U.S. patent number 3,692,114 [Application Number 05/082,925] was granted by the patent office on 1972-09-19 for fluidized sandpacking.
Invention is credited to Carey Epps Murphey, Jr., Theodore Andrew Simon, Robert Steven Torrest.
United States Patent |
3,692,114 |
Murphey, Jr. , et
al. |
September 19, 1972 |
FLUIDIZED SANDPACKING
Abstract
A method for obtaining an improved pack emplacement when packing
a well with sand or gravel. A slurry of sand or gravel is pumped
through the end of a tubing string that is extended to near the
bottom of the interval to be packed; as the slurry is pumped, the
tubing string is raised at a rate that is correlated with the
pumping rate in order to maintain a fluidized bed of sand around
the end of the tubing string as it moves through the interval to be
packed.
Inventors: |
Murphey, Jr.; Carey Epps
(Houston, TX), Simon; Theodore Andrew (Calgary, Alberta, 30,
CA), Torrest; Robert Steven (Houston, TX) |
Family
ID: |
22174336 |
Appl.
No.: |
05/082,925 |
Filed: |
October 22, 1970 |
Current U.S.
Class: |
166/278 |
Current CPC
Class: |
E21B
43/04 (20130101) |
Current International
Class: |
E21B
43/04 (20060101); E21B 43/02 (20060101); F21b
043/04 () |
Field of
Search: |
;166/276,278 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
2652117 |
September 1953 |
Arendt et al. |
2685350 |
August 1954 |
Shea, Jr. et al. |
2986538 |
May 1961 |
Nesbitt et al. |
|
Primary Examiner: Leppink; James A.
Claims
We claim as our invention:
1. In a wellbore cased with tubular string of casing that is
cemented in place and perforated through an interval to be packed
to provide fluid communication with a surrounding earth formation,
a method for packing the wellbore with a granular material
comprising the steps of:
extending a string of tubing into the wellbore to a point adjacent
to the bottom of a selected interval of the wellbore to be packed,
an annular space being defined between the string of tubing and the
tubular casing;
closing the annular space between the string of tubing and the
casing above the interval to be packed;
determining a cylindrical fracture forming pressure less than the
lateral fracturing pressure of said formation which is sufficient
to cause the surrounding earth formation to move outwardly relative
to the cemented string of casing leaving a narrow space between the
cement and the earth formation;
pumping a slurry of a granular packing material through the string
of tubing at a slurry pumping rate sufficient to create a zone of
turbulent flow around the end of the string of tubing which extends
across the diameter of the wellbore and in which turbulent zone the
granular packing material is churned into a fluidized bed in which
the grain density is substantially uniform;
adjusting said slurry pumping rate while pumping said slurry to
maintain a pressure on said earth formation substantially equal to
said cylindrical fracture forming pressure; and
simultaneously raising the string of tubing through the interval to
be packed.
2. The method of claim 1 wherein the slurry of granular packing
material comprises a slurry of grains of particulate matter which
are coated with a solution of epoxy resin components and which are
suspended in a liquid hydrocarbon.
3. In a wellbore penetrating a fluid containing subsurface earth
formation which is cased opposite the fluid containing formation
with a perforate pipe member having a plurality of perforations
vertically spaced along the length thereof, there being at least
one cavity external of the perforate pipe member adjacent one or
more of the plurality of perforations, a method for packing the
interior of the perforate pipe member, the perforations in the
perforate pipe member and the cavity external of the perforate pipe
member with a granular material comprising the steps of:
extending a string of tubing into the well bore to a point within
the perforate pipe member adjacent the lowermost of the vertically
spaced perforations;
pumping a slurry of a granular packing material through the string
of tubing at a slurry pumping rate sufficient to create a zone of
turbulent flow within the perforate pipe member around the end of
the string of tubing in which zone of turbulent flow granular
packing material is churned into a fluidized bed in which the grain
density is substantially uniform, said zone extending across the
diameter of the perforate pipe member adjacent the lowermost
perforation, through the lowermost perforation and into the cavity
external of the perforate pipe member adjacent the lowermost
perforation; and, thereafter,
raising the string of tubing through the perforate pipe member
while continuing to pump the slurry at the slurry pumping rate
whereby the zone of turbulent flow is sequentially moved past each
of the vertically spaced perforations above the lowermost
perforation, each perforation and the interior of the perforate
pipe member as well as the cavity external of the perforate pipe
member adjacent that perforation being filled with granular packing
material as the zone of turbulent flow is moved past the
perforation.
