Method of thermal-mine recovery of oil and fluent bitumens

The method of thermal-mine recovery of oil and fluent bitumens or kerogens includes providing a system of mine workings above an oil-bearing formation and drilling from these workings and from the ground surface a series of injection wells into the oil-bearing formation. An operation gallery is provided within the oil-bearing formation, from which a system of horizontal and inclined recovery wells is drilled. Then a heat carrier is positively injected into the oil-bearing formation to heat it to a temperature whereat the oil attains the required fluidity within the formation. Then a fluid is charged into the formation to force the oil from the oil-bearing formation into the horizontal and inclined recovery wells, toward the operation gallery, from which the oil is directed to the ground surface. The improvement of the method resides in that the heat carrier is injected into the formation through the horizontal and inclined recovery wells extending substantially across the predominant direction of the highly permeable zones of the oil-bearing formation, and, following the heating of the formation to the abovesaid temperature, the injection of the heat carrier is terminated, and the fluid is charged into the injection wells having minimized association with the highly permeable zones of the oil-bearing formation, to force the oil from the oil-bearing formation through the recovery wells toward the recovery gallery.

The invention relates to recovering oil from highly viscous oil-bearing 
formations, and, more particularly, it relates to a method of thermal-mine 
recovery of oil and fluent bitumens or kerogens. 
The invention can be utilized to utmost effectiveness for recovering oil 
from fissured and incoherent oil-bearing strata. 
The invention can be also utilized for recovering oil from exhausted 
oil-bearing strata. 
At present, oil-bearing formations of the abovementioned kinds cannot be 
developed by the conventional technique of drilling boreholes and wells 
from the ground surface, on account of the oil yield being in such cases 
too small for practical purposes. 
There is known a method of mining recovery of highly viscous oil from 
oil-bearing formations or beds, according to which oil is removed to the 
ground surface together with the oil-bearing shale or rock. The method 
includes recovery of oil by providing subterranian mine workings within 
the oil-bearing formation, and subsequent imploding of these workings 
(see, for example, the U.S. Pat. No. 3,437,378; Cl. 299-2, filed Feb. 02, 
1967, dated Apr. 08, 1969). 
This known method, however, is labour-consuming and costly. 
Besides, it involves definite hazards connected with the subsequent 
imploding of the mine workings. 
In addition to that, the method affects the working environment and safety 
of the personnel, because when oil is removed together with the rock or 
shale containing it, as the mine workings are being excavated, gases and 
oil issue from the oil-bearing formation into these workings; furthermore, 
when oil is recovered from an incoherent oil-bearing bed, spontaneous 
caving-in of the workings might occur. 
There is further known a mining method of recovering oil from oil-bearing 
beds, according to which mine workings are provided in impermeable rock 
underlying the oil-bearing formation, and series of wells are drilled 
therefrom. Then high-velocity whirling jets of liquid are directed through 
these wells into the oil-bearing bed, to form a slurry which is withdrawn 
from the bed (see the U.S. Pat. No. 3,934,935; Cl. 299-2, dated Jan. 27, 
1976). 
However, this method, too, is excessively labour-consuming and costly. 
Furthermore, it is significantly complicated in its implementation, on 
account of the great quantities of sand washed away with the oil from the 
oil-bearing bed. 
There is known still another method of mining recovery of oil from an 
oil-bearing bed, without removing the rock or shale containing oil to the 
ground surface (see article by V.P. Tabakov "On Influence of Well Network 
Density upon Oil Yield, as Illustrated by Yarega Field Experience"/in 
Russian/, in Scientific-Engineering Manual on Oil Production, No. 41, 
VNIINeft, "NEDRA" Publishers, Moscow, 1971, p. 155). 
The method includes providing a system of mine workings above the 
oil-bearing bed. The mining field is divided into a plurality of levels. 
Longitudinal field drifts are provided intermediate the levels, and 
drilling chambers are made therein. From these drilling chambers inclined 
and vertical wells are drilled into the oil-bearing bed, down to the 
bottom of the bed. The wells are uniformly spaced throughout the 
oil-bearing bed. 
The spacing of the well faces, the number of the wells and the pattern of 
the mine workings may vary as this method is implemented, depending on the 
properties of the oil-bearing bed, its thickness and physical-chemical 
properties of the oil. 
The structure of the wells requires their provision with casing columns, 
the voids between the casing pipes and the well wall at the well mouth 
being sealed with a cementing composition. The well faces remain open. A 
lift pipe string is lowered into the casing column, and ditches are made 
at the well mouths along the mine workings with an appropriate sloping 
angle for exposed free gravity flow of oil from the wells toward 
collection tanks. 
At the initial stage of the operation of the wells oil, as a rule, gushes 
therefrom, and when the gushing dies away, air is pumped into the space 
between the casing and the lift pipes. 
To provide for better gravity flow of oil, water is supplied into the 
ditches of the mine workings. Oil collected in the tanks is separated from 
water, heated up and pumped to the ground surface. 
However, experience shows that when the last-described method is 
implemented in oil-bearing beds with highly viscous oil, the yield is too 
low. 
Furthermore, the implementation of this method involves a great volume of 
mining work and drilling a great amount of wells uniformly spaced 
throughout the oil-bearing formation. 
The above-mentioned method requires higher costs for lifting oil after its 
gushing is stopped. 
Besides, the great number of operating wells uniformly spaced throughout 
the oil-bearing formation complicates the monitoring of the performance of 
individual wells, their maintenance and repairs. 
The abovediscussed difficulties have brought about the need for developing 
oil recovery methods based on exerting physical-chemical action on the 
oil-bearing bed itself, and on the fluid saturating this bed. 
There is further known a thermal-mine method of oil recovery by exerting 
steam and heat action upon an oil-bearing bed (see article by L.M. Rusin 
"Experience in Pumping Steam into Fissured-Porous Bed of Yarega Field"/in 
Russian/, in the already mentioned Scientific-Engineering Manual on Oil 
Production, No. 41, VNIINeft, "NEDRA" Publishers, Moscow, 1971, p. 109). 
