Note: Descriptions are shown in the official language in which they were submitted.
S;~79
The present invention relates to the development of
oil fields by a mining method and more particularly it relates
to the method of thermal mining oil production.
The invention will be most effective in the development
of oil fields with high-viscous crude and mobile bitumen.
The present invention can also be utilized for deve-
loping oil deposits with depleted reservoir energy.
At present such oil fields cannot, as a rule, be
effectively developed by a conventional method wherein the
oil is withdrawn from the wells drilled from the surface. Oil
recovery attained in such cases is low.
Known in the prior art is a thermal-mining method of
oil production wherein the oil-bearing bed is subjected to a
steam and heat stimulation (cf. V.N. Mishakov et al "Experience
gained in application of thermal methods for mining development
of high viscous oil fields, magazine "Neftyanoe Khozyaistvo"
No. 10t 1974, pp 31-35).
Said method consists in digging a combination of
underground workings above the oil-bearing bed, said combination
including mine-shafts, shaft workings, drifts and drill chambers.
The slant and vertical injection and producing wells
are drilled from the drill chambers located in the drifts.
Then the heat carrier (steam) is supplied through the injection
wells into the oil-bearing bed and said steam drives the oil
from the injection to the producing wells. Then the oil is
air-lifted from the producing well bottoms into the drill chambers.
A disadvantage of said method consists in breakthroughs
of steam into the underground workings and, as a consequence,
reduced efficiency of the thermal mining oil production method.
In another known method of mining oil production
(USA Patent No. 1634235) the wells are drilled from underground
workings located either above or beneath the oil-bearing bed.
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~1~5379
The well bottom-hole zone is treated with steam and the oil is
withdrawn therefrom through shallow wells bored downward or
upward from the underground workings.
The well bottom-hole zones are heated by steam
delivered into the well bottoms through pipes placed in the well
and the oil is withdrawn from the same wells.
A disadvantage of this method consists in a low
producing capacity of the oil-bearing bed.
Known in the prior art is a well method of oil
production (USA Patent No. 1520737) which includes drilling a
vertical shaft passing through an oil-bearing bed, and making
a drill chamber beneath said shaft.
Then radial slant holes are drilled upward into the
oil-bearing bed. In this method the heat carrier is pumped
into the oil-bearing bed through said holes and the oil is
withdrawn from the same holes after the oil-bearing bed has
been sufficiently heated.
This method also provides for delivering a heat
carrier (e.g. steam) through pipes passing through said holes in
order to clean the well bore zone of oxidized oil and tarry
matt~r and to withdraw the well product. The oil is withdrawn
by gravity.
A disadvantage of this method of oil well production
consists, as in the afore-mentioned method, in the absence
of efficient driving of oil from the oil-bearing bed. This, in
turn, results in low oil recovery.
Known in the prior art is a further method of oil
field development, the so-called thermo-cyclic method (USSR
Author's Certificate No. 335370, Cl.E21B 43/24) wherein the heat
carrier is injected into the oil-bearing bed in a cyclic
order, injecting in cold water in between the cycles.
Alternation of heat carrier and cold water delivery
11~5~79
conduces to a reduction of heat losses into the surrounding
rock and, as a consequence, to a reduction in the amount of
required heat carrier. In the stratified-heterogeneous beds
with various permeability of beds this alternation of heat
carrier and cold water delivery eliminates the thermal influence
of one bed on the others thus increasing oil recovery from
the oil-bearing bed as a whole.
A disadvantage of this method consists in that its
efficiency is substantially lower for the oil-bearing beds
10 with a high and zonal heterogeneity and discontinuity than
it is for the monolythic continuous beds. The wash-away
properties of the water and condensate injected into the high-
viscous oil-bearing beds are very low.
Also known in the prior art is a cyclic oil production
method (USA Patent No. 3442331, Cl. 166-263) in which the
withdrawal of oil from an oil-bearing bed with a partly
depleted producing energy is discontinued and the injection
wells are filled with water. As soon as the reservoir
pressure returns to the initial value, the injection of water
to it through the injection wells is stopped and the oil starts
to be withdrawn from the producing wells.
The oil is withdrawn until the bed pressure drops to
a certain level after which the producing wells are laid
off and water is again pumped into the oil-bearing bed through
the injection wells.
The water pumping and oil withdrawal cycles are
alternated until the oil resources in the bed are finally depleted.
A disadvantage of this method consists in its low
efficiency during the development of oil-bearing beds with
high-viscous oils since this method does not provide for
reducing the viscosity of oil in the bed. Besides, this method
provides for increasing the reservoir pressure to the initial
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ll~S379
level. When this method is realized for mining, restoration
: of the initial pressure is not always possible nor expedient,
particularly in the oil fields consisting of fissured and
cavernous-porous reservoirs.
A further prior art method of mining development of
oil fields (USSR Author's Certificate No. 468529, Cl.E21B 43/23)
consists in digging a combination of underground workings and
two working tunnels, drilling the injection wells from the upper
working tunnel and the producing wells from the lower one. The
heat carrier is delivered into the oil-bearing bed through the
injection wells for heating said bed to a temperature at which
the oil becomes sufficiently fluid. Then the heat carrier is
delivered into the injection wells for uniform distribution
of said carrier throughout the oil-bearing bed and for driving
the oil into the producing wells, the oil is withdrawn from the
producing wells to the working tunnel and thence through the
underground workings, to the surface.
A disadvantage of this method consists in the
necessity of constructing at least two working tunnels, i.e. is
a large scope of work on driving said tunnels. The method is
also characterized by heavy thermal losses caused by breaking
of the heat carrier through the underground workings and bed
fissures due to the absence of the adequate interrelation
between the operating conditions of the injection and producing -
wells. These disadvantages result in a reduced current oil
production and the final reservoir oil recovery.
