U.S. patent application number 12/833673 was filed with the patent office on 2011-01-13 for ultra high viscosity pill and methods for use with an oil-based drilling system.
This patent application is currently assigned to TEXAS UNITED CHEMICAL COMPANY, LLC. Invention is credited to James W. Dobson, JR., Benjamin K. Geerdes, Kim O. Tresco.
Application Number | 20110009298 12/833673 |
Document ID | / |
Family ID | 42668353 |
Filed Date | 2011-01-13 |
United States Patent
Application |
20110009298 |
Kind Code |
A1 |
Dobson, JR.; James W. ; et
al. |
January 13, 2011 |
Ultra High Viscosity Pill and Methods for Use with An Oil-Based
Drilling System
Abstract
A fluid pressure transmission pill (FPTP) having an ultra-high
viscosity for use in association with hydrocarbon drilling and
exploration operations, particularly, managed pressure drilling
(MPD) operations, is described. The ultra-high viscosity pill is a
weighted pill composition that includes a hydrocarbon fluid, a
thixotropic viscosifying agent, one or more activators, an
emulsifier/wetting agent, a fluid loss control additive, and a
weighting material. In accordance with selected aspects of the
described fluid pressure transmission pill, the ratio of the amount
of the thixotropic viscosifying agent to the activator is a ratio
of about 7:1, and the weighting material is a barium-containing
solid-phase material. Also described are methods of use of such
FPTP products in subterranean operations, such as well killing
operations during managed pressure drilling.
Inventors: |
Dobson, JR.; James W.;
(Houston, TX) ; Tresco; Kim O.; (Houston, TX)
; Geerdes; Benjamin K.; (Houston, TX) |
Correspondence
Address: |
LOCKE LORD BISSELL & LIDDELL LLP
600 TRAVIS SUITE 2800
HOUSTON
TX
77002-3095
US
|
Assignee: |
TEXAS UNITED CHEMICAL COMPANY,
LLC
Houston
TX
|
Family ID: |
42668353 |
Appl. No.: |
12/833673 |
Filed: |
July 9, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61224136 |
Jul 9, 2009 |
|
|
|
Current U.S.
Class: |
507/125 ;
507/100; 507/103; 507/131; 507/138 |
Current CPC
Class: |
C09K 8/32 20130101; C09K
8/34 20130101; C09K 8/14 20130101 |
Class at
Publication: |
507/125 ;
507/100; 507/103; 507/131; 507/138 |
International
Class: |
C09K 8/34 20060101
C09K008/34 |
Claims
1. A fluid pressure transmission pill (FPTP) for use in a managed
pressure drilling (MPD) operation, the pill comprising: a fluid
phase; a thixotropic viscosifying agent; an activator; and a
weighting material.
2. The fluid pressure transmission pill (FPTP) of claim 1, wherein
the fluid phase is an oleaginous fluid selected from the group
consisting of diesel oil, mineral oil, synthetic oil such as
polyolefins or isomerized polyolefins, ester oils, glycerides of
fatty acids, aliphatic esters, aliphatic ethers, aliphatic acetals,
and combinations thereof.
3. The fluid pressure transmission pill of claim 2, wherein the
fluid phase is a mineral oil.
4. The fluid pressure transmission pill of claim 3, wherein the
mineral oil is a low aromatic content mineral oil.
5. The fluid pressure transmission pill of claim 1, wherein the
thixotropic viscosifying agent is an organophilic clay.
6. The fluid pressure transmission pill of claim 5, wherein the
organophilic clay is present in an amount ranging from about 6
lb/bbl to about 16 lb/bbl.
7. The fluid pressure transmission pill of claim 1, wherein the
activator is a polar activator.
8. The fluid pressure transmission pill of claim 7, wherein the
activator is propylene carbonate.
9. The fluid pressure transmission pill of claim 1, wherein the
weighting material is a solid-phase material selected from the
group consisting of anglesite, barite, calcite, celestite,
crocoite, hematite, ilmenite, or combinations thereof.
10. The fluid pressure transmission pill of claim 9, wherein the
solid-phase material is barium sulfate or a barium-containing
mineral having a weight average particle size diameter between
about 5 .mu.m and about 75 .mu.m.
11. The fluid pressure transmission pill of claim 1, wherein the
pill has a mud weight ranging from about 7 lb/gal to about 20
lb/gal.
12. An ultra-high viscosity pill for use in managed pressure
drilling (MPD) operations, the pill comprising: a mineral oil; an
organophilic clay; an activator; an emulsifier and/or a wetting
agent; a fluid loss control additive; and a weighting material.
13. The ultra-high viscosity pill of claim 12, wherein the mineral
oil is a low aromatic content mineral oil.
14. The ultra-high viscosity pill of claim 12, wherein the
organophilic clay is selected from the group consisting of
bentonite, hectorite, montmorillonite, biedellite, saponite, and
stevensite.
15. The ultra-high viscosity pill of claim 12, wherein the
organophilic clay is present in an amount ranging from about 6
lb/bbl to about 16 lb/bbl.
16. The ultra-high viscosity pill of claim 12, wherein the
organophilic clay has been treated with one or more oil-wetting
agents.
17. The ultra-high viscosity pill of claim 16, wherein the
oil-wetting agent is a quaternary amine having from 6 to 20 carbon
atoms.
18. The ultra-high viscosity pill of claim 12, wherein the
activator is selected from the group consisting of sodium silicate,
sodium fluoride, sodium silicofluoride, magnesium silicofluoride,
zinc silicofluoride, calcium carbonate, sodium carbonate, potassium
carbonate, alkyl carbonates, calcium hydroxide, sodium hydroxide,
potassium hydroxide, sodium sulfate, polar, aprotic compounds, and
mixtures thereof.
