Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02615140 2007-12-17
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FLOW DENSITY TOOL
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present invention claims the benefit of U.S. Provisional Patent
Application
No. 60/870,306, filed December 15, 2006, which is incorporated herein by
reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to a method and apparatus for
logging
discreet media flow density, for example as on drilling rig during drilling
the subsurface
stratas.
BACKGROUND OF THE INVENTION
[0003] During drilling of sub-surface formations, drilling mud is circulated
down the
hole to flow up the drill bit cuttings. The cuttings are separated from the
mud and then may
be directed to an apparatus for further processing and measurements, for
example as
described by the author in US Patent # 6,386,026 "Cuttings Sample Catcher and
Method of
Use" and additionally disclosed in US Patent Application No. 10/711,333
"Drilling Cutting
Analyzer System and Methods of Applications" (Published US 2005-0082468).
[0004] It is, therefore, desirable to provide an improved method and apparatus
for
logging flow density.
SUMMARY OF THE INVENTION
[0005] It is an object of the present invention to obviate or mitigate at
least one
disadvantage of previous flow density meters.
[0006] The method and apparatus disclosed here is the new Flow Density Tool
using
sensors, such as Gamma Ray and Neutron sensors for Logging Flow Density of mud
with
drill cuttings in return flow, while drilling and other discreet media
materials. Neutron sensors
may provide, among other things, an assessment or measurement of the porosity
of the
media flowing through the apparatus. The flow density tool provides a
configuration and two
(2) or more sensors which in combination provide measurement of the flow
density of the
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discreet media moving through the apparatus (for example drilling mud or fluid
containing
drill cuttings or drill cuttings).
[0007] In a first aspect, the present invention provides a flow density tool
for
measuring the density of drilling mud containing drill cuttings, including a
gamma ray source
for directing gamma rays through at least a portion of the drilling mud
containing drill cuttings,
a gamma ray sensor for detecting the gamma rays, and a flow housing for
directing the flow
of the drilling mud containing drill cuttings past the gamma ray sensor.
[0008] Preferably the flow density tool further includes a neutron source for
directing
neutrons through at least a portion of the drilling mud containing drill
cuttings, and a neutron
sensor for detecting neutrons.
[0009] Preferably, the gamma ray sensor and the neutron sensor are housed in a
sensor tube. Preferably, the flow housing is an elongate tubular having a
first end and a
second end, an inflow orifice adapted to receive the drilling fluid containing
drill cuttings
proximate the first end. Preferably, the sensor tube is received in the second
end, forming an
annular gap between the sensor tube and the flow housing.
[0010] Preferably an outflow window is adapted to discharge the drilling fluid
containing drill cuttings from the annular gap. Preferably the annular gap is
between about
0.5 inch (13mm) and about 0.75 inch (19mm). Preferably the flow housing having
an upper
portion and a lower portion, the outflow window formed in the lower portion.
Preferably the
gamma ray source is americium 241. Preferably the neutron source is americium
241 upon a
beryllium target.
[0011] In a further aspect, the present invention provides a method of
calculating the
bulk density of drilling fluid containing drill cuttings including directing
gamma rays through at
least a portion of the drilling mud containing drill cuttings and measuring
gamma rays,
measuring neutron emissions from the drilling fluid containing drill cuttings,
and calculating a
bulk density based on the gamma rays measured and neutrons measured.
[0012] Preferably, the measurement of gamma rays and neutrons measured are
synchronized in time.
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[0013] Other aspects and features of the present invention will become
apparent to
those ordinarily skilled in the art upon review of the following description
of specific
embodiments of the invention in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Embodiments of the present invention will now be described, by way of
example only, with reference to the attached figure, wherein:
Fig. 1 is a cross-section view of a flow density tool of the present
invention.
DETAILED DESCRIPTION
[0015] Generally, the present invention provides a method and system for
measuring
or logging the flow density of a fluid slurry, such as drilling mud (drilling
fluid) containing drill
cuttings.
[0016] Referring to Fig. 1, the flow density tool 20 includes a tubular, such
as a pipe
30 with an inflow orifice 7 and an outflow window 8 and a sensor holder tube 9
inserted from
the opposite side from the inflow orifice 7 within a flow housing 4. Drilling
fluid containing
discrete media 10 are received in the inflow orifice 7.
