It is commonly known of light oil reserves decreasing around the world, therefore production of sticky oil the reserves of which are large is topical nowadays.

It should be noted that the process of sticky oil production is very complicated primarily due to physicochemical properties of sticky oil.

In order to produce sticky oil primarily oil fluidity should be provided. New methods of oil production have been developed in this direction.

One of such methods of sticky oil production is the thermal method, Thus, a method of sticky oil production using the fire flooding technology is known which is applied at the Karazhanbas field being one of the largest sticky oil fields [1].

The method is based on the thermal effect on the stratum as a result of oil fire flooding in which air or oxygen is supplied into the well and filtration connection is established between the wells through caverns. Thus, oil combustion over the surface is provided in the interwell space as well as temperature increase, viscosity reduction and oil fluidity in the productive reservoir.

Disadvantages of this method are process complexity, high cost as well as low reliability and low efficiency caused by combustion temperature instability for oil viscosity reduction that leads to very poor efficiency of oil production resulting in inexpediency of this method.

The nearest analogue of the applied engineering solution is the oil production method by means of in situ rock permeability increase [2]. The method comprises uncovering a mineral stratum with wells, supplying fluid into a well. The fluid is influenced by shock waves of definite structure with their transfer along the fluid channel in the well with subsequent turning from the wave reflector to the oil-bearing stratum.

This method provides light oil production, however the substantial disadvantage of the method is that the wave structure does not influence sticky oil fluidity as a result of which the usage of this method for sticky oil production becomes impossible. The objective of the invention is creation of the method of sticky oil production in which the profitable production regime is achieved by means of providing oil fluidity.

The above objective is achieved in that in the known method of oil production comprising uncovering a mineral stratum with wells, supplying fluid into a well, influencing the fluid by the waves of definite structure with their transfer along the fluid channel in the well with subsequent turning from the wave reflector to the oil-bearing stratum according to the invention elastic waves of symmetric structure (compression) or asymmetrical structure (rarefaction) are emitted on the fluid in the tubing in the direction from the well head to the bottom, and simultaneously elastic waves of asymmetrical structure (rarefaction) are emitted into the annulus from the surface.

At that the wells can be located using the cluster or line method at the reach distance of the wave field.

Besides, the wave influence can be effected on the central well or on the surrounding wells or simultaneously on all the wells.

It is expedient when the wave frequency spectrum is chosen on the basis of minimum wave energy losses in the direction from the well head to the perforation zone and then to the estimated distance along the radius from the well to the oil-bearing stratum. At that at least one wave reflector is located opposite to each oil- bearing stratum uncovered with a well.

Besides, reflectivity of the wave reflectors is increased from the well head to the bottom at each subsequent reflector.

It is expedient when the wave form in the annulus is chosen as corresponding to the law of depression gradient attenuation in the well vicinity of the oil-bearing stratum and the wave form in the tubing is chosen as corresponding to the sinusoidal law.

At that intensity of low amplitude wave influence is chosen above the critical value of Reynolds' number depending on the power supplied.

Besides, the amplitude of the wave pressure of compression- rarefaction of high amplitude wave influence on the fluid is chosen on the basis of condition on which the wave load on a single molecular bond exceeds this bond strength:

V E

P _xe =——> [ql

a n

where P _xe - is wave pressure in the fluid referred to single molecular bond; a - is wave velocity in the fluid (sticky oil);

E - is coefficient of fluid elasticity;

[q] - is single molecular bond breaking force (sticky oil), approximately (5 - 6) · 1(T ¹⁰ kg per one molecular bond;

V _xs - is particle velocity in the wave which is emitted into sticky oil;

n - is amount of molecular bonds in the unit of area of sticky oil.

It is expedient when the length and form of the wave emitted from the well into the well vicinity of the oil-bearing stratum is chosen on the basis of the condition of providing the wave conformance of the emitting well section to the rock environment surrounding it in accordance with the following ratio p _e a _e F _e = p _K CL _K F _K

where ^ * - is density of the medium of emitter and oil-bearing stratum correspondingly;

a _e , a _K - is elastic wave velocity in the medium of emitter and oil-bearing stratum correspondingly;

F _e ,F _K - is the area of surface which at every instant is crossed by the wave perpendicular to the direction of the wave motion velocity in the medium of emitter and oil-bearing stratum correspondingly.