The basic object of the invention resides in providing
a method of thermal mining of high-viscous oil which would
increase the reservoir oil recovery bed as compared with the
known similar methods of oil production.
Another no less important object of the present
invention resides in providing a thermal-mining method of thermal
...-
~5~
. . - ~ . , .
~1~5;~79
mell oil production which would increase the effectiveness of
heating the oil-bearing bed.
One more object of the present invention resides in
providing a thermal-mining method of oil production which
would reduce the water content in the oil recovered from
the oil-bearing beds with a high and zonal heterogeneity and
intermittence of structure.
These and other objects are accomplished by providing
a thermal-mining method of oil production consisting in:
- digging a combination of underground workings and at
least one working tunnel;
- drilling injection and producing wells from said
working tunnel;
- forced delivery of a heat carrier into the oil-bearing
bed for heating it to a temperature at which the oil acquires
the necessary fluidity;
- forced delivery of a heat carrier into the oil-bearing
bed through the injection wells for uniform distribution of said
carrier through the whole oil-bearing bed and for driving
the oil into the producing wells to the working tunnel at time
intervals calculated from the relation:
tl = c ~TL2 /~
wherein c = heat capacity of the oil-bearing bed, J/deg;
Q = temperature conductivity of the oil-bearing bed,
m /s;
r = specific weight of the oil-bearing bed, N/m3;
L = graphic scale, m;
T = dimensionless time (O < T C 1).
- withdrawiny oil from the oil-bearing bed through
producing wells at time intervals t3 in which the time interval
: 30 tl for delivering the heat carrier into the injection wells is
divisible by the time interval t3 for withdrawing oil from the
11~53'~g
producing wells, the multiplicity factor in being
t3 -
A ~M (Pl ~ P2)~
wherein t3 = 2K Q p
A = distance between injection and producing wells, m;
; ~p = pressure drop in the oil-bearing bed between
injection and producing wells, N/m2;
= oil viscosity, N.s/m ;
m = porosity of the oil-bearing bed;
; I0 K = permeability of the oil-bearing bed, D;
Pl- P2 = change per cycle of oil-bearing bed saturation
with heat carrier;
= dimensionless parameter (O < ~ < ~)
- delivering the oil from said working tunnel through
~ the underground workings to the surface.
; The novelty of the disclosed method according to the
invention consists in that the heat carrier is introduced into
the oil-bearing bed in a cyclic manner with the heat carrier
delivered into the injection wells at time intervals tl selected
by the above relation and the oil withdrawn from the producing
wells at time intervals, t3 determined by the above relation
so that the relation of time intervals tl and t3 is equal to or
more than 60 (n = t- > 60).
The oil recovery is increased by heating the oil-bearing
bed and the oil saturating it and, consequently, most of all
by reducing the oil viscosity and by changing the direction of
the filtration flows in the oil-bearing bed.
; The higher efficiency of heating the oil-bearing bed
is achieved by better cyclicity of heat carrier introduction
into the oil-bearing bed and withdrawal of oil therefrom through
the producing wells.
The heating efficiency is increased also by a reduction
`: :
~ -7-
ll~S~7~9
of heat losses through the producing wells.
A reduction in the water content of the recovered oil
is effected by the operational control of the producing and
injection wells with due account of the zonal heterogeneity
and discontinuity of the oil bed structure.
The recovery of high-viscous oil from the wells is
increased by injection steam, into them driving the well product
into the working tunnel and blowing the well bottom with steam
until the initial parameters of said steam are restored.
It is also expedient that the injection wells in the
zonally heterogeneous oil-bearing bed should be divided into
groups and the heat carrier should be injected into each group
in an alternating sequence. This will permit changing the
direction of filtration flow in the oil-bearing bed which
provides for increasing reservoir sweep and increases the
oil recovery.
It is desirable that the producing wells in the zonally
and lithologically heterogeneous oil-bearing beds should be
divided into groups and the oil should be withdrawn alternately
from each group. This makes it possible to create directional
oil streams in the bed and to wash away the oil from the stagnant
zones, thereby increasing the oil recovery of the bed.
It is practicable that the oil should be withdrawn
from the producing wells in the heterogeneous fissured, fissured-
porous and fissured cavernous-porous beds at such a rate that
the time interval of heat carrier delivery into the injection
wells would be divisible by the average time interval of oil
withdrawal from the simultaneously working producing wells. In
the course of development of an oil-bearing bed this will make
it possible to take in account its structure and to increase oil
recovery by changing the direction of filtration flow in the bed
and prevent possible breakthroughs of steam into the producing
, .
8--
11~5~f g
wells. All these factors taken together increase the efficiency
of the thermal-mining method of oil production.
It is desirable that the heat carrier should be
delivered into the oil-bearing bed through pipes located in the
wells, functioning as said injection wells and provided with two
packers, near the well bottom and essentially in the middle
of the wells, and the oil should be withdrawn through the
- perforated holes in the string of casing at the heat of the same
wells, said perforated holes performing the function of said
producing wells. This intensifies the heating of the oil-bearing
bed, increases the drive conformance of said hed, steps up
the oil recovery and the development rates.
It is desirable that in the oil-bearing beds with
poorly-cemented collectors the annular space between the well
walls and the pipes inserted into the wells should be filled
between the packers with quick-hardening heat-carrier-impermeable
compositions (e.g. cement mortar and the like). This will
permit removing part of the string of casing between the
packers, avoiding the breakthrough of steam into the working
tunnel, thereby irnproving the efficiency of the thermal mining
method of oil production.
