Horizontal wells provide a greater pumping challenge
Extracting oil is usually easy at first as liquid gushes to the surface. But
that quickly fades as the pressure eases, so producers rely on pumps that slowly
extract the bulk of the reserves over years or even decades. The most common
variety is a pumpjack -- in the UK, it is more commonly known as a nodding
donkey -- a technology that’s been in use for more than a century.
The nodding donkey has a steel hammerhead hovering over the well, bobbing up and
down to create suction in the hole, aided by a rotating counterweight. The
method is effective on vertical wells that go straight down, but is less so when
used on horizontal ones. It’s not uncommon for a shale well to go down a mile,
then use another 800 ft of pipe to bend from vertical to horizontal before
continuing sideways for a another mile or more.
Pumpjacks on vertical wells can last five or six years without any problems,
said Jesse Filipi, who until last year worked as an engineer for Marathon Oil
Corp. and was responsible for about 700 producing wells in the Eagle Ford Shale
deposit in south Texas. The same pumps might not last two years on the newer
horizontal wells, he said.
There are only about 50,000 horizontal wells in the U.S. and Canada that use
nodding donkeys, compared with a total of 1.2 million production wells in the
region,.But horizontal wells have been central to a resurgence of North American
output. The shale boom helped to double U.S. production since 2005. It’s now the
highest ever, exceeding even Saudi Arabia, according to BP Plc data. Texas, home
to the biggest shale deposits, saw output triple.
Yet some of those oil reserves may get stuck underground if the industry’s pumps
keep failing, which boosts costs for shale deposits that were initially cheap to
exploit and often remained profitable even when crude fell to $50.
It costs about $250,000 to install a nodding donkey, along with all the startup
gear, and as much as $100,000 to repair or replace it.One workaround engineers
have used is to shove natural gas into the hole to lighten the oil and make it
easier to pump to the surface. Another is placing an electric-submersible pump,
or ESP, down in the well. While both techniques work during the early stages in
the life of a well, they often aren’t as effective after output falls.
https://www.worldoil.com/news/2017/12/11/pumpjacks-fail-as-long-shale-wells-make-pumping-oil-harder