American Oil and Gas Reporter - September 2016 - 62

SpecialReport: Horizontal & Innovative Drilling
cement channeling and poor cement bonding. Problems associated with achieving
a poor cement/casing bond include:
* Compromised well integrity during
future operations;
* Failure to isolate weak formations
and provide structural support;
* Decreased reservoir isolation and
protection;
* Encumbered production optimization efforts such as stimulation treatments;
* Potential exposure to corrosive
saline formation water; and
* Fluid/gas migration.
The newest advancement in downhole
vibratory casing technology is an expendable tool design that modulates fluid
flow. This type of "flow-interrupting"
tool utilizes a valve function in which
the flow restriction through the tool varies
with time. The periodic change in flow
restriction causes oscillating back pressure
across the tool as fluid is pumped through
it.
As a column of fluid travels through
the casing string, it encounters this chang-

ing flow restriction. When the flow is interrupted by the vibratory tool, the pressure
above the tool increases. This pressure
increase is caused by both the water hammer effect as the fluid column decelerates
and the continued flow of fluid into the
casing string by the positive displacement
surface pumps.
The increased pressure acts across the
hydraulic area of the casing, causing it to
elongate. The momentary elongation of
the casing breaks static friction and allows
for the downward movement of casing.
When the flow restriction decreases, fluid
pressure above the tool is relieved and
the casing contracts to its original length.
This process repeats over and over as
fluid flows through the tool, causing axial
vibration of the casing.
Strong axial vibratory forces reduce
the surface tension between the drilling
fluid and casing, and between the drilling
fluid and formation wall. Axial vibrations
also help to break up drilling cutting
"bridges," and allow cuttings and fluids
to be pumped out of the wellbore more
easily.

FIGURE 1
Comparison of Liner Running Speeds
0

0

3

6

9

12

15

500

18

21

Distance Rotating (feet)
24
27
30
33

36

42

45

48

51

54

57

Average Liner Run Time:
Casing Tool - 19.6 hr

1,000
1,500

Average Liner Run Time:
Traditional - 42.35 hr

2,000
Distance Rotating (feet)

39

2,500
3,000
3,500
4,000
4,500
5,000
5,500
6,000

Worland 1B (HTSF Threads + Vibratory Tool)

Camaro 1 (HTSF Threads + Vibratory Tool)

Thunderbird 1A (HTSF Threads + Vibratory Tool)

Malibu 1 (HTSF Threads + Vibratory Tool)

Polara 1 (HTSF Threads - No Vibratory Tool)

Biscayne (Buttress Threads - No Vibratory Tool)

Fury 1 (Buttress Threads - No Vibratory Tool)

Shelby 1 (Buttress Threads - No Vibratory Tool)

62 THE AMERICAN OIL & GAS REPORTER

Consistent Casing Rotation
The ability to move the casing string
during cementing operations is an effective
way to counter poorly centralized casing.
Pipe movement increases the effective
volume of fluid moving in the annulus
and supplies a mechanical means for
breaking the gel strength of immobilized
mud or curing cement that otherwise
could not be broken by fluid rheology,
flow rates or centralization.
Torque requirements will exceed capacity periodically when cement reaches
the lateral section, restricting casing rotation
throughout the duration of the cement
job. The oscillating axial vibration combats
static friction, resulting in less torque and
higher rotary speeds to enable consistent
casing rotation from commencing cement
operations until cement is set.
In addition, the benefits of vibratory
casing tools can be observed when well
conditions prohibit casing rotation during
cementing operations. As the tool modulates flow through it, fluid pulsation is
created at the tool's exit point. The tool's
position near the casing shoe allows the
fluid pulses created to be exhausted through
the shoe, causing a change in pressure
between the end of the casing and the
formation, or any object obstructing movement down hole. This changing hydraulic
loading at the end of the casing causes an
oscillating load between the shoe and the
obstruction, creating a "hammer drill"
effect that enhances casing installation.
This fluid pulsation breaks fluid channeling and creates uniform flow up the
outside of the casing. The vibration of
the casing string and fluid pulsation during
cementing operations helps to ensure a
high quality cement job by reducing voids
and channeling, much like vibratory tools
used in the construction industry to attain
quality concrete with no holes or voids.
Moreover, because there are no moving
parts, the tool is very rugged and highly
reliable. It contains no elastomeric components, which negates temperature limitations or issues with gas, fluids, chemicals, or nitrified mud. It is highly customizable for various threads and sizes,
American Oil and Gas Reporter - September 2016

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