Note: Descriptions are shown in the official language in which they were submitted.
CA 02630682 2007-12-21
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Sustainable Method for Recovery of Petroleum
Field at the invention
The present invention refers to a sustainable method
for increasing the recovery of petroleum from
petroleum-bearing subterraneari formations, particularly
formations wherein petroleum is found as oil which is
too viscous to flow or be pumped.
More particularly the present invention refers to a
method of recovery (extracticn) of petroleum from the
original geological formatiori utilising injection of
diesel and/or biodiesel oil through the injection well,
reducing the viscosity of the petroleum, dissolving
heavier and immobile petroleum fractions and traversing
the reservoir acting through the sweeping and
displacement effectiveness, increasing oil recovery and
the proven reserve.
Background of the invention
In view of the increasing need for energy one of the
great challenges of the petroleum industry worldwide is
achieving maintenance of production to satisfy current
demands.
The model currently followed aims to maintain
production and reserves through the discovery of new
accumulations; although such approach has in general
led to the discovery of new offshore accumulations,
they are frequently found at great depths in
increasingly-deep water and frequently in deposits
wherein the oil found is of high viscosity.
The association of viscous oil, great depths and
maritime environment results in enormous technico-
operational complexity and hicfh production costs and
CA 02630682 2007-12-21
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said scenaric afts technical and econorr.ic
effectiveness and production sustainability.
Environmental sustainability under such conditions is
also a critical matter, principally with reference to
the collection and disposal of fluids.
Thus the great challenges for the petroleum industry in
Brazil and worldwide are maintenance of production, to
maintain self-sufficiency, and replacement of reserves,
to ensure sustainable future supply, being understood
as socio-environmentally responsible.
Furthermore in various parts of the world diverse
petroleum-bearing geological formations are found
wherein only conventional methods of petroleum recovery
are used, however others cannot be fully exploited
using such methods because the oil contained in such
formations is too viscous to flow or be pumped.
2D
As a consequence thereof another important aspect of
the current model is the fact of large investments
being made in prospection in the search for new
reserves without appropriately exhausting those already
being worked and still containing a large volume of
remaining oil, signifying the disrespectful extraction
of a natural resource without concern for future
generations.
Therefore increasing the working life of a field is
directly related with the currently-available
techniques of Enhanced Petroleum Recovery (EPR), the
methods hitherto employed solely taking into
consideration immediate technical and economic
effectiveness without great attention being paid to
socio-environmental aspects.
According to the literature there exists a series of
chemical additives having the objective of viscosity
CA 02630682 2007-12-21
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2 _
reduct ion an-3 of relative L;r r~sr.ri r . r . . e r . app7 i cat i on,
normally employed as a method of stimulation in
production wells to eliminate= formation damage or as an
additive in cyclic siLeam-injection processes
(injection/production in production wells). In a
broader sense such products do not satisfy technical,
economic and environmental requirements in the manner
herein proposed by the present invention.
Related art
The use of solvents is already known and widely
employed for the dilution of viscous oils, the
objective whereof being to facilitate transport within
wells or in production lines or even volumetric oil
transfer.
The use of solvents in petroleum production has been
restricted to or concentrated in countries wherein
geological formations are found having ultraviscous
oils and very low ambient temperatures, such as
Venezuela and Canada, in the form of well stimulation,
injection/production through the production well.
In general the currently-existing technology having
this objective has been solely concerned with the
technical and economic effectiveness of the processes
employed and thus the solvents employed heretofore
cause environmental disequilibrium, both on the
surface, having consequences for the ecosystem and
mankind, and within the environment of the geological
reservoir, causing chemical, physical, physico-chemical
and biological disequilibrium in said environment.
Utilisation of substances classified as
env'-ronrnentally-damaging in the diverse methods
hereunto known has shown that said substances were
selected taking into consideration solely availability
and cost to the detriment of environmental matters,
CA 02630682 2007-12-21
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cr õubstances have tiius become t}ze target of
increasing questioning by environmental entities in
various parts of the world, reflecting a new philosoohy
in society.
