U.S. patent application number 12/430154 was filed with the patent office on 2010-10-28 for compositions and methods for servicing subterranean wells.
Invention is credited to Clara Carelli, Loic Regnault De La Mothe, Sylvaine Le Roy-Delage.
Application Number | 20100270016 12/430154 |
Document ID | / |
Family ID | 42211959 |
Filed Date | 2010-10-28 |
United States Patent
Application |
20100270016 |
Kind Code |
A1 |
Carelli; Clara ; et
al. |
October 28, 2010 |
Compositions and Methods for Servicing Subterranean Wells
Abstract
This invention relates to methods for servicing subterranean
wells, in particular, fluid compositions and methods for remedial
operations during which the fluid compositions are pumped into a
wellbore and make contact with well cements placed during primary
cementing or previous remedial cementing operations.
Inventors: |
Carelli; Clara; (Paris,
FR) ; Regnault De La Mothe; Loic; (Paris, FR)
; Roy-Delage; Sylvaine Le; (Paris, FR) |
Correspondence
Address: |
SCHLUMBERGER TECHNOLOGY CORPORATION;David Cate
IP DEPT., WELL STIMULATION, 110 SCHLUMBERGER DRIVE, MD1
SUGAR LAND
TX
77478
US
|
Family ID: |
42211959 |
Appl. No.: |
12/430154 |
Filed: |
April 27, 2009 |
Current U.S.
Class: |
166/277 ;
106/694; 166/292; 523/130 |
Current CPC
Class: |
E21B 33/13 20130101;
C09K 8/52 20130101; C09K 8/5045 20130101; C09K 8/428 20130101 |
Class at
Publication: |
166/277 ;
166/292; 106/694; 523/130 |
International
Class: |
E21B 33/13 20060101
E21B033/13; C04B 28/06 20060101 C04B028/06; C09K 8/46 20060101
C09K008/46 |
Claims
1. A pumpable sealant composition for establishing hydraulic
isolation in a cemented subterranean well, comprising a slurry of
aluminosilicate particles, aluminum compound/silica particles, or
aluminium compound/silicate particles, and combinations
thereof.
2. The composition of claim 1, wherein the aluminosilicate
particles comprise one or more members of the list comprising:
kaolin, metakaolin, fly ash, slag, natural zeolite, artificial
zeolite, natural pozzolan and artificial pozzolan.
3. The composition of claim 1, wherein the subterranean well has
been cemented with Portland cement, a lime/silica blend, a
lime/pozzolan blend, calcium aluminate cement, chemically bonded
phosphate ceramic, or combinations thereof.
4. The composition of claim 1, wherein the average size of the
particles is less than or equal to 15 micrometers.
5. The composition of claim 1, having a liquid phase wherein said
liquid phase comprises water.
6. The composition of claim 1, further comprising one or more
weighting materials chosen from the list comprising: ilmenite,
hematite, barite and manganese tetraoxide.
7. The composition of claim 1, further comprising sodium
hexametaphosphate.
8. The composition of claim 1, further comprising a latex.
9. The composition of claim 1, further comprising soluble silicate
compounds.
10. The composition of claim 1, further comprising hydroxide
compounds.
11. The composition of claim 1, further comprising alkali swellable
polymers, superabsorbent polymers, or both.
12. The composition of claim 11, wherein the alkali swellable
polymers are latexes.
13. A method of servicing a cemented wellbore in contact with a
subterranean formation, comprising: i. preparing a sealant
composition comprising a slurry including aluminosilicate
particles, aluminum compound particle/silica particle blends, or
aluminum-compound particle/silicate-particle blends and
combinations thereof. ii. pumping the sealant composition into
voids in the wellbore that are adjacent to set cement; and iii.
allowing the sealant composition to react with the set-cement
surfaces and form a set product, thereby forming a seal.
14. The method of claim 13, wherein the wellbore has been cemented
with Portland cement, a lime/silica blend, a lime/pozzolan blend,
calcium aluminate cement, or chemically bonded phosphate ceramic,
and combinations thereof.
