American Oil and Gas Reporter - August 2017 - 68

SpecialReport: Horizontal Wellbore Construction
FIGURE 1
Surface Fracturing String (Left) versus
Packer-Based Isolation Bottom-Hole Assembly (Right)

ulated), or running a long frac string
latched into the polished bore receptacle
(no pressure can be applied to the backside
of the frac string). Separate tool/string
runs are necessary for each lateral leg, so
a dual lateral will require either two fracturing string runs or two packer-based
isolation tool runs.
Packer-based junction isolation devices
first were used in the early 2000s for highpressure multistage acid fractures in a Devonian limestone formation in West Texas.
Multiple dual-lateral wells were drilled
with level 2 junctions and then isolated
with these devices to create a temporary,
high-pressure level 5 completion architecture for selective stimulation. This approach resulted in significant cost savings
and ensured the successful stimulation,
testing and production of each lateral.
In the case of surface frac strings,
some operators simply leave the string
assembly in a lateral's stimulated wellbore
and immediately put the well on production. In this case, the frac string assembly
is pulled once the first lateral is produced
to decline, and the second lateral is entered
to complete and produce it.
Hypothetical Case Study

While level 3 and 4 multilaterals have
been drilled and completed in the Granite
Wash, Bakken and Mississippian Lime
plays, most multilateral projects in unconventional resource plays (or conven68 THE AMERICAN OIL & GAS REPORTER

tional reservoirs where multilaterals were
completed with multistage fracturing)
have used level 1 or 2 junctions.
In the Permian Basin, operators have
drilled multilaterals in a number of formations and completed them using multistage fracturing. The majority of the
projects have been level 2 junctions with
7.0-inch main bores and 41⁄2-inch lateral
legs, and used cemented liners with plugand-perf completions. Most of these wells
had very low formation pressures, eliminating the need for mechanical barriers
by using the hydrostatic head of the
flowback fluids to provide temporary
well control.
Based on operators' early experience
using multilateral technology in the basin,
a comparative economic analysis using a
hypothetical Permian case study was performed for a single horizontal well versus
a dual-lateral. The analysis used typical
Permian drilling and completion costs,
and assumed both laterals would be drilled
and stimulated sequentially with a barrier
installed to isolate each lateral.
All of the individual operational steps
to drill, complete/stimulate and produce

a dual-lateral with a level 4 junction
(7.0-inch main lateral and a 4.5-inch secondary lateral) with 15 frac stages a
lateral were compared with a single horizontal well with a 15-stage frac. Both
cases are based on a true vertical depth
of 8,000-10,000 feet, and include all expenses associated with site preparation
and mobilization/skid/demobilization to
drill 4,000 foot laterals and complete/stimulate the lateral sections with cemented
liners and plug-and-perf tools.
The results in Table 1 indicate that
the total cost of one level 4 dual-lateral
will be about 20 percent less than the
combined cost of two single horizontal
wells, and save 15 percent in operational
time. Table 2 shows the estimated operational steps to install a level 4 dual-lateral
completed with multistage fracturing.
High Reliability

The goal with any drilling and completion project is to achieve 100 percent
reliability of equipment and zero nonproductive time in the execution phase. Fortunately, high levels of reliability have
been attained with multilateral technology
through stringent design improvements,
sound operational procedures and consistent
job execution by well-trained onsite personnel. Even the most complex multiplejunction installations have become somewhat routine in some regions of the world.
In resource plays, in particular, reliability
must be balanced with efficiency. After
all, a perfect multilateral installation with
zero NPT is of little value to an operator if
the number of operational steps drive up
costs to the point that the savings gained
from multilateral architectures are lost.

TABLE 1
Cost Comparison of Level 4 Dual-Lateral Versus Two Single Horizontals
Cost
Single Level 4 dual-lateral well

Drilling Costs

Completion Costs

Total Costs

Total Days

$5,623,173

$4,637,500

$10,260,673

Single horizontal well

3,796,805

2,676,500

6,473,305

108
64

Two single horizontal wells

7,593,610

5,353,000

12,946,610

128
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