19. The ultra-high viscosity pill of claim 18, wherein the
activator is present in an amount ranging from about 0.1 wt. % to
about 30 wt. %, based on the total weight of the organophilic
clay.
20. The ultra-high viscosity pill of claim 18, wherein the
activator is propylene carbonate, present in an amount relative to
the organophilic clay in a ratio ranging from about 1:5 to about
1:10.
21. The ultra-high viscosity pill of claim 12, wherein the
emulsifier is a nitrogen-containing compound.
22. The ultra-high viscosity pill of claim 12, wherein the fluid
loss control additive is a styrene-butadiene rubber copolymer.
23. The ultra-high viscosity pill of claim 12, wherein the
weighting material is a barium-containing material.
24. The ultra-high viscosity pill of claim 23, wherein the
barium-containing material is barium sulfate.
25. The ultra-high viscosity pill of claim 12, wherein the
weighting material is a solid-phase material selected from the
group consisting of anglesite, barite, calcite, celestite,
crocoite, hematite, ilmenite, or combinations thereof.
26. The ultra-high viscosity pill of claim 25, wherein the
solid-phase weighting material is barite.
27. A method of drilling a subterranean well using a fluid pressure
transmission pill in conjunction with an oil-based drilling fluid,
the method comprising: providing a fluid phase pressure
transmission pill comprising: a fluid phase; a thixotropic
viscosifying agent; an emulsifier and/or a wetting agent; a fluid
loss control additive; and a weighting agent; and using the
oil-based drilling fluid to drill a well bore in a subterranean
formation.
28. The method of claim 27, wherein the fluid phase further
comprises a brine solution.
29. The method of claim 27, wherein the fluid phase has a mud
weight ranging from about 7 lb/gal to about 20 lb/gal.
30. The method of claim 27, wherein the composition further
comprises an activator.
31. The method of claim 30, wherein the activator is selected from
the group consisting of sodium silicate, sodium fluoride, sodium
silicofluoride, magnesium silicofluoride, zinc silicofluoride,
calcium carbonate, sodium carbonate, potassium carbonate, alkyl
carbonates, calcium hydroxide, sodium hydroxide, potassium
hydroxide, sodium sulfate, polar, aprotic compounds, and mixtures
thereof.
32. The method of claim 31, wherein the activator is propylene
carbonate.
33. The method of claim 27, wherein the weighting agent is a
material selected from the group consisting of anglesite, barite,
calcite, celestite, crocoite, hematite, ilmenite, or combinations
thereof.
34. The method of claim 33, wherein the weighting agent is barite.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Patent Application Ser. No. 61/224,136, filed Jul. 9, 2009, the
contents of all of which are incorporated herein by reference in
its entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
REFERENCE TO APPENDIX
[0003] Not applicable.
BACKGROUND OF THE INVENTION
[0004] 1. Field of the Invention
[0005] The inventions disclosed and taught herein relate generally
to hydrocarbon drilling and exploration operations, and more
specifically are related to fluid pressure transmission pills and
their manufacture and use in support of drilling and exploration
operations.
[0006] 2. Description of the Related Art
[0007] Various types of well bore fluids are used in operations
related to the development, completion, and production of natural
hydrocarbon reservoirs. Typical operations include fracturing
subterranean formations, modifying the permeability of subterranean
formations, logging operations, and sand control, among others. Of
particular interest with regard to the present inventions are
fluids appropriate for use in performing managed pressure drilling
(MPD) operations, particularly those in high-temperature,
high-pressure hydrocarbon fields, where standard drilling fluids
have an insufficient density for tripping drill pipe, wireline
logging, or other operations.
[0008] Managed pressure drilling (MPD) is a relatively recent
adaptive drilling process, similar in some aspects to
under-balanced drilling, used to precisely control the annular
pressure profile throughout the well during the course of a
drilling operation, thereby reducing drilling problems. The primary
objective of the MPD concept is to maintain a balanced well bore
pressure within the critical tolerances defined by the pore
pressure, well bore stability, and fracture pressure. For example,
MPD could be used to manage and maintain the pressure between the
pore pressure and the fracture pressure of a reservoir, while
simultaneously compensating for the influx of fluids that may occur
during drilling without encouraging such an influx. MPD uses a
number of tools to mitigate the risks and costs associated with
drilling wells by managing the annular pressure profile. Typical
techniques applied to date have included controlled backpressure,
fluid density, fluid rheology, annular fluid level, circulating
friction, and hole geometry [see, Hannigan, D., SPE paper 92600,
2005].
[0009] As illustrated in numerous studies, problems in deep wells
can be caused by well bore pressure deviating outside the pressure
gradient window during drilling operations, resulting in
non-productive time. For example, at shallow depths, if the well
bore pressure deviates below the pore pressure gradient, water or
gas can flow into the well bore, and a kick can occur, or in some
instances the well bore may become unstable and collapse on the
drill pipe. A major problem when pressure exceeds the fracture
pressure-gradient is lost circulation, with a loss of mud into the
formation with subsequent reservoir damage. These pressure
deviation issues account for numerous drilling problems, which in
turn have a significant impact on drilling costs and well
performance. Consequently, new methods and systems for managing
well bore pressure in drilling operations, based on managed
pressure drilling (MPD) technologies, is needed to alleviate these
drilling issues.