15. The method of claim 13, wherein the aluminosilicate particles
comprise one or more members of the list comprising: kaolin,
metakaolin, fly ash, slag, natural zeolite, artificial zeolite,
natural pozzolan and artificial pozzolan.
16. The method of claim 13, wherein the average size of the
particles is less than or equal to 15 micrometers.
17. The method of claim 13, wherein the composition comprises a
liquid phase containing water.
18. The method of claim 13, wherein the composition further
comprises one or more weighting materials chosen from the list
comprising: ilmenite, hematite, barite and manganese
tetraoxide.
19. The method of claim 13, wherein the composition further
comprises sodium hexametaphosphate.
20. The method of claim 13, wherein the composition further
comprises a latex.
21. The method of claim 13, wherein the composition further
comprises soluble silicate compounds.
22. The method of claim 13, wherein the composition further
comprises hydroxide compounds.
23. The method of claim 13, wherein the composition further
comprises alkali swellable polymers, superabsorbent polymers, or
both.
24. The method of claim 23, wherein the alkali swellable polymers
are latexes.
25. A method of servicing a cemented wellbore in contact with a
subterranean formation, comprising: i. preparing an aqueous sealant
composition comprising a slurry of particles whose composition
includes members chosen from the list comprising: kaolin,
metakaolin, fly ash, slag, natural zeolite, artificial zeolite and
natural pozzolan; ii. pumping the sealant composition into voids in
the wellbore that are adjacent to set Portland cement; and iii.
allowing the sealant composition to react with the set-cement
surfaces and form a set product, thereby forming a seal.
Description
BACKGROUND OF THE INVENTION
[0001] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
[0002] This invention relates to methods for servicing subterranean
wells, in particular, fluid compositions and methods for remedial
operations during which the fluid compositions are pumped into a
wellbore and make contact with well cements placed during primary
cementing or previous remedial cementing operations.
[0003] During construction of a subterranean well, remedial
operations may be required to maintain wellbore integrity during
drilling, to cure drilling problems, or to repair defective primary
cement jobs. Wellbore integrity may be compromised when drilling
through mechanically weak formations, leading to hole enlargement.
Cement slurries may be used to seal and consolidate the borehole
walls. Remedial cementing is a common way to repair defective
primary cement jobs, to either allow further drilling or to provide
adequate zonal isolation for efficient well production.
[0004] During well production, remedial cementing operations may be
performed to restore production, change production characteristics
(e.g., to alter the gas/oil ratio or control water production), or
repair corroded tubulars.
[0005] During a stimulation treatment, the treatment fluids must
enter the target zones and not leak behind the casing. If poor
zonal isolation behind the production casing is suspected, a
remedial cementing treatment may be necessary.
[0006] Well abandonment frequently involves placing cement plugs to
ensure long-term zonal isolation between geological formations,
replicating the previous natural barriers between zones. However,
before a well can be abandoned, annular leaks must be sealed.
Squeeze cementing techniques may be applied for this purpose.
[0007] Common cementitious-fluid systems employed during
squeeze-cementing operations include, Portland cement slurries,
calcium-aluminate cement slurries, and organic resins based on
epoxies or furans.
[0008] Portland cement slurries prepared from, for example, ISO/API
Class H or Class G cement, are by far the most common cementitious
fluids employed in remedial cementing operations. They perform
satisfactorily in many applications; however, when the size of the
void from which fluid leakage occurs is very small, the
cement-particle size may be too large to enter and seal the void.
This problem has been mitigated to a significant extent by grinding
Portland cement clinker to a finer particle-size distribution. An
example of a fine-particle-size, or "microfine," Portland cement
system is SqueezeCRETE.TM., available from Schlumberger. Generally,
SqueezeCRETE systems are capable of sealing voids or cracks as
small as about 100 micrometers.
[0009] Despite the success of microfine cements, leaks may still
occur when the voids or cracks in the cement sheath are smaller
than 100 micrometers. It is therefore desirable to provide means to
seal such small voids and cracks in or adjacent to the cement
sheath and provide zonal isolation.
