U.S. patent number RE33,747 [Application Number 07/357,602] was granted by the patent office on 1991-11-19 for rigidification of semi-solid agglomerations.
This patent grant is currently assigned to Soli-Tech, Inc.. Invention is credited to Dwight N. Hartley, Tyrus W. Hartley.
United States Patent |
RE33,747 |
Hartley , et al. |
November 19, 1991 |
**Please see images for:
( Certificate of Correction ) ** |
Rigidification of semi-solid agglomerations
Abstract
A method of rigidifying semi-solid agglomerations resulting from
the drilling of an oil or gas well comprises mixing the
agglomerations with a hygroscopic powder and a cementitious binder
to produce a rigid, form-stable matrix.
Inventors: |
Hartley; Tyrus W. (Bay City,
MI), Hartley; Dwight N. (Bay City, MI) |
Assignee: |
Soli-Tech, Inc. (Kawkawlin,
MI)
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Family
ID: |
27425199 |
Appl.
No.: |
07/357,602 |
Filed: |
May 25, 1989 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
627878 |
Jul 5, 1984 |
04668128 |
May 26, 1987 |
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Current U.S.
Class: |
405/266;
405/129.3; 405/128.7 |
Current CPC
Class: |
C04B
28/02 (20130101); E21B 41/005 (20130101); C09K
8/46 (20130101); C04B 28/02 (20130101); C04B
14/361 (20130101); C04B 18/0418 (20130101); C04B
22/062 (20130101); C04B 22/08 (20130101); C04B
28/02 (20130101); C04B 14/361 (20130101); C04B
18/0418 (20130101); C04B 18/162 (20130101); C04B
22/08 (20130101); Y02W 30/91 (20150501) |
Current International
Class: |
C09K
8/42 (20060101); C09K 8/46 (20060101); C04B
28/02 (20060101); C04B 28/00 (20060101); E21B
41/00 (20060101); E02D 003/12 () |
Field of
Search: |
;405/53,128,129,263,266,267 ;175/66 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2430371 |
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Jan 1976 |
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DE |
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2950462 |
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Jun 1981 |
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DE |
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20215 |
|
Feb 1981 |
|
JP |
|
Primary Examiner: Corbin; David H.
Attorney, Agent or Firm: Learman & McCulloch
Claims
What is claimed is:
1. In a method of rigidifying a semi-solid agglomeration of solids
and liquids such as that resulting from the drilling of a well and
contained in a pit excavated adjacent the well site, said
agglomeration having a depth less than that of said pit, the
improvement comprising permitting the agglomeration within said pit
to stand for a period of time sufficient to cause heavier solids to
settle and excess liquids to accumulate atop such agglomeration;
removing at least a substantial portion of said excess liquids;
adding to and mixing with the agglomeration in said pit a quantity
of .[.hygroscopic meal,.]. .Iadd.meal including a hygroscopic
powder and .Iaddend.a cementitious binder, and earthen aggregate
resulting from the excavation of said pit to form a substantially
homogeneous mass, the quantity of said meal.[., said binder,.]. and
said aggregate added to said agglomeration being insufficient to
overflow said pit; and curing said mass to form a substantially
rigid matrix.
2. A method according to claim 1 wherein the quantities of solids
and liquids in said agglomeration are such that it has the
consistency of a slurry having no substantial structural
strength.
3. A method according to claim 1 including covering the bottom and
sides of said pit with a moisture impervious liner prior to
introducing said agglomeration into said pit.
4. A method according to claim 1 wherein said pit has a depth
greater than the height of said matrix, and including covering said
matrix with additional aggregate excavated in the formation of said
pit.
5. A method according to claim 4 including covering said matrix
with a moisture impervious liner prior to covering said matrix with
said additional aggregate.
6. A method according to claim 1 wherein said agglomeration
comprises between about 70 and 75 weight percent of said mass.
7. A method according to claim 1 wherein said .[.meal.].
.Iadd.powder .Iaddend.said mass.
8. A method according to claim 1 wherein said aggregate comprises
between about 20 and 25 weight percent of said mass.
