Note: Descriptions are shown in the official language in which they were submitted.
CA 02286245 1999-07-29
METHOD OF OILFIELD DEVOPMENT
The invention is referred to the oil industry and namely to the methods of
field
development through watertlood pressure control. These methods aim at raising
oil
recovery, however in permeability heterogeneous reservoirs typical for most
pools early
breakthrough of water often happen imo production wells. Due to large
differences in
transmissibility water filtration into low permeability intervals is
negligible, i.e. they are
excluded from production. Besides, water breakthrough to the well bore of the
producing
wells leads to the increase of pressure in highly flooded intervals which
results in the
decrease oil flow from other low filtration reservoir sections into highly
permeable
intervals and a decrease of produced oil and undeveloped intervals and
sections.
Known are methods of avoiding selective water filtration into more permeable
intervals
and decreasing watercut in the product. They involve creating water blocking
barriers in
high permeability sections through injection of various dispersions of
fibrous, granular
and powder materials, emulsion, foams and various gel or sediment forming
compounds
("Increasing efficiency of water injection wells. Summary." VNIIOENG, "Oil
industry"
series, M., 1982, #22 (46) 34 c.; "Applications of Chemicals for Well
Stimulation".
Reference book. M. 1991, page 46-72; "Modern Methods of Enhanced Recovery and
New Technologies in the Russian Oilfield". The Russian Federation. Oil
Industry. # 10,
1993, page 6-15).
These methods aim at increasing displacement rate, however, the methods are
not
sufFlciently efficient, technically complicated, they require specialized
dispersion,
solution and injection equipment for chemicals and their compositions, certain
methods
are expensive. All these are factors that limit extensive application of the
methods in the
oilfield. Besides, the application of known methods controlling sweep coverage
and
decreasing watercut focus on preparation work, i.e. cleaning the near well
bore area and
in particular its highly permeable intervals from plugging substances composed
of solid
mineral particles of various dimensions and chemical nature and viscous (paste-
like)
organic mass composed mostly of highly fusible paraffin and heavy asphaltene-
resin
components (PARC) of oil. This complicaxes and in certain cases makes
impossible
injection of certain water blocking agents into the reservoir without prior
cleanup.
Most often various acid or heat treatments, surfactant and other chemical
injection are
applied to cleanup the near well bore area. This drastically complicates
available methods
leveling out injectivity profile and decreasing watercut and makes them more
expensive.
There exists a known method of well operation (Patent RU 2094594 C 1, 6, E 21
B 43!00,
27.10.97, #30) where to create conditions for continuous oil extraction a
vibrating
acoustic emitter is lowered into the producing well through the lubricator on
the wireline.
The emitter is tuned in the cavitation regime (15-100 kHz) and is lowered to
the mark of
oil bubble pressure. Later to promote gas separation (artificial gaslift) the
source of
acoustic vibraxions is repetitively moved above and below the mark.
CA 02286245 1999-07-29
The disadvantage of the method is a short lasting and insufficient effect of
ultrasound
impact on the oil and gas separation. Operating flooded oil well through this
method it is
possible for a stable highly dispersed water-in-oil emulsion to form.
According to another available method of treating the near well bore area (KG
2105874
C1, 6 E 21 B 43/25, 27.02.98) an impulse pressure generator is lowered into
the
perforation interval and located at the bottom part with the most oil and gas
saturation
and flow intensity. The impulse of 250-400 kJ is created and vibrations last
until their
complete damping after which impulses of 6-8 kJ and 10-15 Hz in frequency are
generated. When the impulse treatment is completed and prior to removing the
generator
from the well a deep drawdown is created in the perforation interval for more
complete
cleanup of the near well bore area form the mechanical impurities and well
stimulation.
The disadvantage of the method is bringing the cleanup products to the surface
and a
possibility of water flow increase in the producing wells as a result of
additional micro
fractiues forming in the near well bore area as a result of impact pulses of
250-400 kJ
There exists a known method of treating the near well bore area of oil wells
and a tool for
its~application (RU # 2055979 C1, 6E 21 B 43/00, 10.03.96 #7) chosen as a
prototype of
the proposed method. The prototype involves well shut-down, injection of
brine, locating
an acoustic emitter at the flooded level of the interval and 22-42 kHz
frequency impact
on the near well bore area at cyclic relocation of the emitter for 05-1.0 hour
with the
ultrasound field of 0.05-2. S kW. Later the acoustic emitter is brought to the
surfae and
the well is started
Using brine (salt water) with low physical and chemical properties (dissolving
and
peptizing properties) towards oil PARC as a fluid media for ultrasound cleanup
of
plugging substances containing a sufl'lcient PARC volume is the major
disadvantage of
this method. Another disadvantage as it will be described further, is the
frequency range
for ultrasound cleanup (dispersion) of solid substances.
