Pipe
Ramming Percussive Power Assists During Giant Pullback:
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by Jim Schill
Laney Directional Drilling,
Inc., Humble, TX has been involved in some if the most celebrated directional drilling projects in the industry.
That reputation was enhanced with their recent role in the Gulfstream
Pipeline project. Working to meet an aggressive timeline, the Laney
crews were put to the test when they encountered extremely difficult
directional drilling conditions during the installation of two major
sections of the pipeline off the coast of Alabama.
To solve the problems that threatened the completion of the project,
Laney Operations Manager Robert D. Hamil called on years of experience
and drilling knowledge. The solution to combine the power of their self-manufactured LDD Series directional drill rigs with
the percussive action world’s largest pipe rammer, the Grundoram Taurus from TT Technologies, Aurora, IL, provided amazing results.
Gulfstream Project
According to published figures, the Florida Public Service Commission
estimates that the State will see a 25% growth in demand for energy
over the next five years. Part of the answer to meet this demand
is natural gas. Being surrounded on three sides by water makes Florida
difficult to access by land.
The Gulfstream pipeline project is aimed at alleviating Florida’s
projected energy crunch. The 753-mile pipeline begins near Mobile,
AL and reaches Florida in Manatee County, traveling a majority of
the way under the Gulf of Mexico. It is one of the most ambitious
pipeline construction projects to originate in the United States
in years and is Florida’s first new natural gas pipelines
in 40 years.
Laney Directional Drilling, Inc. was sub-contracted by Stolt Offshore,
Inc., Middlesex, UK for several directional bores in various locations
along the pipeline route. Some of the most difficult bores took
place where the pipeline transitioned from offshore to onshore,
under a shipping channel in the Gulf of Mexico off the coast of
Bayou LaBatre, AL.
Big Bores
The Bayou LaBatre section called for the completion of two 4,700-ft
parallel bores for the final phase of the Gulfstream project. The
36-inch diameter epoxy coated steel product pipe has a 1.25-inch
wall thickness. The pipes needed to travel under a shipping channel
in the Gulf to a location onshore. One line would serve as the main
line, the other as the supply line. For the massive project, two
LDD drill rigs with close to one million pounds of pullback each
were used.
The Laney crew set up on shore to drill the pilot bore out to the
pre-determined spot in the Gulf for the installation of the first
pipe, the main line. The second bore would install the supply line.
Over the course of several weeks the Laney crew set up, performed
the necessary survey work, and completed the pilot bore and a series
of backreams in preparation for pulling back the mammoth pipe.
Hamil said, "After we completed the almost 9-inch diameter
pilot bore we started backreaming. We utilized a 24-inch backreamer,
then a 36-inch, 48-inch and finally a 64-inch reamer which we pulled
through twice. Usually backreaming 12 inches larger than the product
pipe is standard, but with the product pipe weighing 464 pounds
per foot, we knew this was going to be a difficult pullback. So,
we went above and beyond, up to 28 inches. Then we pulled 48-inch
diameter swabs through the hole to make sure that everything was
ready for pullback."
Pullback
Directional drilling operations under water face distinct challenges.
Difficult soil conditions under river bottoms, lakes and even an
ocean combined with the weight of the pipe and the hydrostatic pressure
of the water itself can create problems during drilling applications.
Reaching a point during product pullback where the pulling forces
required to pull in the pipe exceed maximum capability (a condition
often referred to as hydrolock) is one potential problem.
These were the challenges the Laney crew faced as they began pulling
back the 4,700 feet of 36-inch diameter steel pipe. The pipe lay
underwater and was hoisted to the surface to be connected for pullback
and then lowered back down. Pullback started slowly, but continued
until approximately a third of the way through. The Laney drill
rig began to reach the upper end of its pulling capabilities while
the installation was slowing to a stand still. The decision was
made to stop the pullback and try and recover the pipe.
Hamil said, "At that point we figured that we would still
be able to remove the pipe and start again. Stolt had a large 300-ton
cross winch that they anchored offshore. They attached 3-inch diameter
cable to the back of the pipe. The winch was able to remove the
pipe, but we knew that there would eventually come a point of no
return."
The crew reached that point during the second attempt when the
pullback was halted near the 4,000-ft installed mark. It was decision
time. Hamil said, "At that point, critical path schedules
were coming into the picture. After meeting with Gulfstream officials,
it was concluded that the supply line was more important to keeping
the project on schedule than the main line. So, the decision was
made to begin the next bore."