It is expedient that in driving the oil from hetero-
geneous fissured-porous and fissured-cavernous-porous oil-bearing
beds the heat carrier should be steam and, after said steam
moving along the bed reaches the producing wells, the oil
should be withdrawn together with steam through the producing
wells up to the moment when the steam parameters (degree of
dryness, specific volume and temperature) become equalized
: in the producing and injection wells, i.e. when the initial
parameters of steam are restored in the oil-bearing bed.
In this case the steam drives the oil first of all
from the bigger cavities, pores and fissures of the oil-bearing
_g_
:
~1~5379
bed into which said oil enters from the more solid sections,
rock blocks due to condensation of steam in the porous medium
of the oil-bearing bed.
Restoration of the initial parameters of steam in the
oil-bearing bed after driving out the oil permits maintaining
the temperature of the bed at a preset level and ensuring a
higher productivity.
It is desirable that, concurrently with the supply
of heat carrier into the injection wells and withdrawal of
, ~
oil from the producing wells, one of the injection well groups
should be continuously supplied with the solution of a material
capable of reducing the surface tension on the oil-water and
oil-rock boundaries. This will improve the wash-away
properties of the driving medium and increase the oil recovery.
It is expedient that the oil should be withdrawn from
the producing wells by forcing steam into the producing well
bottoms for driving the oil therefrom to the working tunnel
and then the producing wells should be blown until the steam
restores its initial parameters and is then subjected to
condensing.
The blowing raises the dryness of the steam and
increases its specific volume. The blowing reduces strongly
the specific volume of the working medium during steam
condensation which ensures the influx of a considerable amount
of oil to the well bottom within each cycle. This eventually
steps up the well output and the total oil recovery of the oil-
bearing bed.
Now the invention will be described in detail by way
of example with reference to the accompanying drawings in which:
Fig. 1 is a plan view of a section of underground
workings with horizontal and rising injection and producing wells
arranged radially (the underground workings are shown in a single
--10--
;379
horizontal plane);
Fig. 2 is a section taken along line II-II in Fig. l;
Fig. 3 is a plan view of a section of underground
workings with rising injection and producing wells arranged
parallel to one another (the underground workings are shown in
a single horizontal plane);
Fig. 4 is a section taken along line IV-IV in Fig. 3;
Fig. 5 is a conventional operating time diagram of
injection and producing wells;
Fig. 5a characterizes the operation of injection wells;
Fig. 5b characterizes the operation of producing wells;
Fig. 6 illustrates a section of the oil-bearing bed
with a system of drilled parallel injection and producing wells;
Fig. 6c illustrates operation of the first group of
injection wells;
Fig. 6d illustrates operation of the second group of
injection wells;
Fig. 7 is a conventional operating time diagram of
injection and prod~cing wells with the injection wells divided
into two groups;
Fig. 8 is a conventional operating time diagram of the
injection and producing wells with the injection and producing
wells divided into groups;
Fig. 9 is a conventional operating time diagram of the
injection and producing wells when the average oil withdrawal
time from different groups of producing wells is different;
Fig. 10 is a conventional operating time diagram of
the injection and producing wells when the time period of
injection of heat carrier into the different groups of injection
wells and the average time period of oil withdrawal from the
different groups of producing wells are different;
Fig. 11 illustrates the operation of a group of wells
.
11~5379
: `.
when the heat carrier is injected in and the oil is withdrawn
through the same wells;
Fig. 12 illustrates the layout of injection and
producing wells;
~;~ Fig. 13 illustrates the operation of injection wells
23, 24, 26 and producing wells 25, 27, 29, 31;
Fig. 14 illustrates the operation of injection wells
23, 28, 30 and producing wells 25, 27, 29, 31;
Fig. 15 illustrates the operation of injection wells
23, 24, 28 and producing wells 25, 27, 29, 31;
Fig. 16 illustrates the operation of injection wells
23, 26, 30 and producing wells 25, 27, 29, 31.
The above-described method is carried in effect by
digging a combination of underground workings comprising two
drill holes, i.e. a lifting drill hole 1 (Figs. 1, 2) and a vent
bore hole 2, a stockyard 3 (Fig. 2), near-wellworkings to accomodate
an electric locomotive depot, a pumping plant, storehouses,
etc. (not shown in the drawings), drifts 4 (Figs. 1, 2), slant
workings 5 and 6. The drifts 4 are constructed above the roof
of the oil-bearing bed 7. They are inclined to the horizontal
-in the order of 1 - 3.
~ The oil field is worked by sections. All the sections
- are identical with each other. They may be shaped as right
polygons, e.g. hexagons as shown in Fig. 1 or rectangles as
shown in Fig. 3 or any other shape. ~-
Then slant holes 5 and 6 are dug from the drifts 4
(Figs. 1, 2) into the zone of the oil-bearing bed 7 (Fig. 2)
and at least one working tunnel 8 (Fig. 1, 2)is constructed.
The working tunnel 8 may be either circular (Fig. 1),
square rectangular, elliptical, rectilinear (Fig. 3),
curvilinear or of some other shape to suit the shape of the oil
field section.
-12-
3~9
Then from the working tunnel 8 (Pigs. 1, 2) are drilled
producing wells 9 and injection wells 10. In case of a circular
working tunnel 8 (Fig. 1) said wells are drilled uniformly
around the section are, along the radiuses of the circle.
In the rectilinear working tunnel 8 (Fig. 3) the
producing wells 9 and injection wells 10 are bored uniformly
over the section area, parallel with each other.
The heat carrier (e.g. steam) is delivered to the heads
of the injection wells from a boiler installation 11 (Fig. 2)
through a surface pipeline 12, then through a steam delivery
well 13 and the underground pipes accomodated in the drifts 4
(not shown in the drawings).