[0017] A small nuclear source or sources 5 are covered with a lead blanket 1
or other
shielding from the outside so that the sensors are exposed only to the given
source and
covered by the same other shielding or lead blanket 1 from outside (or
external or
background) radiation.
[0018] The two sensors are preferably a Gamma Ray detector/sensor 2 and a
Neutron detector/sensor 3 similar to conventionally used in logging
optionally, with some
changes that will enhance the signal measurements, such as low temperature
operation. The
drilling fluid with the drill cuttings flows through the inflow orifice 7 past
the sensors 2 and 3
and the gamma ray absorption by the media is measured synchronously as the
neutron
count is measured to provide a signal or other indication usable by one
skilled in the art to
determine the gamma ray absorption and neutron count for determination of bulk
density of
the drilling fluid containing drill cuttings.
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[0019] Other parameters may be obtained from this apparatus with additional
interpretation in combination with the other parameters measured by surface
logging while
drilling (SLWD) as described in US Patent # 6,386,026, and US Patent Pending
application #
10/711,333 mentioned above (Published US 2005-0082468).
[0020] The apparatus of the present invention is preferably situated before
the mini
shaker (for example disclosed in US Patent # 6,386,026) and the cuttings are
pumped with
the mud pump through the mud flow house into the flow density tool 20.
[0021] The apparatus is preferably connected to the mud flow house (e.g.
inflow
orifice 7 receives drilling fluid containing cuttings from the mud flow house)
and the outflow
window 8, preferably at or proximate the bottom of the flow density tool 20
discharges drilling
fluid containing cuttings to the feeder.
[0022] The sensor holder tube 9 may be suspended by the sensor holder 40 at a
spacing of about 0.5 inch (13mm) to about 0.75 inch (19mm) between the sensor
holder tube
9 and the bottom of the flow housing 4 and inserted from the opposite side
from the inflow
orifice 7. Preferably, two or more sources 5 of gamma rays, such as Am 241 may
be placed
from outside of the tool flow housing 4 for creating a gamma ray flow through
the discreet
media 10. As shown, two sources 5 may be placed in the lower portion of the
flow housing 4
so that they are within the drilling fluid containing cuttings. To increase
signal, additional
sources 5 may be placed a distance from the first two sources 5.
[0023] These small nuclear sources 5 are covered with a lead blanket 1 or
other
shielding from the outside so that the sensors 2 and 3 are exposed only to the
given source
and covered by the same lead blanket 1 from outside radiation. A resistivity
sensor 6 may
optionally be placed in the flow density tool 20 to further improve the
accuracy of the bulk
density determination.
[0024] A small neutron source 50 may provide a stream of neutrons into the
drilling
fluid with drill cuttings. As an example, the small neutron source 50 may
include a Americium
241 source directed upon a Beryllium film, or plutonium, or other neutron
source. A shield,
such as water bath 60 or other shielding covers the neutron source 50 and
neutron sensor 3.
[0025] While drilling, an increased density in the drilling fluid flow with
drill cuttings
may indicate the potential caving in of the well bore and a decreased density
may indicate a
plug generating in the well by deficient hydraulic properties of drilling
fluid in the well.
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[0026] Other parameters may be obtained from this apparatus, such as
resistivity
sensor 6 with additional interpretation in combination with the other
parameters measured by
surface logging while drilling (SLWD) as described in US Patent # 6,386,026
(Sample
Catcher), and US Patent Pending application # 10/711,333 mentioned above.
[0027] As used herein, and as known to one skilled in the art, drilling mud
and drilling
fluid are used interchangeably.
[0028] In the preceding description, for purposes of explanation, numerous
details
are set forth in order to provide a thorough understanding of the embodiments
of the
invention. However, it will be apparent to one skilled in the art that these
specific details are
not required in order to practice the invention.
[0029] The above-described embodiments of the invention are intended to be
examples only. Alterations, modifications and variations can be effected to
the particular
embodiments by those of skill in the art without departing from the scope of
the invention,
which is defined solely by the claims appended hereto.
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