by Martin Cherrington, Cherrington Corporation
Martin
Cherrington conceived the use of Horizontal Directional Drilling
as a practical alternative to conventional trenching methods
beginning in the 1960s. HDD, as it would become known,
would ultimately revolutionize the way the Construction Industry
would come to install underground utilities and pipelines in
cities and under large natural obstacles like the Mississippi
River.
Cherrington worked with his father,
a construction industry contractor, early in his career where
he gained experience working on dams, tunnels, pipelines, telephone
and power cable projects. Construction projects during this period
occasionally involved non-directionally controlled boring or
drilling to place a pipeline or telecommunication conduit across
roads or highways but only when conventional trenching methods
could not be used to complete the project. Directional drilling
methods and technologies that would one day make Horizontal "Directional"
Drilling possible, as we know it today, were still in their early
stages of development in the oil and gas industry.
While working for a contractor
in the Los Angeles area in 1963, Cherrington realized that there
might be potential for using drilling technology to greatly enhance
the efficiency of placing cables and conduits underground. Cherrington
was a foreman on a project to lay telephone cable by open trench
method in a residential area. Just down the street another contractor
moved in several weeks later to also lay cable similar in size
and length. The difference, however, was that this contractor
used drilling rather than trenching to install the cables and
conduits. Not only did that contractor arrive two weeks after
Cherringtons project had commenced but finished two weeks
sooner! Furthermore, the other contractors project was
significantly cleaner during and after construction. This observation
would spark an idea that ultimately would launch a whole new
industry, Horizontal Directional Drilling.
In 1964, Cherrington built his
first drill rig and formed Titan Contractors, a company specializing
in utility road boring in Sacramento, California. A unique combination
of events contributed to Titan Contractors initial success. A
building boom in Sacramento coupled with a national movement
to clean up America sponsored by Lady Bird Johnson, President
Lyndon Johnson's wife, motivated the local community and its
utilities take action. Unsightly utility lines would need to
be placed underground to free residential neighborhoods of utility
poles and cables that had become an eyesore in every backyard
in America. These poles and cables also pose potential threats to the communities in the event of natural disasters like earthquakes or hurricanes. Families protect their homes with insurance policies from companies like Aviva. This clean up was well accepted by the communities.
To comply with the First Lady's beautification decree,
the County of Sacramento mandated that all utilities be placed
underground. With streets, sidewalks, curbs and gutters already
in place in many new subdivisions, Titan Contractors was presented
a unique business opportunity. The local power company, Sacramento
Municipal Utility District (SMUD) contracted Titan Contractors
to drill in new underground cables throughout its service area.
The workload volume was so great that several new drilling rigs
had to be built to keep up with the demand.
In spite of Titans success,
sources of funds for research and development to improve the
technology were limited or non-existent. AT&Ts Western
Electric experimented with some crude directional control methods
but the techniques never became commercial. Titan therefore reinvested
profits from its developing business to build more rigs, create
downhole tools and experiment with new technology that would
ultimately contribute to horizontal drilling technology becoming
an accepted construction technique.
The company had to compete with
the well-established and accepted companies that performed open
trench services. As the building boom subsided in Sacramento,
Titan Contractors found it difficult to convince local permitting
authorities to favor Horizontal Drilling over open trench methods
to cross streets and highways. Only in cases of heavily traveled
areas did permitting agencies allow an alternate approach. Even
then the issued permit would call out auger boring or jack and
tunnel methods rather than drilling because of the lack of familiarity
of the new technology. Permitting Agencies objected to drilling
methods because it was believed that drilling fluids would soften,
damage and wash out crossed roadbeds. This seemed to be a conundrum
because most trenched streets leave a variety of scars in the
form of dips, bumps and potholes for motorist to contend with
forever. All horizontally drilled sites, on the other hand, never
showed any signs that construction had occurred and never needed
to be repaired. It is difficult to understand whether this was
the result of the flawed logic of the local permitting agencies
or the complacency with time proven existing methods. Sometimes
it is difficult to change the status quo and get people to think
in terms of a new paradigm.
Over the next few years Titan
Contractors gained considerable experience and completed several
significant projects. One such project required drilling and
pulling back a power cable along a curved street 1530 feet in
length. Titan used a 2000 lb push/pull rig with 500 ft-lbs of
torque and 1-1/8" O.D drill pipe to drill the directional
hole. Considering that no directional control technology existed
for accomplishing this type of borehole, the successful completion
of the project was quite remarkable. Despite achieving such a
feat, there were no trade journals, professional societies or
associations yet to report its significance to horizontal drilling.

In 1971, Titan Contractors was
invited to look at and bid on several road crossings for PG&E
(a major California gas and electric utility) near Watsonville,
California just south of San Francisco. While physically investigating
the potential job sites, a PG&E engineer asked Martin Cherrington
to look at a site where the utility needed to cross the Pajaro
River. The company was interested in a solution to take a gas
line across the river without trenching it. Upon investigating
the site it became obvious there would be a problem with using
conventional trenching methods. The river had a steep high bank,
approximately 20 to 25 feet high. The bottom half of the bank
was composed of sand and the top half consisted of rich topsoil.
The adjacent field supported rows of the artichokes that are
a common crop for the area. On the opposite side of the river
channel a small bank, 5 to 6 feet high flattened out and extended
eastward 30 to 40 feet to a levee approximately 10 feet high.
