Note: Descriptions are shown in the official language in which they were submitted.
` ~3%7133
~THOD OF TREATING PARTS OF A PERMEABLE U~DERGROUND FORMATION FOR
CONSOLIDA~ING PURPOSES
The invention relates to a method of treating parts of a
permeable underground foxmation for consolidating purposes. The
parts to be treated are located around a borehole or well
penetrating said formation.
A consolidating treatment o~ an underground hydrocarbon
producing formation comprising loose or insufficiently consolidated
solid particles is required when the flow of hydrocarbons produced
via a well penetrating such formation carriea unacceptable amounts
of these particles. Such particles are removed or torn away from
the mass of particles around the well and subsequently carried by
the flow of hydrocarbons via the well to the surface eguipment and
deposited partly therein. Frequent cleaning o~this equipment will
have to take place to prevent plugging of the equipment. In certain
cases, these particles may damage the eguipment in the welI and/or
1~ plug the well, or cause polIution of the~environment. Cleaning
operations will ther be required, which are mostly extremely
costly.
For these reasons several consolidating treatments have been
designed in the past for bonding the particles in the area around
a well together to for~ a consolidated mass of particles having
sufficient compressive strength and sufficient permeability. Part
of these treatments are based on tne use o~ resins that bind the
loose sand grains together and thereby prevent entrair~ment of the
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grains or particles by the flow of h~drocarbons passing through the
formation pore space during the subsequent production period,
In a particular type of consolidatine treatment by means of
resins, a solution containing an epoxy compound and a suitable
hardening agent (also indicated as curing agent) is injected down
the well and into the part of the formation to be treated. At the
location of the pore space parts to be treated, the epoxy compound
separates fro~ the solution by the reaction between the epoxy
compound and the hardening agent, which causes precipitation and
subsequent deposition of a viscous resinous material on the walls
of the pore space.
The resinous material after being deposited on the walls of
the pore space coalesces, thereby forming a viscous layer on the
surface of the sand grains. The resinous material is subsequently
sucked for the major part thereof by capillary action to the
locations around the contact points between the sand grains.
Thereafter the resinous material hardens and a strong bond be-
tween the sand grains is formed around the contact points between
the grains.
In the above described technique, between 5 and 30 vol.% of
resin-forming agents may be dissolved in the solution. This
solution is then kept stationary at the location of the pore
space parts to be treated until separation of the epoxy compound
from the solution has taken place. When applying larger amounts
(between 40 and 90 vol.%) of resin-forming agents in the solution,
an overflushing liquid is passed through the pore space parts to ~`
be treated prior to gelation of the solution by the reaction be-
tween the epoxy compound and the hardening agent. The overflushing
liquid is chosen to dissolve the solvent. When passing through
the pore space parts to be treated, the overflushing liquid
displaces part of the resin solution and extracts the solvent
from the solution remaining on the pore space walls. The over-
flushing liquid is retained within the said pore,space parts after
the overflushing step until resin cure has been completed.
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It will be appreciated that the amounts of epoxy compound
and hardening agent (hereinafter also referred to as "resin-
forming agents") to be dissolved in the solution are chosen
such that undesirable reduction in permeability of the pore
space is prevented. The dissolved amounts o~' epoxy compound and
hardening agent should be as small as possible but sufficient
to obtain the desired bond between the grains. The quality of
the bond is measured by compressing a mass of consolidated
granular particles to measure the compressive strength thereof.
The above-described known consolidation treatments usually
require a preflush with an inert liquid prior to the injection
of the solution containing the resin-forming agents in order to
remove the mobile fluid contents of the pore space of the form-
ation parts to be treated. Such preflush liquid may be crude oil
and/or brine.
Immobile water adhering to the walls of the pore space
prevents the resinous material from coalescing on the surface
of the sand grains and bonding them efficiently. Such water
is present in the majority of the formations that require con-
solidation treatments and should therefore be removed prior to
carrying out the treatments. Such water should in particular be
removed when the solvent of the solution containing the resin-
forming agents is a non-aqueous liquid, as is the case when
using an epoxy resin.
Removal of the adherent water prior to injecting the solution
containing the resin-forming agents consisting of epoxy compound
and curing agent into the pore space, allows the resinous material
after being separated from the solution to form a resin layer on
the sand grains, which layer after hardening thereof shows a
sufficient strength. If required, the strength thereof can further
be increased by adding a bonding agent (such as a silane) to the
solution.
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It has now been found that the same results and sometimes
even improved results as to the compressive strength of the con-
solidated sand grains of an underground Eormation can be obtained
by allowing the immobile water adhering to the walls of the pore
space to stay in the formation parts to be treated when the solut-
ion containing the res~in-forming agents flows into these formation
parts.
Thus this invention seeks to provide a method of treating
for consolidating purposes parts of a permeable formation surround-
ing a borehole or a well in a manner that is simple and cheap and
results in a high compressive strength at a minimum reduction of
permeability.
In its broadest aspect this invention provides a method
o treating, for consolidating purposes, parts of a permeable under-
ground formation surrounding a borehole or well, comprising
either a predetermined volume of a solution is injected
into the pore space of the formation parts to be treated,
or both a predetermined volume of pre-flush liquid and a
predetermined volume of a solution is injected in sequence into
the pore space of the formation to be treated,
wherein the solution consists of a solvent having dis-
solved therein resin-forming agents consisting of an epoxy compound
and a hardening agent for this epoxy compound; both the pre-flush
liquid and the solvent being capable of displacing the mobile
flùids present in the pore space but leaving water adhering to
the wall of the pore space, and wherein a predetermined amount of
dimethylaminomethylphenol is dissolved either in the solvent, in
the pre-flush liquid, or in both the solvent and the pre-flush
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liquid.
