RU2245994C1 - Method for preserving collecting properties of productive bed well-adjacent area - Google Patents

Abstract

FIELD: oil and gas extractive industry.

SUBSTANCE: method includes placing alkali waste from kaprolaktam or its solutions production into well as working liquid, in volume not less than volume of pores and/or cracks of productive bed in radius of mudding area from well shaft. Working liquid is pressed into productive bed in saturation mode for this bed along whole thickness thereof. For this saturation of productive bed is performed at pressure of opening of its natural cracks and in cyclic mode of pressure increase, its exposure and pressure drop. This is realized for pressure gradient during loading of productive bed to be 1.1-1.8 times less than pressure gradient during unloading of productive bed.

EFFECT: higher efficiency.

6 cl

Description

The invention relates to the field of the oil industry and can find application in various kinds of impacts on a productive formation during well operation and, in particular, during its perforation, jamming for the possibility of repairing a well, emergency jamming, intensification of oil production, alignment of the injectivity profile while maintaining reservoir pressure , for example, water flooding, etc. The invention can be applied in various geological conditions and mainly in complex geology, characterized by homogeneity producing formation with a high coefficient of its ruggedness.

Moreover, the term "conservation of reservoir properties" should also be understood as the restoration of altered reservoir properties to their original (initial) state. These changes may be due to imperfection of the opening of the reservoir during the drilling process, as well as any other previous operations that are not part of the method according to this invention.

A known method of preserving the reservoir properties of the near-wellbore zone of a reservoir using a working fluid based on aqueous solutions of mineral salts, used individually or in the form of a mixture thereof (Orlov G.A. et al. Use of inverse emulsions in oil production, Moscow, Nedra, 1991, p. .118).

The method allows you to reliably plug the well. However, after putting the well into operation, a sharp decrease in well productivity is observed. At the same time, it is not possible to restore the reservoir properties of the near-wellbore zone of the producing formation to the level of the initial (initial) properties.

The technical result of the invention is to increase the efficiency of the method due to the possibility of preserving the reservoir properties of the productive formation throughout its thickness and at a distance from the well into the formation, not less than the zone of mudding.

The necessary technical result is achieved by the fact that the method of preserving the reservoir properties of the near-wellbore zone of the reservoir includes putting a working fluid in the well with a complex effect on the bottom-hole zone in an amount not less than the pore volume and / or cracks of the reservoir in the radius of the mud zone from the wellbore, followed by working fluid in the reservoir in the mode of impregnation of this reservoir throughout its thickness, for which the impregnation of the reservoir is carried out at a pressure of opening it vertical vertical cracks and in the cyclic mode of increasing pressure, holding it and dumping, realized in such a way that at the stage of cleaning the bottom-hole zone, the pressure gradient when loading on the reservoir is 1.1-1.8 times less than the pressure gradient when unloading the reservoir.

Moreover:

in the gentle mode of killing the well for repair work in this well, the alkaline runoff of caprolactam production (SCHSPK) or its solution in industrial water with the addition of SHCHSPK at least 0.1% of the volume of technical water is used as the working fluid;

in case of emergency killing of a well, ShchSPK or its solution in industrial water with an addition of ShchSPK at least 0.1% of the volume of technical water is used as working fluid, and an increased technological fluid is placed in the form of a salt solution of one or several types above the working fluid in the wellbore;

when opening the reservoir, ShchSPK or its solution in industrial water with the addition of ShchSPK in the amount of not less than 10% of the volume of technical water is used as the working fluid;

during the intensification of oil production after pushing the working fluid with the addition of SHCHSPK into the reservoir, the well is kept for 12-36 hours, then the pressure on the reservoir is reduced and the reaction products are removed from this reservoir;

in order to maintain reservoir pressure in the reservoir, the working fluid is pumped into this reservoir through at least one injection well using a viscous system based on alkali polycarbonate and sodium silicate, the well is maintained until the injectivity profile of the reservoir is equalized and the displacing agent is injected with additive 0 , 05-1.5% ShchSPK.

SUMMARY OF THE INVENTION

With many known types of impact on the reservoir, i.e. during the initial opening of this formation, its temporary killing for a certain period of time, during the second opening, etc., a water-saturated zone is formed (accumulated) in the near-well zone of the formation. This is because the reservoir is hydrophilic. Due to capillary pressure in pores of small diameter, the liquid will rise along the capillary until the capillary pressure is balanced by the hydrostatic pressure of the column of the risen liquid. As a result of this, water is held in the reservoir by capillary forces and blocks the exit of oil from the reservoir.

