gas Reporter - February 2015