The pre-flush liquid may be a brine or a hydrocarbon
liquid. Also, a brine may be injected, followed by a hydrocarbon
liquid. When the formation parts to be treated contain water o
high salinity, a brine having a salinity lower than the salinity
of this water may be used as a pre-flush.
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The amount of dimethylaminomethylphenol is between 0.2 and
10 vol.~ of the volume of liguid in which it is dissolved. The
dimethylaminomethylphenol improves the wetting of the grains or
particles by ~e resinous material that separates from the solution
during the hardening of the epoxy compound. As a result thereof,
the compressive strength of the formation parts treated by the
method of the present invention will be found to be sufficient for
the purpose, notwithstanding the fact that immobile water is
present on the walls of the pore space The presence of this water
has even been found to be beneficial to the final compressive
strength of the treated parts after these have been in contact
with oil and water during a considerable producing period. A
further advantage of the use of dimethylaminomethylphenol is that
no separate injection of a preflush liquid is required to remove
immobile water adhering to the wall of the pore space parts to be
treated.
Particularl~ goodresults will be obtained by using an amount
of dimethylaminomethylphenol that is between 0.2 and 5 vol.% of
the volume of liquid in which it is dissolved.
It will be appreciated that where reference is made in ~e
present specification and claims to "vol~%" there is meant volume
per volume.
The "mobile fluids" referred to in the present specification
and claims are fluids that can be displaced through the pore space
of a formation by fluids of a polarity differing from the polarity
of the said mobile fluids.
"ImmobiIe water" as referred to in the present specification
and claims is water adhering to the walls of the pore space, which
water cannot be displaced from the original position thereof by non-water
30 miscible fluids passing through the said pore space. ~ater ad-
hering to the walls of the pore space includes the water caught
by capillary forces in capillary recesses of the pore space.
It will be apprecia~ed that thê predetermined volume of
liquid hydrocarbon that optionally precedes the injection of the
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resin-containing solution into the formation, will not displace
the immobile water adhering to the walls of the formation space.
The liquid hydrocarbon does remove mobile fluids present in the
pore space of the formatîon part to be treated, these mobile
fluids being gas and/or free-draining liquid such as crude oil
and/or brine not adhering to the waIs of the pore space.
The water in an underground formation is usually a brine.
High salt concentrations may lower the compressive strength of
the consolidated formation part to an undesirable extent. When
it is desirable to replace the adherent water by water of lower
salinity and/or containing salts other than the salts present
in the connate water, a predetermined volume of a brine of pre-
determined desired composition may be injected as a preflush,
either directly preceding the injection of the predetermined
volume of the solution containing the resin-forming agents, or
preceding the above referred injection of a predetermined volume
of liquid hydrocarbons. This brine washes the crude oil and
other mobile fluids from the pore space of the formation part
to be treated, but also the total volume of connate water, that
is the volume of immobile water adhering to the walls of the pore
space as well as the free-draining portion of the connate water.
Subsequently, the mobile portion of the brine is replaced by the
solution of resin-forming agents (or by the volume of liquid
hydrocarbon injected as a preflush)~ which leaves ~nly the immobile
portion of the brine in the formation parts to be treated, which
portion adheres to the walls of the pore space.
The water or brine adhering to the walls of the pore space of
the ~ormation part to be treated has now been found to play an
important role in the consolidated process. As will be shown
hereinafter, the compressive strength of a formation wherein the
resin-containing solution is brought into contact with water-
wetted walls is considerably improved as compared to a treatment
of "dry" walls, that are walls from which the immobile water
7~
adhering to the walls of the pore space has been removed by a
treatment of polar liquid, such as isopropyl alcohol ~IPA) that
is capable of displacing such immobile water. However, to reach
such favourable results~itisa pre-requisite that the immobile
water should contain dimethylaminomethylphenol. Either, the
- original water or brine present in the formation is replaced
by water (or brine) containing dimethylaminomethylphenol, or
the original water (or brine) present in the formation is brought
into contact with a solution of dimethylaminomethylphenol. In the
~latter case, the original brine if being a highly saline brine,
may be replaced by a brine of lower salinity before injecting
the solution of dimethylaminomethylphenol.
The amounts of dimethylaminomethylphenol used in the pre-
determined volume of a preflush and/or the solution of resin-
forming components may be between 0.2 and 10 vol.%, such as between
0.2 and 5 vol.%.
~he expression "epoxy compound" used in the present speci-
fication and claims means a monomeric and/or polymeric organic
polyepoxide having on average more than one epoxy group
/o
C C - per molecule. Preferred polyepoxides are poly-
glycidyl ethers ~ polyhydric phenols; an example thereof is the
liquid epoxy resin "EPIKOTE" ô28 ("EPIKO~E" is a registered trade
mark).
Epoxy compounds according to this definition can be cured or
hardened by reaction with suitable hardening agents to form hard
resinous materials that are insoluble and infusible under form-
ation conditions. The curing or hardening can often be accelerated
by the presence of accelerators such as phenols (or tertiary
amines).
