RU2283945C1 - Method for hydrocarbon deposit development at later stage - Google Patents

Abstract

FIELD: oil production, particularly enhanced recovery methods for obtaining hydrocarbons in difficult geological conditions characterized by tectonic features, in presence of fissures, local or layer non-uniformity with high number of permeable intervals, especially for depletion driven deposits having water-flooded wells or a great number of inactive wells.

SUBSTANCE: method involves separating producing wells having low yields from total group of drilled wells, wherein the selected wells have low production rates, and separating inactive wells from above group; determining zones of abnormal geological stress in productive reservoir rock within reservoir to be developed; applying action to abnormal geological stress zone center from day surface and/or from producing wells by creating elastic vibrations having frequency and duration, which provide spontaneous branched multifractal fissure formation; fixing fissure zone as stress center response to elastic vibrations; determining spatial orientation of spontaneous fissure formation zone; orienting elastic oscillation towards peripheral spontaneously formed fissure zone, which is located at the nearest inactive well; continuing above fissure development by elastic oscillation application; performing periodical elastic oscillation orientation with leading on new oscillation front to direct fissured zone to above inactive well; filling fissured zone with liquid hydrocarbon; blasting inactive wells, wherein at least two blasts are carried out in the wells and blast waves and/or gas bubble pulses are interfered to extend fissure pattern and to provide unsteady hydrodynamic regime of pulsed productive reservoir treatment with filtration direction change in well and remote zones.

EFFECT: increased efficiency of hydrocarbon deposit development with blasting due to previous preparation of productive reservoir rock massif with taking into consideration abnormal stressed state of the massif, group fissuring thereof in predetermined direction and possibility to increase energy in depleted reservoir along with reservoir filtration ability conversion.

13 cl

Description

The invention relates to the oil and gas industry and, in particular, to methods for developing a hydrocarbon deposit at a late stage in difficult geological conditions with tectonic features, fracturing, with zonal and / or layered heterogeneity, characterized by a high coefficient of dissection.

The invention is especially relevant for deposits that have been exploited for a long time in the mode of depletion of reservoir energy, the flow rate in a number of wells has decreased below the permissible value, the wells are flooded and there is a sufficiently large volume of inactive production wells.

When developing such deposits at a late stage, as a rule, the leading production of highly permeable and freely drained reservoirs and sections of the reservoir occurs, with the formation of stagnant zones in the medium and low permeability layers, where cracks are either absent or quite rare. The probability of the formation of such stagnant zones is the higher, the weaker the hydro- or gas-dynamic connection between the highly permeable and low permeable reservoirs or interlayers of the reservoir over its area, the greater the difference in the permeability of reservoirs. In this case, the advanced production of highly permeable, for example, fractured reservoir sections in a stationary long-term filtration mode leads to the involvement of drainage water (filtration) and associated formation water, which is usually characterized by an active filtration mode. With continued exploitation of flooded wells, the situation only worsens. Watering wells increases, the profitability of such wells is sharply reduced.

In deposits with such productive formations, the long-term stationary modes of well operation do not justify themselves due to the rapid flooding of well products through the usual filtration channels, for example, fractures in the productive formation. Well production, such as oil in the reservoir matrix, is blocked by fractured water. The phase permeability of oil decreases and the well is flooded without giving out its reserves. At the same time, often, geological conditions, the adopted scheme for the development of deposits and existing energy resources do not provide the ability to organize or reform the filtration of deposits throughout its thickness with the maximum possible return on the products contained in it.

The task itself is very important when you consider that the actual recovery rate, for example, of oil from the reservoir does not currently exceed 35%, while the average mobile oil content in the reservoir can be twice that index.

A known method for the development of hydrocarbon deposits, including the impact of low-frequency elastic vibrations on the formation rock to intensify fluid recovery in production wells (see, for example, USSR author's certificate No. 832072).

The disadvantage of this method is the locality of exposure to such fluctuations. The propagation radius of the vibrations emitted in the framework of the known method by the vibrators is limited due to the insufficient power of the emitted vibrations and the strong absorption of these vibrations in the near-well zone of the formation. In addition, due to the lack of targeted effects of fluctuations precisely on stagnant low-permeability formations, the latter, in essence, are not intensified.