United States patent US 6 279 653 discloses that the
viscosity of heavy oils may be significantly reduced
converting such oil into a:3table microemulsion. Such
microemulsion is formed combining alkaline reagents
with the oil and subjectinq the same to ultrasonic
energy. Said reduction in oil viscosity permits the oil
to be pumped out of the well and it may then be
conveyed for refining, however introducing extraneous
substances into the environment of the geological
formation, which same require to be removed from such
oil through particular procedures, in addition to the
utilisation of ultrasound.
United States patent US 5 025 863 discloses a process
for well stimulation (injection/production in the
production well) wherein a slug of immiscible natural
gas is injected into a formation through the production
well. The well is then shut in for a given time ('soak
period') for the gas to enter solution. The well is
then put into production when petroleum is then
produced together with the gas utilising conventional
production equipment and techniques, however the fact
of struggling with gas and injecting the same through
the production well raises other questions in terms of
safety and effectiveness of the procedure.
United States patent U5 6 491 053 refers to a known
manner of reducing the viscosity of heavy petroleum
through admixing the same with a liquid component of
lower density. Said component may be petrol, kerosene
or other components such as to better pump the oil. At
its destination the solvent added may be removed and
recycled. This procedure is expensive and when crude
petroleum requires pumping over long distances
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ecircu]L a'ioi: of tr_e v;;=cosity-reducing uqent hec..c,~r.Fs
complicated. This is a process to ensure fi.ushing
pipelines and lines, it is not a method for recovering
petroleum which acts within the reservoir.
United States patent US 4 531 586 also discloses a
process for cyclic stimulation of heavy oil production
in a petroleum reservoir comprising injection (through
the production well) into the reservoir of a liquid
solvent such as diesel oil or a light petroleum and
production of the oil/solver.it admixture. This is a
method of well stimulation, injection and production in
the production well having a reduced scope, not being
an enhanced petroleum recovery method.
United States patent US 3 127 934 refers to the
injection of two slugs of solvents through the
injection well. The first slug comprises solvents of
low molecular weight, specifically gases (Cl to C4)
which as the author discloses dissolve the oil
contacted effectively, however it has a great tendency
to pass around the regions bearing oil creating
preferential channels, that is to say the gases tend to
seek regions of high permeability. The second slug
comprises solvents or other types of material which, in
contact with water, polymerise forming a product
blocking the region washed. This is a different
concept, involving plugging regions of high
permeability. In both cases refex-red to the use of
gases involves very delicate situations in terms of
operational and safety matters, and as to the materials
which polymerise, these may also prevent some areas of
interest in the formation being prevented from
subjection to more efficient washing.
Once the natural energy of a reservoir has been {
exhausted it is normal to commence secondary recovery,
that is to say injection of water or gas as displacing
fluids. The effectiveness of the process is low because
CA 02630682 2007-12-21
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such fiuids have G Ler.der,cy to create arcLcre:itial
channels in regions or beds of hi-gh permeability.
The degree of formation of such preferential channels
is determined by several factors of which the most
important is the ratio between viscosity of the
petroleum to be recovered and viscosity of the fluid
injected.
A manner of minimising formation of such preferential
channels is to seek to more closely approximate the
viscosities of the 'displacing' and 'displaced'
(petroleum) fluids. One option is the addition of
polymeric additives to injection water (displacing
phase) to increase the viscosity thereof. The second
option is to reduce the viscosity of the petroleum
through the use of miscible fluids.
In many cases wherein the oil is of high viscosity the
process of secondary recovery ends by being abandoned
because the oil can no longer be economically produced
due to the high ratios of water injection to oil
produced.
When working with an oil of high viscosity, should the
expected water injectivity into the reservoir not be
achieved, the normal practice is injection of steam
into the formation with the objective of improving the
extraction flow of the oil, acting in a general manner
on the production well which, in a petroleum context,
represents stimulation of the production well.
In general approximately 30% of the petroleum is
recovered through conventiona:L Primary and Secondary
recovery processes. Thus 70% of all the original
petroleum still remains in reservoirs and this is
therefore the target of Tertiary Recovery, also known
as Enhanced Petroleum Recovery (EPR).
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Suc:=r cost-effectiveness is Eo~=rever Ei turic:tiort :f the
effectiver.ess of recovery techniques, investment
wherein nas beeia put aside due to investment in new
discoveries. Investment in such techniques signities
extending the working life of a field and recovering in
a respectful manner a non-renewable natural resource.