Suitable hardening agents for use in the present invention
are polyamines having at least three amino hydrogen atoms per
molecule, and in particular aromatic polyamines of this type
are preferred. Examples of such aromatic polyamines are diamino-
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diphenylmethane, diaminodiphenylsulphone, m-phenylenediamine, with
the first one being preferred.
The choice of the hardening agent may depend on the temper-
ature of the underground formation and the residence time before
initi&l cure and precipitation of resinous material sets in.
Aliphatic polyamines such as diethylenetriamine could be used
as hardening agents when the temperature in the formation is rather
low, for e~ample not above room temperature. Usually, however, the
temperature is higher, in the range from 50 to 100C, and then
the aromatic polyamines provide a better balance between the time
interval after which the resinous material starts to separate
from the solution (the so-c&lled IRS-time or Initial ~esin
Separation-time) and the time period after which final hardening
has taken place. At formation temperatures above 100 C the hardening
agent may even be a tertiary amine, which promotes catalytic
polymerization and cure of the epo~y compound.
Phenols can be used to acce~rate the hardening reactions, and
so a~sist in regulating the IRS-time and final hardening. Suitable
phenols to be used as acce~rator are phenol and alkylated phenols,
such as cresols and xylenols. It should be kept in mind that the
dimethylaminomethylphenol that is used in the method of the present
invention as an essential ingredient for the wetting properties
of the resin-containing solution, is also an accelerator. There-
fore, when adding dimethylaminomethylphenol in the proper amounts
for obtaining the desired wetting properties of the resin-con-
taining solution, the right balance for the rate of hardening
should be found by a a proper choice of type and amount of other
phenols, if any, and possibly of retarders.
Ketones as a solvent componen~ will slightly retard the
hardening reaction, and so permit an even more accurate regulation.
Suitable ketones are acetone, methylethylketone, methylisobutyl-
ketone,and cyclohexanone.
It will be appreciated that the amount of the resin-forming
agents consisting of e-oxy compound and hardening agent should be
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chosen such in relation to the natural co.~pressive strength of
the formation to be treated and the si~e of the solid particles
or grains of said formation that the permeability of the pore
space of the formation is not decreased to an undesirable extent,
and the compressive s-trength after treatment is at a value
sufficiently high to withstand formation pressures occurring
after the well has been re-opened for production therethrough.
For the majority of consolidating treatments, the amount of resin-
forming agents is in the range between 5 and 30 vol.% of the
solution if no overflushing step is applied.
~ he dimethylaminomethylphenol used in the method of the
present invention for improving the wetting properties of the
resin-containing solution has - as will be shown hereinafter -
only a negligible activity as hardening agent for the epoxy
compound in the composition used in the present treating method.
It acts primarily as a wetting agent for the resinous material,
and further also as a reaction rate acce~rator.
Attractive results are obtained by application of the method
of the present invention, wherein dimethylaminomethylphenol is
present in the resin-containing solution and/or the preflush in
amounts between 0.2 and 10.0 vol.% of the volume of liquid
wherein it is dissolved. Optimum results will be obtained in the
range between 0.5-1.5 vol.%.
If desired, a bonding agent may be added to the resin-con-
taining solution for improving the compressive strength of theconsolidated mass of formation particles. Bonding aeents, such
as organo-functional silanes are known components of epoXy com-
pound containing consolidation compositions. The organo-~unctional
silane contains at least one silicon atom, at least one functional
group suitable for reacting with the material of the particles of
the mass to be treated, and at least one other functional group
(such as an amino group, a methoxy group, an ethoxy group, or an
epoxy group) suitable for reaction with the epoxy compound, the
hardening agent, or other reactive material, such as precondensates
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formed by the reaction of the latter components.
Suitable solvents for the epoxy compound, the hardening agent,
the dimethylaminomethylphenol, and the bonding aeent are liquid
aromatic hydrocarbons. Also, mixtures of two or more liquid aromatic
5 hydrocarbons may be used, or a mixture of at least one liquid
aromatic hydrocarbon and at least one other liquid hydrocarbon,
in which latter case the mixture should have an aromatic content
of at least 50 vol.%.
Liquid aromatic hydrocarbons that are suitable for use in
10 the present method, are benzene and alkyl derivatives thereof such
as toluene, xylenes, or liquid aromatic extracts of crude oil
distillates, such as kerosin~ gasoil, spindle oil, lubricating
oil fractions, or liquid aromatic extracts of heavy cat -~racked
cycle oil. The solvent may contain a liquid h~drocarbon mi~ture known
15 under the registered trade mark "SHELLSOL" ~ which has an aromatic
content over ôO vol.%.
Alcohols (such as methanol, ethanol, a propylalcohol or a
mixture of at least two of these liquids) are also suitable solvents
for the solution containing the resin-forming agents, but should,
20 however, be used in minor amounts only (say not more than 20 vol.%).
Since being polar fluids, alcohols will displace immobile water
when being injected into the formation. As has been explained already
above, the presence of water containing dimethylaminomethylphenol
and adhering to the walls of the pore space is a prerequisite for
25 carrying out the method of the present invention, and care should
be taken that the total amount of the immobile water is not re-
moved from the formation pore space to be treated prior to the
period that the resinous material starts to separate from the
solution. Therefore, only minor amounts of alcohols are allowed
30 in the resin-containing solution.
Accelerators and retarders, commonly named hardening con-
trollers, when present, should not displace the majority of the
immobile water adhering to the wall of the pore space, or other-
wise influence the treating process to an undesirable extent.