SUMMARY OF THE INVENTION
[0010] The present invention provides means to seal voids and
cracks in or adjacent to a cement sheath in a subterranean well,
and provide zonal isolation by by involving a pumpable aqueous
sealant composition for establishing hydraulic isolation in a
cemented subterranean well, comprising a slurry of aluminosilicate
particles, aluminum compound/silica particles, or aluminium
compound/silicate particles, and combinations thereof.
[0011] In a first aspect, the present invention discloses pumpable
sealant compositions with the ability to enter and seal
cement-sheath voids and cracks smaller than 100 micrometers. It
will be appreciated that, although the primary focus is to
preferably seal voids and cracks smaller than 100 micrometers, the
invention is not limited to this size criterion. The compositions
may be injected into voids and fractures in, or adjacent to, a
cement sheath.
[0012] The composition of the aluminosilicate particles preferably
includes, but is not limited to, kaolin, metakaolin, fly ash, blast
furnace slag, zeolites (artificial or natural) and pozzolans
(artificial or natural) and mixtures thereof. When a slurry
containing these materials enter voids or cracks in set Portland
cement, the materials react with calcium hydroxide at the cement
surfaces, forming calcium silicate compounds and establishing a
seal. The particle size of the disclosed aluminosilicate and
silicate particles is preferably less than or equal to 15
micrometers, and more preferably less than or equal to 10
micrometers.
[0013] The fluid compositions may also contain alkali swellable
polymers, superabsorbent polymers, weighting materials, dispersants
and buffers to adjust the fluid pH.
[0014] In another aspect, the present invention aims at a method of
servicing a cemented wellbore in contact with a subterranean
formation, comprising first preparing an aqueous sealant
composition comprising a slurry including aluminosilicate
particles, aluminum compound particle/silica particle blends or
aluminum-compound particle/silicate-particle blends and
combinations thereof; second pumping the sealant composition into
voids in the wellbore that are adjacent to set cement; and third
allowing the sealant composition to react with the set-cement
surfaces and form a set product, thereby forming a seal. Said
method of servicing a subterranean well comprising preparing a
pumpable aqueous suspension of particles comprising
aluminosilicates, or a mixture comprising aluminum compounds and
silica or silicates, and combinations thereof, wherein the size of
the particles is less than or equal to 15 micrometers and
preferably less than or equal to 10 micrometers. The suspension
being preferably allowed to flow into voids and cracks in, or
adjacent to, the cement sheath until the suspension gels and forms
a seal.
DETAILED DESCRIPTION
[0015] At the outset, it should be noted that in the development of
any such actual embodiment, numerous implementation-specific
decisions must be made to achieve the developer's specific goals,
such as compliance with system related and business related
constraints, which will vary from one implementation to another.
Moreover, it will be appreciated that such a development effort
might be complex and time consuming but would nevertheless be a
routine undertaking for those of ordinary skill in the art having
the benefit of this disclosure. In addition, the composition
used/disclosed herein may also comprise some components other than
those cited. In the summary of the invention and this detailed
description, each numerical value should be read once as modified
by the term "about" (unless already expressly so modified), and
then read again as not so modified unless otherwise indicated in
context. Also, in the summary of the invention and this detailed
description, it should be understood that a concentration range
listed or described as being useful, suitable, or the like, is
intended that any and every concentration within the range,
including the end points, is to be considered as having been
stated. For example, "a range of from 1 to 10" is to be read as
indicating each and every possible number along the continuum
between about 1 and about 10. Thus, even if specific data points
within the range, or even no data points within the range, are
explicitly identified or refer to only a few specific, it is to be
understood that inventors appreciate and understand that any and
all data points within the range are to be considered to have been
specified, and that inventors possessed knowledge of the entire
range and all points within the range.
[0016] The inventors have surprisingly found that suspensions of
aluminosilicate particles less than about 15 micrometers in size,
and preferably less than 10 micrometers in size will, upon entering
voids or cracks that are in contact with Portland cement, gel and
form a seal. Other suitable suspensions may be made of aluminum
compounds (e.g., colloidal alumina) combined with silica or
silicate particles. In addition, latexes may be added to the
suspensions.