The objective of the invention is to develop the method fiuther, decrease
costs and
increase environmental benefits. The method uses solid hydrophobic particles
0.5 - 20
la,m in dimensions that form at ultrasound dispersion of sediment
(accumulating in the
near well bore area in the process of drilling, servicing and production) in
an active in
relation to sediment liquid with liquid-vapor surface tension within 20-35 mPa
cm
(erg/cm2), density exceeding injection water density by no less than 100 kg/m3
and
viscosity equal to water phase viscosity or no more than 20 times over it and
PARC of oil
contained in the sediment as hydrophobic agents that form molecular or oolloid-
dispersion systems in the active liquid under the impact of ultrasound. The
method is
used to create a hydrophobic barrier permeable for oil and low permeable for
water in
high permeability intervals and fractures of the near well bore area.
Liquid media with aforementioned parameters that are based on the general
understanding of the mechanism of solid bodies dispersion in the ultrasound
field has a
significant impact on the efficiency of the dispersion prows. The media is:
CA 02286245 1999-07-29
Blends (solutions) of low viscous oil (petroleum products) and heavy non-polar
fluids, i.e. tetrachlormethane (Standard 20288-74), APK agent (TU 122-199-05-
76-
34-68-94) etc. and
Solutions of various surfactants in salt water with density and concentration
complying with the aforementioned requireme~s and concentration that drops the
surface tension of the solution at the contact with air (vapor) to required
numbers.
Ultrasound dispersion (destruction) of a solid body in liquid media
('~7ltrasound
Technology", m., "Mettalurgia", 1974, page 285-293, "Ultrasound Eguipment",
issue 2,
1963, page 52-57) is defined mostly by the cavitation process and acoustic
micro flows.
Cavitation bubbles that form under the impact of ultrasound are concentrated
mostly on
the solid particles and micro fractures and bumps on their surface. Later
under the
influence of intensive micro flows formed by the impulses of the bubbles,
pores groves
and micro fractures on the surface of the particles fill with liquid. Gas
(fluid vapor)
compresses to several thousand Atmospheres inside the cavity that decreases in
dimensions approximately to 1 pnn. Rapid secondary expansion of the bubble
provides
micro impact action of cavitation that leads to breakup (dispersion) of solid
particles.
Based on these notions, the lower the viscosity and surface tension of liquid
and the
higher its density, the more effective are the aforementioned cavitation
processes.
Properties of a solid body (brittleness, hardness, continuity) also have a
considerable
influence on frequency, intensity and time of ultrasound dispersion of
particles in various
liquid and the quality of resulting dispersion. For example, the best
dispersion (particle
dimensions no less than 0.1 lun) for kaoline in water is achieved at 960 kHz,
for
monmorilonite it is 320 kHz, for gypsum 16 kHz, for organic solid material 22
and 42
kHz.
Therefore, for the proposed method the optimum fi~equency of the ultrasound
generator is
set in each case based on the data of micro analysis of dispersions formed at
various
frequencies of dispersion of sediment collected from the near well bore area
in the liquid
media.
Focusing on the impact that viscosity and surface tension on the vapor contact
have upon
the process of cavitation the lower these parameters are the more effective
the dispersion
process, for proposed liquids these parameters are minimum. Density of active
fluid
media injected into the well under the reservoir water layer should be no less
that 100
kglm3 more than the reservoir water density for the two types of water not to
mix.
Therefore, the major distinctions of the proposed method are:
1. Lowering the tubing to the bottom hole
2. Injection of liquid media through tubing
3. Lifting the tubing to the surface
4. Lowering the ultrasound emitter to the bottom hole
CA 02286245 1999-07-29
4
5. Setting optimum parameters of ultrasound impact based on prior laboratory
tests at
various frequencies intensity and time of ultrasound dispersion of the
sediment
collected from the near well bore area in various media providing dispersion
with
solid particles dimensions within 0.5-20 N.m.