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The hardening controllers are chosen to control the rate of hardening
in such a manner that the resinous material does not start to be
separated from the solution under the prevailing temperature con-
ditions in the well, prior to the moment that the solution has
permeated the pore space of the formation part to be treated.
Often it will be found desirable to increase the viscosity of
the resin-containing solution to prevent fingering of the solution
through the formation pore space. The viscosity of the solution
should therefore be made higher than -the viscosity of the liquid
contents of the pore space. Any viscosifying agent that is compatible
with the components of the resin-containing solution and the re-
quired reaction between the resin compound and the hardening agent
may be applied for increasing ~e viscosity of the resin-containine
solution to the desired value. Polymers and copolyme~ (such as
isoprenestyrene polymers, polyisobutene polymers, polymethacrylate
polymers, olifene polymers, and the synthetic rubbers such as
butadiene-styrene copolymers) have been found useful in this
respect, provided that concentrations are applied at which gelling
of the~ solution does not occur.
The predetermined volume of liquid hydrocarbons that may
optionally be injected prior to the injection of the resin-con-
taining solution to remove the mobile fluid contents from the pore
space of the parts to be treated, ma~ comprise at least 50 vol.%
aromatic liquid hydrocarbons, such as toluene, xylenes or liquid
aromatic extracts of crude oil distiDates, such as kerosine, gas-
oil, spindle oil, lubricating oil fractions, or liquid aromatic
extracts of heavy cat -cracked cycle oil, and may be supplemented
with other hydrocarbon liquids such as kerosine or diesel oil.
All these hydrocarbons are suitable for displacing the mobile
fluid contents present in the pore space of the formation, and
are further compatible with the resin-containing solution. There
is no objection, however, to place a spacer liquid between the
volume of liquid hydrocarbons and the resin-containing solution.
Use of a spacer liquid may be desirable when considerable mixing
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is expected between the resin-containing solution and the preflush
during the flow thereof through the well.
Suitable spacer liquids are aromatic hydrocarbon liquids~
kerosine or suitable derivatives thereof, or aromatic hydrocarbons
obtained by extraction of kerosine, easoil, etc.
If desired, the dimethylaminomethyl phenol that is required
for improving the wettability of the surfaces of the grains of
the formation may be added to the volume of the liquid hydrocarbon
preflush instead of to the resin-containing solution. Also, the
dimethylaminomethyl phenol may be added to the preflush liquid as
well as to the resin-containing solution.
The brine that may optionally be injected as a preflush either
prior to the volume of liquid hydrocarbons or prior to the solution
of resin-forming agents will be most effective if having a salinity
lower than the salinity of the water present in the formation. ~hus,
if the formation water comprises 10% by wt ~aCl, a brine com-
prising 1.0% by wt KC1 or 1.0% by wt CaC12 may be injected to dis-
place this formation water and other fluid contents present in the
pore space. Thereafter, this low-saline brine is partly displaced
by the volume of liquid hydrocarbons (or the solution of resin-
forming agents), which leaves, however,immobile low-saline brine
adhering to the walls of the pore space. ~he relatively low
salinity of the adhering brine will be compatible with the com-
ponents of the resin-forming solution, and the strength of the
bond thus obtained will be considerably greater than the strength
of the bond obtained without applying the brine preflush.
~ he predetermined volumes of the various liquids and solutions
used in the present invention are chosen in relation to the form-
ation to be treated. Generally good results will be obtained by
30 using the following volumes:
solution of resin-forming agents........... ....... 1 pore volume
preflush of hydrocarbon liquids.................... 1 pore volume
preflush of brine.......................... ~....... 2 pore volumes
preflush of brine followed by liquid hydrocarbons.. 1 pore volume each
35 spacer liquid....................................... 1 pore volume
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The treating method according to the invention is one that
is based on the resin-phase separation principle. By applying a
relatively low concentration of epoxy compound and hardening agent,
an intermediate resinous product will separate from the solvent
as a result of the reaction taking place between the resinous
compound and the hardening agent when the solution is retained
for some time in the pore space between the particles of the
formation part to be treated. ~he intermediate resinous product
; will be deposited in the form of droplets on the surface of the
particles, which surface has been made resin-wettable by dimethyl-
aminomethylphenol to allow the droplets to coalesce and there-
after be concentrated by capillary forces in the small recesses
of the pore space, which recesses for the greater part are near
the contact places of adaacent particles. On further hardening
of the intermediate product, a hard cross-linked resin is formed
which bonds the granular particles together in co-operation with
the bonding agent, thereby forming a consolidated mass of con-
siderable compressive strength and at the same time having a
sufficient permeability to allow flow of fluids therethrough that
pass into or out of the borehole or well penetrating the treated
formation part.