[0017] It will be appreciated that, unlike Portland cement
slurries, the disclosed suspensions have no cementitious properties
in and of themselves. Without being bound by any theory, it is
believed that the particles react with residual calcium hydroxide
in the set Portland cement to form calcium silicate hydrate gel and
establish a seal. Set Portland cement contains roughly 20 wt %
calcium hydroxide when cured below 110.degree. C. The increased pH
resulting from exposure to calcium hydroxide may also activate or
accelerate the dissolution and polycondensation of the
aluminosilicates, leading to the formation of a solid containing
SiO4 and AlO4 tetrahedra linked by shared oxygen atoms.
[0018] It will also be appreciated that the disclosed suspensions
may respond to other cements that provide multivalent ions
including, but not limited to, lime/silica blends, lime/pozzolan
blends, calcium aluminate cement, Sorel cement, chemical modified
phosphate ceramic and geopolymers.
[0019] The particle suspensions may be, but are not limited to,
suspensions of kaolin, metakaolin, fly ash, blast furnace slag,
natural zeolite, artificial zeolite, natural pozzolan, artificial
pozzolan, or combinations thereof. The preferred liquid phase is
water. Because the suspension will not set on its own accord, it
may be prepared in advance, stored, and transported to the wellsite
as needed.
[0020] The structure of the material formed will depend on the
initial fluid composition, the ratio between silica and aluminum in
particular, and the pH. Other soluble silicate compounds (e.g.,
NaSiO3), hydroxides (e.g., NaOH and KOH) and phosphate compounds
such as sodium hexametaphosphate may be added to modify the
Theological and setting properties of the material. The structure
of the final material is also affected by the temperature and
pressure.
[0021] In a preferred embodiment, low- or high-density particles
may be added to adjust the fluid density. Appropriate high-density
particles include common weighting agents such as ilmenite
(FeTiO3), hematite (Fe2O3), barite (BaSO4) and manganese tetraoxide
(Mn3O4).
[0022] In another preferred embodiment, the disclosed particle
suspensions may incorporate alkali swellable polymers,
superabsorbent polymers, or both. The alkali swellable polymers are
preferably added in the form of a latex.
[0023] Alkali swellable latex particles swell when exposed to an
alkaline pH, causing the fluid to viscosify. Non limiting examples
of suitable commercially available alkali swellable latexes include
TYCHEM.TM. 68710-00 (available from Dow Chemical), ACRYSOL.TM. U615
(available from Rohm & Haas), ALCOGUM.TM. SL-120 and SL-920
(available from Alco Chemical, a National Starch Company),
VISCALEX.TM. HV30 (available from Ciba Specialty Chemicals), the
Latekoll.TM. series of products available from BASF, and
Synthomer.TM. 9532 (available from Synthomer). Buffers may be
incorporated to maintain an acidic fluid pH until the fluid is
exposed to the cement surface. In addition, antifoam agents,
defoamers and dispersants known to those skilled in the art may be
added to modify the fluid rheological properties.
[0024] Superabsorbent polymers are swellable crosslinked polymers
that, upon exposure to water, form a gel. They can absorb and store
many times their own weight of aqueous liquids. Suitable
superabsorbent polymers include, for example, the acrylic-base
Sterocoll.TM. series from BASF.
[0025] One method of applying the disclosed invention in a
subterranean well comprises pumping one or more of the reactive
aluminosilicate particles, aluminum compound particle/silica
particle blends, or aluminum-compound particle/silicate-particle
blends and combinations thereof into a subterranean well that has
been cemented. The fluids may also contain weighting materials,
buffers, antifoam agents, defoamers and dispersants.
[0026] Another method of applying the disclosed invention in a
subterranean well comprises adding alkali swellable polymers,
superabsorbent polymers or both to one or more of the
aluminosilicate, aluminum compound/silica or aluminum
compound/silicate suspensions described earlier into a subterranean
well that has been cemented. The fluids may also contain latexes,
weighting materials, buffers, antifoam agents, defoamers and
dispersants. The particle suspension enters voids, cracks or both
in the cement sheath. The particles then react with the cement
sheath and establish hydraulic isolation.
[0027] For the methods described above, fluid placement may
incorporate a variety of remedial techniques generally known to
those skilled in the art.