The method includes providing a system of mine workings above an 
oil-bearing bed. 
Vertical and inclined wells are drilled from these mine workings. Pipelines 
are constructed in these above-bed mine workings for the heat-carrier 
supply, and some of the wells are connected thereto. These wells are 
operated as injection ones, through which the heat carrier, e.g. steam is 
injected or charged into the oil-bearing bed to heat the bed and to force 
oil into the rest of the wells, operated as recovery ones. The injection 
and recovery wells are alternated and spaced uniformly throughout the 
oil-bearing formation. The mouths of the recovery wells are open, for free 
gravity flow of oil down the inclined ditches of the mine workings toward 
collecting tanks. The mouths of both injection and recovery wells are 
provided with gate means. 
At the initial period of the operation, with the oil-bearing bed being 
heated up with the heat-carrier, oil gushes from the wells, and when the 
gushing dies away, air is pumped into the space between the casing and the 
lift pipes to recover oil through the wells. 
However, this known method requires the drilling of a great amount of 
wells, since a single well is insufficient either to heat up the 
oil-bearing bed or to recover oil therefrom, particularly, if the bed is 
relatively thin. 
Furthermore, the method involves additional costs connected with supplying 
compressed air to lift oil through the wells. 
Moreover, with the same mine workings housing both heat-carrier injection 
wells and oil recovery wells, the temperature and gas-content conditions 
of the whole atmosphere in the mine are affected; the working environment 
and safety of the personnel are impaired. 
Besides, there is an eventuality of the heat-carrier finding its way and 
bursting into the open recovery wells. Such breakthrough of the 
heat-carrier into ventilated mine workings significantly steps up the 
consumption of the heat carrier per one weight unit of recovered oil. 
Breaks in the operation of the recovery and injection wells result in sand 
plugs forming therein, and lead to a considerable amount of downtime of 
the wells for maintenance and repair work, which affects the per day rate 
of the oil yield of the oil-bearing formation. 
There is also known a thermal-mine method of oil recovery, wherein a system 
of mine workings is provided above the oil-bearing bed, inclined at an 
angle from 1.degree. to 3.degree. to a horizontal plane (see, for example, 
the SU Inventor's Certificate No. 446,631). 
From these mine workings injection wells are drilled for charging the 
heat-carrier and its uniform propagation through the oil-bearing bed. A 
slope and a man way are provided into the lower part of the oil-bearing 
bed, and a recovery gallery is provided in this part of the bed. 
From the recovery gallery a system of horizontal and inclined oil recovery 
wells is drilled. The heat-carrier is charged into the said injection 
wells for its uniform propagation throughout the oil-bearing bed and for 
forcing oil into the said horizontal and inclined recovery wells, toward 
the said recovery gallery from which oil is withdrawn to the ground 
surface. 
However, the implementation of this method involves the drilling of a great 
number of injection wells, to provide for uniform distribution of the 
heat-carrier through the oil-bearing bed, since a single heat-carrier 
injection well is by far insufficient for taking care of the whole 
oil-bearing bed, particularly when the latter is relatively thin. 
Furthermore, with a smaller number of injection wells the rate of heating 
of the oil-bearing bed is low, whereby the yield is likewise low, which 
considerably increases the time of developing the oil-bearing formation. 
Moreover, non-homogeneity of the oil-bearing bed and the fact that in most 
cases the bed has fissures therein would not enable to conduct in the most 
efficient manner the forcing of oil by the heat-carrier into the 
horizontal and inclined recovery wells, toward the recovery gallery, on 
account of the dominating infiltration and propagation of the forcing-out 
fluid through these fissures and the highly permeable zones of the 
oil-bearing bed, which also affects the oil yield and prolongs the 
development of the oil-bearing formation. 
Besides, the per day yield of the oil-bearing bed is affected by the fact 
that the heat-carrier is charged through the injection wells, while the 
near-face areas of the recovery wells are less heated, and it is here 
where the oil flow meets the strongest resistance to its progress. 
In addition to that, the charging of the heat carrier into the injection 
wells drilled from the mine workings overlying the oil-bearing bed results 
in eventual breakthrough of the heat-carrier into the inclined and 
horizontal recovery wells and into the recovery gallery, which sharply 
decreases the rate of heating the oil-bearing bed, increases the 
consumption of the heat-carrier, affects the working environment and 
safety of the personnel. 
Apart from that, the supply of the heat-carrier into the great number of 
the required injection wells drilled from the mine workings overlying the 
oil-bearing bed, for uniform propagation of the heat-carrier throughout 
the bed, steps up the cost of ventilation of the mining workings, on 
account of a high degree of dissipation of heat into these workings. 
It is the main object of the present invention to provide a method of 
thermal-mine recovery of oil, which should enable to increase the per day 
and total yield of an oil-bearing bed and to cut down the time of its 
development. 
It is a not less important object of the present invention to provide a 
method of thermal-mine recovery of oil, which should enable to reduce the 
cost of recovering oil from an oil-bearing bed, to reduce the number of 
the wells required for charging the heat-carrier and withdrawing oil, and 
to minimize the complications associated with preparing the oil bed for 
development and with recovering the oil, on account of great quantities of 
sand evolving from this oil-bearing bed. 
It is still another object of the present invention to provide a method of 
thermal-mine recovery of oil, which should enable to cut down the cost of 
ventilation of the mine workings required for maintaining the necessary 
gas-content and temperature characteristics of the atmosphere in the mine, 
to enhance the working environment and safety of the personnel. 
