American Oil and Gas Reporter - August 2015 - 68

SpecialReport: Hydraulic Fracturing Technology
FIGURE 2
Well Planning Guide used in Determining Lateral Azimuth

30%

Oil Recovery (Cum/OOIP)

25%

20%

15%

10%

5%
5

Horizontal
Axial Frac Horizontal 5 Horizontal
Transv
11 Transv
Well Type
Fracs
Fracs Incr
Lf

superb blockade to frac height growth.
The only issue is the ability to map and
evaluate the stress barrier in a lateral, but
it is logically assumed that increased
footage of permeability equates to a more
effective barrier mechanism.

Proppant Transport
A predominate consideration in setting
the lateral depth is the lifting capacity of
the carrier fluid. At deeper landing depths,
and especially with a thin fluid, the Darwinesque theory that it is easier to prop
down with gravity than prop upward with
force generally holds true. On the other
hand, running a more viscous fluid at a
shallower setting aggravates the risks of
breaching the upper hard streak.
The transport capacity and minimizing
gel damage dictated the choice of a medium-thin frac fluid. The minimally damaging issue also is closely aligned with
the density, shape and sphericity considerations of the ceramic proppant, which
plays a significant role in determining
the horizontal landing depth. Specifically,
the proppant and frac fluid properties,
together with the injection rate (frac velocity), control propping of the pay zone
above the lateral.
As part of this evaluation, proppant
transport was defined by a simplified
Navier-Strokes equation relating to settling
rates. The drag coefficient and proppant
68 THE AMERICAN OIL & GAS REPORTER

0.005

ity

m

Horizontal

ea

0.05
Vertical
Frac

Pe
r

Vertical

bil

0%

m
d

0.5

area were the key elements in the transport
analysis, since they characterize the drag
of spherical versus nonspherical proppant.
Considering that ceramic rods settle faster
in fluid than spheres of the same density,
spherical ceramic proppant was deemed
preferable.

In addition, sphericity was considered
to account for both high potential flow
rates and frac fluid cleanup, thus the selection of a proppant with the lowest
beta factor to accommodate drag from
Forchheimer porous-flow forces.
The four depth simulations (Table 1,
with selected landing depths shown in
red) employed the same frac design, injection rate and proppant ramp schedule,
making the only variable the source of
the frac entering the pay section. Justification for the selected depth setting
(Figure 4) was based on proppant mapping
showing higher coverage of proppant
concentrations in all three pay sections,
and the low to modest net pressure trend
during the treatments, improving the
ability to repeat each stage along the lateral.
Multisleeve Frac System
The fifth barrier to be addressed (and
which continues to be studied) was optimizing the operational components-specifically relating to fracture spacing-monitoring back-stress, and developing a permeability model from mud logging data.
The subject wells were perforated with
limited-entry tools using three evenly
spaced clusters with 20 perforations at
the farthest (toe) measured depth, 15 in
the middle depth, and 12 at the shallowest
(heel) depth. Absent microseismic map-

FIGURE 3
Type Log of a Third Bone Springs Vertical Section

11,200 ft

11,400 ft

11,600 ft
American Oil and Gas Reporter - August 2015

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