Besides, physically or chemically active fluid components are entered into the annulus.

Due to emitting elastic waves of symmetric structure (compression) or asymmetrical structure (rarefaction) on the fluid in the tubing in the direction from the well head to the bottom and simultaneously emitting elastic waves of asymmetrical structure (rarefaction) from the surface into the annulus the change of the physicochemical properties of sticky oil is provided by means of the wave fields, and sticky oil fluidity is achieved in situ and in the well and also directed oil mass transfer is provided along the radius to the well and then in the well to its head.

The wells can be located using the cluster or line method at the reach distance of the wave field and the wave influence can be effected on the central well or on the surrounding wells or simultaneously on all the wells depending on the physicochemical properties of oil of a specific field.

At that when the central well functions as the wave emitter for the whole well cluster the surrounding wells are not equipped with the wave generators and located around the central well at the reach distance of the wave field emitted by the central well. However in case of very sticky oil the well functions are changed- the surrounding wells are equipped with the wave generators and the oil is pumped off from the central well without its equipping with the wave generators.

In the most complicated case of extra sticky oil it is expedient to equip all the wells with the wave generators and simultaneously provide oil pumping off through all the operating wells.

Besides, for production of oil of bituminous consistency it is expedient to enter physically and chemically active fluid components into the annulus which increase the oil-bearing stratum (reservoir) temperature to the estimated thus providing fluidity of oil of bituminous consistency and required reservoir desorption.

Wave frequency spectrum is chosen on the basis of minimum wave energy losses in the direction from the well head to the perforation zone and then to the estimated distance along the radius from the well to the oil- bearing stratum, at that it is expedient when the wave energy losses do not exceed 50-70% of the initial value of each wave energy thus providing optimal usage of the wave energy and maximum distance between the wells and decrease of the scope of drilling.

Due to location of at least one wave reflector opposite to each oil- bearing stratum uncovered with a well the longitudinal axial waves emitted into the annulus are turned to be reflected along the direction of each oil- bearing stratum uncovered with a well thus providing turning of the particle velocity vector in the wave from the axial to radial direction and facilitating in situ sticky oil fluidity and controlled oil mass transfer in the oil-bearing stratum. The estimated amount of such the reflectors can be located at each of thick oil-bearing strata. Due to increasing the wave reflector reflectivity from the well head to the bottom at each subsequent reflector the estimated dosed emission of the wave energy is provided into each oil-bearing stratum at the wave moving from the well head to its bottom in the annulus.

Due to choosing the wave form in the annulus as corresponding to the law of depression gradient attenuation in the well vicinity of the oil- bearing stratum and the wave form in the tubing as corresponding to the sinusoidal law the full usage of the wave energy in the oil-bearing stratum and sticky oil fluidity is achieved as well as controlled oil mass transfer along the radius to the well and then in the well to its head.

Intensity of the low amplitude wave influence is chosen above the critical value of Reynolds' number depending on the power supplied due to which in the turbulence regime created by the waves the following phenomena are initiated and activated in the fluid medium such as micro flows, cavitation thus providing at macrolevel appearance of inertia forces and frictional forces sufficient for molecular bond breaking and on this basis decreasing molecular weight and fluid viscosity to the estimated values which provide required sticky oil fluidity in the regime of thixotropy and cold cracking of sticky oil.

For providing sticky oil fluidity in the regime of compression- rarefaction the amplitude of the high amplitude wave influence on the fluid is chosen on the basis of condition on which the wave load on a single molecular bond exceeds this bond strength: . =— a - n > [<?].

where P _xe - is wave pressure in the fluid referred to single molecular bond; a - is wave velocity in the fluid (sticky oil); E - is coefficient of fluid elasticity;

[q] - is single molecular bond breaking force (sticky oil), approximately (5 - 6) · 10 ^-10 kg per one molecular bond;

V _xe - is particle velocity in the wave which is emitted into sticky oil;

n - is amount of molecular bonds in the unit of area of sticky oil.