These and other objects are attained by the creation of the method of 
thermal-mine recovery of oil, including: providing a system of mine 
working above an oil-bearing formation or bed; drilling from these mine 
workings and/or from the ground surface a plurality of injection wells for 
charging a fluid into the oil-bearing bed; providing a slope and a man way 
in the area of the oil-bearing bed; providing a recovery gallery in this 
area of the oil-bearing bed; drilling from the recovery gallery a system 
of horizontal and inclined recovery wells for recovering oil; charging a 
heat-carrier into the oil-bearing bed for heating same to a temperature 
whereat oil attains sufficient fluidity within the oil-bearing bed; 
charging a pressurized fluid into the oil-bearing bed to force oil from 
the oil-bearing bed into the horizontal and inclined recovery wells toward 
the recovery gallery; and withdrawing oil from the recovery gallery to the 
ground surface, in which method, in accordance with the invention, the 
heat-carrier is charged into the oil-bearing bed through the horizontal 
and inclined recovery wells extending substantially across the dominating 
direction of the highly permeable zones of the oil-bearing bed, and, 
following the heating of the oil-bearing bed to the required temperature, 
the heat-carrier supply to the recovery wells is terminated, and the 
pressurized fluid is charged into the injection wells minimally associated 
with the highly permeable zones of the oil-bearing bed, to force oil from 
the oil-bearing bed into the horizontal and inclined recovery wells toward 
the recovery gallery. 
The method enables to increase the yield of the oil-bearing bed and to cut 
down the period of its development, owing to the enhanced penetration of 
the heat-carrier into the oil-bearing bed and to the stepped-up rate of 
the heating of the oil-bearing bed through the latter's greater volume, as 
well as to reduce the resistance to the oil flow encountered at the 
near-face areas of the recovery wells and in the highly permeable zones of 
the oil-bearing bed, connected therewith, at the infiltration of oil 
therein; the method further expanding the borders of the process of 
forcing oil from the oil-bearing bed. 
The method enables to cut down the costs of recovering oil from an 
oil-bearing bed, owing to the improved pattern of the layout of the 
recovery wells throughout the bed, extending as they do across the 
direction of the highly-permeable zones of the bed, and also owing to the 
better yield of these wells and the possibility of reducing their number, 
as well as the number of the mine workings which have to be provided to 
drill the recovery wells therefrom. 
The operating costs of the well system are reduced by the lesser number of 
the recovery wells required, by the reduced ingress of sand from the 
oil-bearing bed into the recovery wells and by the minimized eventuality 
of sand plugs forming therein and involving additional efforts of 
eliminating these plugs. 
The method further enables to cut down the cost of ventilating the mine 
workings, in order to maintain therein acceptable atmospheric conditions, 
and to enhance the working environment and safety of the personnel, owing 
to the reduced number of ventilated mine workings. 
It is expedient that the recovery gallery should be provided in the lower 
part of the oil-bearing bed. 
This would enable to utilize in the fullest degree both the phenomenon of 
forcing-out the oil with the pressurized fluid, and the phenomenon of 
gravity flow of oil into the recovery wells. 
Alternatively, when oil is recovered from an incoherent oil-bearing 
formation, particularly, one decreasing its stability upon being heated, 
it may be preferable that the recovery gallery should be provided below 
the oil-bearing bed, so that it should be separated from the bed by a 
low-permeability stable interbed of rock. 
This would enable, when recovering oil from an incoherent oil-bearing bed, 
to reduce the cost of providing mine workings, by making them in rock more 
suitable for the purpose, and also to reduce the undesirable propagation 
of heat from the oil-bearing bed into the mine workings. 
It is also expedient that the heat-carrier should be charged into the 
oil-bearing bed through the horizontal and inclined recovery wells to heat 
the oil-bearing bed until the latter is heated up to a temperature above 
which the viscosity of the oil at further heating is reduced but 
insignificantly. 
This would enable to reduce the consumption of the heat-carrier by the oil 
recovery process and to enhance the quality of the atmosphere in the mine. 
It is further expedient, if the injection wells penetrate the highly 
permeable zones of the oil-bearing bed, prior to charging the fluid into 
the injection wells, to fill the highly-permeable zones of the oil-bearing 
bed communicating with these wells with a plugging composition retaining 
oil-permeability of the porous body of the oil-bearing bed. 
This enables to enhance the homogeneity of the oil-bearing bed, to conduct 
the forcing-out of oil by the fluid in an efficient way and to increase 
the yield of the oil-bearing bed. 
It may be also expedient, if one and the same recovery gallery has some of 
the recovery wells penetrating the highly permeable zones of the 
oil-bearing bed and other recovery wells not communicating with these 
highly permeable zones, to perform, simultaneously with the charging of 
the heat-carrier into the oil-bearing bed through the horizontal and 
inclined recovery wells extending substantially across the dominating 
direction of the highly permeable zones of the oil-bearing bed, recovering 
of oil through those of the horizontal and inclined recovery wells which 
have the minimum communication with the highly permeable zones of the 
oil-bearing bed. 
This enables to recover oil simultaneously with the heating of the 
oil-bearing bed and to accelerate the heating of the oil-heating bed 
itself with partial heating and creating improved conditions for the 
propagation of the heat-carrier into the porosity space of the oil-bearing 
bed. 
It is further expedient that at a later stage of the oil recovery from the 
oil-bearing bed the recovery gallery should be periodically filled with a 
fluid of a density in excess of that of the oil. 
This enables to increase the total yield of the oilbearing bed, by creating 
a non-stationary duty of the performance of the bed, the variation of the 
direction of infiltration flows in the bed and its better capillary 
impregnation. 
Furthermore, it enables to reduce the degree of breakthrough of the 
heat-carrier into the recovery gallery, and thus to improve the working 
environment and to reduce the ventilation costs. 
It is expedient, in the case of an incoherent oil-bearing bed, with the 
recovery gallery having been provided under the bed, prior to the charging 
of the fluid into this incoherent oil-bearing bed, to wash out with a 
liquid through the injection wells an area in the lower part of the bed, 
and then to supply into this area materials forming a stable strong 
structure permeable for the oil, and to drill ascending recovery wells 
into this area. 
This enables to bring down the cost of drilling ascending recovery wells in 
an incoherent oil-bearing bed which is unstable during the heating and 
under the action of a flushing liquid, to reduce the ingress of big 
quantities of sand into the ascending recovery wells and into the recovery 
gallery, and to operate these wells efficiently and without undue 
complications. 