4. The method of claim 3 including the step of closing the well
bore external of the string of tubing to fluid flow at a point
above the perforate pipe member before pumping said slurry.
5. The method of claim 2 wherein said slurry pumping rate is a rate
within the range of 1 barrel per minute to 3 barrels per
minute.
6. The method of claim 3 wherein the step of extending a string of
tubing in the well bore to a point within the perforate pipe member
adjacent the lowermost of the vertically spaced perforations
comprises lowering a string of tubing into the well bore to a point
at which the lowermost end of the string of tubing is less than
about 2 feet above the lowermost perforation.
7. The method of claim 3 wherein the step of raising the string of
tubing comprises raising the string of tubing through the perforate
pipe member at a substantially constant rate.
8. The method of claim 7 including the steps of:
determining a selected amount of granular material to be used in
packing the well bore adjacent the fluid-containing formation,
and
correlating the substantially constant rate at which the tubing is
raised with the slurry pumping rate so that when the lower end of
the tubing reaches the top of the well bore portion to be packed an
amount of granular material equal to the selected amount of
granular material has been pumped into the well bore.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of completing wells. More
particularly, the invention concerns the placement of a pack of
granular material in a well which penetrates an unconsolidated
earth formation.
2. Description of the Prior Art
In producing petroleum from subterranean reservoirs, many wells are
drilled into or through loosely cemented or unconsolidated
formations. When such a well is placed on production, sand is often
carried from the formation by the fluid and deposited in the well
bore. Some sand is usually entrained in the produced fluid, thus
causing severe erosion and damage to equipment which is employed in
the production of the fluid. The production of the sand interfers
with the normal production operations and gives rise to numerous
operating problems. It can be generally said that in the production
of a fluid from a loosely consolidated formation, workovers are
frequently necessary to remove sand from the bottom of the
borehole. If the erosion of the sand around the casing in the
bottom of a borehole is sufficiently great, it will leave the
casing inadequately supported and the casing may eventually buckle
or collapse. In some instances, the sand problem is so severe that
the well has to be abandoned.
Various methods have been attempted or suggested to date for
solving the problem of sand production in wells that penetrate
unconsolidated formations. One of the most widely practiced methods
is to place packs of granular material such as sand or gravel
behind a slotted liner or a perforated casing in such wells to
prevent an inflow of material from the surrounding incompetent
earth formation.
Such packs are installed by pumping a slurry of granular material
into the well so that the grain-suspending liquid is forced into
the surrounding earth formation while the suspended grains are
screened out on the face of the earth formations. In a borehole
that contains a perforated casing, the slurry must flow through the
perforations that extend laterally through the casing and through a
surrounding sheath of cement.
In accordance with conventional practice, the slurry of granular
packing is pumped through a stationary tubing string positioned so
that the lower end of the string is located at or above the top of
the interval to be packed. This placement of the tubing string is
believed to be desirable in order to avoid the pack's being formed
around a significant length of the tubing string thus binding the
tubing string within the well.
The use of a tubing string that ends above the interval to be
packed causes the slurry to flow downward past the perforations in
the casing or liner. The jetting effect of fluid emerging from the
tubing string causes a well mixed turbulent zone of slurry within a
distance of a few casing diameters from the end of the tubing
string. However, below this jet mixed zone, slurry moves down the
casing in a relatively slow flow and forms a deposit within the
well bore as lower perforations cease taking slurry. This well bore
deposit can build up to the lower end of the turbulent slurry zone
in the region of the tubing string. Thus, in the conventional
practice it is inevitable that a relatively large proportion of the
sand remains within the well rather than being displaced into the
formation.
SUMMARY OF THE INVENTION
The present invention provides an improved method for packing a
well with a granular packing material. According to the invention a
string of tubing is extended into the wellbore to near the bottom
of the interval to be packed and a slurry of packing material is
then pumped through the tubing string while the string is being
raised at a rate that is correlated with the pumping rate to
maintain a fluidized bed of packing material around the end of the
tubing string as it moves through the interval to be packed. In a
preferred embodiment of the present invention, when packing a well
having a cemented and perforated casing the slurry is pumped at a
pressure great enough to create a cylindrical fracture between the
casing and/or cement and the walls of the formation penetrated by
the well.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1 we see an unconsolidated earth formation 10
such as an unconsolidated sand formation penetrated by a well 9
having a well bore 11 which has been cased with a tubular casing 12
that is fixed in place with a cement 13. The well bore 11 has been
opened into fluid communication with the formation 10 through a
number of perforations 14-18 which penetrate the casing 12 and the
surrounding cement 13. There are a number of cavities or zones of
high porosity 19-23 in the formation 10 adjacent to the
perforations 14-18 which zones are of a type that may be caused by
sloughing or realignment of sand particles from the unconsolidated
earth formation 10 as fluid flows into the well bore 11 through the
perforations 14-18.