A known method for the development of hydrocarbon deposits using directed underground explosions (see, for example, patent RU 2224097, 02/20/2004).

The known method involves the use of explosions at a late stage of reservoir development using water flooding through injection wells in low-permeability reservoirs with an orientation toward the use of energy resources of the explosions themselves.

The disadvantage of this method is that it provides for the use of a large fund of production and injection wells. The explosions used affect the previously unprepared mass of rocks composing the reservoir, and therefore, even with their large number and high power, they have only a local effect on the rock mass.

The technical result of the invention is to increase the efficiency of the method of developing hydrocarbon deposits with explosive technology due to the preliminary preparation of the rock mass of the reservoir, taking into account its abnormal stress state, the development of mass fracturing in it like multifractals oriented in a given direction, and the possibility of pumping energy from a depleted reservoir with conversion of its filtration.

The necessary technical result is achieved by the fact that the method of developing hydrocarbon deposits in a fractured reservoir at a late stage involves isolating low-production wells characterized by reduced production rates and inactive wells from the entire stock of production wells drilled into the reservoirs, determining the zone of abnormal geological stress state of the rocks of the reservoir in the limits of the developed deposit, the impact on the center of the zone of the abnormal geological stress state of the rocks productive formation from the surface of the earth and / or from production wells by elastic vibrations with frequencies and duration that provide spontaneous branched crack formation according to the type of multifractals, which is recorded as the response of the stress center to elastic vibrations, determine the spatial orientation of the spontaneous crack formation zone, then the elastic vibrations are oriented to the peripheral zone spontaneously formed cracks located at the side of the nearest inactive well of at least one, and these cracks due to elastic vibrations, which periodically reorient to their new front to guide the crack zone to the said inactive well, after which the crack zone is filled with hydrocarbon fluid, and inactive wells carry out underground explosions, at least two, with the possibility of interference of their waves and / or pulsations of their gas bubbles to expand the network of cracks and provide non-stationary hydrodynamic regime of the pulsating treatment of the reservoir with a change in the direction of the fil tration in the well bore and the remote zone.

Besides:

as a hydrocarbon reservoir, an oil reservoir is used;

use explosions in the combustion mode of their charge;

the spontaneous fracture formation zone is additionally directed to at least one well;

the abnormal zone of the geological stress state of the rocks of the reservoir is determined by aerospace data and / or geological and geophysical data;

the abnormal zone of the geological stress state of the rocks of the reservoir is determined by aerospace data and / or by data of broadband acoustic logging;

in the fountain mode of production wells, low-rate wells are periodically shut down to reform the fluid flow structure and pressure drops, which provide a value in excess of hydrostatic pressure and take 0.6-0.9 fracturing pressure;

periodic shutdown of low-production wells from work is carried out by an automatic shut-off valve at the mouth of these wells, depending on the structure of the fluid flow, its speed, content and flow rate of liquid and gas, pressure differences in the reservoir and on the bottom of the wells;

in case of multiple explosions, each of the subsequent explosions is carried out with hydro-gas-dynamic pulsations in the rocks of the reservoir from previous explosions;

the borehole zone of the wells is filled with a homogeneous hydrocarbon fluid - light oil or diesel fuel, or kerosene;

explosions are carried out in the zone of the reservoir;

explosions are carried out in the underlying aquifer;

the spatial orientation of the zone of spontaneous cracking is recorded by seismic three-dimensional measurements.

The essence of the invention lies in the fact that the known methods of intensifying oil production by an explosion when developing a deposit are characterized, as a rule, by high energy intensity, but do not provide sufficient efficiency due to the fact that the stress state of the rock mass in the zone of the productive formation is not taken into account.