When killing a well with aqueous solutions of salts with additives of surface-active substances (surfactants) of the IVV-1 type, they reduce the interfacial tension by several times when aqueous solutions of salts come into contact with oil. However, it is necessary to reckon with the salting-out ability of highly concentrated aqueous solutions of salts to this surfactant. With increasing reservoir temperature, this property is enhanced and well killing using this technology becomes ineffective. In addition, the surfactants used have a narrow spectrum of physicochemical action on the borehole zone of the reservoir. The technology used does not provide an effective impact on the reservoir over its entire thickness, especially in conditions of strong heterogeneity of the reservoir, and on the necessary depth of the borehole zone. As a rule, they are exposed to zones of increased filtration, where the main entrainment of expensive reagents goes, which does not provide the planned result. At the same time, the rest of the matrix of the reservoir, characterized by reduced filtration, remains indifferent both at the stage of impact on the reservoir and at the stage of subsequent commissioning of the well. With such a response of the reservoir with each impact on it, the situation only worsens. From this it becomes clear why the oil recovery rate from wells barely exceeds 35% (with an average value of mobile oil in the reservoir of at least 70%).

In the framework of the present invention provides for the activation of the entire system of the existing and potential filtration of the reservoir, including its micro and macropores, along its entire height and radius within the zone of mudding. This activation is carried out in such a way that after any technological operations in the well, this system can be put into operation in the shortest possible time and at the lowest cost. For this, the borehole zone is activated by supplying the working fluid with a complex effect on the bottomhole zone into the zone of the reservoir. In general, the ideal supply pressure is the opening pressure of natural vertical fractures in the reservoir. With the opening of natural vertical cracks, all interbeds heterogeneous in permeability are combined and provide increased injectivity of the reservoir as a whole along its thickness. However, this pressure precedes the development of full-volume hydraulic fracturing with the formation of horizontal cracks, which in this case is unacceptable, since it is fraught with repeated “familiar” hydraulic fractures even at lower pressures. Therefore, the displacement of the working fluid into the reservoir is carried out in the mode of impregnation, i.e. at the opening pressure of natural vertical cracks (at a pressure of 5-15% less than the hydraulic fracturing pressure) and in the cyclic mode of pressure increase-relief. It is noted that the cyclic nature of the pressure change creates the conditions for the continuous manifestation of elastic forces. In a heterogeneous formation between different layers and interlayers of different permeabilities, hydrodynamic pressure gradients arise, which contribute to the intensification of fluid flows from one layer to another with the forced introduction of fluid into low-permeability sections at lower pressure than is required for the stationary version of the working fluid. The minimal inertia of the response of low-permeable sections to cyclic pressure changes, close to the opening pressure of natural vertical fractures of the formation, with additives in the working fluid with a complex effect on the bottom-hole zone, namely, the alkaline runoff of caprolactam production (SHSCP), is noted. ShchSPK (TU 113-03-488-84) is a dark brown opaque liquid without mechanical impurities, low toxicity, with a density of 1.1-1.2 g / cm ³ , pH 10-13 and a freezing temperature of -25 ° С . Contains 18-30% sodium adipate, up to 10 resins and up to 0.8% cyclohexanol. It is highly soluble in water, has alkaline properties, and properties of surface-active substances (surfactants). As a result of the application of alkaline-sand clay, a complex effect on the near-wellbore zone of the formation is achieved, namely, they dissolve asphalt-resin-paraffin deposits (AFS), reduce surface tension at the phase boundaries, and prevent colmatization, including salt deposits, and clay swelling. Facilitates the process of killing and subsequent well development, including due to the possibility of controlling the specific gravity. The universal properties of SHCHSPK in combination with the described technology of its feeding into the reservoir provide processing of the entire matrix of the reservoir with all its macro- and micropores. This creates a reliable system of hydraulic shutter reservoir, necessary, for example, when killing the reservoir. At the same time, the impact on all kinds of pores of the formation during the time of quenching of SHCHSPK with its universal properties provides the preparation of these pores for subsequent drainage of oil throughout the thickness of the formation. In this case, the time of putting the well into operation after killing it can be reduced to several hours (in comparison with several days according to the known method). This ensures the preservation of the filtration properties of the reservoir in their expanded interpretation (restoration of these properties to the original) due to the dispersion of the asphalt-resin-paraffin formations and wedging of the borehole zone. This provides significant savings in time and money in comparison with the known method in which putting a well into operation takes several days with an irrevocable partial loss of the filtration properties of the reservoir.

At the initial stage - the stage of cleaning the bottom-hole zone, the cyclic mode is ensured in such a way that the pressure gradient during loading on the reservoir is 1.1-1.8 times less than the pressure gradient during unloading of the reservoir. It is this regime that prevents the productive formation from being compacted by the products of mudding and their entry into the far zone, from where their removal is a problem with a considerable degree of complexity.

A feature of the secondary opening of the reservoir using the present invention is that this opening is carried out, for example, using explosives (BB) with high gas evolution and a low detonation velocity to increase the duration of the explosive pulse, for example ammonium nitrate explosives (such as igdanite). At the same time, such an explosion power is selected at which the opening of natural vertical cracks occurs without gas and gas fracturing of the reservoir. The gaseous products of the explosion form a so-called gas bubble, which in the hydrodynamic medium pulsates in auto mode for a sufficiently long time. This ensures the subsequent delivery of the working fluid with SCHPK to the reservoir in the mode of impregnation of this layer throughout its thickness, i.e. at the opening pressure of natural vertical cracks and in non-stationary (cyclic) mode of pressure increase-relief.