Thus in spite of advances in the art there still exists
a requirement for an Enhanced Petroleum Recovery
process, either for normal exploitation or even for
better utilisation of the oil contained in a geological
formation, thus increasing the working life of a
reservoir_
Summary of the invention
The present invention presents a method of Enhanced
Petroleum Recovery combining general, economic,
environmental and social effectiveness in order to
increase the recovery factor of onshore or offshore
fields, more precisely through the use of a miscible
substance for use in reservoirs, having the objective
of reducing viscosity and fluidifying the petroleum.
Such substance is selected front the group consisting of
diesel oil or fractionated gas oil from petroleum, or
even biodiesel, being similar and derived from plants,
or light oil, which products may be utilised pure or
with additives, in an isolated manner or together with
other fluids or methods such as: steam, polymers, etc.
Such substances, subject of the present patent, require
to be highly-miscible with the oil contained in the
geological formation wherein it is intended to act,
injection being executed througfi the injection well and
traversing the entire reservoir to the production well,
which in the petroleum context represents Enhanced
Petroleum Recovery (EPR).
For the purposes of the present invention solvent is
understood to be biodiesel or oil, having
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A_aracLexiUt.ics simi7ar to ~he di.esPi :I Gtuallv
produced from mineral sources, being prociuced riowever
from renewable sources, normally agricultural sources.
More specifically the present invention refers to the
use of solvents such as light liquid petroleum
fractions, for example diesel. oil or gas oil, a light
petroleum, and essential oils derived from renewable
sources such as, for example, biodiesel, used in a pure
form or in a common admixture in any proportion for
injection into a geological formation through the
injection well, resulting in a final admixture
(petroleum/injected solvent) having a much lower
viscosity and much greater fluidity than that of the
original petroleum, impacting on the entire petroleum
production chain. The present invention presents a real
advantage in all phases of the production chain:
1) increase in recovery factor;
2) increase in proven reserves;
3) reduction in loss in lifting and transport;
4) elimination of the necessity for using additives
to render paraffinic oil viable;
5) adjustment of oil viscosity to refining conditions
plus, in the case of solvents derived from
petroleum, their recovery and it being possible to
return them to the process or be marketed.
The method of the present invention is especia?ly
indicated for utilisation when petroleum is of high
viscosity or paraffinic and/or the formation is of low
permeability, resulting in conditions wherein the
petroleum possesses low fluidity characteristics
throughout the formation.
Thus the use of diesel and/or biodiesel and the other
products recommended in the present invention is
indicated for petroleums of the paraffinic type, being
the case of some occurrences of petroleum of the
CA 02630682 2007-12-21
paraf:fir.ic t:ype in 1~ruzilian territary, or ever.~ for
petroleums in lew-tempera u:re environments or wi:ich
require to be transported under the rigours of such
environments.
The present invention may also be employed for the
displacement of immovable reserves of petroleums of the
asphaltenic type wherein a small addition of aromatics
to the diesel extraction charge greatly enhances the
positive results with said technique.
In this context such diesel and/or biodiesel is not to
be considered primordially as a solvent fluid but
should be interpreted as being a fluid whose
utilisation is indicated due to it being miscible with
the petroleum found in the reservoir, and not be
considered as a substance extraneous to the environment
wherein it is applied, in addition to also satisfying
other requisites of a technical, environmental and
economic nature, as aforestated.
An objective of the present invention is to provide a
sustainable method of recovery by means of which
significant quantities of oil may be extracted from a
reservoir bearing petroleum of low fluidity through
reduction in viscosity of said viscous oil with the
objective of improving flow within the reservoir and
pumping conditions.
Another objective of the present invention is to
provide an improved process by means of which
additional quantities of oil may still be recovered
from reservoirs containing oil of low fluidity,
principally those reservoirs which have already been
normally treated by water and/or steam flooding and
which in many cases would now be considered as being
exhausted, wherein the procedure occurs by means of
injecting into such geological formation, containing
said petroleum of low fluidity, the miscible fluid
CA 02630682 2007-12-21
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refe-~-ed s uch reccvery bAinq ;ca=i sed %y L::out
requ-ring injection of excessive quantities of fluid
miscible with the petroleum within the reservoir and
which same is pushed throughout the extent of the
reservoir by means of a displacing fluid such as, for
example, water.
