Note: Descriptions are shown in the official language in which they were submitted.
CA 02380237 2002-O1-21
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METHOD FOR INJECTING DENSE ADDITIVE
INTO DRILLING WELLS AND COMPOSITION THEREFORE
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to an improved additive for use in control of lost
circulation,
fluid loss and/or seepage loss of drilling fluid during drilling operations.
In particular, the
additive is formed such that the additive can be incorporated into the
drilling fluid with
S much greater speed than powdered or ground additives of similar components.
Description of the Prior Art
Various additives are known in the art that are used to control lost
circulation or
seepage in a drilling operation. While the types of additives used for this
purpose range
from organic products to mineral products to plastics, most of these additives
are
introduced into the drilling fluid as a powder. There are numerous
disadvantages to the
use of a powder. The primary disadvantage is that the additive is very light
causing it to
mix slowly with the highly viscous drilling fluid. In drilling operations,
speedy
incorporation of the additives into the mud and circulation down through the
hole is
essential and afl'ects the profitability and occasionally the safety of the
operation. To
overcome this disadvantage of slow incorporation, hoppers have been designed
with
cyclones, venturis and jets to enhance mixing and to attempt to pull the
additives from the
hopper into the fluid at a higher rate. In spite of the improvement in
technology, mixing
is still relatively slow. The flow through the cyclones is slow, clogging
occurs, and dust
becomes a problem. In certain areas of the world where a zero emission
standard is in
place, dust is a particular problem. Regardless of the level of emission
standards, dust
creates a hazard for the workers.
Another problem of traditional powdered additives arises due to the general
change in drilling operations. There is a trend toward drilling in deeper
water with bigger
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rigs thus requiring larger volumes of mud. The muds being used tend to be more
expensive muds and synthetic oils emphasizing the need for lost circulation
and seepage
control additives. These factors also create a need for larger volume of
additives.
However, storage space, particularly on an offshore rig, is a limiting factor.
S In the search for a better additive, huge numbers of organic substances have
been
tested for their efficiency as lost circulation and seepage control agents. In
US 4,217,965
issued to Jim G. Cremeans, it is disclosed that discarded cattle feed can be
used as an
additive. This organic material is made from cottonseed hulls in combination
with
cottonseed meal, bentonite, some cottonseed lint and a surface active agent.
To make
feed for the cattle, these components are heated and then compressed and
extruded as
pellets. Cremeans discloses that the advantage of using discarded cattle feed
is that it
avoids the steps of grinding, shredding, and pretreatment processes required
when using
other organic waste products. The surface active ingredient in the pellet acts
as a wetting
agent to improve mixing time without further chemical additions. The cattle
pellets are
relatively dense and thus require less storage space. A shortcoming of the
cattle feed is
that it does not immediately break down upon contact with the mud but instead
maintains
its shape and structure as it is added to the mud. They only begin breakdown
when they
are well down the drilling hole.
There is a need to provide additives in a form that minimizes space required
for
storage and/or shipping. There is a need to provide additives in a form which
mixes with
the drilling fluid at substantially faster speeds. There is a need for a low
or no-dust
alternative for delivery ofthe additives to the drilling fluid. It is an
object and a goal of
this invention to meet these and other needs. It is an object and a goal of
this invention
to provide an additive that is quickly and efficiently distributed throughout
the drilling
fluid upon introduction. These and other objects of the invention will appear
to one
skilled in the art as the description thereof proceeds.
BRIEF SUMMARY OF THE INVENTION
The present invention discloses a method for creating a dense additive for use
in
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drilling fluids as well as the composition. A method of creating a dense
additive from lost
circulation and seepage control material for use in drilling operations
includes grinding of
the lost circulation and seepage control material to produce a small particle
size, heating
the lost circulation and seepage control material, and applying pressure to
the lost
circulation and seepage control material such that it densifies and is forced
through
apertures creating a pelletized dense additive. While many lost circulation
and seepage
control materials are appropriate, a preferred embodiment includes organic
material as the
lost circulation and seepage control material. This pelletized dense additive
for use in
drilling operations made from a ground lost circulation and seepage control
material that
is compressed into a pellet has a density substantially greater than that of
the ground lost
circulation and seepage control material before being compressed.
Ofthe organic lost circulation and seepage control materials available to
produce
the dense additive, a preferred embodiment includes a cellulosic material. In
particular,
one or more ofthe following in combination are preferred: ground wood, pine
bark, fruit
pomace, vegetable pomace, yellow pine, pine bark, corn cobs, peanut hulls,
pecan piths,
almond shell, corn cob outers, bees wings, cotton buns, oat hulls, rice hulls,
seed shells,
sunflower, flax, linseed, cocoa bean, feathers, peat moss, jute, flax, mohair,
wool, paper,
sugar cane, bagasse, sawdust, bamboo, cork, popcorn, tapioca, and grain
sorghum.
The pelletized dense additive, while characterized by increased density, is
preferably in the range of 1/8 inch to 3/4 inch for diameter and a range of
1/8 inch to 1
inch for length. The density ofthe additive ranges widely according to the
lost circulation
and seepage control material, with the preferred density being the highest
ratio of
compression achievable based on the characteristics of the material. Many
organic
materials can be compressed to between two and three times the density of the
ground
material.