It will be appreciated that the present treating method will
be considerable simpler and cheaper than the methods requiring
pre-flushing of the pore space by liquids for displacing the
adherent water from the formation parts to be treated. The use
of these liquids, such as alcohols (e.g., isopropyl alcohol) adds
considerably to the cost of the treatment. Moreover, when pre-
flushing by means of alcohols (as are often chosen for their
excellent displacement efficiency) plugging of the pore space
may occur since the alcohols when passing through the well tubing
will remove dirt and rust from the inner wall of the tubing, which
dirt and rust will be deposited in the pore space and in the
entrance openings to the formation pore space, and may thereby
seriously decrease the permeability thereof. Further, when in
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contact with saline water in the pore space, the alcohols may
precipitate salts that cause then further plugging of the form-
ation pore space. In contact with wax~ crudes, the alcohols will
further cause precipitation of wax, and when in contact with clays
(as are often present in hydrocarbon-containing formations) swelling
and flocculation will occur. It will be appreciated that although
a~cohols have excellent water-displacing properties, the actual
application thereof will be accompanied by undesirable permeability
reduction of the formation being treated. The present method which
does not require the use of a water-displacing liquid is therefore
applicable in various types of formations, and has the advantages
of simplification and consequently better chances on a successful
job (since a limited number of liquia slugs are to be injected),
low cost (since no expensive alcohol preflushes are required), low
permeability reductions (since injected fluids are compatible with
the conditions prevailing in the well and the formation), and high
compressive strength (since the presence of adhering water has been
found to favourably influence the compressive strength after a
prolonged contact with water during the subsequent recovery period).
The method according to the invention will now be described
by way of example in detail with reference to the drawings. ~he
dimethylaminomethylphenol used was the commercial product DMP-10
of Rohm and Haas (DMP is a registered trade mark).
Figure 1 is a diagram showing the influence exerted by DMP-10
(in vol.% along the X-axis) on the unconfined compressive strength
(in kg/cm along the Y-axis) of a mass of particles consolidated
with and without previous removal of adherent water.
Figures 2-5 show various stages of the liquid displacements
and the resin separation in a pore space ~ a~formation being treated
by the method of the present invention.
Figure 6 shows the influence of acetone on the Initial Resin
Separation time ~n minutes along the Y-axis) when using resin
containing solutions having various amounts of DMP-10 (indicated
in vol.% along the X-axis) in the range of 1-5 vol.% of this solution.
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Figures 7 and 8 show the relationship between the compressive
strength (in kg/cm along the Y-axis) and the hardening agent/epoxy
compound volume ratio R (along ~e X-axis) when using different
amounts of DMP-10 dissolved in the resin-forming solution, and
when measuring the compressive strength with and without flushing
of the consolidated mass by gasoil or water.
Reference is first made to Figure 1 of the drawings.
Tests have been carried out to ascertain the influence of the
addition of various amounts of DMP-10 to a solution containing
resin-forming agents and applied for consolidating sandpacks that
have been subjected to a preceding step of removing adherent water.
Identical tests have further been carried out in sandpacks con-
taining adherent water. After consolidation, the sandpacks were
subjected to load tests at a temperature of 60C to determine the
unconfined compressive strength thereof, that is the compressive
strength of a cylinder of 3.7 cm diameter and 3.7 cm height, loaded
in its axial direction, and not supported at the side walls thereof.
The unconfined compressive strength after 24 hours hardening at 60 C
was measured at this hardening temperature:
20 - directly after hardening (see curves A-1 and A-2 in
Figure 1);
- after being contacted with gasoil for a period of a week
at 60 C (see curves B-1 and B-2 in Figure 1), and
- after being contacted with fresh water for a period of a
week at 60 C (see curves C-1 and C-2 in Figure 1).
The sandpacks were formed by filling glass cylinders with Oude
Pekela sand, and subsequently flushing the sandpack with gasoil
followed by brine (containing 1 vol.% ~aCl).
To show the beneficial effect of the presence of adhering water
when applying the present method, two series of tests were carried
out in the sandpacks. In the first series of tests, the total liquid
content of the pore space, including the adhering water, was removed
from each sandpack by flu~ing the sandpack with three pore volumes
of isopropylalcohol. Then two pore volumes of a solution containing
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resin-forming agents were injected into the sandpack and kept in
place in the pore space until hardening of the resin had taken
place.
The resin-forming agen-ts dissolved in this solution were:
11.2 v~1.% epoxy compound;
3.7 vol.% hardening agent, being diaminodiphenylmethane
(DDM).
The solution used was a liquid composition consisting oP:
2.4 vol.% isopropylalcohol (IPA);
7.8 vol.% acetone;
27.0 vol.% kerosine, and
62.8 vol.% xylene.
Further, DMP-10 was added to the various solutions in amounts
equal to 0, 0.5;1;2;3 and 5 vol.%. This range of 0-5 vol.%
DMP-10 is being indicated on the X-axis of the diagram of Figure 1.
Curves A-1, B-1 and C-1 relate to this first series of tests.
In the second series of tests, each sand pack ~as flushed by
means of two pore volumes of gasoil, as a result whereo~ the mobile
liquid, but not the adherent water, was displaced from the pore
space of the sandpack. Subsequently, two pore volumes of the~resin-
containing solutlon of the same compositlon as used ln the first
series of tests were injected and kept in place in the pore space
of the sandpack until the resin had hardened. The amounts of DMP-10
added to the various solutions in the second series of tests were
equal to the amounts of 0; 0.5; 0.75; 1; 1.5; 2, 3 and 5 vol.% as
in the flrst series of tests. Curves A-2, B-2 and C-2 relate to
this second series of tests.
After the curing, the consolidated sandpack of eaoh test was
detached from the glass cylinder and three samples of 3.7`centimetres'
length were cut therefrom. One sample of each test was subjected
to a load test to determine the unconfined compressive strength
thereof. The compressive strength~(in kg/cm ) was indicated~along
the Y-axis of ~igure 1 in~relation to~the amount of DMP-10 added
to the solution~ and curves~A-1 and A-Z in Figure 1 indicate this
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~3~83
relationship for the first and second series of tests, respectively.