[0010] The inventions disclosed and taught herein are directed to
viscous isolation pills, also referred to herein as fluid pressure
transmission pills (FPTP) used during managed pressure drilling
(MPD) operations. FPTP serve as a barrier to prevent intermixing of
the lower density drilling fluid being utilized in the drilling
operation and a heavier density fluid which is applied to achieve a
total hydrostatic pressure overbalance in the fluid column that is
sufficient for well control when tripping drill pipe, conducting
wireline logging, or performing other subterranean operations.
BRIEF SUMMARY OF THE INVENTION
[0011] Applicants have invented ultra-high viscosity well treatment
pill compositions, also referred to herein equivalently as fluid
pressure transmission pills (FPTPs), suitable for use in managed
pressure drilling (MPD) operations, wherein the composition has an
overall viscosity greater than 100,000 centipoise (cP) (measured at
0.0660 sec.sup.-1), a mud weight of at least 7.0 lb/gal, and which
exhibits pill stability for more than 24 hours.
[0012] In accordance with a first embodiment of the present
disclosure, a fluid pressure transmission pill (FPTP) for use in a
managed pressure drilling (MPD) operation is described, wherein the
pill comprises an oleaginous (hydrocarbon oil) phase, a thixotropic
viscosifying agent, an activator, an emulsifier/wetting agent, a
fluid loss control additive, and a weighting material. In
accordance with aspects of this embodiment, the thixotropic
viscosifying agent is an organophilic clay, present in an amount
ranging from about 6 lb/bbl to about 16 lb/bbl, and more preferably
from about 10 lb/bbl to about 14 lb/bbl. In accordance with further
aspects of this embodiment, the weighting material is a solid-phase
material selected from the group consisting of barite, calcite,
hematite, ilmenite, or combinations thereof.
[0013] In accordance with a further embodiment of the present
disclosure, an ultra-high viscosity treatment pill for use in
managed pressure drilling (MPD) operations is described, wherein
the pill composition comprises a low aromatic content mineral oil,
an organophilic clay, a polar activator, an emulsifier/wetting
agent, a fluid loss control additive, and a weighting material. In
accordance with aspects of this embodiment, the organophilic clay
is included in the composition in an amount ranging from about 6
lb/bbl to about 16 lb/bbl, and the activator is included in an
amount which is about 0.1 on a weight-to-weight basis of the amount
of the organophilic clay in the composition. In accordance with
further aspects of this embodiment, the weighting material is a
solid-phase material selected from the group consisting of barite,
calcite, hematite, ilmenite, or combinations thereof. In one
additional aspect of this embodiment, the weighting material is
preferably barite.
[0014] In accordance with yet another embodiment of the present
disclosure, a method of drilling a subterranean well utilizing a
fluid pressure transmission pill (FPTP) in conjunction with an
oil-based drilling fluid in a managed pressure drilling (MPD)
operation is described, wherein the drilling fluid comprises an
oleaginous liquid, a thixotropic viscosifying agent, emulsifiers,
wetting agents, fluid loss control additives, and weighting
material, all of which are described within this disclosure. In
accordance with aspects of this embodiment, the drilling fluid may
include a brine solution to form an invert (water-in-oil) emulsion
wherein the aqueous phase is dispersed within the oleaginous phase,
and stabilized by one or more emulsifiers which are effective in
invert emulsions.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0015] The File of this patent contains at least one drawing
executed in color. Copies of this patent with color drawing sheets
will be provided by the Patent and Trademark Office upon request
and payment of the necessary fee.
[0016] The following figures form part of the present specification
and are included to further demonstrate certain aspects of the
present invention. The invention may be better understood by
reference to one or more of these figures in combination with the
detailed description of specific embodiments presented herein.
[0017] FIG. 1A illustrates a 12.5 lb/gal fluid pressure
transmission pill (FPTP) composition of the present disclosure
above 12.5 lb/gal CaBr.sub.2 brine and below 17.0 lb/gal
Zn/Br.sub.2 brine at hour 0 at a vertical orientation.
[0018] FIG. 1B illustrates the FPTP (12.5 lb/gal) composition of
FIG. 1A at 24 hours at a vertical orientation.
[0019] FIG. 1C illustrates the FPTP (12.5 lb/gal) composition of
FIG. 1A at 48 hours at a vertical orientation.
[0020] FIG. 1D illustrates a FPTP (12.5 lb/gal) composition of the
present disclosure above 12.5 lb/gal CaBr.sub.2 brine and below
17.0 lb/gal Zn/Br.sub.2 brine at hour 0 at a 45.degree. angle of
deviation.
[0021] FIG. 1E illustrates the FPTP (12.5 lb/gal) composition of
FIG. 1D at 24 hours at a 45.degree. angle of deviation.
[0022] FIG. 1F illustrates the FPTP (12.5 lb/gal) composition of
FIG. 1D at 48 hours at a 45.degree. angle of deviation.
[0023] FIG. 1G illustrates a FPTP (12.5 lb/gal) composition of the
present disclosure above 12.5 lb/gal CaBr.sub.2 brine and below
17.0 lb/gal Zn/Br.sub.2 brine at hour 0 at a 60.degree. angle of
deviation.
[0024] FIG. 1H illustrates the FPTP (12.5 lb/gal) composition of
FIG. 1G at 24 hours at a 60.degree. angle of deviation.
[0025] FIG. 1I illustrates the FPTP (12.5 lb/gal) composition of
FIG. 1G at 48 hours at a 60.degree. angle of deviation.
[0026] FIG. 2 demonstrates a reduced viscosity FPTP (12.5 lb/gal
with 6 lb/bbl of organophilic clay) mixing with 15.0 lb/gal
CaBr.sub.2/ZnBr.sub.2 brine during pill placement in a vertical
orientation.
