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PeneDRILL is a downhole tool system designed to produce clean
communication tunnels, radially from an existing wellbore into reservoir rock,
for up to 2 meters in length. The tool drills one tunnel at a time, each
requiring 10 to 20 minutes to complete, and is capable of making multiple
tunnels during a single run. Factors such as well depth, rock lithology and
fluid type will govern the number of tunnels that can be completed on a single
trip normally the tool will be capable of 4 to 8 tunnels per run.
This system represents a unique
opportunity to expose new pay in a clean and non-damaging manner utilizing
light and compatible completion fluids.
The PeneDRILL tools consist
of four major components plus accessories such as an anchor, filter and
circulating valve. These components are:
CONTROL SECTION a hydraulically actuated
valve assembly allowing actuation of the tools by the operator at surface.
MOTOR & DRILL SECTIONS develop the
required rotation plus extension and retraction of the diamond rock bit to
drill clean 17mm diameter tunnels into the formation.
MILL SECTION mills a neat 26mm hole in the
production casing to allow the rock bit access to the formation.
PeneDRILL tools are currently stocked for casing sizes of 114.3mm to 177.8mm O.D. Larger sizes can be accommodated on request.
A CYCLE OF THE PeneDRILL TOOL
Once the tool has been run into the well and
positioned on depth, the mechanically set anchor is engaged to prevent tool
movement at any time during the penetrating sequence. A surface pump (usually
supplied by Penetrators) will then build pressure in the tubing to begin
actuation of the tools control section. The tubing-casing annulus will be left
open at surface to prevent pressure build-up against the formation, casing, or
BOP. Fluid returns, if any, will travel up the annulus to the rig tank. The
treatment can be performed underbalanced if the well is not sour and if any
fluid/gas returns to surface can be controlled without closing in the annulus.
By pumping at different pressures, the tool
operator is able to take the tool through a cycle of functions beginning with
actuation of the milling assembly which rotates a 26mm mill cutter to mill a
neat hole in the casing. The hole is clean, burr-free, and causes no damage or
distortion to the casing. Because the hole was created in a "low
force" manner, it does not damage the primary cement surrounding the
casing. The mill cutter is then retracted into the tool housing, rotation
stops, and a hydraulically driven index carriage is shifted within the tool
housing to move the milling head downward and bring a bit guide into alignment
with the hole in the casing. During this indexing procedure, the tool does not
move in relation to the casing only the internal index carriage moves.
Now a hydraulic motor begins rotating the
flexible drillstem and diamond rock bit which are then extended radially
through the hole in the casing. Fluid circulation is maintained down the
drillstem and through the bit so that all cuttings are flushed from the tunnel
and back into the wellbore. The bit drills into the formation rock for up to 2
meters.
Once drilling is complete, the drillstem and
bit are hydraulically retracted back into the tool housing. The tubing pressure
is reduced to zero, and the tool can then be repositioned to a different
orientation and depth for the next tunnel. An entire milling and drilling
procedure to make one tunnel normally takes 10 20 minutes and requires that
less than 1 cu. m. of fluid be pumped down the tubing at maximum pressures of
26 mPa. When all the tunnels are complete, a circulating valve at the top of
the tools is opened and the tool is ready for retrieval.
FLUID SELECTION
The PeneDRILL tool can be
operated with most clean, sweet, water or oil based fluids, excepting acids.
The more important consideration in fluid
choice is the reservoir. A light, compatible fluid such as a light oil would
often be a good choice, and may allow an opportunity to expose new pay while
the well is in an underbalanced condition.
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