The well 9 is provided with equipment suitable for the practice of
this invention. A string of tubing 24 extends from the surface down
the well bore 11 to near the lowermost perforation to be packed 14.
At the surface the tubing 24 passes through a wellhead closure
assembly 25 that is operatively connected to the casing 12 and
which is adapted to carry a wellhead seal-off means 36 of a type
which may provide a fluid-tight seal-off of the annulus between the
casing 12 and the tubing 24 while allowing the tubing 24 to be
raised and lowered through the wellhead assembly 25. The top of the
tubing 24 is connected in fluid communication with a flexible
conduit means such as a hose 26 adapted to maintain fluid
communication between the tubing 24 and a conduit means such as a
flow pipe 27 as the tubing 24 is raised and lowered. The flow pipe
27 is in fluid communication with a slurry pumping apparatus of a
conventional type (not shown).
The tubing 24 is operatively connected to a raising and lowering
means of a conventional type which may be a workover rig comprising
a draw works 28 powered by a motor means 29 and operatively
connected to a wire line 30 that is strung through a crown block 31
mounted near the top of a mast or derrick means 32 and then through
a traveling block 33 that is connected by suitable means to a hook
34 which may be coupled to a tubing elevator 35 operatively
connected to the tubing string 24.
To pack zones 19-23 behind the perforated casing 12 with a granular
packing material 37 according to the process of this invention, the
tubing 24 is lowered into the well bore 11 until it extends to a
point adjacent the lowermost perforation 14 in the interval to be
packed. Preferably, the lower end of the tubing 24 is spotted about
12 to 24 inches above the lowermost perforation 14. The annulus
between tubing 24 and casing 12 is preferably closed to fluid flow
above the interval to be packed as by wellhead seal-off means 36 or
any other suitable means. A slurry of granular packing material 37
is then pumped through the tubing 24 into the well bore 11 at a
rate sufficient to create a zone of turbulent flow extending below
the lowest perforation 14. Injection rates in the range of about 1
barrel per minute to about 3 barrels per minute are normally
suitable for this purpose; however, the injection rate used in the
practice of this invention may range from the minimum rate at which
a slurry of a given packing material may be pumped through the
tubing 24 without plugging to the maximum rate which can be
achieved without fracturing the formation 10. As the slurry is
pumped through the tubing 24, the tubing 24 is slowly raised
through the interval to be packed at a substantially constant rate
correlated with the slurry pumping rate so that when the lower end
of the tubing 24 reaches top of the interval to be packed all of
the granular packing material intended to be used in packing the
interval has been used. This raising of the tubing 24 may be done
either incrementally or substantially continuously.
Referring to FIG. 2, we see an illustration of the flow of slurry
in the well bore 11 near the end of the tubing 24. Since the
annulus between the casing 12 and the tubing 24 is closed to fluid
flow at some point above the interval to be packed, as by the
seal-off means 36 in the wellhead closure assembly 25 of FIG. 1,
the fluid pumped down the tubing 24 into the well bore 11 can flow
out the well bore only through openings such as perforations 14-18
in the walls of the casing 15. As the slurry of packing material 37
flows through the perforations 14-18 into the cavities 19-23 behind
the casing 15, the grain suspending liquid component of the slurry
is forced into the surrounding earth formation 10 while the packing
material 37 is screened out on the face of the formation 10.
As the slurry is pumped out of the tubing 24, a zone 38 of
turbulent flow extends across the diameter of the well bore 11 and
into any adjacent perforations, such as perforations 15 and 16 for
a distance of about 1 to 2 feet below the end of the tubing 24.