For providing full wave energy transfer from the well into the oil- bearing stratum medium the wave is emitted from the well into the well vicinity of the oil-bearing stratum in the conditions of providing wave conformance of the emitting well section to the rock environment surrounding it in accordance with the value ratio of their wave resistance:

P _e a _e F _e = p _{K K} F _K

where p _e ,p _K - is density of the medium of emitter and oil-bearing stratum correspondingly;

α _β , α _λ . - is elastic wave velocity in the medium of emitter and oil-bearing stratum correspondingly;

F _e ,F _K - is the area of the surface which at every instant is crossed by the wave perpendicular to the direction of wave motion velocity in the medium of emitter and oil-bearing stratum correspondingly.

For oil viscosity reduction and providing desorption in the oil-bearing stratum chemically and physically active fluids can be entered into the central well of the cluster or line block of the wells through the annulus simultaneously with wave emission till the fluid appearing in the surrounding wells.

At that physically and chemically active fluid components can be entered periodically or continuously through the annulus depending on the oil viscosity level. Therefore, the method provides oil fluidity in the oil-bearing stratum in situ and in the well and also control of saturation and directed oil mass transfer in the oil-bearing strata thus making possible profitable production regime.

The invention is disclosed in the drawings where Fig.1 represents the well completion scheme for sticky oil production from several oil- bearing strata by means of the wave fields, Fig. 2 represents the scheme of cluster position of the wells at sticky oil production by means of the wave fields, Fig. 3 represents the scheme of the wave motions in the tubing and in the annulus of the interacting wells of the operating technological cluster, Fig. 4 represents comparison of the law of depression gradient attenuation in the well vicinity and the wave form in the annulus.

Sticky oil production method is effected the following way.

A productive reservoir 1 of sticky oil represented with several layers is uncovered with a well and a casing string 2 is installed (Fig. 1 , Fig. 2). Inside the casing string 2 a tubing column 3 is inserted fixed on the Christmas tree 4 with the bottom end installed at the head of the casing string 2. The wave generators 5 for wave emission into the tubing and the wave generators 6 for wave emission into the annulus are installed on the upper end of the Christmas tree 4.

The arrows indicate the directions of the wave motion velocity in the oil in the tubing, annulus and beyond the casing string 2 (Fig. 1 , Fig. 3). The Christmas tree 4 is provided with the taps 7, 8 and 9 for liquid oil dumping and for injection of physically and chemically active reagents into the productive stratum. Reflection of the waves of axial direction to the direction along the radius in the oil-bearing stratum is provided by the reflectors 10 installed on the tubing couplers. A wave adapter 11 is installed opposite to the wave reflectors in the well vicinity. The wells equipped 12 are located using the cluster scheme or the line scheme (Fig. 2). In the wells of cluster technological scheme the wave reflectors 10 are located at the same level in the plane of each oil-bearing stratum (Fig. 3).

Geometric shape 13 of the directed wave emission into the oil- bearing stratum is shown in the Fig. 1. The wave form 15 is provided as corresponding to the law of depression gradient attenuation in the well vicinity 14 as it is shown in the Fig. 4.

The wave form and other parameters are provided in the wave generator.

The oil-bearing stratum 1 is uncovered with wells and equipped with the casing strings 2 (Fig. 1 ). The Christmas tree 4 is installed on the casing string 2 at the well head. The tubing column 3 is hung on the lower flange of the Christmas tree 4.

For implementation of the method filling of the well with spacer fluid, for example, with light oil is effected through the taps 7, 8, 9. After filling with fluid static superpressure is created in the fluid column in the well. Upon achieving the defined level of static superpressure in the well the wave generators 5 and 6 are brought into operation and the waves of the defined structure are generated in the fluid column and then in the oil column, namely: elastic waves of symmetric structure (compression) or asymmetrical structure (rarefaction) are emitted on the fluid in the tubing in the direction from the well head to the bottom, and simultaneously elastic waves of asymmetrical structure (rarefaction) are emitted from the surface into the annulus, at that the wave form in the annulus corresponds to the form of the law of depression gradient attenuation in the well vicinity (see Fig. 4) and the wave form in the tubing corresponds to the sinusoidal law. Besides, the wave frequency spectrum is chosen on the basis of the conditions of minimum wave energy losses in the direction from the well head to the perforation zone and then to the estimated distance along the radius from the well to the productive oil-bearing stratum provided that the wave energy losses do not exceed 50-70% of the initial value of each wave energy.