As can be seen, the compressive strength of the samples wherein
the a &erent water has been removed prior to injection of the
resin-containing mixture (see curve A-1) is - for all amounts of
DMP-10 added - greater than the compressive strength of the
samples wherein the water has not been removed (see curve A-2).
During oil production periods, however, the consolidated
formation part will be contacted with large amounts of crude oil
flowing through the pore space. This contact will increase the
unconfined compressive strength of the consolidated mass, and to
determine the influence of the crude oil on the compressive strength
with respect to various amounts of DMP-10 in the above referred two
series of tests, a sample of each test was subjected to a gasoil flush
at 60 C over a period of a week. Curves B-1 and B-2 show the results
and as can be seen from the diagram the compressive strength of the
sample wherein the a &erent water has not been removed (curve B-2)
is over the whole range lower than the compressive strength of the
sample wherein the adherent water has been removed prior to the
treatment by the resin-containing solution (curve B-1).
Apart from being contacted by crude oil, the walls of the form-
ation pore space will, however, also be contacted by water during
the productive period of the well around which a consolidation
treatment has been carried out. The compressive strength is
negatively influenced by such water contact as can be seen by
comparing curves A-1 and C-1 in the diagram of Figure 1, wherein
curve C-1 shows the relationship between the unconfined compressive
strength and the amount of DMP-10 after one week flushing at 60 C
by water in samples wherein the adherent water has been removed
prior to the treatment by the resin-containing solution. Curve C-2
shows the same relationship but now in samples wherein the adherent
water has not been removed.
Comparing the final unconfined compressive strengths that are
being measured in the test samples that are being subjected to
water flooding, it will be obvious that the best results are being
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~13Z783
obtained by the use of DMP-10 in consolidating treatments that are
carried out in sandpacks that have water adhering to the wall of
the pore space. By dissolving DMP-10 in the above referred resin-
containing solution in amounts in the range of 0.25-4.3 vol.%,
the final unconfined compressive strengt~ of the water-flooded
samples that did not have the immobile water removed from the pore
space thereof prior to the consolidating treatment (see curve
C-2), will be higher than the corresponding compressive strengths
of water-flooded samples that had the immobile water removed from
the walls of the pore space prior to consolidating (see curve C-1).
Thus, in actual field operations where water will be produced
together with oil via the consolidated areas around a producing
well, the use of dimethylaminomethylphenol in consolidating treat-
ments without prior water removal from the treated areas will yield
the highest compressive strength during the operational life of
the well.
The above-described tests resulted in an acceptable decrease
in permeability of the sandpack. ~he original single-phase per-
meability of the sandpack was about 8.5 Darcy, at a porosity of about
37%. The permeability after treatment ranged between 5 and 7 Darcy,
which was considered quite acceptable for production purposes.
Figure 2 of the drawings shows (on an e~larged scale) an
assembly of sand-grains 1, containing connate water and oil in the
pore space between the grains. The surface of the grains is water-wet,
as a result whereof the grains are covered by water layers 2 between
which oil 3 is present.
In one of the modes of treating the sand-grains by the method
according to the present invention, a hydrocarbon pref`lush 5 (see
Figure 4) is injected into the pore space of the formation parts to
be consolidated, whereby the mobile liquid contents of this pore
space are removed therefrom, but an immobile thin layer of adherent
water 4 remains on the surface ~ the grains 1 (compare Figures 2
and 4). ~he hydrocarbon preflush 5 is subsequently displaced by a
~Bin-containing solution 6 (see Figure 5), which solution leaves the
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adherent water 4 in place. DMP-10 is dissolved in this solution which
DMP-10 will upon contact of the resin-containing solution with the
water layer 4, partially enter this layer, thereby rendering the
surface of the grains 1 wettable by the resin that starts separating
from the solution by the react~n between the resin and the curing
agent present in the solution 6 containing the resin-forming agents.
The separated resin is deposited in the form of droplets on
the surface of the grains, which droplets coalesce by the presence
of DMP-10 on the surface, thereby forming resin layers that are
partly sucked by capillary action into the spaces of minute di-
mensions around the contact points of the grains. After hardeningof the resin, the grains -~ill be bonded by the resin present around
these contact points, whereby the passageways through the pore
space are left substantially unobstructed to allow flow of form-
ation fluids to the production well.
If the connate water 2 (see Figure 2) has a salt content that
would undesirably reduce the compressive strength, the pore space
between the grains 1 should first be treated by passing a pre-
determined volume of brine 7 therethrough, which brine has a
considerably lower salt content. Figure 3 shows the pore space
after such flushing treatment with brine. The total volume of the
pore space now contains brine 7. This brine is subsequently dis-
placed by injecting a predetermined ~olume of hydrocarbon li~uid
through the pore space whereby only adherent water 4 of the brine
composition is left on the surface of the grains (see Figure 4).
Thereafter, the resin-containing solution 6 is injected into the
pore space, which solution displaces the hydrocarbon 5, but leaves
the adherent water 4 (of brine composition) on the surface of the
grains (see Figure 5). DMP-10 from this solution then enters the
adherent water 4, and the resin on being separated from the
solution 6 is deposited on the surface of the grains in the form
of droplets that coalesce under influence of the DMP-10 and are
collected in the locations around the contact points of the
grains.
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If desired, a suitable spacer liquid (not sho~7n) may be injected
after the hydrocarbon liquid 5 (see Figure 4) and prior to the
injection of the resin-containing solution 6 (see Figure 5) to
separate the liquid 5 from the solution 6. The spacer liquid
should be compatible with the liquid 5 as well as with the
solution 6l and should not displace the water layer ~.