It is likewise expedient, in the case of consolidation of the lower part of 
the oil-bearing bed through the injection wells drilled from the ground 
surface, to provide the recovery gallery below this oil-bearing bed and to 
drill therefrom ascending recovery wells into the consolidated area of the 
oil-bearing bed, and also to seal the faces of the injection wells and to 
charge the fluid through the injection wells into the area of the 
oil-bearing bed, disposed above the consolidated area of the bed, so as to 
force oil from the oil-bearing bed into the ascending recovery wells 
toward the recovery gallery. 
This enables to use in the most efficient way the phenomenon of forcing oil 
by the fluid in combination with the gravity flow of oil, to minimize the 
possibility of the fluid breaking through directly into the ascending 
recovery walls drilled from the recovery gallery underlying the 
oil-bearing bed and to reduce the ingress of sand into the ascending 
recovery wells. 
It is further expedient, if the fluid infiltrates into the ascending 
recovery wells, to close periodically the ascending recovery wells 
simultaneously with the feeding of the fluid into the injection wells, 
and, following this closing, to withdraw oil from the area underlying the 
closing points. 
This enables to step up the oil yield of the oil-bearing bed, on account of 
periodic enforced fluid recovery, creating non-stationary mode of its 
performance, with periodic withdrawal of oil and cleaning of the near-face 
areas of the ascending recovery wells, and also to control the propagation 
of the heat-carrier through the oil-bearing bed, for the latter to be 
heated evenly throughout its volume.

The herein disclosed method is preferably performed, as follows. 
The entire oil-bearing formation or bed is subdivided into a plurality of 
mining elements or blocks 1 (FIG. 1). 
A system of mine workings 2 is provided above the oil-bearing formation or 
bed 3 (FIG. 2) in low-permeability above-bed rock 4. 
Then from these mine workings 2 there are drilled vertical and inclined 
injection wells 5 for charging a fluid into the oil-bearing bed 3. If 
practical, e.g. in case of shallowly extending oil-bearing beds 3, the 
vertical and inclined injection wells 5 are drilled from the ground 
surface. Then a slope 6 and a man way 7 (FIG. 1) are provided into the 
oil-bearing bed 3, and a recovery gallery 8 is excavated within the 
oil-bearing bed 3. 
The slope 6 and the man way 7 (FIG. 1) are descending mine workings 
extending toward the area of the oil-bearing bed 3 (FIG. 2) and necessary 
for the provision of the recovery gallery 8. Alternatively, the slope 6 
and the man way 7 (FIG. 1) may be vertical. Here and in the disclosure to 
follow the expression "the area of the oil-bearing bed" is used to 
describe the oil-bearing bed 3 per se and the under-bed rock 9 (FIG. 3) 
adjoining the bed. 
Provided intermediate the slope 6 and the man way 7 (FIG. 1) is a pumping 
chamber 10 to accommodate pumps operable to raise oil to the ground 
surface. The recovery gallery 8 is used to drill therefrom horizontal 
recovery wells 11 (FIG. 2) and inclined recovery wells 12. 
The term "inclined wells 12", as used here, is meant to describe both 
ascending and descending wells. 
While providing the mine workings 2 above the oil-bearing bed, the slope 6, 
the man way 7 (FIG. 1) and the recovery gallery (FIG. 2), and while 
drilling the injection wells 5 and the recovery wells 11, 12, there is 
conducted a structural analysis of the geological formation of the 
oil-bearing bed 3, and there is determined the direction of the highly 
permeable zones of this oil-bearing bed; there is also investigated the 
relationship between these zones and the injection wells 5, and the 
recovery wells 11 and 12. 
The expression "highly permeable zones of the oil-bearing bed 3" is used 
here to describe oriented abnormally permeable zones in the porous body of 
the oil-bearing bed 3, i.e. those zones of the oil-bearing bed of which 
the permeability is several times that of the main body of the oil-bearing 
bed, as well as fissures 13 (FIG. 5). 
In case of an absence in the oil-bearing bed 3 of a system of natural 
fissures 13, or else of abnormally permeable zones in the porous body of 
the oil-bearing bed 3, man-made fissures are provided therein, e.g. by 
conducting hydraulic fracturing of the oil-bearing bed 3, e.g. by charging 
through the recovery wells 11 and 12 a liquid with a breakdown agent, 
under a pressure in excess of the rock pressure. 
Following the preparation of the oil-bearing bed for the development, a 
heat-carrier, e.g. steam is fed through a system of pipelines into the 
horizontal recovery wells 11 and inclined wells 12 extending substantially 
across the dominating direction of the highly permeable zones, e.g. 
fissures 13 of the oil-bearing bed, to heat the latter to a temperature 
whereat oil acquires sufficient fluidity within the oil-bearing bed 3. 
Instead of steam the heat-carrier may be in the form of warm or hot water, 
as well as of steam-water mixtures with surface-active agents or gases. 
Arrows "A" in the drawings indicate the direction of propagation of the 
heat-carrier through the oil-bearing bed. 
As a result of the heat-carrier being charged into the horizontal recovery 
wells 11 and inclined recovery wells 12 extending across the dominating 
direction of the highly permeable zones, e.g. of the main pattern of the 
fissures 13 of the oil-bearing bed 3, the heat-carrier uniformly and 
swiftly propagates throughout the body of the oil-bearing bed 3. Thus, to 
heat up the oil-bearing bed 3, there is utilized the maximum available 
surface of the recovery wells 11, 12 and of the fissures 13 of the 
oil-bearing bed 3, which is of a particular importance at the initial 
stage of the development of the oil-bearing bed, when the viscous 
low-fluent oil opposes the access of the heat-carrier into the porous body 
of the oil-bearing bed, and the heat transfer to the oil-bearing bed can 
be effected practically exclusively owing to its heat conductivity. This 
enhances the optimum impact of the action of the heat-carrier upon the 
oil-bearing bed 3, speeds up the heating-up of this oil-bearing bed 3 and 
rapidly reduces the viscosity of oil, so that the latter attains 
sufficient fluidity in the porous body of the oil-bearing bed 3, which 
cuts down the oil field development time. 