The oil-bearing bed 7 is heated through the system of
injection wells 10 to a temperature at which the oil acquires
the necessary fluidity.
For various oil fields this temperature may vary
within considerable limits from about 80 to 250 and depends
on the properties of the oil.
Thanks to a well-developed pattern of injection wells
10 extending through a large length over the oil-bearing bed 7,
the latter is uniformly and quickly heated throughout its volume. ;
:
This is achieved because the horizontal and rising injection
wells 10 extending through the oil-bearing bed 7 over tens and
. ,: .
hundreds of meters interconnect its heterogeneous zones,
various channels, cavities and increase the degree of
development of the oil-bearing bed.
The presence in the oil-bearing bed 7 of fissures
mostly vertical, of highly permeable zones and cavities is
conducive to rapid heating of said bed. With an increase in
~ 30 the temperature of the oil-bearing bed 7 the viscosity of oil
decreases and its fluidity increases.
In the cases when the delivery of the heat carrier
-13-
ll~S3'7~
through the injection wells lO alone results in a prolonged
heating period of the bed, this process can be intensified
by heating the oil-bearing bed 7 through both the injection
wells lO and the producing wells 9 by one of the conventional
methods utilized in the practice of thermal-mining oil production.
The distance between the producing wells 9 and
injection wells lO is selected depending on the concrete
geological conditions. They may be either identical or
different.
The oil withdrawn from the producing wells 9 and deliver-
ed into the working tunnel 8 is directed into the grooves
constructed in the drifts 4.
The oil together with the water delivered into the
grooves is transported by gravity due to the inclination of the
underground workings in the order of l - 3 to the
horizontal and flows to the inst~llations ~not shown in the
~ drawings) where it is separated from the bulk of the water.
; The oil with the associated water can also be trans-
~ ported from the working tunnel 8 through slanted workings 5 and 6,
20 drifts 4 and pipes to said water-separating installations by means
of pumps. From these installations thq oil is pumped into the
central underground oil collectors (not shown in the drawings) -
from where after primary preparation and heating it is delivered
,i,
through pipes, special wells 14 or the mine-shaft into the
surface reservoirs 15 of the oil storage depot.
The substance of the method does not change if the
drifts 4 (Fig. 4) are built below the oil-bearing bed 7.
More than that, this arrangement of the drifts 4 provides better
conditions for the delivery of oil from the working tunnels 8
into said drifts. In this case the oil is transported by gravity.
The working tunnel 8 may have the shape of two twinned
underground workings as shown in Fig. 3 or of one circular
-14-
.. . ... . . ,. . .. ~. ~,. ~
1 ~ . : . /
: -- ,
1~5;~79
working (Fig. 1), either rectilinear or curvilinear.
In all cases the length of the working tunnel 8 is
selected, apart from all other conditions, on the basis of
reliable venting. The ventilation system must guarantee
adequate standards of labour protection and safety of the
operating personnel.
After heating up oil-bearing bed (Fig. 2), it is
supplied through injection wells 10 with heat carrier at time
intervals calculated from the relation:
tl = CryTL~
wherein c = heat capacity of the oil-bearing bed J/deg;
= temperature conductivity of the oil-bearing bed,
m2/s;
; ~ = specific weight of the oil-bearing bed, N/m ;
L = graphic scale, m;
- ~ = dimensionless time (O < T < 1), depending on the
thickness of the oil bearing bed, 7, temperature at the bottoms -
`, of the injection wells 10 and the number and arrangement of the
injection wells 10. The value of T iS found from the equation
comprising all the above-mentioned parameters. When the injection
wells 10 are located in the roof and bottom portions of the bed,
- the equation for determining the dimensionless time is as
follows:
X = YlFl(h,~) + Y2F2(h, T)
., .
wherein Yl = ~1 ~o ; y = ~2 ~o
~1 and 2 = temperature on the bottoms of the injection wells
in the roof and bottom portions of the bed, deg.. C
OO = initial temperature of the oil-bearing bed, deg. C;
O = temperature seall, deg. C;
X = average temperature of the oil-bearing bed;
-15-
11~5;~'79
= Jacobi theta function;
a = L
h = thickness of the oil-bearing bed.
Oil is withdrawn from the producing wells 9 at such
time intervals t3 in which the time interval tl of delivering
the heat carrier into the injection wells 10 is divisible
by the time interval t3 of withdrawing the oil from the producing
wells 9, the multiplicity factor n being:
[tl ~ 60 where [ tl ~ stands for the operation
of taking the whole part of the relation of two values
i A J~S M ( Pl - P2 ) ~
t . _ _ .
:^ 3 2K Q p
where A = distance between injection and producing wells, m;
Qp = pressure drop in the oil-bearing bed between injection
and producing wells, N/m2;
= oil viscosity, N.s/m ;
K = permeability of the oil bearing bed; D;
m = porosity of the oil~bearing bed;
. ,, ~
Pl P2 = change per cycle of the oil-bearing bed saturation
, with heat carrier;
= dimensionless parameter depending on the character ::-
of phase permeabilities of oil and heat carrier is
determined from the relation:
2Q [F (~O) - a ~ Fl(~) Fl(~)d~ +
wherein ~ = ~
kl, k2 = per~eability of the oil-bearing bed with
respect to oil and heat carrier, D;
-16-
lll~S~7~
2 = viscosity of oil and heat carrier, N.s/m
Fl(~ O) ~ fl(~) + f2(~)
~ fl (~) F (~);
fl(~) and f2(~) = phase permeabilities with respect to oil and
heat carrier;
} = saturation of the oil-bearing bed with heat
carrier;
= saturation of the oil-bearing bed at the drive
zone.