[0027] FIG. 3A shows brine (15.0 lb/gal CaBr.sub.2/ZnBr.sub.2)
descending through a 12.5 lb/gal reduced viscosity FPTP (8 lb/bbl
of organophilic clay) in a vertical orientation.
[0028] FIG. 3B illustrates the top view of a 12.5 lb/gal reduced
viscosity FPTP (8 lb/bbl of organophilic clay) after all the 15.0
lb/gal CaBr.sub.2/ZnBr.sub.2 has channeled through the pill.
[0029] While the inventions disclosed herein are susceptible to
various modifications and alternative forms, only a few specific
embodiments have been shown by way of example in the drawings and
are described in detail below. The figures and detailed
descriptions of these specific embodiments are not intended to
limit the breadth or scope of the inventive concepts or the
appended claims in any manner. Rather, the figures and detailed
written descriptions are provided to illustrate the inventive
concepts to a person of ordinary skill in the art and to enable
such person to make and use the inventive concepts.
DETAILED DESCRIPTION
[0030] The Figures described above and the written description of
specific structures and functions below are not presented to limit
the scope of what Applicants have invented or the scope of the
appended claims. Rather, the Figures and written description are
provided to teach any person skilled in the art to make and use the
inventions for which patent protection is sought. Those skilled in
the art will appreciate that not all features of a commercial
embodiment of the inventions are described or shown for the sake of
clarity and understanding. Persons of skill in this art will also
appreciate that the development of an actual commercial embodiment
incorporating aspects of the present inventions will require
numerous implementation-specific decisions to achieve the
developer's ultimate goal for commercial embodiment. Such
implementation-specific decisions may include, and likely are not
limited to, compliance with system-related, business-related,
government-related and other constraints, which may vary by
specific implementation, location and from time to time. While a
developer's efforts might be complex and time-consuming in an
absolute sense, such efforts would be, nevertheless, a routine
undertaking for those of skill in this art having benefit of this
disclosure. It must be understood that the inventions disclosed and
taught herein are susceptible to numerous and various modifications
and alternative forms. Lastly, the use of a singular term, such as,
but not limited to, "a," is not intended as limiting of the number
of items. Also, the use of relational terms, such as, but not
limited to, "top," "bottom," "left," "right," "upper," "lower,"
"down," "up," "side," and the like are used in the written
description for clarity in specific reference to the Figures and
are not intended to limit the scope of the invention or the
appended claims.
[0031] Applicants have created new compositions for use in
performing managed pressure drilling (MPD) of subterranean
formations. In particular, a fluid pressure transmission pill
(FPTP), or `balanced mud pill`, has been developed, which is useful
in balancing subterranean reservoir and well bore pressures during
a number of hydrocarbon exploration and recovery operations.
[0032] In accordance with aspects of the present disclosure, a
fluid pressure transmission pill (FPTP) for use in controlling
and/or balancing subterranean pressures during a drilling operation
within a well bore has been developed, wherein the pill has an
ultra-high viscosity (the term `ultra-high viscosity` as used
herein meaning a viscosity greater than about 100,000 cP, measured
at 0.0660 sec.sup.-1), and comprises at least a fluid phase, a
thixotropic viscosifying agent, an activator, and a weighting
material. The composition may optionally comprise one or more
emulsifiers and/or wetting agents, and fluid loss control
additives, as appropriate, and in association with the viscosifying
agent.
[0033] The fluid phase which is suitable for use in the fluid
pressure transmission pill (FPTP) compositions of the present
disclosure include but are not limited to hydrocarbons and
oleaginous liquids. As used herein the term "oleaginous liquid"
means a hydrocarbon or an oil which is a liquid at 25.degree. C.
and is substantially immiscible with water. Oleaginous liquids
suitable for use herein typically include substances such as diesel
oil, mineral oil (including low aromatic content mineral oils),
synthetic oil such as polyolefins or isomerized polyolefins, ester
oils, glycerides of fatty acids, aliphatic esters, aliphatic
ethers, aliphatic acetals, or other such hydrocarbons and
combinations of these fluids. In one illustrative embodiment of
this invention, the fluid phase includes an oleaginous liquid that
is a low aromatic mineral oil. As used herein, the term `low
aromatic mineral oil` means that the oil contains less than about
1% aromatics.
[0034] The thixotropic viscosifying agents suitable for use herein
include, but are not limited to, clays, and in particular include
organophilic clays. The organophilic clay is a well-known,
commercially available thixotropic viscosifying agent for organic
liquids. Suitable organophilic clays also include the reaction
products of smectite-type, hectorite clays, or other clays and
organic cations, i.e., quaternary ammonium cations (sometimes
referred to as organophillic clay gellants); smectite clays; kaolin
clays; and the like. The preferred organophilic clays used as a
thixotropic viscosifying agent, in accordance with one aspect of
the present invention, is a smectite-type clay that is selected
from the group consisting of bentonite, hectorite, montmorillonite,
nontronite, biedellite, saponite, stevensite, and mixtures thereof,
most preferably bentonite or hectorite. The preferred quaternary
ammonium cations, in the event that the clay used is the reaction
product of a clay and a quaternary ammonium compound, are selected
from the group consisting of methyl trihydrogenated tallow
ammonium, dimethyl dehydrogenated tallow ammonium, dimethyl benzyl
hydrogenated tallow ammonium, methyl benzyl dehydrogenated tallow
ammonium, and mixtures thereof. Exemplary organoclays and clay
gellants suitable or use with the compositions described herein are
set forth in the following U.S. patents, all incorporated herein by
reference in relevant part: U.S. Pat. No. 2,531,427; U.S. Pat. No.