While the Laney crew started moving equipment into position for
the second bore, Laney Directional Drilling President, Mark Laney
contacted TT Technologies Pipe Ramming Specialists Fred Burlbaw
and Rick Melvin about getting a pneumatic pipe rammer on site to
assist with the project.
Hamil said, "We were aware of the pipe ramming techniques
designed to assist during drilling operations. We had seen it in
action at a jobsite recently and had been contemplating adding
a pneumatic pipe rammer to our equipment arsenal for some time.
This project expedited our plans."
HDD Rescue
Several
pipe ramming techniques have been developed over the few years to
assist directional drill rigs in difficult situations. The techniques
have been used to successfully remove stuck drill stems, assist
directional drill rigs during difficult pullbacks, free immobilized
product pipes and even salvage failed bores by removing stuck pipe
from the ground.
Melvin said, "By utilizing the percussive action of the Grundoram pipe
rammer we can really help drilling operations. These techniques
can help avert costly situations where product pipes or drill stems
get stuck. We’re actually seeing drilling contractors bring
pneumatic pipe rammers to job sites as a kind of insurance policy.
It’s been very positive for the industry."
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Pullback Assist
When
the Taurus pipe rammer arrived at the site, the second pilot bore
and series of backreams were complete and pullback was ready to
begin. Burlbaw said, "We decided to ready the rammer to assist
during the second pullback. That way we would be able, if needed,
to assist with pullback immediately if problems occurred. Laney
had fabricated a special ramming adapter to fit on the back of the
product pipe so we were essentially ready to go."
Pullback of the second pipe proceeded without incident until the
Laney crew was within 800 feet of completion when pullback stopped
again. In addition to facing the same conditions on this bore as
the first, the crew had to contend with a 1,500-ft section of 3-inch
cable that was being dragged behind the pipe. The cable was attached
the pipe in case the pullback stalled. According to Hamil the cable
acted like an anchor and dug into the sand adding more resistance.
The rammer was taken to the awaiting work-barge in the Gulf by another
barge equipped with a large crane, the pipe adapter and large air
compressors. Adding to an already difficult project were the tides.
All work had to be done in conjunction with the right tide conditions.
Melvin said, "We were working from barges in the Gulf, but
the area that we were working was still fairly shallow, only 9 feet
deep at a mile off shore and it was filled with sand bars. At low
tide the boats and barges can’t navigate through that area.
So everything we did was based on the timing and the tides."
Once at the work-barge, a crane was used to lift then remove the
1,500-ft section of cable. The end of the product pipe was also
carefully lifted with the crane and rested on the surface work-barge.
The pipe was fitted with the specially fabricated adapter and the
24-inch diameter Grundoram Taurus
put into position, completing the assembly.
With the Grundoram in
place, the crew pulled with the directional drill rig. The rammer
was started and within a few minutes the pipe began to move. The
hammer and drill rig worked in tandem until the section drill stem
needed to be removed. The crew shut the rammer off, removed the
31-ft section of drill stem and started pulling again. The rammer
assisted for a few more minutes, then the rig was able to complete
the pullback on its own. The second bore was complete, but the
first bore was still waiting, immobilized for over 21 days.
Push & Pull
Despite
sitting for three weeks, everyone was optimistic about getting the
first pipe all the way in the ground. The crews repositioned the
drill rig and moved the barges out to the end of the first pipe
string. Again the end of the pipe was carefully lifted out of the
water and the Grundoram,
pipe adapter and pipe were fitted together in the same way as before.
The crew started the drill rig and pulled back at approximately
50 percent. Then the hammer was started and the crew let it run
for a few minutes. When they believed that the energy from the
ramming had moved through the pipe string, more pulling force was
applied and the pipe began to move.
Hamil said, "This pipe had been sitting for quite some time.
We wanted to let the hammer work on it. We pulled through a couple
sections of drill stem and let the rig pull on its own. We pulled
a couple hundred more feet and the pipe started to become tight
again. We reconnected the hammer, put some more energy down through
it and we were back in motion again."
This time there were no more stops. The Laney crew was able to
complete the remaining few hundred feet and successfully install
the pipe. Burlbaw said, "Everyone associated with the project was ecstatic.
The Laney crew had been working pretty much 24 hours a day, seven
days a week for three months. They all were excited to get the pipe
in the ground."
Hamil said, "Getting the pipes in the ground made everyone
happy. I think everyone learned something on this project. Combining
the rammer with the directional drill proved extremely effective.
We won’t hesitate to use it again."
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Pipeline & Gas Journal, May 2002