A further objective of the present invention is to
provide a process of recovery by means of which an oil
of low fluidity may be recovered from geological
formations in a shorter time through the injection of
smaller quantities of fluid and in more favourable
ratios of oil to injected fluid than are possible
through application of presently-known processes.
By virtue of diesel being homogeneously miscible with
petroleum and both the diesel and the petroleum/diesel
solution possessing relatively low densities and
viscosities, flow throughout the formation is thus
stimulated and the process of the present invention
renders recovery possible in locations heretofore
considered difficult and inefficient or even costly or
impossible.
A yet further relevant aspect of the method of the
present invention is that the fluid miscible with the
oil contained in the formation rather than being
injected through the production well is injected into
the geological formation through the injection well
resulting in the solvent traversing the formation from
the injection well to the production well and, as a
function of the difference in viscosity between the
miscible fluid, lying in the intermediate band between
water and the oil, it acts in a decisive manner on the
effectiveness of displacement through the reduction in
viscosity and dissolution of the heavier fractions of
the oil impregnated in the formation and on the
sweeping effectiveness.
CA 02630682 2007-12-21
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Ei~h,3nce~ I'e~roieu~r, Recovery, together with Secondary
Recovery, always presuppose an injected (displacing)
phase with the objective of displacement of the oil.
In this manner the method of the present invention has
a yet further consequence of its mechanism of acting,
being a significant improvement in displacement
effectiveness and sweeping effectiveness within the
geological petroleum-bearing formation, being the two
key points of attack of the methods of Enhanced
Petroleum Recovery.
Thus the final recovery factor is a function of the
effectiveness of the displacing phase, being:
(i) Sweeping Effectiveness, associated with viscous
forces or the difference in viscosity between the
displacing/displaced (petroleum) phases; and
(ii) Displacement Effectiveness, associated with the
effectiveness of driving or displacement of the
oil from the swept area, combined with capillary
forces.
Such characteristics are of operational importance
insofar as their acting conjoiritly contributes to more
homogeneous distribution of capillarity, preventing
preferential routes through the subject formation, in
addition to preventing separation along the route
traversed by the drive fluid.
A further important aspect is that the method of the
present invention may be applied employing the same
devices and equipment utilised for secondary recovery,
injection of water and/or steam, at the pressure and
the temperatures of the environment of the geological
formation to be treated.
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I3rief dPscriptian of t'ie fiqures
Figure 1 presents a table referring to the survey of
technical, economic and environmental data of a number
of viscosity reducers available in the Brazilian
market.
Figure 2 presents a graph showing the reduction in
viscosity following utilisation of a number of
substances utilised as viscosity-reducing agents.
Detailed description of the invention
The present invention refers to the injection of liquid
petroleum fractions, the classification of such
petroleum fractions according with the number of
carbons in the chain, as shown in Table I below.
TABLE I
REFINERY PRODUCT HYDROCARBON BAND
Gas Cl - C4
Petrol C5 - Clo
Kerosene Cll - C18
Diesel C14 - Cls
Heavy gas oil C12 - C25
Lubricating oil C20 - C40
Residue > Cao
Within this phase we emphasise the band of hydrocarbons
from C14 - C18 corresponding to diesel being that
presenting the most suitable technical and
environmental effectiveness. The liquid fractions (CS -
C13) prior to those of diesel (C.14 - C318) also offer
technical effectiveness, however as the number of
carbons in the chain decreases vapour pressure
increases and, flowing therefrom, environmental risks
also increase. In addition, in the liquid fraction
CA 02630682 2007-12-21
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having a number of carbons exceP:iing fourteen
as ttie number of carbons in the chain increases, always
being linear, environmental effectiveness increases and
technical effectiveness diminishes. For application in
heavier oils, generally containing significant levels
of asphaltenes, a small fraction of an aromatic solvent
such as xylene or toluene should be admixed with the
viscosity reducers subject of this patent to prevent
precipitation of asphaltenes.
Injection of gas to increase the recovery yield of oils
of high viscosity is already known, being classified as
conventional recovery.
In accordance with the Table presented in Figure 1 and
taking into consideration the objective of working in a
sustainable manner, that is to say prioritising social
and environmental responsibility, the first criterion
for the evaluation of viscosity reducers has been that
of the least environmental impact which they might
cause.