[0028] The following examples serve to further illustrate the
invention.
EXAMPLE 1
[0029] Fluids containing metakaolin have been tested. The
metakaolin MetaStar.TM. 501 from Imerys was used. MetaStar.TM. 501
is a highly reactive pozzolan with an average particle size below 5
micrometers.
[0030] Three formulations, shown in Table 1, were investigated.
Formulation 1 was a dispersion of metakaolin in water to which
sodium hexameta-phosphate [(NaPO3)6] had been added as a
dispersant. In Formulation 2, a sodium silicate solution
(containing .about.60% water and .about.40% Na2SiO3) had also been
added to the fluid, while in Formulation 3 a small amount of
potassium hydroxide had been further added as activator.
TABLE-US-00001 TABLE 1 Metakaolin-base fluid compositions.
Formulation 1 2 3 MetaStar 501 57.05 56.22 55.99 (wt %) H.sub.2O
42.78 42.89 42.81 (wt %) (NaPO.sub.3).sub.6 0.17 0.17 0.17 (wt %)
Na.sub.2SiO.sub.3 -- 0.72 0.72 (wt %) KOH -- -- 0.32 (wt %)
[0031] Rheology measurements were performed at 25.degree. C. for
the different formulations. The shear stress was measured as a
function of shear rate in the range 5-500 s-1. For all the
formulations, the plastic-viscosity (PV) values, obtained by
assuming a linear dependence between shear rate and shear stress,
varied between .about.70 cP and .about.140 cP.
[0032] To check the stability of the different dispersions, all of
the fluids were aged for 4 hours at ambient temperature. After this
time no significant traces of sedimentation were observed. Rheology
measurements were performed again. The results showed no
significant differences in the PV values. Therefore, it is evident
that the Theological properties are stable for several hours. This
suggests that no chemical reactions are taking place.
EXAMPLE 2
[0033] The reactivity of the compositions described in Table 1,
exposed to calcium hydroxide, was investigated. Some solid Ca(OH)2
was added to the different formulations. Visual observations and
measured PV values after the addition of different quantities of
Ca(OH)2 are reported in Table 2. Adding 0.5 wt % to 2 wt % calcium
hydroxide caused a significant viscosity increase leading to the
formation of pastes and solid materials. Thus, the presence of
Ca(OH)2 activates the fluids which start and triggers the formation
of calcium silicate hydrates.
TABLE-US-00002 TABLE 2 Properties of Formulations 1-3 after
addition of different amounts of Ca(OH).sub.2. Ca(OH).sub.2
Formulations added 1 2 3 0% Liquid Liquid Liquid PV ~70 cP PV ~72
cP PV ~140 cP 0.5% Viscous liquid Viscous liquid Gel/paste PV ~500
cP PV ~90 cP 1% Gel/Paste Solid Solid 1.5% Gel/Paste Hard solid
Hard solid 2% Solid Hard solid Hard solid
[0034] It can also be observed that, for Formulations 2 and 3 which
contain some silicate, a solid structure was obtained by adding
less Ca(OH)2. This may suggest that the presence of sodium silicate
leads to the formation of some geopolymeric structures.
EXAMPLE 3
[0035] To investigate the reactivity of the fluids in contact with
Portland cement, Formulations 1 and 2 (described in Table 1) were
poured on top of a cement core. After about 1 hour, the formation
of a solid layer on the cement surface was observed. This confirms
the reactivity of these fluids when in contact with a
Portland-cement surface.
EXAMPLE 4
[0036] To test the properties of repaired materials, experiments
were performed to evaluate the adhesive properties of the different
fluid formulations. A Portland-cement core (height: 5 cm; diameter:
2.5 cm) was cut vertically into two halves. One of the surfaces was
covered with a thin layer of metakaolin fluid, and the halves were
joined. For all of the formulations described in Table 1, the
halves were glued together and were difficult to separate. The
presence of sodium silicate (Formulations 2 and 3) enhanced this
effect.
EXAMPLE 5
[0037] Experiments were performed with fluids containing SuperFine
Class F fly ash (from Scotash), with an average particle size below
10 micrometers. The fluid formulations are presented in Table
3.