Selection of the divisible ratio of the time intervals
of the heat carrier pumping cycle (e.g. steam) and the oil
withdrawal cycle is necessary because the geometrical symmetry
~; and orderliness of the oil field sections is supplemented
in this case by the time symmetry in the sense of the multiplicity
of the time intervals for pumping in the heat carrier and with-
drawing the oil. Under the conditions of the divisibility of
the time intervals for pumping in the heat carrier and withdrawing
~ the oil the influences exerted on the filtration processes
:',
- 20 acquire a periodical or nearly periodical nature. Such
. .
influences on the processes of filtration are favourable for
.
^ increasing the oil recovery.
The minimum multiplicity factor 60 between the time
interval t1 of delivering the heat carrier into the injection
; wells and the time interval t3 of withdrawing oil from the
producing wells is arrived at through thermohydrodynamic
calculations of the heat balance of the oil-bearing bed in which,
along with the heating of said bed, account has been taken of
the heat losses through the roof and bottom of the oil-bearing
bed and of the heat losses with the recovered oil within each
o;~1 withdrawal cycle from the bed through the producing wells.
; ~11 the injection wells 10 of the worked sections 16
.
~ 1~ 5379
(Figs. 1 and 3) separated ~rom one another by arbitr~ry
boundaries 17 are supplied within a certain time tl (Fig. 5)
with a heat carrier after which the injection wells 10 (~igs. 1,2)
are closed and kept closed within a time interval t2 (Fig~ 5).
In a particular case the time tl ~f delivery of the heat
carrier (Fig. 5) through the injection wells 10 (Figs. 1, 2)
may be equal to their idle time t2. The entire working cycle T
(Fig. 5) of the injection wells 10 (Figs. 1, 2) is equal to
the sum of time intervals tl and t2 (Fig. 5).
The oil is withdrawn through all producing wells 9
(Figs. 1, 2) both during the delivery of the heat carrier into
the injection wells 10 and when they are laid off.
The time interval t3 (Fig. 5) of oil withdrawal from
the producing wells 9 (Figs. 1, 2) is alternated with their
lay-off time t4 (Fig. 5). In a particular case the time interval
t3 may be equal to the time interval t4. The entire cycle of ~ -
oil withdrawal T' from the producing wells is equal to the sum
~^ of time intervals t3 and t4.
The above-described process is shown in the operational
time diagram of the injection and produciny wells (Fig. 5).
!:'.,
Fig. 5a illustrates the functioning of the injection
wells 10 (Figs. 1, 2). The cross-hatched zone shows the time
of heat carrier delivery through the injection wells 10.
Fig. 5 illustrates the functioning of the producing
wells 9 (Figs. 1, 2). The vertical-hatched zone shows the
time of oil withdrawal from the producing wells 9.
In the course of heat carrier delivery into the oil-
bearing bed 7 (Fig. 2) and oil withdrawal from the producing
wells the oil is hydrodynamicall~ driven out of the oil-
~earing bed 7. ~hen the heat c~rrier is injected into theil~bearin~ bed 7 and the withdrawal of oil from the producing
wells 9 ceases, this leads t~ a ~ise of pressure and temperature
-18-
t ~ ' , ", ; ' . ,, . !
llS~ 9
in the oil bearing bed.
Owing to this phenomenon the oil during the next with-
drawal cycle is driven from the injection wells 10 to the
producing wells 9.
While the injection and producing wells are laid off,
there occurs capillary inhibition of the rock blocks in the
fissured beds and of the low~permeability sections of the heter-
ogeneous beds, this being accomplished by a redistribution
of pressure.
,, ,~
When the oil is being withdrawn from the producing wells
~; 9, the filtration flow change their direction thus increasing
the oil recovery.
In another embodiment of the disclosed method all the
injection wells in the zonally heterogeneous oil-bearing beds
are divided into groups and altexnately filled with the heat
carrier depending on the technological conditions.
Shown schematically in Fig. 6 is a section of the
,
oil-bearing bed 7 (Fig. 4) drilled out from the working tunnel
8 tFig. 3) by a system of parallel injection wells 10 and produc-
ing wells 9. The injection wells 10 are divided into two groups,
every other well in each group~ Figs. 6c and 6d illustrate
the functioning of the first and second groups Nl and N2 f
injection wells, respectively, in the same section.
Fig. 7 shows an operating time diagram of the injection
and producing wells.
tl = time of delivery of heat carrier into the oil-
bearing bed through the first group Nl (Fig. 6j
of injection wells (cross-hatched zone).
t2 = time of delivery of heat carrier into the oil-
bearing bed thr~ugh the second group N2 f
iniection wells (zone cross~hatched in another
direction) .
--19--
ll(~S~79
The idle time of the first group Nl of injection wells
is t2 (Fig. 7) while that o~ the second group N2 (Yig. 6)
is tl, which means that during the delivery of heat carrier
through the first group Nl of injection wells the second group
N2 of injection wells is laid off and vice versa, i.e. when the
heat carrier is being injected into the second group, the first
group stays idle.
The entire operating cycle of one group of injection
wells T = tl + t2.
t3 = time of oil withdrawal from the producing
wells 9 (Fi~. 6) (vertical-hatched ~one)
t4 = idle time of producing wells 9.
The idle time of the producing wells 9 depends on the
physical properties of the oil-bearing bed and of the oil
saturating it. In some cases the time of oil withdrawal
from the producing wells 9 may be equal to their lay-off -
- - I
~ time.
., .
The entire operating cycle of the producing wells
T = t3 + t4 (Fig. 7b).
'
-19a-
- . , . , . , ,; . .
.. . ( ~ . . . . .: . . .- . . . . .