In this manner in this initial selection all those
which presented a high negative environmental impact
were rejected, even in detriment to their technical
advantages. Among the same there were also eliminated
naphtha, C5+, petrol, and the aromatic extract.
Also in conformity with the '.Cable shown in Figure 1,
diesel oil, a light petroleum represented here by oil
from a specific well (Petrobras, Brazil), turpentine
and kerosene presented the least negative environmental
impact, that is to say less toxicity, less danger, less
risk of explosion than the other solvents due to having
lower vapour pressures than the others.
In the specific case of the aromatic extract and
similar products, in spite of not having a high vapour
pressure like the others referred to, they present a
CA 02630682 2007-12-21
high degree of toxic_ty due to their ca'~1I1oCi?hic and
mutaaenic characteristics.
Frorn among the viscosity reducers approved, those
having least economic cost were diesel oil and analysed
light oil proceeding from said well (Petrobras,
Brazil). The interpretatior.i of this analysis is
consolidated in the Table presented in Figure 1.
In a second stage the products selected, that is to say
diesel oil and the light oil because they presented
least environmental impact and least cost, were
evaluated in accordance with their rheological
performance, viscosity reduction, based on admixtures
having diverse proportions of the solvent and the
viscous oil from the Nativo Oeste field (Petrobrgs,
Brazil), on which were executed measurements of dynamic
viscosity. Said analyses were compared with others
executed on the same oil and other solvents under the
same conditions, confirming the technical potential of
said selected viscosity reducers. The results are shown
in graph form in Figure 2.
Thus diesel oil and the light oil were approved in the
environmental, technical anci economic context as
viscosity-reducing agents, however diesel oil was found
to be best in terms of the viscosity drop obtained as a
function of the proportion of petroleum.
Thus far the products were analysed and approved in an
isolated manner, that is to say merely as
viscosity-reducing agents. A further application for
such substances was considered taking as a basis not
solely their viscosity-reducing power but, in addition,
the interaction thereof with the formation and their
mechanism of action as a method of Enhanced Petroleum
Recovery.
CA 02630682 2007-12-21
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I,o- operat-or_al purposes wich refer.encc Lu faci__7_tating
pumping condirions for lifting and transporting irl
pipelines the oil produced, this latter should possess
a viscosity lower than 300 cP, preferably lower than
250 cP, more preferably lower than 200 cP.
Description of the preferred embodiment
The understanding of Enhanced Petroleum Recovery (EPR)
takes into consideration tiqe concept of Secondary
Recovery. The injection of water or gas (displacing
fluids during Secondary Recovery) has as its purpose
displacement of the (displace(i) oil in the reservoir by
means of purely-mechanical behaviour, that is to say on
injecting water or on subjecting the reservoir to a
process of immiscible gas injection it is not expected
that there will be chemical or thermodynamic
interaction of such fluids with the oil or with the
rock. The fluid injected displaces the oil, occupying
the pores vacated by the oil as the latter is expelled
from the formation, however not the entire volume swept
by the displacing fluid ex.pels the oil. Such oil
remaining in the regions invaded by the fluid injected
is denominated residual and is a consequence of the
effect of capillarity.
EPR and Secondary Recovery always presuppose an
injected (displacing) phase having the objective of
displacing the oil. The final recovery factor is a
function of two aspects of effectiveness of such
displacing phase: Sweeping Effectiveness, linked to
viscous forces or the water/oil viscosity difference;
and Displacement Effectiveness, linked to the
effectiveness of driving the oil from the swept area,
associated with capillary forces. Said two aspects
define the points of attack of Enhanced Petroleum
Recovery causing modifications to the physico-chemical
and thermodynamic nature of the fluids and interactions
between the same and the formation.
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In order to act on Sweeping Effectiveness we require to
increase the viscosity of the displacing phase or
reduce the viscosity of the displaced phase (petroleum)
and to affect the Displacement Effectiveness it is
necessary to act on the interfacial tension between the
displacing and displaced fluids and/or the wettability
of the fluids/rock system.
The novel concept herein presented proposes a method of
Enhanced Petroleum Recovery based on the injection of a
slug of diesel oil through the injection well of the
formation followed by injection of water.