The application of dimethylaminomethylphenol in the con-
solidating treatment according to the present in~ntion is not
restricted to the addition of dimethylaminomethylphenol to the
solution containing the resin-forming agents. Good results will
also be obtained by adding the dimethylaminomethylphenol either
only to the preflush liquid (that is the brine and/or the hydro-
carbon liquid) or to the preflush liquid and the solution containing
the resin-forming agentsO and/or to a spacer liquid.
As has been observed already above, the compressive strength
of the formation parts treated by the method o~ the present in-
vention may further be improved by adding a bonding agent to the
solution containing the resin-forming agents.
Suitable bonding agents are organo-functional silanes which
silanes are ~ganic substances containing at least one silicon
atom, at least one functional group suitable ~or reacting with
the particles to be treated, and at least one other functional
group suitable ~or reacting with one of the resin-forming agents
or with the product formed thereby.
An example of an organo-functional silane is an "amino-
functional silane", which is an organic substance containing at
least one silicon atom, at least one functional group suitable
for reacting with the particles to be treated, and at least one
amino group suitable for reacting with one of the resin-forming
agents or with the product formed thereby.
A further example of an organo-functional silane is an
"epoxy-functional silane'~, which is an organic substance con-
taining at least one silicon atom, at least one functional group
suitable for reacting with the particles to be treated, and at
1~3'~7783
least one epoxy group suitable for reacting with one of the resin-
form ng agents, or with the product formed thereby.
If the particles to be treated substantially consiat of
siliceous material, the functional group suitable for reacting
with the particles is preferably formed by a methoxy group or an
~hoxy group.
Examples of amino-functional silanes are N-aminoethyl-amino-
propyltriethoxy-silane and aminopropyltriethoxy-silane.
Examples of epoxy-functional silanes are glycidoxypropyltri-
methoxy-silane and 3,4-epoxycyclohexylethyltrimethoxy-silane.
The bonding agents may be added in amounts between 0.1 and
1 vol.% of the solution containing the resin-forming agents.
Optimum results will be obtained by using amounts between 0.2 and
0.3 vol.%.
The addition of dimethylaminomethylphenol increases the re-
action rate between the epoxy compound and the curing agent. At
relatively high temperatures of the formation to be treated, it
may therefore be required to add reaction rate retarding agents,
such as ketones (e.gO, acetone, methylethylketone, methylisobutyl-
ketone and cyclohexanone).
Figure 6 shows the influence of acetone on the so called
IRS-time of the reaction between the epoxy compound and the
hardening agent. By the expression IRS-time is meant the Initial
Resin Separation-time that is the time interval between the
moment of preparation of the solution and the moment at which the
first droplets of the intermediate resinous product start to
separate from the solution.
The solution containing resin-forming agents applied in the
tests having the results thereof shown in Figure 6, consists of:
3011.2 vol.% epoxy compound, and
3.7 vol.% diaminodiphenylmethane (hardening agent)
dissolved in a solvent, consisting of:
2.4 vol.% IPA;
7.8 vol.% acetone;
1 3527.0 vol.% kerosine, and
62.8 vol.% xylene.
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22
The graph in Figure 6 shows the IRS-time (in minutes) along
the Y-axis and the vol.% of DMP-10 in the resin-forming solution
along the X-axis. Curves D, E and F indicate the relationship
between the IRS-time and the vol.% of DMP-10 at extra acetone
amounts in the solution of O vol.%, 5 vol.% and 10 vol.%,
respectively, at curing temperatures of 60C.
The graphs in Figures 7 and 8 o~ the drawings show that the
unconfined compressive strength of a mass of particles treated by
the present method is influenced by the ratio o~ the hardening
agent/epoxy compound in the solution containing the resin-forming
agents. In the solution9 a constant amount of 11.2 vol.% epoxy
compound "EPIKOTE" 828 was used, and an amount of hardenine agent
diaminodiphenylmethane (DDM) was added to obtain the hardening
agent/epoxy compound volume ratio R indicated along the X-axis
of the graphs.
~he resin-forming components were dissolved in a solvent
consisting of:
2.4 vol.% isopropylalcohol (IPA),
7.8 vol.% acetone,
27.0 vol.% kerosine, and
62.8 vol.% xylene.
The mass of particles was equivalent to the sandEack as
described with reference to Figure 1. The mass was preflushed by
two pore volumes of "SH~LLSOL" N. No spacer liquid was used.
The results shown in Figure 7 are obtained by adding 0.5 vol.%
DMP-10 to the solutions, whereas the results shown in Figure 8
were reached by adding 2.0 vol.% D~P-10 to the solutions.
In each of the Figures 7 and 8, the Y-axis indicates the
uncon~ined compressive strengths o~ the samples in kg/cm2,
measured at a hardening temperature of 60 C. Curves A, B and C
indicate the relationshipsbetween the strength and the hardening
agent/epoxy compound ratio R a~ter 24 hours a~ter hardening, after
seven days gasoil ~lushing and after seven days water ~lushing,
respectively.
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23
As can be seen from the graphs in Figures 7 and 8, the amount
of DMP-10 added to the solution hardly ;nfluences the hardening
agent/epoxy compound ratio R at which maxim~m compressive strength
of the sandpack is obtained, and therefore it can be concluded
that dimethylaminomethylphenol has only a negligible activity as
a hardening agent at formation temperatures.