The greater surface of the opening-up of the oil-bearing bed 3 by the 
recovery wells 11 and 12 and by the fissures 13 associated and 
communicating therewith enables to reduce significantly the number of the 
wells required for oil recovery, and thus to save the cost of drilling and 
operating these wells. 
This also cuts down the volume of the mining work associated with the 
provision of the mine workings, such as the slope 6 (FIG. 1), man way 7 
and recovery gallery 8 required for drilling the recovery wells 11 (FIG. 
2) and 12. 
The greater surface area of the opening-up of the oil-bearing bed 3 also 
eliminates the necessity of charging the heat-carrier into the formation 
under a very high pressure, which helps prevent breakthrough of the 
heat-carrier into the mine workings 2 overlying the oil-bearing bed, into 
the slope 6 (FIG. 1), man way 7 and recovery gallery 8 (FIG. 2) and its 
bleeding beyond the area of the portion of the oil-bearing bed 3, which is 
being developed; and which also improves the working environment in the 
mine workings and enhances safe working conditions. The consumption of the 
heat-carrier is reduced, too. 
The heating of the oil-bearing bed 3 from the recovery wells 11 and 12 
enables to bring down considerably the infiltration resistance to the flow 
of oil from the oil-bearing bed 3 into the fissures 13 (FIG. 5) and the 
recovery wells 11 and 12. 
This fact, in its turn, enables to increase significantly the per day yield 
of the oil-bearing bed, as well as to prevent the ingress of great 
quantities of sand into the recovery wells 11 and 12, and thus to preclude 
eventual faults in the operation of these wells. 
Upon the oil-bearing bed 3 having been heated up to a temperature whereat 
the oil acquires sufficient fluidity within the oil-bearing bed 3, the 
feed of the heat-carrier into the recovery wells 11 and 12 is 
discontinued. 
Then a pressurized fluid, e.g. warm water is charged into the injection 
wells 5 which are minimally associated with the highly permeable zones, 
e.g. fissures of the oil-bearing bed 3, to force oil from this oil-bearing 
bed 3 into the horizontal recovery wells 11 and inclined recovery wells 12 
toward the gallery 8. 
The direction of propagation of the fluid through the oil-bearing bed 3 is 
indicated in the drawings with arrows "B" (FIGS. 7 and 8). 
The direction of the flow of oil forced from the oil-bearing bed 3 is 
indicated in the drawings with arrows "C". 
From the recovery gallery 8 oil is lifted to the ground surface by pumps 
installed in the pumping chamber 10 (FIG. 1). 
The charging of the fluid through the injection wells 5 (FIGS. 7 and 8) 
minimally associated with the fissures 13 enhances the efficiency of the 
forcing of oil from the oil-bearing bed into the recovery wells 11 and 12 
(FIG. 7) and steps up the oil yield of the oil-bearing bed 3. 
This also enables to minimize the eventuality of the fluid breaking through 
into the recovery wells 11 and 12, as well as to reduce the amount of the 
fluid required for forcing oil from the oil-bearing bed 3. The conditions 
for the ingress of sand from the oil-bearing bed 3 into the recovery wells 
11 and 12 are likewise impaired, thus eliminating eventual faults in the 
performance of these wells. 
With oil being forced from the oil-bearing bed by the fluid into the 
horizontal recovery wells 11 and inclined recovery wells 12 of which the 
infiltration area is more heated than the rest of the zones of the 
formation, so that oil therein has the lowest viscosity, the oil yield of 
the oil-bearing bed 3 is stepped up, and the productivity of the recovery 
wells 11 and 12 is maintained at the maximum. 
The utilization of the horizontal recovery wells 11 and inclined recovery 
wells 12 opening up to the maximum the highly permeable zones, e.g. 
fissures 13 of the oil-bearing bed for charging the heat-carrier 
therethrough at the bed-heating stage, and, following the heating up of 
the oil-bearing bed 3, for collecting therein the oil forced by the fluid 
charged into the injection wells 5 saves the cost of drilling extra wells 
and providing either extra or greater mine workings, such as the slope 6 
(FIG. 1), man way 7 and recovery gallery 8; it further saves ventilation 
costs associated with ventilation of greater mine workings, and cuts down 
the time of the development of the oil-bearing bed 3 (FIG. 7). 
To utilize to the fullest possible degree the phenomenon of gravity flow of 
oil for oil recovery into the recovery wells 11 and 12, simultaneously 
with the forcing of oil by the fluid into the same wells 11 and 12, in one 
embodiment of the present invention the slope 6 and the man way 7 (FIG. 1) 
are provided into the lower part of the oil-bearing bed 3 (FIG. 3), and 
then there is provided in this lower part of the oil-bearing bed 3 the 
recovery gallery 8 from which the horizontal recovery wells 11 and the 
inclined recovery wells 12 are drilled. 
This enables to step up the productivity of the recovery wells 11 and 12 
and to increase the per day yield of the oil-bearing bed 3. 
In another embodiment of the invention, in the case of recovering oil from 
an incoherent oil-bearing bed 3 becoming unstable when heated, the slope 6 
and the man way 7 (FIG. 1) are provided into low-permeability stable rock 
9 underlying the oil-bearing bed 3. 
Then the recovery gallery 8 is provided so that it is separated from the 
incoherent oil-bearing bed 3 by a low-permeability steady interbed 14 
(FIG. 4) of the rock 9. Then ascending recovery wells 15 are drilled from 
this recovery gallery. 
In this case the cost of the provision of the recovery gallery 8 is 
reduced, the undesirable propagation of heat from the oil-bearing bed 3 
into this recovery gallery 8 being curbed down, and the ventilation costs 
being reduced, too. 
In a preferred embodiment of the present invention, the heat-carrier is fed 
into the oil-bearing bed 3 through the recovery wells 11, 12 and 15 until 
the oil-bearing bed 3 is heated up to a temperature above which the 
viscosity of the oil is practically not reduced by further heating. 
The practical experience of the inventors has proved that various crude oil 
grades with different compositions have each a definite temperature above 
which this oil grade does not become more fluid at further heating. 