11¢5379
The cyclic pumping in of theheat carrier through
different groups of injection wells 10 into the oil-bearing bed
and the cyclic withdrawal of oil through all producing wells 9
results in a change of directions of the filtration flow in the
bed, in washing-away of oil from the stagnant zones and bed ~^~
sections with a low permeability which raises the productivity
of the oil-bearing bed 7 (Fig. 4).
In another embodiment of the disclosed method the produc-
ing wells 9 (Fig. 1 and 2) in the zonally and lithologically
heterogeneous beds are also divided into groups and theoil is
withdrawn from each group in an alternating order depending on
the technological conditions.
Shown in Fig. 8 is the time tl of injectingthe heat
carrier, into the first group of injection wells, the time t2
v;~ of injecting it into the second group of injection wells and the
., .
cymbols t3 and t4 stand for the time of withdrawing the oil from
the first and second groups of producing wells, respectively.
t3 = the time of oil withdrawal from the first group
of producing wells is shown by vertical hatching.
t4 = the time of oil withdrawal from the second group
of producing wells is shown by horizontal hatching.
The idle time of the first aroup of producing wells 9
(Fig. 1,2) is t4 while that for the second group is t3 which
means that while the oil is being withdrawn from the first
group of producing wells the second group of producing wells stays
idle and vice versa, while the oil is being withdrawn from the
second group, the first group stays idle.
The cyclic injecting of steam into the various groups of
injection wells 10 (Figs 1,2) with the cyclic withdrawalof oil
permits raising the drive conformance of the oil-bearing beds with
a high zonal and lithological heterogeneity thereby increasing the
oil recovery.
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11~5;~r~9
In still another realization of the disclosed method
the oil is withdrawn from the producing wells 9 tFigs 1,2) in the
heterogeneous fissured, fissured-porous and fissured-cavernous-
porous oil-bearing beds in such a manner that the time of in-
~:
~;`` jection of the heat carrier into the injection wells 10 is divisible
by the average time of oil withdrawal from the concurrently working
producing wells 9.
'~ In Fig. 9 is shown an operating time diagram of two groups
of injection wells and of two groups of producing wells, the time
,. 10 t3 and t4 being the average time of oil withdrawal from the
i~
~ different groups of producing wells.
,~ Withdrawal of oil from the individual wells of each group
is effected within different time intervals which depend basically
on the breakthroughs of steam or water thereinto.
.. . .
This permits creating filtration flow in the oil-bearing
bed so that the oil-bearing bed 7 (Fig. 2) would be driven out to
,' the fullest extent which would increase oil recovery and reduce the
water content in the recovered oil.
With different time periods of oil withdrawal from the
producing wells 9 it becomes possible to prevent steam breakthroughs
into the underground workings through the producing wells 9 and thus
to economize on the heat carrier.
Fig. lO shows schematically a general example when the
time intervals tl and t2 required for injecting the heat carrier
into different groups of injection wells are different and the
average time periods t3 and t4 of oil withdrawal from the dif-
ferent groups of producing wells are also different.
The number of wells in the different groups of injection
and producing wells may be either the same or different.
The durations of the cycles tl and t2 of injection the
heat carrier (e.g. steam) into the different groups of injection
wells depend on the geological and physical characteristics of the
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11~5;~79
oil-bearing bed and may range from 10 to 30 days and more. The
injection pressure may dwell at a level of 20 kgf/cm .
The durations of the cycles t3 and t4 of withdrawing oil
from the different groups of producing wells may vary from one to
several hours.
In one practical realization of the disclosed method the
; heat carrier is injected into the oil-bearing bed through pipes
19 inserted into the wells 18 (Fig. 11) and functioning as said
injection wells; said pipes are provided with two packers, one (20)
- 10 at the well bottom and the other one (21) essentially in the middle
-~ of the well 18 whereas the oil is withdrawn through the perforations
in the string of casing 22, said perforations acting as said pro- -~
' ducing wells, near the heat of the same wells so that the time of
heat carrier injection into said pipes would be divisible by the
-` time of oil withdrawal through said perforations in the string of
casing 22 at the head of the wells 18.
In the disclosed method the heat carrier is injected into
the oil-bearing bed and the oil is withdrawn therefrom through
the same wells either concurrently or separately, depending on the
adopted technological procedure.
To prevent the heat carrier supplied into the oil-bearing
; bed from possible breaking through into the working tunnel 8, the
wells 18 are provided with two packers one (20) installed near the
bottom of the wells 18 and the other one (21), essentially in the
middle of the well 18. The wells 18 are drilled from the working
tunnel 8 (Figs 1,2).
This version can be realized as described in any one of
the version described above.
In this case the operational time diagrams of the in-
jection and producing wells given in Figs 5,7-9 hold true. The
term "injection wells" in this case should be understood as the
portions of the wells 18 (Fig. 11) extending from their bottom
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~1~5~9
; to the first packer 20 and the term "producing wells", as the
`~ portions of the wells 18 from their head to the second packer 21.
For an example, let us consider an instance when the
injection of heat carrier and withdrawal of oil are effected with
the aid of parallel horizontal wells divided into groups, of say,
every other well.
, i ,
Fig. lla shows the functioning of the first group of
injection wells and of the second group of producing wells;
.,. :
Fig. llb shows the functioning of the first group of
' 10 injection wells and of the first group of producing wells;
Fig. llc shows the functioning of the second group of
injection wells and of the second group of producing wells;
,
Fig. lld shows the functioning of the second group of
injection wells and of the first group of producing wells;
Fig. 11 shows by arrows the flows of the driving medium
and driven-out oil.