Such novel concept offers technical, economic,
environmental and social contributions.
1) Technical: The mechanism of acting of the method
is divided into two phases: the first during
displacement of the slug of diesel oil through the
formation and the second during the recommencement of
water injection.
1.1) During displacement of said slug of diesel
oil: the slug injected enters the formation in the
regions of least resistance and reduces the
viscosity of the petro:Leum contacted becoming
incorporated into said slug of diesel oil, its
viscosity increasing in proportion to the original
quantities and viscosities of the components of
the admixture (diesel oil and petroleum). This is
the mechanism of acting on the Displacement
Effectiveness of the method, that is to say
solubilisation of the icnmovable oil, i.e. oil
which would remain in the formation even following
contact with injected water, rendering it mobile
with consequent reductior. in viscosity of such
mobile oil.
CA 02630682 2007-12-21
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1.2) D.:ring r:ecomriencement of water iiij ectiori: the
water front enters the formation contacting and
displacing the oily phase (now petroleum/diesel
oil) of lower viscosity than the previous phase
(original petroleum). Said viscosity reduction of
the displaced phase is translated into an increase
in the Sweeping Effectiveness of the displacing
phase due to reductiorl in the difference in
viscosity between the displacing (water) and
displaced (admixture) phases.
1.3) Additionally a wettability reversal (rock/oil
to rock/water) may occur promoting even further
displacement of the remaining oil by water
injected subsequent to passage of the slug of
diesel.
2) Environmental:
Upstream: Injection of the slug of diesel oil may be
executed using the same water injection system already
installed, however such system requires adaptation and
certification in accordance with the Safety,
Environment and Health (SEH) regulations and standards
for handling inflammable substances.
In the formation: The method herein presented will not
cause biochemical disequilibrium in a reservoir because
from the chemical point of view said oil already forms
part of the composition of the petroleum therefore the
injection of diesel oil into a formation does not
introduce substances extraneous to such formation. In
the same manner disequilibrium will not arise in the
biota of the formation given that the microorganisms
existing therein are already adapted to this component,
being one of the fractions of petroleum.
Downstream: As the product (viscosity reducer) used in
this novel concept is an integral part of the petroleum
CA 02630682 2007-12-21
and will be produced together therewich, the care
required in thi.s phase is identical to that already
implemented for the petroleum.
3) Economic: As the diesel oil is a subproduct of the
petroleum it has a cost being dependent on the price of
petroleum and the processing for its obtainment
therefrom. However, introduction of a mixture having
approximately 20% diesel already significantly reduces
the viscosity of the original petroleum to less than
300 cP, being sufficient to change an immovable into a
movable oil. More precisely, in this case each barrel
of diesel oil recovers four of petroleum and, in
addition, the diesel oil extracted admixed with the
petroleum may return to the process following normal
processing of the recovered o:il.
An economic alternative to the process wherein the
price of diesel is not linked to the price of petroleum
is the use of biodiesel rather than utilisation of
diesel oil from petroleum. :Cn this case a renewable
source of energy would be being used for the extraction
of a non-renewable natural resource, being attractive
in terms of economic support for diverse agricultural
regions in the world.
As well as diesel and/or biodiesel, gas oil or a light
petroleum may be used.
The use of crude petroleum does not involve refining
costs however it does not offer the same results in
reduction of viscosity when cocnpared with diesel.
Gas oil offers as an economic advantage over diesel one
less process being hydrotreatment, thus the cost should
be slightly less than that of diesel, however it also
presents disadvantages in mattera relating to Safety,
Environment and Health (SEH)..
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Social: Tiic= great challenges for tt_e petroleum
industry in Brazil and worldwide are maintenance of
production to maintain self-sufficiency and replacernent
of reserves to ensure future supply with
sustainability, that is to say environmental and social
responsibility. Currently, to satisfy such demand
companies are investing massively in new reserves
exploration and particularly in Brazil the majority
thereof are found in environments at great depth on the
continental platform wherein the majority are
constituted by heavy oils. Thus, as a consequence of
the application of said operational strategy, a large
quantity of oil, approximately 70* or more in onshore
formations having all the support structure and in the
majority of cases containing a light oil of excellent
quality, now no longer require to be 'abandoned' due to
a matter of economics, by virtue that the utilisation
of the technique of the pr.esent invention greatly
increases the possibilities of recovery, extending the
working life of a formation, extracting natural assets
in a respectful manner, taking into account the concern
for future generations.