If the oil-bearing bed 3 is inadequately heated, i.e. if it is not heated 
to reduce the oil viscosity to the necessary level, the efficiency of the 
forcing out of oil by the pressurized fluid is affected; however, on the 
other hand, excessive heating of the oil-bearing bed 3 would not 
significantly enhance this efficiency and increase the oil yield. 
The heating of the oil-bearing bed 3 to the abovementioned optimum 
temperature reduces the overall consumption of the heat-carrier by the oil 
recovery process. In this way excessive heating of the oil-bearing bed 3 
is precluded, the atmosphere in the mine workings is improved, and the 
costs of ventilation of the mine workings 2 (FIG. 1) above the oil-bearing 
bed 3, of the slope 6 and of the man way 8 are reduced. 
In another embodiment of the present invention, in the case of the presence 
in the oil-bearing bed (FIG. 5) of a dense network of natural 
high-permeability zones, e.g. fissures 13, the injection wells 5 drilled 
from the mine workings 2 and from the ground surface inadvertently 
penetrate or open up at least some of these fissures 13. 
Therefore, prior to forcing oil by the pressurized fluid into the recovery 
wells 11, 12 and 15 (FIG. 4) toward the recovery gallery 8, there is 
charged into those of the injection wells 5 (FIG. 5), which are 
communicating with the fissures 13, a plugging composition selected to 
retain the oil-permeability of the porous body of the oil-bearing bed, 
e.g. a binder based on a mixture of phenols with water, a solvent and a 
setting agent. 
Then into the same injection wells 5 there is charged a neutral liquid, 
e.g. crude oil, to force the plugging solution from these injection wells 
5 into the fissures 13 of the oil-bearing bed 3. 
And only then the pressurized fluid is charged into the injection wells 5 
to force oil from the oil-bearing bed 3 into the recovery wells 11, 12 and 
15 (FIG. 4), toward the recovery gallery 8. 
The filling up of the fissures 13 (FIG. 5) associated with at least some of 
the injection wells 5 with the plugging solution enables to level out the 
homogeneity of the oil-bearing bed 3 as far as its oil-permeability is 
concerned, and to enhance the efficiency of the forcing-out of oil from 
this oil-bearing bed 3 by the pressurized fluid. This enables to increase 
the oil yield of the oil-bearing bed 3, to prevent breakthrough of the 
pressurized fluid via the fissures 13 into the recovery wells 11, 12 and 
15, and to reduce the amount of the pressurized fluid required for forcing 
out oil. 
In another embodiment of the invention, in a case when the amount of the 
fissures 13 in the oil-bearing bed 3 is relatively small, and some of the 
recovery wells 11, 12 and 15 (FIG. 4) do not penetrate these fissures 13 
(FIG. 5) of the oil-bearing bed 3, the heat-carrier is charged into the 
recovery wells 11, 12 and 15 extending across the direction of the main 
system of the fissures 13, and simultaneously oil is collected from the 
oil-bearing bed 3 through those of the recovery wells 11, 12 and 15 which 
have the minimum degree of communication or association with the fissures 
13 (FIG. 6). 
This enables to recover oil simultaneously with the heating of the 
oil-bearing bed 3, to relieve partly the porous space of the oil-bearing 
bed 3 from oil, thus offering this space for better propagation of the 
heat-carrier thereinto and to speed up the heating of the oil-bearing bed 
3, owing to the greater area of the contact of the heat-carrier with the 
oil-bearing bed 3. 
Following the heating up of the oil-bearing bed to the predetermined 
temperature, the feed of the heat-carrier into the recovery wells 11 and 
12 is discontinued, and the pressurized fluid is charged into the 
injection wells 5 to force oil from the oil-bearing bed 3 into the 
recovery wells 11 and 12, toward the recovery gallery 8. 
However, in certain practical cases, at a later stage of the oil production 
process the oil-bearing bed 3 becomes partly exhausted, and the 
productivity of the recovery wells 11 and 12 becomes insufficient. 
In this case the recovery gallery 8 (FIGS. 2 and 3) provided within the 
oil-bearing bed 3 is preferably filled with a fluid having a density in 
excess of that of oil, e.g. with warm water. 
Then a heat carrier under a relatively high pressure, e.g. steam is charged 
as the pressurized fluid into those of the injection wells 5, which have 
the minimum communication or association with the fissures 13. 
This feed of the heat-carrier into the oil-bearing bed 3 is carried out 
until the latter is heated to a predetermined higher temperature. 
Then the charging of the heat-carrier into the said injection wells 5 is 
terminated, warm water is charged thereinto as the pressurized fluid, and 
from the recovery gallery 8 the fluid, e.g. water is pumped by pumps 
installed in the pumping chamber 10 (FIG. 1) into the mine workings 2 
(FIG. 2) overlying the oil-bearing bed 3 and/or to the ground surface, to 
charge this fluid once again into the said injection wells 5. 
Following the pumping out of water from the recovery gallery 8, the 
operation of forcing out oil from the oil-bearing bed 3 by the pressurized 
fluid into the recovery wells 11 and 12 toward the recovery gallery 8 is 
continued as long as the productivity of these wells 11 and 12 remains at 
a satisfactory level. 
Upon the reduction of the productivity of the recovery wells 11 and 12 
below the said level, the recovery gallery 8 is once again filled with 
warm water, and the heat-carrier is charged into the injection wells 5. 
The abovedescribed pattern of filling the recovery gallery 8 with water and 
pumping water therefrom is repeated periodically, as long as the 
oil-bearing bed 3 remains adequately heated, and the productivity of the 
recovery wells 11 and 12 remains at the satisfactory level. 
