American Oil and Gas Reporter - September 2018 - 55

SpecialReport: Horizontal Wellbore Construction
above the kickoff point. The kickoff plug
also served to isolate the previous wellbore
from the new well. Then, a casing string
was run and cemented above the kickoff
plug to ensure adequate hole cleaning in
the vertical section.
A 40-foot mouse hole was drilled and
cased next to the wellhead to allow easy
rig up. The BHA could be changed out
quickly since it was made up and prepared
horizontally (including tool face offset calibration) before being picked up and placed
in the mouse hole. Only the top connection
to the coil connector had to be made up
while the BHA was vertical in the mouse
hole and on the critical path of operations.
The re-entry plan was to kick off
from a kickoff cement plug at 1,750
feet true vertical depth below ground
level (TVDBGL) into a relatively soft
formation. The plan was then to hold
the drilling angle at approximately 7.0
degrees before building to land horizontally at 2,400 feet TVDBGL. The
nonproductive portion of the sidetrack
was to be drilled with water only to
reduce the use of nitrogen, and then
once the wellbore approached the target
reservoir, nitrogen injection would begin
to switch to underbalanced drilling. The
drilled section would be left barefoot
and a pump would be installed to lift
the well.

FIGURE 4
Drilling Parameters and Vibration Levels during Cement Plug Kickoff

distinguish between radial, axial and torsional vibration. The high density of data
is particularly advantageous for steering
the BHA, and coupled with the short distance from the bit to the survey tool, allows
highly accurate wellbore placement.
The BHA was run on 10,000 feet of
23⁄8-inch coiled tubing with a seven-conductor electric line inserted. The coiled
tubing and associated equipment were
trailer mounted. A crane was used to suspend the injector and lubricators above
the blowout preventer stack. The BHA's
total length was short enough to be contained within a 48-foot lubricator to permit
safe and efficient deployment in one run.
Produced water was used as the drilling

fluid for the overbalanced section and
the fluid column then was lightened by
adding cryogenic nitrogen for the underbalanced section. The reservoir historically
had produced low levels of natural gas,
so fluid separation was achieved with
gravity tanks and a gas buster to separate
the entrained nitrogen. Any oil that was
produced was skimmed from the top of a
three-stage tank.
Before the DCTD equipment arrived
on the well site (AnTech Oilfield Services
Inc. provided the BHA hardware and
modeling software, and C&J Energy Services provided the CT and pumping services), a cement plug was set from the
total depth of the original wellbore to

Operations Overview
During the process of kicking the well
off the cement plug, the BHA was exposed

FIGURE 5
Comparison of Modeled versus Actual Measured Results
Drilling Ahead in Single-Phase (Water)
Depth = 2,403 feet
0

200

400

600

800

1,000

Drilling Ahead in Two-Phase (Water and N2)
Depth = 2,443 feet
1,200

1,400

19:40

22:50

19:39

22:54

19:38

22:53

19:37

22:52

19:36

22:51

19:35

22:50

19:34

22:49

19:33

200

400

600

800

1,000

1,200

1,400

22:48
Ext Press (psi)

Dif Press (psi)

Comparison

Ext Press (psi)

Flow Rate

Measured

Predicted

Error

105 gal/min

1,080 psi

1,164 psi

Flow Rate
105 gal/min
250 cf/min

Measured
819 psi

Dif Press (psi)

Comparison

Predicted
831 psi

Error
1%

SEPTEMBER 2018 55

American Oil and Gas Reporter - September 2018

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