American Oil and Gas Reporter - June 2014 - 96

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Determining the right artificial
lift solution can be challenging
at best. Our highly trained
engineers configure, install,
and maintain systems on
wells that require artificial lift
for production.
We also provide follow-on
parts, maintenance, and
repair services to an installed
base of pumps.

Hydraulic Lift
Gas Lift
ESP
®

96 THE AMERICAN OIL & GAS REPORTER

At minimum, we would have had to
use the oversized "Mother Hubbard" mud
anchor. With this design, the liquid falls
through a narrow channel between the
edges of the anchor and the tubing, accelerating and forcing more gas out. Unfortunately, this design increases the
chance of recovery problems and introduces the possibility that the gas will
break out at the anchor's inlet, where it
can still create problems for the pump.
For maximum effectiveness, we could
have used a packer-type separator. However, these are three or four times more
expensive than Mother Hubbard designs
and often become stuck if sand accumulates on the packers. Fortunately, the jet
pump recovered the frac sand so quickly
and effectively that none of these devices
was required and the rod pump could be
placed below perforations to produce
more oil.
Jet Pump Principles
Jet pumps handle sand, gas and high
liquid volumes so well because of the
way they work. A pump at the surface
sends power fluid down the tubing and
into the jet pump. This fluid passes
through a narrow nozzle and throat assembly, which creates a Venturi effect,
reducing the fluid's pressure, and therefore,
the pressure on the formation. This causes
formation fluid to flow up through the
standing valve and into the diffusion
chamber, where it mixes with the power
fluid and then continues up the casing.
A jet pump operator can change two
variables to influence production rates:
the velocity of the power fluid and the
relative size of the nozzle and throat. If
the velocity is too high, the nozzle too
narrow, or the throat too small, the power
fluid will lose so much pressure as it
passes through the nozzle that it will cavitate. This wastes energy converting the
power fluid to a gas and creates shock
waves that damage the pump.
Fortunately, it is easy to calculate the
appropriate fluid speed, and nozzle and
throat size, for a given tubing diameter
using the expected fluid volume and bottom-hole pressure. This should keep cavitation from occurring.
At the surface, the power fluid must
be separated from the formation fluid
and cleaned so that it can be sent down
the hole without plugging the nozzle and
throat assembly. We ran the fluid through
a pressure vessel to remove the gas and
oil, and then put the water through a tank

to knock out the sand. The setup mirrored
a typical installation.
Horizontals
Initially, Broad Oak planned to use
jet pumps in its horizontal wells. Because
we had no experience with jet pumps,
we thought it would be wise to work out
any operational issues on relatively lowcost verticals.
Once we were comfortable with jet
pumps, we tried one in a Wolfcamp horizontal. At first, the results were promising,
with fluid production reaching 1,000
bbl/d and gas production around 1 million
cubic feet a day. However, as the gas-tooil ratio increased, fluid production
dropped. Eventually, the well was converted to gas lift to turn the gas into an
advantage and reduce operating costs.
Why was the oil production falling?
Jet pumps have limited space, and gas
takes up as much room as fluid, so as gas
production increases, it blocks the fluid.
This makes jet pumps a poor choice once
the gas-to-oil ratio reaches 3 Mcf a barrel,
which will happen in all but the oiliest
horizontals. As a result, jet pumps are
probably not a long-term solution in most
horizontal wells.
The pumps have other limitations,
such as low horsepower efficiency and
the need for high-pressure surface lines.
In laterals, their maximum depth is capped
by the packer setting depth and how far
slickline tools can go.
Despite these limitations, the pumps
can be a great temporary tool even in
gas-prone horizontals. As an illustration,
consider Broad Oak Energy II's experience
in the Wolfcamp Shale play. As of midMay, we had drilled 10 horizontal wells
targeting Wolfcamp intervals in Irion
County, Tx. We started the first well on
gas lift, thinking that if the gas compressor
went down, we could use the gas from a
gathering line on the lease to bring it
back up.
Because the gathering line was lengthy
and ran at low pressure, that only worked
once, and only early in the life of the
well, when it still wanted to flow. The
next time the gas compressor went down,
a nitrogen unit had to be moved to the
location to get the gas lift going, and
then clean the nitrogen out of the production line. That was difficult and expensive.
To prevent similar problems, the next
five wells were produced initially using
a jet pump/gas lift combo. The five wells

American Oil and Gas Reporter - June 2014

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