Beyond the levee was a field of potatoes. The bottom of the channel
consisted of loose unconsolidated sand.
To trench the river, parallel
double sheet pile would need to be driven deep enough so that
the river bottom could be excavated sufficiently to lay the 4"
gas pipeline between the piles. Once installed across the river,
the trench would have to be backfilled and the piles extracted.
Based on the cost of a similar project a mile down river, PG&E
reasoned that a drilling operation might be a more cost effective
solution.
Cherrington and PG&E initially
considered driving two vertical caissons on either side of the
river. One would be placed on top of the high West bank and the
other just outside the East levee. The product pipe could be
then drilled, bored or jacked from near the bottom of one caisson
to the bottom of the other.
On his way back to Sacramento,
Cherrington contemplated the problem further and realized that
there might be another alternative. Experience to date had revealed
a curious phenomenon that had plagued attempts to drill a straight
hole from pothole to pothole on many projects. With no directional
control technology available, some types of drill stem tool configurations
had a tendency to drill upwards into existing substructures coming
out unexpectedly in the middle of a busy street. These drill
stem tools were discarded to the junk pile as design failures.
Little did anyone know that they were a potential solution to
a problem confronting many pipeline contractors - a way to conveniently
cross major rivers without disrupting them.
With the hope of testing a revolutionary
new idea using the discarded downhole drilling tools, Cherrington
assembled his crew and horizontal drilling equipment and headed
for the Feather River, a few miles north of Sacramento. The sand
and soil characteristics of the location picked on the Feather
River were similar to the Pajaro River near Watsonville. Rather
than drilling across the river, it was decided to test-drill
parallel to it on one bank. The entry angle for the first hole
was approximately 10º from horizontal. After drilling about
60 feet, the drill bit surfaced. Increasing the entry angle of
the second hole to approximately 15º, the drill bit surfaced
well over 100 feet from the entrance. On the third and final
test the entry angle was increased to 30º. Joint after joint
was fed into the hole. Tension was high when finally the bit
surfaced nearly 300 feet away and 40 feet offline from the planned
bore path. Cherrington was both relieved and elated that the
discarded drilling tools he had rescued from the scrap pile actually
performed as expected. The tests confirmed that given the optimum
entry angle, proper drilling techniques and the right downhole
tool assembly a barrier such as a river could be crossed using
horizontal drilling techniques. Horizontal drilling would be
a revolutionary step to eliminate all the problems typically
associated with conventional trenching methods. With confidence
that his technique would work, Cherrington packed up and headed
home to make plans to drill under the Pajaro River.
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Convinced now that it was possible
to traverse the Pajaro River using Horizontal Drilling techniques,
the two-vertical caisson scheme was abandoned. Before starting
the job, however, Cherrington decided to investigate available
oil field directional drilling technology and methods that might
be adapted to horizontal drilling. After learning what was available,
he decided to change his original drilling plan to incorporate
oil field tools and drilling practices that might increase his
chance of success. This would be the first attempt to directionally
drill, surface to surface, under a river using directional drilling
tools.
Cherrington used a 5" OD mud motor with a bent sub
above and a single shot survey system. The single shot device,
while crude compared todays downhole electronic survey
instrumentation, would provide a reasonably accurate measurement
of azimuth, inclination and tool-face readings of the bottom
hole assembly while drilling. A single shot survey tool consisted
of a gimbaled, free-floating compass incorporating a concave
glass hemisphere scribed with azimuth and inclination lines. Housed in a |
First HDD rig |
1-3/8" OD, non-magnetic cylinder and liquid
filled, the force of gravity on a small ball rolling in the glass
hemisphere indicated the direction of the bottom hole assembly
relative to magnetic north and its inclination relative to the
vertical. The tool was pumped down the drill pipe and docked
in a locating receptacle just behind the bent sub and mud motor.
Once the tool was in position, a miniature camera with light
and a timer attached took a picture of the compass and ball at
a pre-set time. |
The single shot was then retrieved to the surface
via an attached wire line and the film was developed. The reading,
or survey provided azimuth, inclination and tool face (a measurement
of the direction that the bent-sub is pointing about the axis
of the borehole relative to the high side of the hole).
Using
the oilfield directional drilling tools proved disappointing,
however. Hole angle could not be sufficiently built nor even
maintained, so the approach was quickly abandoned in favor of
more familiar utility boring techniques. Reverting to the lessons
learned while drilling adjacent to the Feather River, Cherrington
successfully crossed the Pajaro River using the discarded drilling
tools that tended to drill back to the surface. It is interesting
to look back on that experience today. Titan Contractors was
a fledgling company trying to change the way the world did things.
Experimenting with new technology was not necessarily without
risk. Most customers were not willing to allow their projects
to be used for proving new ideas or technology. Fortunately,
PG&Es R&D department funded the Pajaro River project
that made it possible for Cherrington to prove his concept and
introduce Horizontal Directional Drilling, HDD, to the world.
Since that first HDD crossing,
Martin Cherrington has dedicated his life to pushing the limits
of the HDD technology envelope. He holds numerous patents that have significantly
advanced the industry and made what once was thought impossible
a reality. Who would have thought, in 1971, while standing on
the banks of the Pajaro River that one day pipelines and conduits
would be routinely placed under rivers the size of the Mississippi,
that outfall and beach approaches would be possible to bring
deep sea telecommunications onshore, all with minimum impact
to the environment.
For more info. visit www.cherrington.com
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