2,966,506; U.S. Pat. No. 4,105,578; and U.S. Pat. No. 4,208,218.
Exemplary, commercially available organophilic clays suitable for
use with the compositions described herein are CLAYTONE.RTM. IMG
400, available from Southern Clay Products, Inc., Gonzalez, Tex.,
U.S.A., or BENTONE.RTM. 38 Organoclay (a commercial hectorite-based
product, available form a number of suppliers).
[0035] The activator suitable for use in accordance with the
compositions and methods of the present disclosure includes any
suitable activator for use with clay-type thixotropic viscosifying
agents. Suitable activators for use with the presently described
compositions include, but are not limited to, sodium silicate,
sodium fluoride, sodium silicofluoride, magnesium silicofluoride,
zinc silicofluoride, calcium carbonate, sodium carbonate, potassium
carbonate, alkyl carbonates, calcium hydroxide, sodium hydroxide,
potassium hydroxide, sodium sulfate, polar, aprotic compounds, and
mixtures thereof. In accordance with one aspect of the present
disclosure, the polar activator is a cyclic carbonate, propylene
carbonate. In further accordance with aspects of the present
disclosure, the amount of polar activator included in the fluid
pressure transmission pill compositions is generally less than the
amount of thixotropic viscosifying agent added to the composition,
on a weight-to-weight basis. In accordance with further aspects of
the present disclosure, the amount of polar activator included in
the composition with regard to the amount of thixotropic
viscosifying agent is in a ratio ranging from about 1:5 to about
1:10, as well as ratios within this range, and more preferably in a
ratio of about 1:7 of activator to viscosifying agent.
[0036] The ultra-high viscosity fluid pressure transmission pill
(FPTP) may also include an emulsifier, a wetting agent, or both
(that is, a compound that may be classified as either an emulsifier
or a wetting agent). Emulsifiers and wetting agents suitable for
use with the compositions of the present disclosure include
nitrogen containing compounds, such as quaternary amines having one
or more straight or branched alkyl chains containing from 6 to 20
carbon atoms. These include, but are not limited to, various fatty
acid soaps, including oxidized tall oil soaps, preferably the
calcium soaps whether pre-formed or prepared in-situ in the fluid;
polyamides; alkylamidoamines; imidazolines; alkyl sulfonates; fatty
acyl esters; lecithin; and the like. These may also include the
so-called primary emulsifiers and secondary emulsifiers. Exemplary
emulsifiers suitable for use with the compositions and methods of
the present disclosure include, but are not limited to, those
described in U.S. Pat. Nos. 2,876,197; 2,994,660; 2,962,881;
2,816,073; 2,793,996; 2,588,808; 3,244,638; 4,504,276; 4,509,950;
4,776,966; and 4,374,737, all of which are incorporated herein by
reference in relevant part.
[0037] The preferred oil-soluble polymeric fluid loss control
additive for use in the invention comprise styrene-butadiene
copolymers known in the art as SBR (styrene-butadiene rubber). The
styrene content of the SBR is preferably from about 15% by weight
to about 45% by weight of the SBR, more preferably from about 20%
to 35% by weight, and most preferably from about 20% to about 25%
by weight of the SBR. It is known to prepare SBR by emulsion
polymerization using either a "hot process" or a "cold process".
The hot process is conducted at a temperature of about 50.degree.
C. whereas the polymerization in a cold process is about 15.degree.
C. to about 20.degree. C. The cold process results in a SBR which
contains less branching than in the hot process, i.e., the SBR
molecules from the cold process contain more linear molecules than
the SBR from the hot process. It is preferred that the SBR be
prepared using a cold process. It is also preferred that the SBR
not be crosslinked. Other oil-soluble polymers for use in this
invention include, but are not limited to, polystyrene,
polybutadiene, polyethylene, polypropylene, and copolymers
consisting of at least two monomers selected from the group
consisting of styrene, butadiene, isoprene, ethene and derivatives
thereof, and propylene.
[0038] In accordance with one aspect of the present invention, the
weighting material suitable for use in accordance with the present
disclosure is preferably a solid-phase material selected from the
group consisting of anglesite (PbSO.sub.4), barite (BaSO.sub.4) and
other barium-containing minerals or materials, calcite
(CaCO.sub.3), celestite/celestine (SrSO.sub.4), crocoite
(PbCrO.sub.4), hematite (Fe.sub.2O.sub.3), ilmenite (FeTiO.sub.3),
or combinations thereof. Preferably, in accordance with certain
aspects of the present disclosure, the weighting agent is barite, a
solid-phase barium-containing compound or mineral, or a sulfate of
the Strunz Class 07.A or 07.AD (as described in the Nickel-Strunz
10.sup.th Ed. Mineralogical Tables, by Hugo Strunz and Ernest H.