At that the wells are located using the cluster or line method where the central well functions as the wave emitter for the whole well cluster while the surrounding wells are not equipped with the wave generators and positioned around the central well at the reach distance of the wave field emitted by the central wave, however in case of very sticky oil the well functions are changed- the surrounding wells are equipped with the wave generators and the oil is pumped off from the central well without its equipping with the wave generators, and in the most complicated case of extra sticky oil all the wells are equipped with the wave generators and simultaneously all the wells operate for oil pumping off, besides, for production of oil of bituminous consistency the central well is used for wave injection of physically and chemically active substances which increase the reservoir temperature to the estimated thus providing fluidity of oil of bituminous consistency and required oil-bearing stratum desorption.

While moving along the well from the head to the bottom in the annulus the waves are reflected in the wave reflectors 10 opposite to each oil-bearing stratum 1 providing turning of the velocity vector of the wave motion from axial in the well to radial in the oil-bearing stratum (geometric wave shape 13, Fig. 1 ). The reflectors 10 have reflectivity changing throughout the well for providing turning of the velocity vector of the wave motion from the axial to radial direction at the estimated dosed emission of the wave energy into each oil-bearing stratum at wave moving along the annulus from the well head to its bottom.

For full wave energy transfer from the well to the reservoir the wave conformance of the fluid channel and rock channel is provided.

Besides, intensity of low amplitude wave influence is chosen above the critical value of Reynolds' number depending on the power supplied at which in the turbulence regime created by the waves the following phenomena are initiated and activated in the fluid medium such as micro flows, cavitation due to which at macrolevel inertia forces and frictional forces are appeared sufficient for molecular bond breaking and on this basis decreasing of molecular weight and fluid viscosity to the estimated values thus providing required sticky oil fluidity.

The wave compression-rarefaction amplitude of high amplitude wave influence on the fluid is chosen on the basis of condition on which the wave load on a single molecular bond exceeds this bond strength.

At the cluster position of the wells 12 (as it is shown in Fig. 2) depending on the oil viscosity level the waves are emitted into the oil- bearing stratum from the central well and the offset wells serve for the oil pumping off or alternatively, the offset wells are equipped with the wave generators and the oil pumping off is effected through the central well. In case of too high oil viscosity level all the wells are equipped with the wave generators and simultaneously all of them serve for pumping off the wave thinned oil.

Besides, wave thinning of the oil in the tubing facilitates the free-flow oil production regime. At asymmetrical wave influence on the oil in the reservoir and in the well the mechanism of the directed wave fluid mass transfer is used such as the mass transfer by means of driving pressure differential in the direction of the wave motion velocity vector. Such the regime can move the oil in the defined direction including its lifting to the well head (Fig. 3). In case the reservoir pressure is insufficient for the flowing regime the well can be equipped with a pump, primarily with the most efficient screw pump - the tubing is free for it.

Upon activating the wave generators the well filled with spacer fluid starts emitting the waves of the estimated structure into the sticky oil- bearing stratum surrounding the wave. The oil contained in the oil-bearing stratum is thinned out and transferred towards the surrounding wells of the technological cluster by means of the wave pressure differential. The wells start filling with the thinned oil and the reservoir pressure starts working which lifts the oil to the well head for unloading.

The oil production regime is chosen on the basis of the open flow production potential of the well at the constant wave emission from the central well, offset wells or all the wells of the technological cluster simultaneously. The regime is regulated with the valves 7, 8, 9 (Fig. 1 ). In particular cases of production of oil of bituminous consistency the necessity of stratum temperature increase arises. For this purpose the strictly normed amount of chemically active substances providing the oil- bearing stratum temperature increase to the estimated are entered through the valve 7 into the annulus thus providing fluidity of the oil of bituminous consistency and required reservoir desorption.

Therefore, the method provides the oil fluidity in the oil-bearing stratum in situ and in the well and also control of saturation and directed oil mass transfer in the oil-bearing strata thus making possible profitable sticky oil production regime.

References

"Adoption of wet fire flooding technology at the Karazhanbas field",

M.Zh. Selimgereev, N.N. Chervyakov, V.A. Simonov, K.T. Tuleshov,

E.I. Naftova and gas industry", series "Development of oil fields and enhanced oil recovery methods"; No. 10, M. 1991 , p. 23.

USSR Certificate of Authorship No. 1240112, IPC3 E21 B43/28,

1983.