9. A method according to claim 1 wherein said binder comprises
between about 0.3 and 1.0 weight percent of said mass.
10. A method according to claim 1 wherein said meal is composed of
a powder containing a substantial quantity of oxides which react
with liquids in said agglomeration to form water insoluble
hydroxides.
11. A method according to claim 10 wherein said quantity of oxides
includes calcium oxide.
12. A method according to claim 1 wherein said agglomeration
includes brine.
13. A method according to claim 1 wherein said agglomeration
includes drilling mud, well cuttings, and brine.
14. A method according to claim 1 wherein said .[.meal.].
.Iadd.powder .Iaddend.comprises cement kiln dust and said
cementitious binder comprises cement.
15. A method according to claim 1 wherein said agglomeration
comprises between about 70 and 75 weight percent of said mass, said
.[.meal.]. .Iadd.powder .Iaddend.comprises between about 4 and 11
weight percent of said mass, said aggregate comprises between about
20 and 25 weight percent of said mass, and said cementitious binder
comprises between about 0.3 and 1.0 weight percent of said
mass.
16. In a method of rigidifying a semi-solid agglomeration of solids
and liquids contained in a pit having a depth greater than that of
said agglomeration, said method comprising permitting the
agglomeration within said pit to stand for a period of time
sufficient to cause heavier solids to settle and excess liquids to
accumulate atop such agglomeration; removing at least a substantial
portion of said excess liquids; adding to and mixing with the
agglomeration in said pit a quantity of .[.hygroscopic meal,.].
.Iadd.meal including a hygroscopic powder and .Iaddend.a
cementitious binder, and earthen aggregate to form a substantially
homogeneous mass, the quantity of said meal.[., said binder,.]. and
said aggregate added to said agglomeration being insufficient to
overflow said pit; and curing said mass to form a substantially
rigid matrix. .Iadd.17. In a method of rigidifying a semi-solid
agglomeration of materials composed of solids and liquids confined
in a containment, the improvement comprising permitting the
agglomeration within said containment to stand for a period of time
sufficient to cause heavier solids to settle and excess liquids to
accumulate atop such agglomeration; removing at least a substantial
portion of said excess liquids; adding to and mixing with the
agglomeration remaining in said containment a quantity of meal
including a hygroscopic powder and a cementitious binder, and an
aggregate to form a substantially homogeneous mass, the quantity of
said meal and said aggregate added to said agglomeration being
insufficient to overflow said containment; and curing said mass to
form a substantially rigid matrix. .Iaddend. .Iadd.18. A method
according to claim 17 wherein said powder comprises cement kiln
dust and said binder comprises cement. .Iaddend.
Description
This invention relates to the rigidification of semi-solid
agglomerations of the kind resulting from the drilling of oil and
gas wells.
BACKGROUND OF THE INVENTION
In the drilling of an oil or gas well it is conventional to employ
a drilling rig to power a rotary, hollow drill pipe at the lower
end of which is a drill bit which is advanced downwardly into the
earth. Operation of the drilling apparatus is accompanied by the
delivery of water to the upper end of the drill pipe and under such
force as to cause the water to flush the cuttings from the bottom
of the bore and return and carry them to the surface.
Conventionally, the water is supplemented with clayey material
commonly referred to as drilling mud. The drilling mud may contain
a number of ingredients, including fresh or salt water, so as to
render the mud sufficiently plastic to flow while retaining
sufficient body or viscosity to effect sealing of the walls of the
well bore and to maintain in suspension the drill cuttings as the
latter are moved upwardly of the well bore. Typical muds are
provided by Wyoming bentonite or sodium montmorillonite. Another
clay commonly used for mud is attapulgite.
The particular kind of clay or similar substance used for a
drilling mud will depend upon a number of factors which are of no
particular significance to the method herein disclosed. All of the
materials used for drilling muds, however, have the common
characteristic that, when the drilling operations are completed,
the spent muds are agglomerated with well cuttings and liquids,
usually brine, in a semi-solid slurry or mass having no form
stability or structural strength and a consistency similar to that
of toothpaste with a funnel test viscosity of between about 40 to
60 sec./l.