The recurrent filling of the recovery gallery 8 with the fluid, e.g. water 
enables to charge the heat-carrier at a high pressure through the 
injection wells 5, and thus to increase the rate and to enhance the 
efficiency of the heating-up of the oil-bearing bed 3 and of the 
forcing-out of oil therefrom, while reliably sealing away the recovery 
wells 11 and 12 and precluding the breakthrough of the heat-carrier, e.g. 
condensed steam into the recovery gallery 8 and into the mine workings 2 
overlying the oil-bearing bed 3, including the slope 6 and the man way 7 
(FIG. 1 In this way the costs of ventilation of the said mine workings are 
substantially reduced, and the working environment and safety of the 
personnel are enhanced. 
The filling up of the recovery gallery 8 (FIG. 2) extending within the 
oil-bearing bed 3 with the fluid, e.g. water provides for a substantial 
increase in the water-saturation of the oil-bearing bed 3, owing to the 
water inflow through the recovery wells 11 and 12 and the fissures 13 
associated therewith, and for more intense capillary impregnation of the 
oil-bearing bed 3, while the pumping out of this fluid from the recovery 
gallery 8 provides for enforced recovery of liquid from the oil-bearing 
bed 3. 
In this manner a non-stationary mode of performance of the oil-bearing bed 
3 is provided for, with recurrent oscillations of the liquid flow rates 
and variation of the velocity and direction of the infiltration flows, 
which enables to involve into the development by the recovery wells 11 and 
12 of low-permeability intervening portions of the bed 3, its blind 
portions, the least heated portions, and the like. 
The abovedescribed processes increase the productivity of the recovery 
wells and cut down the time of the total oil production from the 
oil-bearing bed 3. 
In another embodiment of the present invention, when oil is to be recovered 
from an incoherent oil-bearing bed 3 (FIG. 9), particularly a bed that 
becomes unstable upon being heated, following the drilling from either the 
mine workings 2 or from the ground surface of the injection wells 5 into 
the oil-bearing bed 3 to the bottom thereof, the slope 6 and the man way 7 
are excavated into the low-permeability rock formation 9 underlying the 
oil-bearing bed 3. 
Then the recovery gallery 8 is provided under the oil-bearing bed 3 so that 
it is separated from the latter by a low-permeability stable interbed 14 
of the rock 9. 
Following this, the casings of the injection wells 5 are perforated at 
points 16 within the lower part of the oil-bearing bed, and through the 
perforations there is charged into this incoherent oil-bearing bed 3 under 
a hydraulic fracturing pressure, i.e. a pressure in excess of the rock 
pressure, a cold liquid, e.g. water containing an expanding agent, e.g. 
sand. 
Following the hydraulic fracturing of the oil-bearing bed 3 between the 
injection wells 5, cold liquid is pumped through the latter to wash away 
an area in the lower part of the oil-bearing bed 3. 
Then materials are fed into this washed-away part of the oil-bearing bed, 
e.g. a binding agent based on a mixture of phenols with water, a solvent 
and a setting agent, to form a stable strong structure 17 of adequate oil 
permeability. 
To enhance the permeability of this consolidated area, the binding or 
consolidating agent is preferably supplied into the washed away area of 
the oil-bearing bed together with granulated materials, and, also 
preferably, the binding or consolidating agent is forced through into the 
peripheral portions of the washed away area being consolidated by charging 
into the injection wells 5 a liquid which is neutral with respect of this 
agent, e.g. oil. 
Following the consolidation of this area of the incoherent oil-bearing bed 
3, ascending recovery wells 15 are drilled from the recovery gallery 8 
into this consolidated area 17 of the oil-bearing bed 3. 
Then the heat-carrier is charged through these recovery wells 15 into the 
oil-bearing bed 3 until at least the bottom part of the latter is heated 
up to a temperature whereat oil acquires the necessary fluidity within the 
oil-bearing bed 3. 
With this attained, the charging of the heat-carrier through the recovery 
wells 15 is discontinued, and the pressurized fluid, e.g. steam is charged 
into the oil-bearing bed 3 through the injection wells 5 to force oil into 
the recovery wells 15 toward the recovery gallery 8. 
The consolidation of the incoherent oil-bearing bed 3 through the injection 
wells 5 drilled either from the ground surface or from the mine workings 2 
overlying the oil-bearing bed 3, and the subsequent drilling of the 
recovery wells 15 into the consolidated and adequately permeable area 17 
enable to preclude complications otherwise associated with the drilling of 
the ascending recovery wells 15 in the incoherent oil-bearing bed 3, e.g. 
the inflow from the bed 3 of big quantities of sand on account of the 
action upon this bed 3 with the drilling tools and the drill mud. Thus, 
the cost of drilling the ascending recovery wells 15 is reduced. 
Furthermore, the conditions of creating an infiltration zones of the 
ascending recovery wells 15 in the incoherent oil-bearing bed 3 are 
significantly facilitated; the complications involved in the creation of 
such zones are precluded, and conditions are created for supplying into 
the oil-bearing bed 3 greater volumes of the required filtration 
materials, including granulated materials. 
There is provided a possibility of creating an infiltration zone of a great 
area adjacent to the ascending recovery wells 15 with the use of 
granulated materials, which enables to improve its permeability and to 
enhance the productivity of the recovery wells 15. 
The complications associated with the operating of the ascending recovery 
wells are also minimized, owing to the minimized ingress of great 
quantities of sand from the incoherent oil-bearing bed 3 into these wells, 
which also increases the productivity of these wells 15. 
The utilization of a large volume of granulated material for consolidation 
of the infiltration zone of the ascending recovery wells 15 in the lower 
portion of the incoherent oil-bearing bed 3 provides for better draining 
coverage by the recovery wells 15 of a greater area of the oil-bearing bed 
3 and steps up the productivity of the wells. 
Ultimately, this enables to reduce the volume and number of the mine 
workings which are to be provided, i.e. of the slope 6 (FIG. 1), of the 
man way 7 and of the recovery gallery or galleries 8, owing to the smaller 
number of the recovery wells (FIG. 9) required for the development of the 
oil-bearing bed 3. 