The present invention proceeds from the logic that the presence of cracks in the reservoir already implies the fatigue nature of their development, as a result of stress relaxation. Moreover, the presence of individual cracks does not mean that the stresses in the rock mass are completely relaxed. This is confirmed by core studies, as well as geophysical studies directly in the wells, for example, broadband acoustic logging in the interval of occurrence of the reservoir. The process of stress relaxation in a rock mass of a productive formation develops or can develop over a period of time characterized by geological scales, i.e. a very long time. The present invention contemplates accelerated reforming of a productive formation array into a matrix with multidimensionally relaxed rock stresses with a highly developed structure of microcracks based on vertical cracks. We are talking about the inclusion of the mechanism of fatigue development of cracks in the rock according to the multifractal principle, characterized in that the total length of the fatigue fracture cracks all the more tends to infinity, as large levels of fracture detail (micro levels) are taken into account. Such cracks develop according to the principle of conditional self-similarity, starting from the micro level and ending with the macro level. Conditional self-similarity is explained by the fact that a regular fractal with full self-similarity in natural conditions is not real. For rocks with distinct anisotropy properties, random processes are characteristic that preclude the development of ideal forms of self-similarity. Nevertheless, multifractals, not being regular fractals and therefore difficult to characterize in a simple form, with their unusual aforementioned property of the infinite total length of a fracture crack, can be successfully used in practice.

It turns out, as shown by field studies, the mechanism of multifractal formation can be quite simply triggered by the action of the center of stress concentration in the rock by elastic vibrations from the surface of the earth or from wells. In practice, the result of spontaneous cracking was observed according to a random law, with randomly sorting through the acting frequencies of elastic vibrations, with a peculiar game in chaos, which, like a trigger mechanism, triggers the relaxation mechanism of fatigue stresses, which manifests itself in the form of branched cracks, similar to multifractals, based on vertical cracks as the least energy intensive. In some cases, the generator of elastic vibrations can be placed on the surface of the earth or in a well, sometimes directly in the center of the anomalous stress state of the rocks. The frequency of exposure is chosen in the range, for example, 60-1500 Hz. In this case, it is possible to use a group of elastic wave generators. Sources are placed at a distance from each other equal to 1/8 of the wavelength of the fundamental frequency sent to the rock mass. First, the massifs are brought into vibrational state by elastic vibrations with a frequency of 60–1500 Hz over a period of time at which compression strains are changed to tensile strains with the development (opening) of primarily fatigue relaxation cracks. Then they switch to impacts with the frequency of natural rock oscillations, i.e. to resonance mode. By acting on the stress center, the desired result can be achieved with minimal energy consumption. Then, the initially obtained zone of cracks is developed, for example, extended (developed). For this, the process of cracking is constantly monitored, for example, by geophysical surveys. The spatial orientation of the cracking zone is determined using, for example, seismic three-dimensional measurements. The initial fracture zone is developed in that elastic vibrations are directed to the peripheral zone of the formed fractures, and on the side that is in the direction of the nearest inactive well. In this case, the elastic vibrations periodically reorient (direct) either the new front of the cracks or the adjacent not yet fractured massif. Thus, the rock mass along which the initial fracture zone passes is preliminarily prepared (as if tapping) to guide the zone of initial spontaneously formed fractures into the said inactive well. After that, the entire zone of fractures thus formed, where the bore of the idle well is located, is continued to be treated with elastic vibrations with priority treatment of the central zone of the abnormal stress state of the rocks. The zone is, as it were, pumped with additional energy for further relaxation (unloading) of all stresses in the reservoir and additional crack formation. As a result, there is a massive repackaging of the structure of the reservoir with its response to prolonged processing by the response vibrations (seismic emission) of elastic waves resulting from mass repackaging, with a frequency range of these waves significantly exceeding the range of the impacting waves. This phenomenon is recorded by geophones. After that proceed to the next stage. For example, the resulting fracture zone is developed to another inactive well or a low-yield well. Ultimately, the crack zone is filled with hydrocarbon fluid. In a preferred embodiment, the crack zone is filled with a homogeneous hydrocarbon liquid to prevent the formation of paraffin-resinous sediments in it. Then inactive wells carry out explosions of at least two. The explosions are carried out from the condition of increasing the time of the impact of the explosion pulses on the crack zone. To do this, an explosion is carried out, for example, in the combustion mode of the explosive used (EXPLOSIVES) or explosives are used with a reduced detonation velocity, for example, of the type igdanite. In any case, it is preferable to use explosives with increased gas evolution. This is because the gaseous products of the explosion must form a gas bubble in the fracture zone with a pressure in it from several tens to hundreds of atmospheres. In this case, a phenomenon occurs in which the compressed products begin to expand and expand until the pressure inside the gas bubble is equal to the hydrostatic pressure at the depth of the explosion. The fluid surrounding the gas bubble, having accumulated a kinetic energy supply during expansion, continues to move in the same direction and stretches the gas bubble. The pressure in the latter becomes lower than hydrostatic. The gas bubble begins to shrink. Due to the inertia of the surrounding liquid, the compression of a gas bubble occurs until its pressure becomes a certain amount higher than hydrostatic. With pulsations of a gas bubble, a powerful hydroflow occurs in an unsteady mode. It is especially important that the hydroflow occurring during pulsation of a gas bubble carries an energy impulse comparable to the impulse carried by the primary shock wave, despite the low values of the operating pressures. The combination of the cyclic effect on the highly branched fracture zone according to the multifractal type by the hydroflow with a change in the direction of the filtration flows ensures first hydrophobization and then drainage of the productive formation of its products (oil) with the entire matrix of the reservoir with locking of the water filtration channels. At the same time, in the most inactive well, as a result of the explosion, for example, directly in the zone of the reservoir, composed of stable rocks, for example limestone, caverns with a significantly increased filtration surface are formed, which allows a multiple increase in the influx of products to the well. The stability of the caverns (their stability) is increased due to the preliminary saturation of the explosion zone with hydrocarbon liquid. Depending on the size of the fracture zone, explosions can be carried out in one well or several wells simultaneously or alternately. In one well, one explosion or several explosions dispersed throughout the depth of the well can be carried out. In this case, explosions can be carried out in such a way as to ensure the further development of fracturing in an existing fracturing zone. In this case, the preliminary processing of the zone of the reservoir by elastic waves can be reduced or redistributed due to the use of one or another explosive technology, namely:

providing explosions in one or different wells in such a way that a superposition of direct blast waves is ensured;

providing explosions in one or different wells in such a way that a superposition of direct and reflected blast waves is ensured.

The method, in a specific example, is as follows.

For example, they carry out the development of an oil reservoir in a reservoir represented by fractured limestones and occurring at a depth of 3000 m. 50 production wells have been drilled in the reservoir. Of these, 10 producing wells are inactive. Allocate these 10 wells from the entire well stock. The zone of the abnormal geological stress state of the rocks of the reservoir within the developed oil reservoir is determined. This is carried out according to aerospace data, seismic and geological and geophysical data in the area of oil deposits. For example, active faults are identified that are associated with the modern center of anomalous stress state of rocks, which is located, for example, at the intersection of these faults in the contour or near the contour of an oil deposit. The impact is carried out from the surface of the earth by directed elastic vibrations with frequencies of 60-1500 Hz. Oscillators (in the amount of 6 pcs.) Orient to the center of the abnormal stress state. The wavelengths at frequencies of 60 Hz are 25 m, and at frequencies of 1500 Hz - 1 m. The oscillation generators are located at 1/8 of the wavelength of the fundamental frequency from each other. Exposure is carried out with random selection of frequencies and during the time until spontaneous cracking as multifractals. The course of operations, the game of chaos and their results are constantly checked against the results on the geological-mathematical model and data obtained in real conditions, for example, from acoustic studies. On the same model, the choice of the main frequency of elastic vibrations and the mechanism for triggering spontaneous cracking according to the type of multifractals are worked out.

The phenomenon of spontaneous crack formation (rock response by crack formation to elastic vibrations) is recorded by the acoustic emission of rocks by geophones or by the data of acoustic broadband studies of the rock mass. The fracture zone is pumped with the energy of elastic vibrations for 2-3 days.

The spatial orientation of the spontaneous fissure formation zone is determined by acoustic three-dimensional studies. Then, the elastic vibrations are oriented to the peripheral zone of spontaneously formed cracks located in the direction of the nearest inactive well. These cracks continue (lead them) with elastic vibrations to an idle well. Pump the zone with an idle well for 1 day. In the same way, other inactive wells are connected to the created fracturing zone. Each time, the total area is treated for at least 1 day. elastic vibrations.

The resulting total fracture zone in the form of multifractals, i.e. as a single hydrodynamic zone, they are filled with diesel fuel under pressure above 30 MPa.