As can be seen from the above figures, the realization
of these versions of the method produce filtration flows with
varying directions of oil f]ow. The injection of heat carrier into
the pipes 19 allows the temperature of the well bottom zonè to be
maintained at a preset level thereby maintaining a high fluidity
of oil.
All these factors taken together intensify the process
of heating the oil-bearing bed, increase the drive conformance of
the bed increase the oil recovery and the development rates of the
oil-bearing bed.
In another version of realization of the disclosed
method when the oil-bearing bed is characterized by poorly cemented
rocks, the annular distance between the walls of the wells 18 and
the pipes 19 disposed therein between the packers 20 and 21 is
filled with quick-hardening compositions impermeable to the heat
carrier (e.g. cement mortar).
,
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11~5~79
~: ;
;' In this case there is no need in casing off the well
18 by the string of casing throughout its length and to install
two packers. It is enough to install one packer only, essentially
`~` in the middle of the well and to lower the string of casing 22 only
to the point of packer installation. Efficient sealing of the
; annular space eliminates the break-throughs of steam into the
working tunnel:8. This, in turn, increases the thermal-mining
~- method of oil production.
.. .
In another version of realization of the disclosed
method in the heterogeneous fissured-porous and fissured-
cavernous-porous oil-bearing beds 7 the oil is withdrawn after
the heat carrier comes from the injection wells 10 to the pro-
ducing wells 9 and the oil begins to be withdrawn together with
~ the heat carrier through the producing wells up to the moment
-~ when the steam parameters (dryness, specific volume and temperature)
become equaIizedin the producing wells 9 and in the injection
wells 10.
The heat carrier (e.g. steam) injected into the oil-
; bearing bed 7 (Fig. 2) through the injection wells 10 creates
certain flows in the oil-bearing bed 7. The characteristics
of the pumped in steam (dryness, termperature and specific volume)
are selected on the basis of the physical properties of oil and
oil~bearing bed. The characteristics of the steam breaking
through into the producing wells 9 differ from those of the steam
injected into the injection wells 10. This is caused by the
losses of heat through the roof and bottom of the oil-bearing
bed 7 and with the produced liquid. When the producing wells 9
are closed at the moment of the breakthrough of the first portions
of steam at the sections of the oil-bearing bed adjoining the
producing wells 9, the characteristics of said steam are lower
than those of the injected steam because the process of oil
driving in the oil-bearing bed 7 is accompanied by an intensive
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.
:,
11~5~
heat exchange.
-,~. When the oil is withdrawn after the steam has broken
i, .,
'- through intothe producing wells 9, the steam parameters (dryness,
~; specific volume and temperature) increase to the values closely
. ~ .
~ approaching those existing at the heads of the injection wells 10.
: ,~
At the next stage, during condensation of steam in the
` oil-bearing bed 7,there occurs heat and mass exchange whose
~- intensity rises with the increasing closeness of the steam para-
meters to the initial values. The oil-bearing bed 7 is heated
more strongly, the oil flows from the less permeable sections into
` the larger pores and fissures due to capillary inhibition. When
the steam is condensed in large pores and fissures, the additional
local pressure differentials ensure favourable conditions for
the influx of oil from the smaller pores of the oil-bearing bed
7 and from its low-permeability sections.
During the next cycle of oil withdrawal from the produc-
ing wells 9 this oil flows into the working tunnel 8.
Equalization of said steam parameters in the producing
and injection wells increases the efficiency of heating and the
productivity of the oil-bearing bed 7.
In another embodiment of the disclosed method the
; injection wells are divided into groups and one of said groups is
continuously supplied with a solution of the substance which
reduces the surface tension at the oil-water and oil-rock bound-
aries, the uniformity of flow of this substance through the oil-
bearing bed being controlled by the operation of the producing
wells. One of such substances is alkali NaOH.
The filling of the oil-bearing bed with a water solution
of alkali results in the formation of an emulsion of the "oil-in-
water" type and in the transition from the hydrophobic to hydro-
philic wettability of the rock. The emulsification of oil in a
hydrophilic oil-bearing bed caused by the injection of alkalinous
- - 25 -
~1~?5379
~ solutions increases the fluidity of oil and decreases the fluidity
;~ of water.
~ The change of the nature of wettability of the rock
-~ and a great reduction of the surface tension in the "oil-water"
` system can be attained only through a definite relation of
concentrations of alkali and salt in the solution.
-~ The interaction of alkali with organic acids of the
- oil produces surface-active substances.
~; It is preferable that the aqueous solutions of alkali
should be formed by the use of a water containing no multivalent
ions (e.g. calcium). The presence of sodium chloride in water
is conducive to a reduction of surface tension.
The concentration of the aqueous alkali solution for
;~ emulsification of oil should be 0.001 - 0.1 wt.-% while for
changing the nature of wettability of the bed rock it should be
from 0.5 to 3.0 wt.-%~ The amount of alkali solution injected
into the bed is, as a rule, 0.1-0.3 of the pore volume.
The reduction of the surface tension on the "oil-water"
boundary from 25-30 dyne/cm to 0.01-O.OOldyne/cm permits the
formation of finely-divided emulsions of ~he "oil-in-water" type
which are capable of moving through solid low-permeable rocks of
the oil-bearing bed. This phenomenon conduces to the injec-
tivity of the injection wells.
Inasmuch as the aqueous alkali solution is injected
into the already heated bed, the improvement of the wash-away
properties of the drive medium increases the oil recovery and
raises the efficiency of the driving process.
The increased efficiency of the process of thermal-
well oil production and of the oil-bearing bed productivity are
also achieved because the molecules of the formed surface-active
materialsgetting onthe "rock-oil"boundaries conduceto thebreakaway
ofthe oildroplets fromthe surfaceof therock whi~legetting onthe Uoil-
waterUboundaries they form theabove-mentioned finely-dividedsystem.