This invention also encompasses a method of performing drilling operations
wherein a drilling fluid is circulated in a well being drilled in the ground
including grinding
a lost circulation and seepage control material to produce granules, heating
the granules
to liquify naturally occurring binding agents, pressing the heated granules
through
apertures such that pellets are formed that are of substantially greater
density than the lost
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circulation and seepage control material, adding the pellets to the drilling
fluid for
circulation in the well. The heating is typically a result of the fiiction
produced during the
pressing process. The grinding process can also produce a small quantity of
heat: With
certain lost circulation and seepage control materials, additional heat input
is desirable.
In the situation where naturally occurring binding agents are not present in
the lost
circulation and seepage control material, the preferred embodiment includes
minimizing
the amount of heat produced by the process and adding an appropriate binding
agent.
Frequently, sources of fiber as a lost circulation and seepage control
material are
already in a ground form, such as sawdust. The method of creating a dense
additive for
such a lost circulation and seepage control stock includes obtaining the
ground fiber and
compressing the ground fiber into a pellet such that the pellet has
substantially greater
density than the ground fiber before being compressed.
The structure and method of the present invention as well as other features,
advantages, benefits and objects thereof over other structures and methods
known in the
art can be better understood with reference to the detailed description which
follows.
DETAILED DESCRIPTION OF THE INVENTION
The present invention includes many advantages over traditional art. Among
such
advantages are an increased rate at which additives can be added to drilling
fluid, reduced
area required for storage and shipping, and reduced or eliminated dust
emission. A
characteristic of the present invention is that the dense additive immediately
begins to
hydrate on contact with the drilling fluid. With the quick hydration, the
dense additive
promptly disperses such that the additive is uniformly distributed through the
drilling fluid
as the drilling fluid is pumped down the hole. A preferred embodiment includes
distributing the dense additive through the drilling fluid using a traditional
hopper known
in the art for mixing non-dense or traditional additives. A typical hopper
will have an
outlet diameter in the range of 4-6 inches. The pellets are of a size to
easily and
compactly flow through the outlet. As with the non-dense additives known in
the art, the
hopper creates a mixing effect to contact the dense additive with the fluid.
When
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necessary, the pellets can be added to the drilling fluid without the use of a
hopper. In
this case, the pellets will hydrate as they come into contact with the
drilling fluid and will
immediately break down into fibers or other lost circulation and seepage
control material,
but it will take longer for the mixing action of pumping the drilling fluid
into the hole to
uniformly distribute the fibers throughout the fluid. Although not uniform
when added
in this manner, the additive is readily available to perform its function
after being mixed
with the drilling fluid at the surface and the rheological properties of the
fluid at the
surface are consistent with the properties down hole.
One of the advantages of use of the densified additive is the substantial or
complete reduction of dust during addition to the drilling fluid. Traditional
powders
added through a hopper create volumes of dust which create a hazard to the
environment
and to the working personnel. Certain areas, such as the North Sea, have
stringent
regulations on dust. The use of the densified additive results in a virtually
dust-free lost
circulation and seepage control additive.
Traditional powder or finely-ground additives, particularly cellulosic
additives,
have a maximum speed at which they can be introduced into the mud or drilling
fluid.
This rate of addition is related to the additive's angle of repose that
impacts the speed at
which the additive can be discharged. While previous attempts to increase
speed of
introduction have focused on the design of the hopper, including varying
outlet size, and
the addition of cyclones and other physical aids, the current invention is
directed toward
reducing the angle of repose of the additive to allow the material to flow
faster. The angle
of repose relates to how a material will stack and thus relates to the speed
at which it will
flow. By increasing density of the additive, the angle of repose is reduced
allowing the
same amount of material to be added to drilling fluid in substantially less
time.
The pellets can be made in a variety of shapes and sizes. The preferred size
of the
pellet depends upon the particular application, such as the diameter of the
outlet of the
hopper, the materials used to create the pellets and stacking behavior of
specific shapes
and sizes. The pellets can range from very small dense granules and dense
flakes up to
several inches. A preferred size is a pellet from 1/8 inch up to 3/4 inch in
diameter with
a length between 1/8 inch and 1 inch. Any apparatus useful for forcing
material through
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apertures can be employed in this invention. A preferred embodiment includes a
belt drive
pellet mill, such as the commercially available Ace Pellet Mill from Koppers
of Muncy,
Pennsylvania. This traditional pellet mill includes a feed screw forcing the
material into
a conditioner chamber. Steam can be injected when necessary into the feeder
section or
the conditioning chamber. A roll assembly forces the material through a die at
the end of
the conditioning chamber. Capacity is based in part on hole size of the pellet
die. The
force generated by such a pellet mill is generally sufficient to achieve
maximum or
optimum compressibility of the ground material. Also, the heat generated as a
result of
the friction is generally sufficient to release oils or binders of those
materials containing
such components without the addition of heat. Other methods of compressing the
ground
material can also be used. Likewise, it is encompassed within the invention
that the
grinding and compressing processes can also be performed in one apparatus.