6. Application of active liquids for effective dispersion of solids in the
ultrasound field
in the near well bore area. Liquids have surface tension of 20-35 mPa.sec-1
(erg/cm2)
at liquid-vapor contact, density that is no less than 100 kg/m3 over the
density of
flood water and viscosity equal to water phase viscosity or exceeding it no
more than
20 times. It is proposed to use blends (solutions) of low viscous oil and
liquid
petroleum products and viscous non-polar fluids, i.e. tetrachlormethane, APK
agent
(TU 2122-199-OS-76-34-68-94) etc. or solutions of various surfactants in salt
water
with density complying with the aforementioned requirements and concentration
of
surfactant in solution that drops the surface tension of the solution at the
contact with
xir (vapor) to required maximum numbers.
7. Application of solid hydrophobic particles of 0.5-20 p,m formed at the
bottom hole by
ultrasound dispersion in active liquid media. The particles are mineral solids
of
various dimensions and chemical nature composing treated sediment. This will
create
a hydrophobic barrier permeable for oil and low permeable for water in the
near well
bore area.
8. As hydrophobic agents for the solids and reservoir rock surface the
application of
PARC of oil that compose the sediment which forms molecular or colloid
dispersions
in the liquid media under the impact of ultrasound.
9. Upon the completion of the process of ultrasound treatme~ the application
of thinly
dispersed hydrophobic dispersion of solids and oil PARC in their complete
volume to
regulate injectivity profile and create water blocking barrier in producing
wells.
10. Should the near well bore area treated by the active liquid media and the
ultrasound
contain no sediment and plugging deposits (or contain little sedimem) to
prepare a
thinly dispersed suspension of solid particles and oil PARC in the near well
bore area
in the ultrasound field instead of active liquid media (distinct feature 6) a
dispersion
of oil sludge waste is injected such as bottom sedimem formed in holding tanks
while
storing merchantable oil. The sludge is mixed prior to that with active liquid
media at
the pump (or another blender) at volume ratio between 1:10 and 1:5 depending
on the
solids convent in the oil sludge.
Features 1,2,3 and 4 are common with the prototype and known methods, features
5,6,7;8,9 and 10 are not traced in known in the industry technical approaches.
Consequently, the proposed method complies with "sufficient distinctions"
category.
The method is applied as follows:
The type of active liquid media (ALM) that should be used for ultrasound
treatment of
the near well bore area is determined for the well selected for the enhanced
recovery
program based on the geological parameters of the reservoir and current
development
parameters as well as results of prior laboratory testing. Major ultrasound
generator
parameters are determined as well.
CA 02286245 1999-07-29
Depending on the type of ALM the procedure of its preparation contains:
For hydrocarbon based ALM: blending of low viscosity oil or any petroleum
product
(benzene, kerosene etc) with heavy low viscosity non-polar liquid i. e.
tetrachlormethane
(GOST 20288-74) or APK agent (YU 2122-199-OS-76-34-68-94) at such volume ratio
that the specific weight (density) of the blend (solution) exceeds the density
of flood
water by no less than 100 kg/m3. The density of water used in flooding varies
between
1,000-1,120 kg/m3. Correspondingly, the density of hydrocarbon ALM can vary
between
1,100 and 1,220 kg/m3. Based on the chemical nature of blended non-polar
fluids with
low numbers of surface tension at the Liquid-vapor contact hydrocarbon AFM wih
have
surface tension not over 20-35 mPa.seo-l (erg/cm2) and viscosity within 1-20
cPs at
20°C.
For water based ALM (produced water is used, i.e. salt water): to dissolve a
required
volume (between 5 and 10% of mass) of water soluble surfactarn (preferably non-
ionic)
such as AF-12 (TU 38.507-63-171-91), CHO-3B (1'U 39-579-46-88) and others
which
would provide a decrease of surface tension of water at the vapor conta,cx
from 72-73
mPa seo-l (erg/cm2) and if required additionally dissolve a certain volume of
chloride
salts, i.e. calcium chloride, sodium chloride etc. in produced water so that
the density of
water based ALM would exceed the density of flood water by no less than 100
kg/m3
Table 1
Ultrasound dispersion of various sediment forming materials and oil sludge
waste in
various liquid media.
