GEOTHERMAL DRILLING
Insulated drill pipe offers new
tool to enable efficient drilling
of ultra-deep geothermal wells
Testing in New Mexico, Utah FORGE project
illustrates pipe’s effectiveness in lowering
temperatures, protecting downhole equipment
BY STEPHEN WHITFIELD, SENIOR EDITOR
To drill the ultradeep, high-temperature
wells needed for geothermal applications,
it’s critical to make sure that downhole
tools are protected. Insulated drill pipes
(IDP) have been used in oil and gas drilling
to maintain sufficiently low temperatures
for the drilling fluid as it moves downhole,
and thanks to a recently launched effort
from Eavor Technologies, they can now
help drillers and operators better navigate
the ultra-high temperatures often seen in
geothermal wells.
“Insulation is really important when
you’re drilling hot resources,” said Alex
Vetsak, Well Construction Advisor at Eavor.
“The geothermal business requires you
to drill as hot as possible – we’re talking
temperatures downhole exceeding 500°F.
When we’re talking about these numbers,
it’s critical to be able to deliver cold drill-
ing fluid from the surface to the downhole
tools. You don’t want to burn the sensitive
electronics at the bottom, and if your fluids
are exceeding the temperature limit for
those tools, they will burn and fail.”
The temperature ratings of different
bottomhole assembly (BHA) components,
such as the measurement-while-drilling
(MWD) and rotary steerable systems (RSS),
are particularly significant limiting fac-
tors, Mr Vetsak said at the IADC Drilling
Engineers Committee’s Technology Forum
in Houston on 1 November. To address this
issue, Eavor developed its IDP as part of a
suite of tools aimed at enabling high-tem-
perature drilling. By insulating both on the
outside and inside of the pipe with several
layers of a proprietary coating solution,
the heat transfer between the drilling fluid
traveling down the drill pipe and the hot
fluid traveling up the annulus is reduced.
This results in cooler fluid being delivered
to the BHA.
When used in conjunction with Eavor’s
other technologies – the Rock-Pipe drill-
ing fluid, its turbogenerator, and its mag-
netic ranging technology – the IDP helps
create what the company calls an “Eavor-
Loop,” a closed-loop geothermal system.
An Eavor-Loop is the connection of two
vertical wells with horizontal multilateral
wellbores that create a closed-loop sys-
tem. The company’s proprietary working
fluid – the fluid used to generate heat
from a geothermal reservoir – is selected
and added at surface, then circulated to
harvest heat. Eavor-Loops can also be
directionally drilled from centralized sur-
face pads.
The company first manufactured a full
IDP string in 2022 and tested its perfor-
mance in a geothermal formation in Q3-Q4
that year at the Eavor-Deep project in
New Mexico. An 18,000-ft well was drilled,
along with a sidetrack, in a granite forma-
tion with rock temperatures of around
480°F. The project aimed to demonstrate
all the technical elements required to con-
struct a commercial Eavor-Loop system
in deep, high-temperature hard rock, and
testing focused primarily on gathering
temperature measurements from MWD
tools. In this well, the IDP was able to help
the well maintain circulating tempera-
tures below 300°F at the bottom. Compared
with the circulating temperatures from
using a standard drill pipe – which Eavor
calculated would be approximately 370°F,
according to a transient thermodynamic
drilling model – the IDP reduced downhole
circulating temperatures by as much as
194°F, with a median of 142°F. Drilling was,
therefore, enabled by keeping the tempera-
ture below the 300°F tool limit.
Alex Vetsak, Well Construction Advisor at Eavor Technologies, spoke about the test-
ing and performance of the company’s insulated drill pipe for geothermal wells at
the IADC Drilling Engineers Committee’s Technology Forum on 1 November.
38 JAN UARY/FEB RUARY 2024 • D R I LLI N G CO N T R ACTO R
“Insulated pipe”
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