Nickel). Such a preferred weighting agent includes preferentially
the naturally occurring mineral composed primarily of barium
sulfate, BaSO.sub.4 (although other minerals may be included
therein, such as lead, zinc in the form of zinc sulfide, and the
like), although drilling grade barite such as produced from barium
sulfate-containing ores from a single source or by blending
material from several sources may also be used. Exemplary
barium-containing minerals which may be used as a weighting
material in accordance with the compositions of the present
disclosure include but are not limited to alstonite
(CaBa(CO.sub.3).sub.2), barite (BaSO.sub.4), barytocalcite
(BaCa(CO.sub.3).sub.2), celsian (BaAl.sub.2Si.sub.2O.sub.8),
kukharenkoite (Ba.sub.3CeF(CO.sub.3).sub.3), psilomelane
(Ba(Mn.sup.2+)(Mn.sup.4+).sub.5O.sub.16(OH).sub.4), sanbornite
(BaSi.sub.2O.sub.5) and witherite (BaCO.sub.3), as well as
combinations thereof. The American Petroleum Institute (API) has
issued international standards to which ground barite must comply
in association with drilling operations, specifically API
Specification 13A, Section 2, which are incorporated herein by
reference, and which standards include a minimum density of about
4.1-4.2 g/cm.sup.3, a weight average particle size diameter between
about 5 .mu.m and about 75 .mu.m, an amount of water-soluble
alkaline earth metals (as calcium) of less than about 40 ppm, and
an amount of barite particles having a size less than about 6 mm by
weight in an amount of no more than 25 wt. %.
[0039] According to one illustrative embodiment, the weight average
particle diameter of the weighting agent suitable for use in the
compositions disclosed herein ranges from about 5 .mu.m to about 50
.mu.m. In another illustrative embodiment, the weighting agent
includes at least 50% by weight particles in the range of about 10
.mu.m to about 50 .mu.m. In a further illustrative embodiment, the
weighting agent includes at least 70% by weight of particles in the
range of about 5 .mu.m to about 50 .mu.m. The use of these particle
sizes, in association with the weighting agents used in the instant
compositions, enables one to achieve the objective of maintaining a
separation between a high density drilling fluid above and a lower
density drilling fluid below, without undesirably increasing the
well bore fluid viscosity or allowing a loss of integrity in the
pill itself.
[0040] The fluid pressure transmission pills (FPTP) described
herein may also include a number of other additives, including but
not limited to corrosion inhibitors, scale inhibitors, and fluid
loss control additives. Any of the typically used fluid loss
control additives known in the industry can be present in the fluid
pressure transmission pill, such as gilsonite, asphalt, oxidized
asphalt, organophilic lignites, and the like. Exemplary
organophilic lignites suitable for use in compositions of the
present disclosure are set forth in the following U.S. Pat. Nos.
3,168,475 (Jordan et al.); 3,379,650 (Beasley, et al.); 3,494,865
(Andrews, et al.); 4,421,655 (Cowan); 4,597,878 (House, et al.);
and 4,853,465 (Cowan, et al.), all of which are incorporated herein
by reference in pertinent part.
[0041] The fluid pressure transmission pills (FPTP) described
herein can be used in a number of applications related to
hydrocarbon exploration, including, but not limited to, managed
pressure drilling (MPD), both horizontal and vertical drilling
operations, tripping operations, wireline logging operations,
completion operations, well control operations, well logging
operations, and the like. In particular, the compositions described
herein are particularly suited for use in high-pressure,
high-temperature subterranean environments. In a non-limiting
example, the FPTP described herein exhibits thermal stability
across a broad range of temperatures, and may be used with a
drilling fluid for drilling wells in subterranean formations having
a variety of geologies, wherein the subterranean formation has
temperatures ranging from about 15.degree. F. to about 450.degree.
F.
[0042] As will be recognized by those skilled in the art, other
additives suitable for use in subterranean well bore drilling
operations also may be present in the drilling fluids of the
present invention if desired, including but not limited to,
antifoams, biocides, bridging agents, corrosion control agents,
dispersants, flocculants, fluid loss additives, foamers, H.sub.2S
scavengers, lubricants, oxygen scavengers, scale inhibitors,
viscosifiers, and weighting agents. One of ordinary skill in the
art with the benefit of this disclosure will be able to determine
if any of these such additives are needed for a given application.
Further, when the fluid pressure transmission pill (FPTP)
compositions of the present disclosure are used in drilling
operations, such as in managed pressure drilling (MPD) operations
and the like, the fluid may further comprise one or more brines.
Suitable brines for use with the FPTP compositions of the present
disclosure include, but are not limited to, both light and heavy
brines comprising KCl brines, NaCl brines, CaCl.sub.2 brines,
NaCO.sub.2H brines, KCO.sub.2H brines, CsCO.sub.2H brines, NaBr
brines, CaBr.sub.2 brines, KBr brines, CaCl.sub.2/CaBr.sub.2
brines, ZnBr.sub.2 brines, ZnCl.sub.2 brines, ZnBr.sub.2/CaBr.sub.2
brines, and ZnBr.sub.2/CaBr.sub.2/CaCl.sub.2 brines, alone or in
combination as appropriate. The brines, both light and heavy, can
be described in accordance with certain aspects of the present
disclosure as an aqueous solution which contains from about 10 to
about 350,000 parts per million of metal ions, such as lithium,
sodium, potassium, magnesium, cesium, zinc, or calcium ions. In
accordance with aspects of the invention, the brines used in the
compositions described herein may be described as containing from
about 2% by weight to the saturated amount (e.g., about 35% by
weight for CaCl.sub.2) of the salt, which will vary by salt used in
forming the brine. The brines used to in the compositions of the
present invention may also contain various amounts of other
dissolved salts, including but not limited to sodium bicarbonate,
sodium sulfate, sodium acetate, sodium borate, potassium chloride,
or sodium chloride, without limitation.
[0043] The fluid compositions of the present invention include at
least one oleaginous liquid, and may include a brine so as to form
an emulsion, an invert fluid, or oil-as based invert emulsions. The
term oil based drilling fluids as used herein are defined as a
hydrocarbon-based drilling fluids. Oil based invert emulsions have
an oil "continuous" phase and an aqueous internal phase. The term
"emulsion" as used herein is used to describe systems in which
water is the external or continuous phase and oil is dispersed
within the external phase. By the term "invert", it is meant that
the hydrocarbon-oil substance is the continuous or external phase
and that an aqueous fluid, such as water or a brine, is the
internal phase.