a anal zed sedimentand slu onents erties
oil a and
their pro
comp
# Code ~tnd Com onenta, Pro riles
% of
mass
'
source of solids PARC Emul~ed Specific PreoentaNon
Sam le ( water mwss kg/m3
1 Material #1 35.2 41.7 23.1 1,330 Viscous
(sediment from sticky
'
in black mass
ector
2 Material #2 25.4 52.9 21.7 1,110 Same, dark
(sediment from brown
roducer
3 Material #3 47.4 12.3 40.3 1,420 Concentrat
(concentrated ed brown
waste of drilling pie
mud
4 Material #4 10.2 44.3 25.5 1,210 Viscous
(bottom sticky
sediment from black mass
a
holding tank,
merchantable
oii
stor a
CA 02286245 1999-07-29
b ro 'es of ion
li uid in was
which ultrasound undertaken
dis
# Code and Li
uid
fro-perties
major Density, Surface Viscosity
lig/m3 tension re
water
components mPa/sec- (conventional
unit)
1
a
cm2
1 Liquid #1 1,050 73.0 1
(water
brine)-
roto a
2 Liquid #2 1,160 25.0 1-5*)
(hydrocarbon
proposed
method
3 Liquid #3 1,160 30.0 1
(salt
water AFM
+
f
sur
actant
c)
description
of
systems
formed
after
dispersion
of
analyzed
sediment
forming
materials
by ltrasound
u in various
fluid. Content
of dispersed
sediment
in the system:
15% of
mass-const.
# Contents Pro erties stem
of of
formed
dispersed Presenta- Dimensions Particles~m V'iscoaity
(cm-4) to
g~nl lion (minimum) (maiimum)(average) water
1 Material Flaky 1,000 5,000 2,000 -**)
#1+Liquid separating
#1
rot s stem
2 Material Homogene 1 20 S.0 15-50*)
#1+Liquid ous low
#2
(proposed) viscosity
hydropho-
bic
sus nsion
3 Material Flaky 1,000 5,000 2,000 -**)
#2+Liquid separating
#1
roto s stem
4 Material Homogene 1 20 5.0 15-50*)
#2+Liquid ous low
#2
(proposed) viscosity
hydropho-
bic
sus ension
Material Homogene 10 50 20 15
'
#3+Liquid ous low
#1
(prototype) viscosity
sus nsion
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6 Material Homogene 1 20 5.0 15-50*)
#3+Liquid#1 ous low
(proposed) viscosity
hydropho-
bic
sus nsion
7 Material Flaky 1,000 5,000 2,~0 -**)
#4+Liquid separating
# 1
roto a s stem
8 Material Homogene 1 20 5.0 15-50*)
#4+Liquidd#2ous low
(proposed) viscosity
sus nsion
9 Material Homogene 0.5 5 10 15
#1+Liquid#3 ous low
(proposed) viscosity
sus sion
Material Low 0.5 5 10 15
#2+Liquid viscosity
#3
(proposed) homogene
ous
su nsion
11 Material Low 0.5 S 10 10
#3+Liquid viscosity
#3
(proposed) homogene
ous
sus nsion
Reference:
*)
Viscosity
of
hydrocarbon
ALM
mainly
depends
on
viscosity
of
the
hydrocarbon
liquid
selected
to
be
blended
with
the
non-polar
heavy
solvent
such
as
tetrachlormethane
or
APK,
viscosity
of
which
is
similar
to
water
viscosity
at
**)
Due
to
high
adhesion
property
(stickiness)
and
low
kinetic
stability
(tendency
to
separate)
the
rheological
properties
of
the
system
were
not
established.
Di
ersion
conditions
are
constant
for
ev
test.
Table 2
Nature of change in phase permeability (filtration velocity) of oii and water
through
heterogeneous highly permeable reservoir model (K=1 and over lunm2) depending
on the
type of dispersion system selected for reservoir treatmem.
# Dispersion Filtration Change
velocity, (decrease,
mm/min
system mufti le
Oil Vo Watcr Vo after Vw after
Vw
Vo Vo Vw Vw Vo prior Vw prior
rior after rior after
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8
1 System #1 15 0 53 0 0 ~ ~ 0
roto a
2 System #2 16 12 55 2 1.3 27.5
ro sed
3 System #3 15 0 50 0 0 0
roto
4 System #4 16 13 50 5 1.2 10.0
ro sed
S System #5 15 0 54 0 0 0
rot a
6 System #6 16 14 53 7 1.1 7.5
ro sed
7 System #7 15 0 58 0 0 0
roto a
8 System #8 16 13 55 4 1.2 13.7
ro sed
9 System #9 16 15 56 25 I.06 2.2
roto a
System #10 15 14 57 29 1.07 2.0
ro sed
11 System #1 16 14 55 27 1.1 2.0
i
ro sed
Preparation method and description of analyzed dispersions are contained in
Table 1.