At the completion of well drilling operations a large quantity of
the agglomerated materials must be disposed of. These materials may
not simply be scattered about the well site, or even collected in a
pit adjacent the drilling site, for several reasons. One reason is
that the chlorides from the brine will contaminate the soil and
adjacent ground waters. Another reason is that, since the
agglomeration has no appreciable stability, it is not possible to
restore the ground to the condition it had prior to the excavation
of the pit. That is, excavated earth cannot simply be returned to
the pit with the agglomerated materials inasmuch as the latter
would ooze from the pit and result in the formation of a
quagmire.
Because of the difficulties encountered heretofore in disposing of
well cuttings and materials associated therewith at the well site,
it has been the practice to load such materials in tank trucks and
transport them to a central disposal site. The time and expense of
such practice make the cost of such disposal exorbitant.
SUMMARY OF THE INVENTION
The method according to the invention is especially adapted for use
in disposing of residues from the drilling of oil and gas wells at
the well site and in such manner as to avoid ecological
contamination and at the same time enabling the land adjacent the
drilling site to be restored to its original appearance and
use.
In the practice of the method aqueous agglomerated residues from a
well drilling operation are discharged to a pit that has been
excavated adjacent the well site and which has been lined with a
moisture impervious liner. The agglomerated materials are permitted
to settle, following which excess liquid is removed. A powdery meal
composed of a hygroscopic powder and a cementitious binder, is
mixed with the agglomerated material, following which some of the
aggregate resulting from the excavation of the pit is mixed with
the mixture of agglomerated materials and meal. The powder of the
meal will absorb the moisture and encapsulate the solids, whereas
the cementitious material will bind the encapsulated solids
together to form a rigid matrix. After appropriate curing of the
matrix the latter may be covered with other aggregate remaining
from the excavation of the pit, whereupon the rigidified matrix not
only will provide support for the covering material, but also
support for tractors and other machinery, thereby enabling the site
of the pit to be farmed or otherwise used. The excess of the
aggregate material resulting from the excavation of the pit may be
distributed over a wider area or, if desired, hauled away for other
purposes.
THE DRAWINGS
A process of solidifying the semi-solid residues from well drilling
operations is disclosed in the following description and
illustrated in the accompanying drawings, wherein:
FIG. 1 is a top plan view of a typical pit that has been excavated
adjacent a well-drilling site;
FIG. 2 is a sectional view taken on the line 2--2 of FIG. 1 and
illustrating one stage of the method; and
FIGS. 3-5 are views similar to FIG. 2 but illustrating successive
stages in the performance of the method.
THE PREFERRED EMBODIMENT
Preparatory to the practice of the method according to the
invention an open top enclosure or .Iadd.containment such as a
.Iaddend.pit 1 is excavated adjacent the site at which an oil or
gas well is to be drilled. The pit 1 preferably is square in plan
view, but can be of any other shape. The pit also preferably has a
flat bottom 2 and downwardly sloping side walls 3. Again, however,
the particular shape of the pit's bottom and side walls may vary.
It is preferred, however, that the pit have a regular, geometric
configuration, thereby facilitating computation of the pit's
volume.
Following excavation of the pit, a moisture impervious liner 4
formed of polyvinylchloride or the like is placed in the pit so as
to span the bottom, cover the side walls, and extend away from the
pit over the upper surface of the adjacent ground. The marginal
edges 5 of the liner thus form a protective apron adjacent the
upper marginal edges of the pit.
In the drilling of a well it is conventional practice to utilize
fluids and clayey materials, referred to as drilling muds, to
assist in the support of the drill pipe and to flush chips or
cuttings from the bottom of the bore for discharge from the mouth
of the bore. In the process of drilling it is common for the drill
to pass through levels containing brine which becomes mixed with
the mud and cuttings and is discharged from the mouth of the bore
as an aqueous agglomeration. These materials conventionally are
delivered to a settling tank from which some portion of the mud may
be reclaimed for recirculation through the well bore. Eventually,
however, the used mud becomes spent and must be replaced with fresh
mud. The spent mud, along with cuttings, brine, and other materials
resulting from the the drilling operation are discharged to the pit
1, thereby enabling the settling tank to be used repeatedly during
the drilling operation.