In still another embodiment of the present invention, to enhance the 
efficiency of forcing out oil by the pressurized fluid into the recovery 
wells 15 toward the recovery gallery 8 and to utilize to the fullest 
degree the phenomenon of gravity flow of oil into the recovery wells 15, 
prior to charging the pressurized fluid into the injection wells 5 to 
force out oil from the incoherent oil-bearing bed 3, the faces of the 
injection wells 5 are sealed, e.g. with aid of packers 18. Then 
perforations 19 are made through the respective casings of the injection 
wells 5 centrally of the oil-bearing bed 3, and the heat-carrier is 
charged into the injection wells 5 as the pressurized fluid, e.g. steam, 
to force oil into the ascending recovery wells 15 toward the recovery 
gallery 8. 
This enables to enhance the efficiency of the utilization of the 
pressurized fluid, e.g. steam as both the agent for forcing out oil and as 
the heat-carrier for heating the oil-bearing bed, and thus to reduce the 
consumption of this pressurized fluid. 
The sealing of the faces of the injection wells 5 with the packers 18 and 
the charging of the pressurized fluid into the central part of the 
incoherent oil-bearing bed 3 prevents breakthrough of this fluid, e.g. of 
condensed steam, into the ascending recovery wells 15 and into the mine 
workings 2 overlying the oil-bearing bed 3, the slope 6, the man way 7 and 
the recovery gallery 8, which improves the state of the atmosphere in the 
mine and reduces the ventilation costs. 
The charging of the pressurized fluid into the central part of the 
incoherent oil-bearing bed 3 also prevents the ingress of great quantities 
of sand into the ascending recovery wells 15. 
As the pressurized fluid, e.g. steam is charged through the injection wells 
5 into the incoherent oil-bearing bed 3 to force oil therefrom into the 
ascending recovery wells 15 toward the recovery gallery 8, the portion of 
the incoherent oil-bearing bed 3 intermediate the wells 5 and 15 is under 
the action of the most pronounced pressure drop (or, as it is sometimes 
said, under the greatest depression). 
Oil within this portion of the oil-bearing bed 3 is under the most 
pronounced action of the pressurized fluid, e.g. of steam, and is the 
first to be forced out into the recovery wells 15, i.e. this portion is 
the first to become highly permeable for the pressurized fluid, e.g. 
steam. 
Condensed steam becomes capable of breaking through into the ascending 
recovery wells 15, affecting thereby the state of the mine atmosphere and 
doing no useful work of forcing oil from the oil-bearing bed 3. Besides, 
the breakthrough of the pressurized fluid directly into the recovery wells 
15 sharply increases the quantity of sand carried into these wells and 
clogs their infiltration zone with sand. 
In this case, according to a further embodiment of the present invention, 
simultaneously with the charging of the pressurized fluid into the 
injection wells 5, the ascending recovery wells 15 (FIG. 10) are 
periodically closed off, e.g. with a gate 20. Following their closing-off, 
oil is pumped from a zone underlying the closing-off point, i.e. from the 
recovery well 15 below the gate 20, and from the oil-collecting manifold 
21 through the recovery gallery 8 to the ground surface. 
The period between the opening and closing of the recovery well 15, during 
which oil is recovered from the open well 15, is set to correspond to the 
satisfactory productivity of the well 15 and to the tolerable content of 
the fluid, e.g. of condensed steam in its product. 
As soon as the said parameters fail to meet the predetermined standards, 
the ascending recovery well 15 is closed off with the gate 20, and 
recovery of oil therefrom is discontinued for the preassessed period of 
restoration of these parameters of the preset norm, during which period 
oil is recovered from the adjacent open recovery wells 15. 
With the abovementioned period having lapsed, the said ascending recovery 
well 15 is reopened, and the liquid having in the meantime accumulated in 
this recovery well 15 flows at a high rate into the empty oil collector 
21, causing a pressure drop at the face of the well 15. 
The periodic closing of the ascending recovery wells 15 enables to vary the 
direction of infiltration flows of the fluid in the incoherent oil-bearing 
bed 3 and to increase the oil yield thereof; and when the heat-carrier is 
charged through the injection wells 5 as the pressurized fluid for forcing 
out oil, there is ensured the regulation of the thermal action upon the 
incoherent oil-bearing bed by maintaining the uniformity of the 
propagation of the heat-carrier throughout the volume of the bed; 
moreover, the conditions for the heat-carrier breaking through into the 
ascending recovery wells 15 are minimized. 
This decreases the value of the consumption of the heat-carrier per weight 
unit of recovered oil and enhances the state of the atmosphere in the 
mine. 
The periodic closing of the ascending recovery wells 15, followed by 
withdrawal of oil from the zone underlying the closing spot through the 
recovery gallery 8 to the ground surface also enables, and that without 
additional cost, to periodically create depressions acting upon the 
oil-bearing bed and to clear the near-face areas of the ascending recovery 
wells 15. 
This enables to step up the productivity of the recovery wells 15. 
The charging of the heat-carrier through the ascending recovery wells 15 
into the oil-bearing bed 3 at the stage of heating the latter to a 
temperature whereat oil acquires sufficient fluidity in the oil-bearing 
bed 3 is preferably effected via tubes 22 (FIG. 11) accommodated within 
the casings 23 of the ascending recovery wells 15. 
The about-tube space intermediate the casing 23 and the tubes 22 is sealed 
away at the mouth of the well with a plugging solution, e.g. one 
containing a liquid hydrocarbon and a pulverulent mineral weighing agent, 
such as finely ground silica with particle size short of 1 micron. 
The said solution is to have a high boiling point, to prevent evaporation 
thereof in the outside-tube space, as it is heated by the heat-carrier. 
The solution, which can be any suitable known per se one, is to be 
adequately stable, proof against disintegration within a preset time, 
sufficiently dense and viscous at elevated temperatures, of low heat 
conductivity and of fine sealing properties. 
The sealing away of the mouths of the ascending recovery wells 15 at the 
stage of the charging of the heat-carrier at an elevated temperature into 
the oil-bearing formation enables to prevent the breakthrough of the 
heat-carrier into the recovery gallery 8 and to reduce the emanation of 
heat into the recovery gallery 8 on account of heat conductivity. This 
enhances the state of the mining atmosphere and reduces the ventilation 
costs.