Filtration conditions for all tests were constant, volume of injected
suspension was 1 pore
volume of the reservoir.
METHOD OF OILFIELD DEVOPMENT
Invention formula
1. Method of oilfield development includes creating a hydrophobic barner with
selective
phase permeability (low for water and high for oil) in high permeability
intervals and
fractures of the near well bore area includes lowering the tubing to the
bottom hole,
injection of liquid media through tubing into the near well bore area, lifting
the tubing
to the surface, lowering the ultrasound emitter with frequency range 10-15
kHz, 22-
44 kHz and 320-964 kHz into the liquid media and locating it at treated
reservoir
interval. The method is distinct due to the fact that to modify it, cut costs
and increase
environmemal benefits cleanup of the near well bore area from sediment and
other
plugging particles is done through their dispersion and dissolving under the
impact of
ultrasound in active liquid media until the products of cleanup turn into
thinly
dispersed hydrophobic suspension with the dimensions of solid particles of 0.5-
20
wln.
2. The method, as per paragraph 1 is distinct due to the fact that as active
liquid media a
fluid is use with low surface tension on liquid-vapor contact (20-35 mPa-sec-
I)
CA 02286245 1999-07-29
9
(erg/cm2), density exceeding the density of flood water by no less than 100
kg/m3
and viscosity equal to water phase viscosity or exceeding it by no more than
20 times.
3. The method as per paragraphs 1 and 2 is distinct due to the fact that as
active liquid
media blends (solutions) of low viscosity oil (or petroleum products) and
heavy non-
polar fluid such as tertachlormethane, APK agent (TU 2122-199-OS-76-34-68-94);
or
5-10% solutions of various surfactants (primarily non-ionic surfactants) in
salt water
with density exceeding density of flood water by no less than 100 kg/m3 are
used.
4. The method, as per paragraphs 1, 2 and 3 is distinct due to the fact that
setting
optimum parameters of ultrasound impact on the near well bore area is
performed on
the basis of prior laboratory testing of ultrasound dispersion conditions for
the
sediment collected in the near well bore area. The testing is performed in
various
active liquid media and provides thinly dispersed hydrophobic suspension with
the
dimensions of solid phase of 0.5-20 Eun.
5. The method, as per paragraphs 1, 2, 3 and 4 is distinct due to the fact
that as
hydrophobic agents for the surface of thinly dispersed solid particles and
rock surface
of the reservoir asphaltene-resin and paraffin components (PARC) of oil are
used that
compose the sediment and form molecular and colloid dissolved hydrophobic
dispersion systems in the active liquid media under the impact of ultrasound.
6. The method, as per paragraphs 1, 2, 3, 4 and 5 is distinct due to the fact
that after the
process of ultrasound treatment of the near well bore area is completed formed
thinly
dispersed hydrophobic suspension in its complete volume is used to level out
the
injectivity profile or create a water blocking hydrophobic barrier to limit
water inflow
in producing wells.
7. The method, as per paragraphs 1, 2, 3, 4, 5 and 6 is distinct due to the
fact that
treating the near well bore area of wells with little sediment or wells that
were
previously cleaned from sediment through other methods to form thinly
dispersed
hydrophobic suspension in the near well bore area before running the
ultrasound
wave generator into the well in place of active liquid media a dispersion of
petrol~m
sludge-waste is injected into the well (i.e. bottom sediment formed in storage
tanks)
that were blended with the active liquid media at the pump (or other blender)
prior to
that, volume ratio being between 1:10 and 1: 5 depending on the content of
solid
phase in the sludge.
Abstract
The invention is referred to the oil industry and namely t s of oilfield
development through waterflood and aims at g the costs and raising ecological
benefits of methods of near well cleanup from plugging particles through their
dispersion and dissol ' a impact of ultrasound in the active liquid media umil
the
deposits a thinly dispersed hydrophobic suspension with the dimensions of
solid
es within 0.5-20 pm with further injection of formed suspension into the
reservoir