TABLE-US-00003 TABLE 3 Compositions of fluids containing fly ash,
and properties of materials obtained after curing. FORMULATION 1 2
3 4 5 6 7 Class F 59 56 54 50 50 50 50 fly ash (wt %) H.sub.2O 41
39 39.4 50 50 50 50 (wt %) Na.sub.2SiO.sub.3 -- -- 1.6 -- -- -- --
(wt %) Ca(OH).sub.2 -- 5 5 -- 2.9 4.7 6.4 added (wt %) After 1-
Liquid, Paste Solid -- -- -- -- hour PV curing at ~20 cP 60.degree.
C. After 1- Liquid, Solid Hard -- -- -- -- day PV solid curing at
~20 cP 60.degree. C. After 10 -- -- -- Liquid Solid Hard Hard days
solid solid curing at 60.degree. C.
[0038] Formulation 1 is a dispersion of fly ash in water.
Formulation 2 contains some Ca(OH).sub.2 to test reactivity.
Formulation 3 contains a small amount of sodium silicate solution
(containing .about.60% water and .about.40% Na.sub.2SiO.sub.3). All
the blends were prepared at room temperature and placed in an oven
at 60.degree. C. after mixing. After 1 hour the resulting materials
were compared. As shown in Table 3, the simple dispersion of fly
ash (Formulation 1) remained liquid. Rheology measurements showed
that the PV, calculated by applying a linear dependence between
shear stress and shear rate, was .about.20 cP. Formulation 2 became
a paste, proving that the fly-ash dispersion became reactive after
the addition of Ca(OH).sub.2. Composition 3 developed into a hard
solid, confirming that the presence of extra silicate leads to the
formation of a different solid structure as observed for fluids
containing metakaolin. After 24 hours at 60.degree. C., the
materials were compared again. No significant differences are
observed for Formulation 1, which remained a liquid with
approximately the same viscosity, while Formulations 2 and 3
continued to harden and form stronger solids. Formulations 4-7 were
50:50 blends by weight of fly ash and water. Formulation 4
contained no calcium hydroxide and was still liquid after ten days.
Formulations 5-7 became solid.
EXAMPLE 6
[0039] A blend of alkali swellable latex (ASL) and metakaolin was
prepared. For these experiments the metakaolin MetaStar 501 from
Imerys and the alkali swellable latex TYCHEM 68710-00 from Dow
Reichold were used. This ASL is a styrene-butadiene based latex
with a particle size smaller than 200 nm. The formulation tested
contained 90% wt of ASL and 10% wt of metakaolin. The metakaolin
was added slowly to the ASL, and the blends were mixed for several
minutes.
[0040] Rheology measurements were performed. The shear stress was
measured as a function of shear rate in the range 5-500 s.sup.-1.
The PV values, obtained by assuming a linear dependence between
shear rate and shear stress, are reported in Table 4. To verify
stability, the two blends were left at room temperature for 4
hours. After storage the two formulations remained fluid. Rheology
measurements detected showed no significant differences from the
results obtained upon mixing.
TABLE-US-00004 Blend ASL 90%/metakaolin 10% P.sub.v (cP) 14 at
25.degree. C. P.sub.v (cP) 18 at 25.degree. C. after 4 hr
Table 4. PV values obtained at 25.degree. C. for blends containing
90 wt % ASL and 10 wt % metakaolin after mixing and after 4 hours
storage.
EXAMPLE 7
[0041] Experiments were performed to evaluate the adhesive
properties of the ASL/metakaolin blend. As described in Example 4,
a Portland-cement core (height: 5 cm; diameter: 2.5 cm) was cut
vertically into two halves. One of the surfaces was covered with a
thin layer of ASL/metakaolin fluid, and the halves were joined.
After a few minutes the halves were glued together and were
difficult to separate. The adhesion improved with time.
[0042] Although various embodiments have been described with
respect to enabling disclosures, it is to be understood the
invention is not limited to the disclosed embodiments. Variations
and modifications that would occur to one of skill in the art upon
reading the specification are also within the scope of the
invention, which is defined in the appended claims.
* * * * *