At the conclusion of the drilling operation the remaining contents
of the settling tank are discharged to the pit 1, but the depth of
the pit preferably is 3-6 feet greater than the height of the
materials discharged to the pit. These materials comprise a
semi-solid agglomeration 6 composed of the liquid-saturated mud,
the cuttings, and the liquids. The liquids conventionally
constitute a brine which, in some sections of the country, is
composed of about 75% water and 25% water soluble sodium chloride
and other soluble salts. The constituency of the brine is not
critical to the method, although it is desirable that the brine
contain a high percentage of chlorides.
Following discharge of the agglomeration and liquids to the pit,
the materials are permitted to stand for a period of time, such as
one to two days, more or less, to permit the denser fractions of
the contents to settle to the bottom of the pit. This will result
in the provision of a layer of excess liquid 7 atop the
agglomeration 6. Thereafter, the excess liquid is pumped into tank
trucks or the like and transported elsewhere for disposal. The
residue in the pit still contains a high percentage of liquid, as a
consequence of which the agglomeration comprises a slurry having a
consistency corresponding substantially to that of toothpaste and
no appreciable stability or load bearing strength.
Following removal of the layer of excess liquid from the pit, a
meal 8 is added to the contents of the pit 1. Preferably, the meal
is delivered to the site in a truck equipped with pneumatic
discharge means which feeds the meal to a portable cyclone mounted
at the free end of a boom carried by a crawler-type vehicle which
has a backhoe. The vehicle may traverse the perimeter of the pit so
as to discharge the meal in a substantially uniform layer over the
entire surface of the pit's contents. For best results, the width
of the pit should not be so great that the boom cannot reach at
least half way across the pit.
The meal 8 comprises a mixture of cement kiln dust (CKD) and a
cementitious binder such as Type I cement. CKD is a waste product
resulting from the manufacture of cement. In the United States
alone CKD accumulates at the rate of several million tons per year
and represents a significant pollution control problem confronting
the cement industry. CKD is not a hazardous waste, but is produced
in euch large volume that it poses a severe disposal problem. Some
commercial uses have been proposed for CKD, such as its being used
as a substitute for lime, but the extent of such usage thus far has
been relatively small in comparison to its production. Utilization
of CKD as a major constituent of the meal used in the process
according to the invention represents the largest commercial use of
CKD presently known.
Following the addition of the layer of meal 8 to the pit's
contents, the meal and the agglomeration 6 are mixed mechanically
by means of the aforementioned backhoe to form a substantially
homogenous mixture 9. The mixing causes the CKD, which is highly
hygroscopic, to encapsulate the solids of the agglomeration. The
mixing also causes the cement phase of the meal to coat the
encapsulated solids and serve as a binder therebetween.
Following mixing of the agglomeration and the meal, the mixture 9
may be allowed to cure, but it is preferred to combine the mixture
with an aggregate 10. The aggregate may comprise the earth, stones,
gravel, sand, clay, and the like which were excavated in the
formation of the pit 1. The aggregate may be added to the pit by
means of backhoes, bulldozers, and the like and is mixed with the
mixture of agglomeration and meal by means of backhoes until there
is a substantially homogenous mass 11. The combined amount of
meal.[., binder,.]. and aggregate added to the pit is insufficient
to overflow the latter. The solids of the agglomeration 6 and the
solids of the aggregate 10 will be encapsulated by the CKD and
coated with the cement. Following formation of the mass 11, the
latter is permitted to cure and form a rigid matrix. The curing
time will vary according to climatic conditions, but a period of 12
to 24 hours usually is sufficient to enable the mass to rigidify
adequate L4. The presence of chloride as a constituent of the mass
accelerates the curing thereof.
A field test for rigidification of the matrix may be performed by
the use of a backhoe. The boom of the backhoe may be extended over
the pit and the bucket at the free end of the boom placed atop the
matrix. The boom then may be extended. If the bucket enters the
matrix, curing is incomplete. If the crawler vehicle on which the
boom is carried is caused to tilt, however, then curing is
complete. The matrix formed according to the invention conforms to
the compaction requirements of the Resource Conservation and
Recovery Act of 1976 (RCRA).