The non-stationary mode of the impregnation pressure of the reservoir ensures the connection to the zones of active drainage of low-permeability zones of difficult drainage with the saturation of all zones of alkali-ferrous clay, reinforcing the hydrophobization of these zones, wedging and dispersion of paraffin deposits from cycle to cycle. As a result, during the subsequent call of oil inflow from the reservoir, the latter ensures the removal of all reaction products and oil recovery by the entire system of macro- and micropores.

A feature of the method for the case of its use to maintain reservoir pressure in the reservoir (during development) is the use of rims of sodium silicate or a solution of calcium chloride. These rims can be separated from the rims of the working fluid (in the form of ShchSPK or the working fluid with additives ShchSPK) other rims, such as fresh water. This creates the necessary conditions for mixing solutions of alkali hydrogen chloride and calcium chloride or sodium silicate. The well can withstand the necessary time. The result is a thickened mixture with the properties of a viscoelastic fluid that retains all the necessary properties by the method and provides an additional property of alignment of the injectivity profile in the borehole zone. A displacing agent, for example, water with the addition of 0.05-1.5% ShchSPK, is injected into this well, which is already essentially an injection one.

The method is as follows.

In the well against the reservoir, a working fluid with the addition of SCHSPK is placed. The value of the additives ShchSPK choose depending on the impact on the reservoir. For example, in a sparing mode of killing a well, ShchSPK or its solution is taken with a ShchSPK amount of 0.1-1.5% of the volume of process water (working fluid). The volume of the working fluid is taken in the volume of pores and / or cracks in the reservoir in the zone of mudding (for example, within a radius of 0.3-2.0 m from the wellbore). Then push the working fluid into the reservoir in the mode of impregnation of the reservoir throughout its thickness. For this, preliminary, the opening pressure of natural vertical fractures of the reservoir is established in neighboring wells or rock samples. Actually impregnation of the reservoir is carried out, for example, at a pressure less than the opening pressure of natural vertical cracks by 5-15% and in a cyclic mode of pressure increase-relief. The cyclic exposure mode at the stage of cleaning the bottom-hole zone is carried out in such a way that the pressure gradient when loading on the reservoir is 1.1-1.8 times less than the pressure gradient when unloading the reservoir. For this, for example, the dynamics of pressure buildup and depressurization, as well as holding the well under high pressure and low pressure, are worked out under this condition. In different geological conditions and with different types of working fluid, the response of the well is different.

After that, the planned impact on the reservoir is carried out, for example, perforation or killing for the possibility of repairing the well, or emergency killing, or intensification of oil production, or alignment of the injectivity profile while maintaining reservoir pressure, for example, water flooding, etc.

Claims (6)

1. A method of preserving the reservoir properties of the near-wellbore zone of the reservoir, including placing in the well of the working fluid — alkaline runoff of caprolactam — SHCHPK or its solution in an amount not less than the pore volume and / or cracks of the reservoir in the radius of the mud zone from the well bore, followed by working fluid into the reservoir in the mode of impregnation of this reservoir throughout its thickness, for which the impregnation of the reservoir is carried out at a pressure of opening of its natural vertical cracks and in the cyclic mode of increasing pressure, holding it and dumping it, realized in such a way that at the stage of cleaning the bottom-hole zone, the pressure gradient when loading on the reservoir is 1.1 - 1.8 times smaller than the pressure gradient when unloading the reservoir. 2. The method according to claim 1, characterized in that in a sparing mode of killing the well for repair work in this well, ShchSPK or its solution in industrial water with the addition of ShchSPK at least 0.1% of the volume of technical water is used. 3. The method according to claim 1, characterized in that in case of emergency jamming of a well ShchSPK or its solution in industrial water with the addition of ShchSPK not less than 0.1% of the volume of technical water, and a heavier technological fluid is placed over the working fluid in the wellbore in the form salt solution of one or more species. 4. The method according to claim 1, characterized in that when opening the reservoir, ShchSPK or its solution in industrial water with the addition of ShchSPK in an amount of at least 10% of the volume of technical water is used. 5. The method according to claim 1, characterized in that during the intensification of oil production after selling the working fluid with the addition of SCHSPK to the reservoir, the well is kept for 12 to 36 hours, then the pressure on the reservoir is reduced and the reaction products are removed from this layer. 6. The method according to claim 1, characterized in that in order to maintain reservoir pressure in the reservoir, the working fluid is forced into this reservoir through at least one injection well using a viscous system based on alkali polycarbonate and sodium silicate, the well is maintained until leveling the injectivity profile of the reservoir and inject the displacing agent with the addition of 0.05-1.5% ShchSPK.