Within the turbulent zone 38 packing material 37 is churned into a
fluidized bed in which the grain density (i.e., the number of
grains per unit volume) is substantially uniform. Each perforation
that is adjacent to the turbulent zone 38 tends to be penetrated by
a substantially equal amount of packing material 37 as the
fluidized packing material 37 flows into the perforation. Above the
turbulent zone 38, there is a zone 39 in the well bore 11 in which
the direction of flow is mainly upward. In this zone 39, the
velocity of fluid flow decreases at each perforation, such as
perforation 17, in proportion to the amount of slurry entering that
perforation and becomes substantially zero at about the depth of
the uppermost perforation 18. Because of the decrease in slurry
flow velocity in the zone 39 the flowing fluid in this zone 39 soon
becomes free of suspended packing material 37. Thus, only a small
proportion of the packing material 37 is carried above the top of
the turbulent zone 38. Below the turbulent zone 38, the well bore
11 becomes filled with packing material 37 that has settled out of
the slurry.
As the tubing string is moved upward through the interval to be
packed, the zone 38 of turbulent flow is advanced up through the
perforated interval of the casing 15 assuring that each of the
cavities 14-18 behind the perforated casing 15 is filled with a
substantially equal number of grains of the packing material 37 per
unit of volume if the character of the formation is uniform. The
upward movement of the tubing 24 and the fluidized bed of sand in
the turbulent zone 38 avoids the sticking of the tubing 24 by
keeping it above any sand that is not part of a fluidized bed. The
process also prevents a premature filling of the well bore 11 with
packing material 37. Since the packing material 37 is introduced at
the bottom, no static deposit is allowed to form at the depth of
any of the perforations 14-18 until after the perforation has been
filled with the fluidized bed of packing material.
In an embodiment of this invention, when packing an interval in a
cemented and perforated casing 12, the grain suspending liquid
component of the slurry of packing material 37 is forced into the
surrounding earth formation 10 at an injection pressure less than
fracturing pressure of the formation 10 but great enough to
compress the formation 10, moving the face thereof radially outward
relative to the casing 12 and cement 13 and creating a narrow void
space or "cylindrical fracture" substantially surrounding the
cement 13. The pressure at the face of the formation 10 required to
create a cylindrical fracture 40 may be determined by injecting a
quantity of the grain suspending liquid into the formation prior to
the injection of the slurry of packing material 37 at a relatively
low injection pressure and then increasing the bottom hole
injection pressure (without exceeding the pressure at which
fractures will be created which extend laterally into the formation
10 which lateral fracturing pressure may be known from other wells
in the area or may be determined by methods well known in the art)
while determining the injectivity of the well 9 from data obtained
by measuring the injection pressure and the injection rate. Tests
show that a marked increase in injectivity can be expected to occur
at that pressure at which a cylindrical fracture is formed.
In operating the present process, the slurry of grains to be used
in forming a sandpack or gravel pack can comprise a slurry of
grains of particulate matter which are coated with a solution of
epoxy resin components in a resin component solvent and are
suspended in a liquid hydrocarbon that has a limited solubility
with the resin component (as disclosed in a copending patent
application of E. H. Bruist et al, Ser. No. 867,631, filed Oct. 20,
1969.)
While the process of this invention has been described primarily
with respect to packing an interval in a well wherein a casing has
been cemented and then perforated, it should be understood that the
method is equally applicable to the placement of granular packing
material in wells completed in other ways, for example, as with an
uncemented slotted liner or other perforated pipe member.
In summary, the present invention provides an improved method for
packing a well bore with a granular material in a well that is at
least partially cased with a tubular casing. The method comprises
the steps of extending a string of tubing into the well bore to a
point adjacent the bottom of an interval of the wellbore to be
packed, closing the annular space between the string of tubing and
the casing above the interval to be packed, pumping a slurry of a
granular packing material through the string of tubing at a pumping
rate sufficient to create a zone of turbulent flow around the end
of the string of tubing which extends across the diameter of the
wellbore and in which turbulent zone the granular packing material
is churned into a fluidized bed in which the grain density is
substantially uniform, and simultaneously raising the string of
tubing, preferably at a rate that is correlated with the pumping
rate to maintain a fluidized bed of packing material around the end
of the string of tubing as it moves through the interval to be
packed. In a wellbore cased with a tubular string of casing that is
cemented in place and perforated through an interval to be packed,
an embodiment of the invention may comprise the additional steps of
determining a cylindrical fracture forming pressure less than the
lateral fracturing pressure of said formation which is sufficient
to cause the surrounding earth formation to move outwardly relative
to the cemented string of casing leaving a narrow space between the
cemented string of casing and the earth formation, and adjusting
the slurry pumping rate while pumping the slurry to maintain a
pressure on the earth formation substantially equal to the
cylindrical fracture forming pressure.
* * * * *