Finally, a treatment to be carried out by the method of the
present invention will be described.
Samples of the liquids present in the formation part to be
treated indicated that apart from crude oil, connate water was
present comprising 10~ by wt ~aCl. In view of this high salinity
it was decided to displace the liquid in the pore space of the
parts to be treated by a brine of low salinity and comprising
potassium chloride in an amount of 1.5% by wt which was found in
laboratory experiments to reduce the compressive strength
only slightly. The temperature in the formation at a depth of
1965 metres was 61 C and the components of the resin-containing
solution were selected such that an IRS-time of 150 minutes was
reached that was considered sufficient to pump the solution
tafter preparation thereof) down to ~e formation layer to be
treated, prior to resin droplets being separated from the
solution.
The amounts of the resin-forming agents were selected such that
a minimum of permeability reduction was reached in the laboratory
simulation treatments, at the required compressive strength.
Also, a viscosifying agent was selected to improve the
distribution of the solution containing the resin-forming agents
over the formation layers of various permeabilities in the in-
I terval to be treated.
The treating method to be carried out for consolidating the
particular formation consists of the following steps:
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1. Clean the production tubing present in the well by
pumping a volume of about 1200 lit~es of 15% HCl
down the well to the lower end thereof and sub-
sequently producing it back.
2. Set packers to limit the interval to be treated.
3. Inject 8000 litres of brine containing 1.5% by w KCl
through the tubing and into the interval to be
treated.
~. The brine injection is followed by the injection
of a volume of 4000 litres hydrocarbon liquids
consisting of 50 vol.% "SHELLSOL"-~;
50 vol.% gasoil, to which were added
35 kg/m3 "SHELLVIS"-50 ("S$ELLVIS" is a
registered trade mark) as a viscosifying agent.
5. Inject 4000 litres of the solution containing resin-
forming agents after its preparation do~n the well
to the interval to be treated.
This solution comprises:
12.6 vol.% "EPIKOTE"-828 (epoxy compound);
4.2 vol.% DDM (hardening agent);
0.75 vol.% DMP-10 (dimethylaminomethylphenol)
and 0.25 vol.% A 1100 (registered t.rade mark)
(bonding agent)
dissolved in a solvent consisting of:
2.4 vol.% IPA (isopropylalcohol);
7.8 vol.% acetone;
27.0 vol.% kerosine, and
62.8 vo}.% x~lene
To the solution were added 40 kg/m3 "SHELL~IS"-50 as a
viscosifier.
6. The solution is pumped down the well and into the interval
to be treated by means of a volume of diesel oil, until
the sol~tion has ~ully entered the pore space to be treated.
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A volume of spacer liquid (4000 litres, consisting of
50 vol.% "SHELLSOL"-N and 50 vol.% gasoil) is in~ected
between the diesel oil and the solution.
7. The well is shut in for 16 hours to allow the epoxy compound
to harden.
8. Subsequently, the well is opened for production.
It will be appreciated that the method according to the in-
vention apart from being used for consolidating particles or grains
that originally form part of the underground formation to be
treated, may also be used for consolidating particles that have
been supplied to the formation during a preceding treatment, or
simultaneously with the solution containing the resin-forming
agents. Such particles are, e.g.,grains that are used for gravel-
packing purposes, or propping agents that are applied in fractures
to counteract closing of the fracture after its formation. These
particles or grains, after being placed down in the well or in a
fracture, form part of the formation and should often be con-
solidated to prevent them from being entrained by the production
fluids flowing therealong.
FinaIly, it is observed that the method according to the in-
vention may also include an overflushing step. The concentration
I of the resin forming agents in the solution is then chosen between40 and 90 vol.%. In the overflushing step, a predetermined volume
of an overflushing liquid is passed through the pore space parts
to be treated prior to the gelation of the solutionby thereaction
between the resin-forming agents. The overflushine liquid is
suitable for dissolving the solvent for the epoxy compound and
the hardening agen-t, but water, epoxy compound, hardening agent,
dimethylaminomethylphenol as well as any other components
dissolved in the solution containing the~epoxy compound are
virtually insoluble in this liquid. After the overflushing step,
the overflushing llg id is kept statlonary in the pore space part
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~3~83
26
to be treated until resin cure has been completed.
Suitable overflushing liquidsare predominantly aliphatic
hydrocarbon fractions of crudes such as brightstock oils, diesel
oils and the like. The viscosity of the overflushing liquid
should be chosen such that the viscosity of the liquid is
approximating that of the solution containing the resin compound.
The method including the overflush step is in particular
useful for consolidating shaley formations having large surface
areas because of the presence of silt materials. This method
allows the use of concentrations of epoxy compound in amounts
sufficient to coat the silt materials, and furthermore, since
extracting the solvent from the gelled resinous material
deposited on the walls of the pore space being treated, will
promote shrinking of the gelled resinous material, thereby
pulling silt particles into the interstation spaces contiguous
to the larger formation grains. The final permeability of the
pore space after the treatment that results therefrom will
not decrease the productivity of the well to an unallowable
extent. This, and other details of the overflush technique
applied to consolidating treatments of underground formations
by means of a solution of epoxy compound and hardening agent
has already been extensively described in the ~SA patent speci-
fication ~o. 3,339,633 (Inventor: E.A. Richardson; filed 27th
July, 1965; granted 5th September, 1967).
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