In some jurisdictions it is required to cover the matrix with a
moisture impervious liner. If so, the marginal edges 5 of the liner
may be turned inwardly so as to overlie the upper surface of the
matrx. Any unlined area which may exist then may be covered by an
additional liner. Thereafter, additional aggregate 12 resulting
from the excavation of the pit may be used to fill the pit. The
excavated material in excess of that which can be returned to the
pit then may be distributed over the adjacent area or trucked
elsewhere.
The method according to the invention enables the pit site to be
returned to its original condition following drilling operations
with the exception that the site includes the buried, rigid matrix.
The rigidity of the matrix is sufficient to support farm vehicles,
thereby enabling the land to be farmed if desired.
Cement kiln dust furnished by a number of cement manufacturers has
been used in the practice of the process. Although the specific
chemical analysis of each manufacturer's CKD may vary, and
successive batches from each manufacturer often also may vary, the
variations are relatively small and do not appear to have any
effect on the rigidification of the agglomeration.
A chemical analysis of CKD used in the method and furnished by one
cement manufacturer is as follows:
______________________________________ Compound Weight Percent
______________________________________ CaO 51.64 SiO.sub.2 14.76
Al.sub.2 O.sub.3 4.64 Fe.sub.2 O.sub.3 1.97 MgO 1.56 SO.sub.3 10.30
K.sub.2 O and Na.sub.2 O 3.26
______________________________________
An analysis of another manufacturer's CKD used in the method is as
follows:
______________________________________ Compound Weight Percent
______________________________________ CaO 44.86 SiO.sub.2 13.94
Al.sub.2 O.sub.3 4.25 Fe.sub.2 O.sub.3 2.61 MgO 2.74 SO.sub.3 7.05
K.sub.2 O and Na.sub.2 O 4.90
______________________________________
An average analysis of all CKDs used thus far is as follows:
______________________________________ CaO 49.0% SiO.sub.2 15.3%
Al.sub.2 O.sub.3 3.8% Fe.sub.2 O.sub.3 2.3% MgO 2.2% SO.sub.3 8.7%
K.sub.2 O and Na.sub.2 O 4.2%
______________________________________
All of the CKDs used thus far include a substantial quantity of
oxides which react with liquids in the agglomeration to form water
insoluble hydroxides.
Chemical analyses of typical agglomerated materials delivered to
the pit 1 revealed that solids constituted about 54% of such
materials and the remainder of the material was a brine composed of
about 25% calcium, potassium, and sodium chlorides and traces of
other minerals.
The specific proportions of ingredients used in the method
according to the invention may vary according to the kinds of
drilling muds and liquids used, as well as the kinds and particle
sizes of the well cuttings and the aggregate used. In practice it
has been found that the following ranges of proportions of the most
commonly used materials produce satisfactory results:
______________________________________ Material Weight Percent
______________________________________ Drilling mud 70-75 Cement
kiln dust 4-11 Cement 0.3-1.0 Aggregate 20-25
______________________________________
The particular order in which the materials are mixed does not
appear to make any significant difference in the effectiveness of
the method. It is easier to obtain a good mixture of the
agglomeration and the meal by mixing them prior to the addition of
the aggregate, however, because of the fluidity of the
agglomeration and the lower quantity of meal compared to that of
the aggregate.
Neither is it necessary to place the meal atop the agglomeration
prior to mixing. The meal could be added to and mixed with the
agglomeration in buckets-full, and the same observation applies to
the addition and mixing of the aggregate. Applying these materials
in layers, however, facilitates the measurement of the respective
materials.
Once the agglomeration is in condition for solidification, i.e., it
has settled and the excess liquid has been removed, it requires
only between about 2 and 3 hours to mix about 1,050,000 pounds of
agglomerated materials with about 70,000 pounds of meal and about
325,000 pounds of aggregate. The method, therefore, is relatively
quickly performed with consequent economy.
This disclosure is representative of a presently preferred
embodiment of the invention, but is intended to be illustrative
rather than definitive thereof. The invention is defined in the
claims.
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