[0044] The ratio of water (or brine) to oil in emulsions of the
present invention should generally provide as high a brine content
as possible while still maintaining a stable emulsion since a high
water content drilling fluid is less expensive and less
objectionable to work with than a drilling fluid containing a low
water content. Oil/brine ratios in the range from about 95 to 5
(95:5) to 50 to 50 (50:50) have been found to work satisfactorily,
depending upon the particular oil/oleaginous fluid chosen. Thus the
water (or brine) content of a typical fluid prepared according to
the teachings of the invention may have, in accordance with certain
embodiments, an aqueous (water or brine) content ranging from about
0 volume percent (vol. %) to about 50 volume percent, with the most
preferred range being about 5 to 40 volume percent.
[0045] The following examples are included to demonstrate preferred
embodiments of the invention. It should be appreciated by those of
skill in the art that the techniques disclosed in the examples
which follow represent techniques discovered by the inventor(s) to
function well in the practice of the invention, and thus can be
considered to constitute preferred modes for its practice. However,
those of skill in the art should, in light of the present
disclosure, appreciate that many changes can be made in the
specific embodiments which are disclosed and still obtain a like or
similar result without departing from the scope of the
invention.
[0046] Further, in the examples herein, in expressing or converting
between U.S. and S.I. or metric measurements, the following U.S. to
metric conversion factors are used: 1 gal=3.785 liters; 1 lb=0.454
kg; 1 lb/gal=0.1198 g/cm.sup.3; wherein 1 bbl=42 gal; 1
lb/bbl=2.835 kg/m.sup.3; 1 lb/100 ft.sup.2=0.4788 Pa.
EXAMPLES
Example 1
Preparation of Ultra-High Viscosity Fluid Pressure Transmission
Pills (FPTP)
[0047] An organophilic clay (CLAYTONE.RTM. IMG 400, available from
Southern Clay Products, Inc., Gonzalez, Tex.) was added to 0.675
bbl of a low aromatic mineral oil (PUREDRILL.RTM. HT-30, available
from Petro-Canada, Calgary, Canada) and allowed to disperse equally
before adding 0.18 gal/bbl of propylene carbonate (JEFFSOL.RTM.,
available from Huntsman Petrochemical Corp., Houston, Tex.). The
ingredients were then mixed for 10 minutes at 5000 rpm with an
impeller-style mixer forming a `clay gel`. To this clay gel
composition was added 0.144 gal/bbl of an emulsifier/wetting agent
(STAB 2-CA, available from Quim Export, Inc., Houston, Tex.) and
the solution was mixed for 5 minutes at 3000 rpm. Additionally,
4.32 gal/bbl of an oil-soluble copolymer slurry containing 17.5
lb/bbl of styrene-butadiene rubber (SBR 8113 Crumb, available from
ISP Elastomers, Port Neches, Tex.), solubilized in 39.9 gal/bbl of
low aromatic mineral oil (PUREDRILL.RTM. HT-30, available from
Petro-Canada, Calgary, Canada), was then added and the solution
mixed for an additional 2 minutes at 3000 rpm. Barium sulfate
(Barite, available from Federal Wholesale Drilling Mud, Houston,
Tex.) at a concentration of 288 lb/bbl was then added, and the
final fluid composition was mixed for an additional 30 minutes at
5000 rpm before analyzing and testing as described below.
[0048] A viscosity measurement for the ultra-high viscosity pill
thus prepared was performed by determining the Low Shear Rate
Viscosity (LSRV) with a Brookfield LVDII+ viscometer at 0.3 rpm
using a No. 3 cylindrical spindle. The result is shown in Table 1,
below.
[0049] In order to assess the ability and integrity of the
ultra-high viscosity pill to isolate a high-density oil-base
drilling fluid in the upper region of a well bore from a lighter
oil-base fluid in the deeper section, a series of observational
laboratory tests were conducted using both vertically-oriented and
angled 250 mL graduated cylinders to simulate a well bore. The
focus of these tests was to determine the long-term stability of
the fluid pressure transmission pills (FPTP) over an extended
period of time. In a typical test for demonstration purposes,
brines were substituted for oil-base drilling fluids above and
below the FPTP to provide a more visible interface between stages.
First, 85 mL of a 12.5 lb/gal CaBr.sub.2 brine was added to a 250
mL glass graduated cylinder, and then 85 mL of a 12.5 lb/gal
high-viscosity pill prepared as described above was added on top of
the brine by slowly releasing it from a syringe down the side of
the cylinder. Finally, a 17.0 lb/gal ZnBr.sub.2 brine was added on
top of the pill. The total volume placed in the cylinder was about
255 mL. Vertical, 45.degree., and 60.degree. angles of deviation
were established, and visual observations were made, and the
observations were documented with photographs taken at time zero
(0), 24-hours, and 48 hours. These results are illustrated in FIGS.
1A-1I, herein. As can be seen from these figures, the pill remains
intact over the entire time period tested, with no brine channeling
through the FPTP, even at cylinder test inclination angles of
45.degree. and 60.degree..