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.. . .. .
.: ,: . ;. :: .
.: . .
I r ~
11a~5379
;
-- The improved wettability of the rock due to its hydrophi-
` ~ lization under the influence of the aqueous alkali solution as
~ .~
well as emulsification of oil in the drive zone contribute to
a stronger driving of oil from the bed as compared with water
and steam, and to a better drive conformance which improves the
most important factor of oil field development, i.e. productivity
~- of oil-bearing bed.
The method includes the following operations:
1. The oil-bearing bed is heated by one of the conven-
~ 10 tional methods to a temperature at which the oil acquires the
-~ required fluidity.
2. The injection wells are divided into groups. At
least one group of the injection wells is filled with a heat
` carrier (e.g. steam). The other group is filled with an alkali
solution.
The number of injection wells for injection heat carrier
into the oil-bearing bed should be sufficient for maintaining the
above-stated temperature in the bed.
The number of injection wells for the injection of
aqueous alkali solution into the oil-bearing bed should be
sufficient for acting on the bed both horizontally and vertically
;,
i.e. the well pattern must be uniform throughout the volume of
said bed.
In the zone of the well used for acting on the bed with
an alkali solution there must be several wells for injecting in
steam.
3. The oil-bearing bed is constantly filled with an
aqueous alkali solution through the wells selected for this
operation, the amount of the alkali solution being 0.1 - 0.3 of
the pore volume of the bed.
4. Other groups of the injection wells are filled with
steam in accordance with one of the above-described versions.
79
5. The oil is withdrawn from the producing wells as
described in one of the versionsabove so that the time of heat
` carrier injection into the injection wells would be divisible
by the time or oil withdrawal from the producing wells.
Control of the injection of heat carrier into the oil-
bearing bed through the injection wells and of the oil withdrawal
through the producing wells permits changing the direction of the
filtration flows of the aqueous alkali solution so as to ensure
a maximum drive conformance of the bed.
Let us consider the functioning of the wells in the bed
section when the injection and producing wells are drilled from
the working tunnel 8 (Fig. 3).
Shown by black dots in Fig. 12 are the producing wells;
a dot in a circle shows the wells for injection in steam and a
dot with a cross inside indicates the wells for injection in an
alkali solution.
The injection wells are divided into groups, the first
groups being filled with an alkali solution and the second one,
with steam.
The injection well 23 (Fig. 12) filled with the alkali
; solution functions continuously.
The injection wells 24, 26, 28, 30 filled with steam
function intermittently and their working order may be as follows.
First version. 1st half-cycle: wells 24 and 26 (Fig. 13)
are operating and wells 28 and 30 are idle.
Meanwhile the zone of the alkali solution will be moving
towards the wells 28, 29 and 30.
2nd half-cycle: wells 24 and 26 (Fig. 14) stay idle,
wells 28 and 30 are in operation.
The zone of the alkali solution starts moving towards
the wells 24, 25 and 26.
Cross-hatched in different directions in Figs 13,14 are
~ .
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;379
the drive conformance zones with respect to the alkali solution
; during different half-cycles while dats show the zones with heat
carrier.
Second version
1st half-cycle - wells 24 and 28 (Fig. 15) are in
operation, wells 26 and 30 stay idle.
The zone of oil driving by the alkali solution moves
towards the wells 25, 26,27 and 29, 30, 31.
2nd half-cycle - wells 26 and 30 (Fig. 16) are in
operation, wells 24 and 28 are laid off.
The driving zone moves towards the wells 31, 24, 25
and 27, 28, 29.
Like in Figs 13,14 the cross-hatching in different
directions in Figs 15 and 16 shows the driving conformance zones
under the effect of injected alkali solution in different half-
cycles; dotted zones stand for theparts of the bed swept by the
heat carrier.
The selection of the method of injection steam depends
on the system of oil field facilities and on the geological
structure of the oil-bearing beds.
The producing wells 25, 27, 29 and 31 (Figs 13-16) also
operate cyclically in the above-stated order. This plays the
role of an auxiliary element in the control of the process.
In another realization of the disclosed method the oil
id withdrawn from the slant and vertical producing wells by
injecting steam onto the bottoms of the producing wells through an
annular space between the string of casing and the pipes designed
to drive the oil through the pipes to the working tunnel after
which the producing wells are blown through until the steam
restores its initial parameters and is then condensed by cutting
off its delivery.
The method is carried in effect by carrying out the
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,i
11~5;~'79
` following operations:
(1) The steam is injected in onto the bottoms of the
producing wells through the annular space between the well walls
or the string of casing and the string of pipes for driving the
oil therefrom to the working tunnel.
(2) The production wells are blown with steam until
the latter restores its initial parameters, i.e. the parameters
exactly or nearly the same at which it was injected. The blowing
increases the degree of dryness and the specific volume of steam.
(3) The production wells are closed thereby providing
conditions for condensation of steam therein.
Theprocess of blowing results in a radical reduction of
the specific volume of steam during its condensation which ensures
the influx of oil from the oil-bearing bed into the well.
During the next steam injecting cycle the oil is injected from the
well into the working tunnel.
Due to the additional pressure drops this increases
the productivity of the oil-bearing ~ed not only in the slanting
and vertical producing wells but also in the horizontal and rising
producing wells.
When being regularly filled with steam, the wells are
freed from theproduct entering thereto from the oil-bearing bed
(oil, water and sand), the blown steam cleans the walls of the
wells which facilitates the entrance of new portions of oil from
the oil-bearing bed during the next condensation of steam.
The present invention can be utilized with no lesser
success for producing fluid (free-flowing) bitumens.
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.. ~
.