Explosive charges with increased gas release are lowered into inactive wells. They act on the fracture zone by at least two explosions with the possibility of interference of pulsations of their gas bubbles. The first explosion is set with the pulsation of a gas bubble for 20 minutes. After 15 minutes, a second explosion is carried out. By imposing pulsations, the effect of the explosion is prolonged with pumping of the fractured zone with new energy. This ensures the expansion of the network of cracks and the provision of non-stationary hydrodynamic regime of the pulsating treatment of the reservoir due to multiple changes in the direction of filtration. Due to the special nature of the cracks in the form of a single filtering system, power and the nature of the impact, the borehole and remote zone are treated.

Claims (13)

1. A method of developing a hydrocarbon deposit in a fractured reservoir at a late stage, including isolating from the entire stock drilled into the reservoir producing low-yield wells, characterized by reduced production rates, and inactive wells, determining the zone of abnormal geological stress state of the rocks of the reservoir within the developed reservoir, the impact to the center of the zone of abnormal geological stress state of the rocks of the reservoir from the surface of the earth and / or from the mining x wells with elastic vibrations with frequencies and duration that provide spontaneous branched crack formation in the form of multifractals, which is recorded as the response of the stress center to elastic vibrations, the spatial orientation of the spontaneous crack formation zone is determined, then the elastic vibrations are oriented to the peripheral zone of spontaneously formed cracks located in the direction of the nearest inactive wells of at least one, and continue to expand the zone of cracks due to elastic vibrations that per Directionally reorient them ahead of their new front to point the crack zone to the said idle well, after which the crack zone is filled with hydrocarbon fluid, and at least two underground explosions are carried out, with the possibility of interference of their waves and / or pulsations of their gas bubbles to expand the network of cracks and to provide non-stationary hydrodynamic regime of the pulsating treatment of the reservoir with a change in the direction of filtration in the near-wellbore and remote areas. 2. The method of developing a hydrocarbon deposit according to claim 1, characterized in that an oil reservoir is used as a hydrocarbon deposit. 3. The method of developing a hydrocarbon deposit according to claim 1, characterized in that explosions are used in the mode of burning their charge. 4. The method of developing a hydrocarbon deposit according to claim 1, characterized in that the area of spontaneous fracturing is additionally directed to at least one debit well. 5. The method of developing a hydrocarbon deposit according to claim 1, characterized in that the anomalous zone of the geological stress state of the rocks of the reservoir is determined by aerospace data and / or geological and geophysical data. 6. The method of developing a hydrocarbon deposit according to claim 5, characterized in that the anomalous zone of the geological stress state of the rocks of the reservoir is determined by aerospace data and / or by data from broadband acoustic logging. 7. The method of developing a hydrocarbon deposit according to claim 1, characterized in that during the fountain mode of producing wells, low-rate wells are periodically turned off to reform the fluid flow structure and pressure drops, which provide a value in excess of hydrostatic pressure and take 0.6-0, 9 fracturing pressure. 8. The method of developing a hydrocarbon deposit according to claim 7, characterized in that the periodic shutdown of low-production wells from work is carried out by an automatic shut-off valve at the mouth of these wells, depending on the structure of the fluid flow, its speed, content and flow rate of liquid and gas, pressure difference the reservoir and at the bottom of the wells. 9. The method of developing a hydrocarbon deposit according to claim 1 or 2, characterized in that in case of multiple explosions, each of the subsequent explosions is carried out with hydro-gasdynamic pulsations in the rocks of the reservoir from previous explosions. 10. The method of developing a hydrocarbon deposit according to claim 1, characterized in that the borehole zone of the wells is filled with a homogeneous hydrocarbon liquid - light oil, or diesel fuel, or kerosene. 11. The method of developing a hydrocarbon deposit according to claim 1 or 2, characterized in that the explosions are carried out in the zone of the reservoir. 12. The method of developing a hydrocarbon pool according to claim 1 or 2, characterized in that the explosions are carried out in the underlying aquifer. 13. The method of developing a hydrocarbon deposit according to claim 1, characterized in that the spatial orientation of the spontaneous fracture formation zone is fixed by seismic three-dimensional measurements.