The lost circulation and seepage control material useful for the present
invention
includes any material that performs the function of a lost circulation
additive and/or a
seepage control agent. At least one of the lost circulation and seepage
control materials
should be somewhat compressible to allow the pellet formed from such material
to be
denser than the lost circulation and seepage control material prior to
compression. Some
of the organic materials useful as lost circulation and seepage control
material in this
invention include cellulosic products such as ground wood, pine bark, pomace
or pulp of
fruits andlor vegetables, yellow pine, pine bark, corn cobs, peanut hulls,
which is also a
Garner for insecticides, pecan piths, almond shell, corn cob outers, bees
wings, cotton
buns, kenaf, sillage, oat hulls, rice hulls. Other representative organic
materials include
seed shells, sunflower, flax, linseed, cocoa bean, feathers, peat moss, jute,
flax, mohair,
wool, paper, sugar cane, bagasse, sawdust, bamboo, cork, popcorn, tapioca, and
grain
sorghum. Many assorted organic materials useful as lost circulation additives
are also
appropriate for this invention including carrageenan guam, guar gum, and other
soluble
gums.
Organic materials frequently contain natural binders such as lignin
sulfonates,
wood sugar, oils or other binding agents. With most organic materials useful
as additives,
to create the dense additive, the material is exposed to friction through a
grinding process
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to produce a fine material. This ground material is then subjected to pressure
that forces
the material with its oil through small openings or aperture to create
pellets. The process
of pressing produces heat that, in turn, releases oils and other readily
liquified components
of the material. These oils and other materials act to bind the material such
that it is
maintained as a pellet. When inorganic materials alone are used or when
insufficient oil
is present for binding of the pellets, oil or other binder can be added to the
lost circulation
and seepage control materials. Likewise, in cases where the oil contained
within the
material is of a higher melting point, additional heat can be input.
The pellet can be formed of one or more additives effective as lost
circulation
additives or seepage control agents. Also, the step of applying fi-iction to
produce a fine
material can produce material of various sizes such that the pore openings of
the
permeable formation are effectively plugged without adverse effects. Thus, the
particle
distribution in the drilling fluid resulting from the pellet of the invention
not only ensures
an even mix of additive, but an even mix of various sizes of particles of
additive should
a mix of granule sizes be desirable.
Among the inorganic materials usefizl in this invention, mineral components
are
readily available, such as calcium carbonate, mica, diatomaceous earth,
Fuller's earth and
other silicates, activated charcoal, bauxite, alumina gel, graphite, gilsonite
and the like.
Such materials are frequently provided in fiber or ground form. Carbonate may
be used
alone or in combination with other desirable additives. The effect of adding
carbonate to
organic additives is an improved acid solubility. This also results in a
pellet of increased
density. Also usefi~l are plastics.
A substantial increase in density is observed between the lost circulation and
seepage control materials useful in this invention and the dense additive. A
typical
example includes a cellulosic additive with a density of 10 Ibs/cf. Upon
pelletizing this
additive with mica, the resulting density is about 17 Ibs/cf. Substantial
greater density is
defined as a non-trivial increase in density as compared to the density of the
raw materials
used to create the denser additive. Thus, while the addition of a component
such as mica
would increase the density of the mixture of the raw materials, compression
into a pellet
substantially increases the density of the mixture. The increase in density is
directly
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related to the size and shape of the particles being compressed and the nature
of the
material. Thus, for example, increasing of density from 10 lbs/cf to 11 lbs/cf
for a specific
material can be a substantial increase in density creating a faster flow of
the material out
of the hopper with reduction of dust. Preferred materials for use in the
invention include
those which have low density and are highly compressible. In addition to the
advantages
listed above relating to speed of incorporation, such low density materials
can be highly
compressed resulting in a product which requires far less space for storage.
For example,
corn cobs can be compressed into a pellet approximately double the density of
corn cobs
in ground form.
From the foregoing it will be seen that this invention is one well adapted to
attain
all ofthe ends and objects hereinabove set forth, together with other
advantages which are
obvious and which are inherent to the apparatus and structure.
It will be understood that certain features and subcombinations are of utility
and
may be employed without reference to other features and subcombinations. This
is
contemplated by and is within the scope of the claims.
Because many possible embodiments may be made of the invention without
departing from the scope thereof, it is to be understood that all matter
herein set forth or
shown in the accompanying drawings is to be interpreted as illustrative and
not in a
limiting sense. For example, the dense additive can also include insecticides,
biocides or
other biological operatives to reduce susceptibility to various types of
degradation or to
repel pests. While one of the advantages to this invention is to use
agricultural
byproducts as a lost circulation and seepage control material thus minimizing
what would
otherwise be a waste product, some agricultural products and other lost
circulation and
seepage control materials usefixl to this invention are provided in a ground
form. The
method of creating a dense additive from such a lost circulation and seepage
control stock
includes obtaining the ground lost circulation and seepage control material.
Obtaining the
material in ground form as opposed to grinding the material is also
encompassed within
this invention.
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