In this manner the addition of diesel oil and/or
biodiesel provides the following economic advantages:
- it renders the extraction of heavy or ultraviscous
oil possible or feasible;
- it increases the recovery factor reducing residual
saturation;
- it contributes to the transport of petroleum in
the lifting phase and flushing in pipelines in a
general manner, principally in low-temperature
environments;
- i.t increases the value of petroleum through
viscosity reduction and raises its API grade,
rendering such oil more suitable for marketing;
- it adjusts the petroleum for the most favourable
refining conditions;
CA 02630682 2007-12-21
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the diesel and/cr b'odi.esel injected is noL lost,
it is produced admixed with the oil and may be
recovered during processing and be recycled once
again into the flow to be injected through the
injection well for continuation of the recovery
process of high-viscosity petroleum.
In this manner the present invention is a method of
Enhanced Petroleum Recovery combining technical,
economic, environmental and social effectiveness to
increase the recovery factor of onshore or offshore
fields having a high level of exploitation, more
precisely the use of solvent, diesel oil, biodiesel and
other similar products, used separately or in
conjunction with other fluids or methods such as steam,
polymers, etc, its acting mechanism being improvement
in Displacement Effectiveness and Sweeping
Effectiveness, the two key points of attack of Enhanced
Petroleum Recovery (EPR) methods.
In addition, application of the method of the invention
permits rendering high-viscosity petroleum suitable for
the operational conditions of lifting and transport by
virtue of ensuring flushing in production wells, lines
and pipelines.
Example
The example provided below presents a specific
application of the invention to an oil produced in
Brazil; due to the high-viscosity characteristics of
the type of Brazilian paraffinic petroleum denominated
Nativo Oeste (API-13, viscosity 3500 cP) the present
invention was applied util:Lsing a number of more-
available substances havino been tested with the
objective of use as viscosity-reducing additives in the
injection operation throuqh injection wells in
production activities.
CA 02630682 2007-12-21
~ =~
_ 2 _
he application of the preser_~ ir_,re nt in ~he
rheology determination tests with the objective of
selecting a more appropriate viscosity reducer for use
in the field to render viable steam injection into a
formation through the injection well, led to the graph
shown in Figure 2.
In accordance with Figure 2, diesel achieves the result
of lowering viscosity from 3500 cP to less than 250 cP
at concentrations of solely 15 - 20%, placing it in an
advantageous position with respect to the other
reducers analysed, taking into account the technical,
economic and environmental parameters considered for
the diverse solvents available in the Brazilian market_
More precisely we observe that for each barrel of
diesel injected to treat said high-viscosity oil there
exists the possibility of recovering approximately five
barrels of petroleum from the reservoir due to the fact
of injection of diesel oil achieving a reduction in the
viscosity of the oil conta_ined in the formation to
approximately 250 - 300 cP.
In addition the diesel oil extracted admixed with said
petroleum may be returned to the injection process
following normal processing of the oil recovered by
extraction.
The Table shown in Figure :1 shows the results with
reference to the technical, economic and environmental
data of the various solvents existing in the Brazilian
market, taking into account the parameters relatir_g to
their Safety, Environment and Health (SEH) aspects.
Although the present invention has been presented in
its preferred method of embodiment together with a
specific example, it shall be understood that the same
are merely provided illustratively and shall not be
CA 02630682 2007-12-21
- 22
considered as limiting the spirit and scope of the
present invention.
Those skilled in the art will be capable of determining
the most economically-favourable percentages of
utilisation for application., based on the guidance
herein presented, which shall be incorporated within
the spirit and scope of the present invention.
In this manner modifications to the bands of
application of diesel oil and/or biodiesel which may be
made over and above. those herein presented will be
obvious to those skilled in the art. Such modifications
shall be the subject of experimentation to bring about
percentage increases in the desired recovery of high-
viscosity petroleum, providing benefits from the
technical and economic point of view in accordance with
their nature and industrial purpose. However it is
clear that such modificatioris are incorporated within
the spirit and scope of the present invention.