Example 2
Preparation of Fluid Pressure Transmission Pills (FPTP) with Varied
Amounts of Thixotropic Viscosifier
[0050] Two FPTP having reduced organophilic clay concentrations,
were prepared in order to demonstrate how lesser viscosity pills
fail to create the barrier required to retain heavier fluids. An
amount of organophilic clay (CLAYTONE.RTM. IMG 400 available from
Southern Clay Products, Inc., Gonzales, Tex.), ranging from about 6
lb/bbl to 8 lb/bbl was added to 0.772 bbl of a low aromatic mineral
oil (PUREDRILL.RTM. HT-30, available from Petro-Canada, Calgary,
Canada) and allowed to disperse equally before adding 0.12 gal/bbl
of propylene carbonate (JEFFSOL.RTM., available from Huntsman
Petrochemical Corp., Houston, Tex.). The ingredients were then
mixed for 15 minutes at 4600 RPM with an impeller-style mixer,
forming a `clay gel`. To this clay gel composition was added 0.30
gal/bbl of emulsifier/wetting agent (STAB 2-CA, available from Quim
Export, Inc., Houston, Tex.), and the solution mixed for 5 minutes
before adding 298 lb/bbl of barium sulfate (Barite, available from
Federal Wholesale Drilling Mud, Houston, Tex.). The complete pill
composition was then mixed for an additional 15 minutes at 3000 rpm
before analyzing and testing as described below.
[0051] Viscosity measurements were carried out as described above,
and were obtained at 0.0636 sec.sup.-1 and 0.0660 sec.sup.-1. The
results of these viscosity tests are presented in Table 1,
below.
[0052] Similar to the test in Example 1 above, in order to assess
the ability and integrity of the high-viscosity pills with varying
amounts of thixotropic viscosifying agents to isolate the
high-density oil-base drilling fluid in the upper region of a well
bore from a lighter oil-base fluid in the deeper section, a series
of observational laboratory tests were conducted using
vertically-oriented 250 mL graduated cylinders to simulate a well
bore. In a typical test, for demonstration purposes, brines were
substituted for oil-base drilling fluids above and below the fluid
pressure transmission pills (FPTP) to provide a more visible
interface between stages. First, 85 mL of a 15.0 lb/gal
CaBr.sub.2/ZnBr.sub.2 brine was placed in the bottom of a 250 mL
glass graduated cylinder, and on top of that, 85 mL of a 12.5
lb/gal high viscosity pill prepared as described above was added,
and then an additional 85 mL of a 15.0 lb/gal CaBr.sub.2/ZnBr.sub.2
brine was added on top of the pill by slowly releasing it from a
syringe down the side of the cylinder. The total volume placed into
the cylinder was about 255 mL, with (preferably) the brine
remaining above the FPTP, with little to no downward channeling. A
vertical orientation was established, visual observations were
made, and the observations were documented with pictures taken at
time zero (0), and after 2 hours. These results are illustrated in
FIGS. 2, 3A, and 3B, herein. As can be seen from these Figures, the
6 lb/bbl (12.5 lb/gal) pill does not establish a barrier and mixes
with the 15.0 lb/gal brine as it is pipetted into position, while
the 8 lb/bbl pill allows the 15.0 lb/gal brine to channel through
to the brine below, thereby displacing the pill upward.
TABLE-US-00001 TABLE 1 Viscosity data for the pill compositions of
Examples 1 and 2. Viscosity of 12.5 lb/gal pills with varied
Composition/Parameters levels of thixotropic viscosifier (cP)
Mineral Oil, bbl 0.772 0.772 0.675 Organophilic Clay, lb/bbl 6.0
8.0 12.5 Polar Activator, gal/bbl 0.12 0.12 0.18 Emulsifier/Wetting
Agent, 0.3 0.3 0.144 gal/bbl Copolymer Slurry, gal/bbl -- -- 4.32
Barite, lb/bbl 298.0 298.0 288.0 Temperature, .degree. F. 75 75 75
LSRV, cP 0.0660 sec.sup.-1 7,040 -- 119,000 0.0636 sec.sup.-1 --
52,300 --
[0053] Other and further embodiments utilizing one or more aspects
of the invention described above can be devised without departing
from the spirit of Applicant's invention. For example, the fluid
pressure transmission pill (FPTP) can be used in various other
hydrocarbon recovery operations, including well-killing operations
such as the simultaneous killing and cementing of a live well
(e.g., kill the well so that the cement could be placed and allowed
to set while at the same time not breaking down and losing
circulation into the weak upper zones). As used herein, the phrase
"well-killing operation" refers to the operation of placing a
column of heavy fluid into a well bore in order to prevent the flow
of reservoir fluids without the need for pressure control equipment
at the surface, the procedure operating on the principle that the
weight of the "kill fluid" or "kill mud" will be enough to suppress
the pressure of the formation fluids. Further, the various
embodiments of the ultra-high viscosity pill composition and
methods of preparation and use in subterranean operations can be
included in combination with each other to produce variations of
the disclosed methods and embodiments. Discussion of singular
elements can include plural elements and vice-versa.
[0054] The order of steps can occur in a variety of sequences
unless otherwise specifically limited. The various steps described
herein can be combined with other steps, interlineated with the
stated steps, and/or split into multiple steps. Similarly, elements
have been described functionally and can be embodied as separate
components or can be combined into components having multiple
functions.
[0055] The invention has been described in the context of preferred
and other embodiments and not every embodiment of the invention has
been described. Obvious modifications and alterations to the
described embodiments are available to those of ordinary skill in
the art. The disclosed and undisclosed embodiments are not intended
to limit or restrict the scope or applicability of the invention
conceived of by the Applicants, but rather, in conformity with the
patent laws, Applicants intend to fully protect all such
modifications and improvements that come within the scope or range
of equivalent of the following claims.
* * * * *