WO2020139167A1

WO2020139167A1 - Method for increasing oil recovery from a carbonaceous oil formation by building up formation pressure

Info

Publication number: WO2020139167A1
Application number: PCT/RU2019/050215
Authority: WO
Inventors: Шафагат Фахразович Тахаутдинов; Фанис Хаматович ВАЛИЕВ; Раис Салихович ХИСАМОВ; Владимир Александрович КАЛАБУХОВ; Дмитрий Александрович МАРУНИН
Original assignee: Общество с ограниченной ответственностью "Фонд НДК"
Priority date: 2018-12-27
Filing date: 2019-11-15
Publication date: 2020-07-02
Also published as: RU2708924C1

Abstract

A method comprises selecting a well with a current formation pressure of a maximum of 0.6·Р, wherein the operations are carried out in two stages. In the first stage, a working fluid – water with a total salinity of 0.8-1.2 of the total salinity of the formation water – is injected into the well, injection being carried out until the well-head pressure increases to a value of a maximum of 0.2·Ρ, then a 1-10% solution of a surfactant in the working fluid is injected under a well-head pressure of (0.2-0.4)·Ρ, after which working fluid is again injected until the well-head pressure increases to 0.4·Ρ. Soaking is carried out for a maximum of 48 hours. If the well-head pressure drops, working fluid is injected until the pressure increases to 0.4·Ρ. In the second stage, a complex acid composition is injected with the addition of surfactant, water, acid-rock reaction retarders, clay stabilisers, and reagents for producing self-deflecting acid compositions and/or acid emulsions depending on the filtration properties of the formation. Injection is carried out with a well-head pressure of a maximum of 0.45·Р, and the complex acid composition is driven by working fluid at a well-head pressure of a maximum of 0.45·Р. Soaking is carried out for a maximum of 24 hours.

Description

A method of increasing oil recovery carbonate oil reservoir with

reservoir pressure recovery

The invention relates to the oil industry and may find application to increase oil recovery of a carbonate oil reservoir with the restoration of reservoir pressure and conducting complex acid treatment of the reservoir.

A known method of acid treatment of the near-wellbore zone, including at the first stage injection into the well of a 10-15% aqueous solution of hydrochloric acid in a volume of 0.25-0.5 m ³ per 1 linear m perforated formation thickness, at the second stage injection 10 -15% aqueous hydrochloric acid solution with an inhibitor of the reaction of acid with rock in the amount of 2-5% of the volume of the acid solution in the injection volume at the rate of 1 -1, 5 m ³ per 1 running m of perforated formation thickness at an initial pressure equal to the final injection pressure at the previous stage, oil sales in the amount of 5-15 m ³ at an initial pressure equal to the final injection pressure at the previous stage, technological exposure for 16-48 hours and putting the well into operation (RF patent N ° 2490444, class E21 In 43/27, publ. 08/20/2013).

The closest in technical essence to the proposed method is a method for processing the near-wellbore zone, which includes, at the first stage, injection of a 0.5-1, 5% solution of surfactant in produced water in a volume of 100-200 m ^3; at the second stage, an injection of 10-15 % aqueous solution of hydrochloric acid in a volume of 0.25-0.5 m ³ per 1 linear meter of perforated reservoir power at an initial pressure equal to the final injection pressure in the previous stage; in the third stage, the injection of 10-15% aqueous hydrochloric acid solution with a moderator of the reaction of acid with rock in the amount of 2-5% of the volume of the acid solution in the injection volume at the rate of 1 -1, 5 m ³ per 1 linear meter of perforated reservoir power at an initial pressure equal to the final injection pressure in the previous step, the injection of produced water in a volume of 100-200 m ³ at an initial pressure equal to the final injection pressure at the previous stage, technological exposure for 16-48 hours and putting the well into operation. Previously, they can perform injection of produced water into the well to increase the injection pressure at the wellhead to 1-2 MPa (RF patent N ° 2494246, class E21 B 43/27, publ. September 27, 2013 - prototype).

A common drawback from the application of known methods is the low oil recovery due to heterogeneity of the reservoir and uneven injection of the components specified in the methods.

In the proposed invention solves the problem of increasing oil recovery carbonate oil reservoir. The problem is solved in that in a method for increasing oil recovery of a carbonate oil reservoir with restoration of reservoir pressure, which includes injecting solutions of a surfactant — surfactant, acid, acid-rock retarders, acid rejectors, water, and process shutter — according to the invention, select a well, operating an oil-saturated formation with a current reservoir pressure of not more than 0.6- P, where P is the initial reservoir pressure, operations are carried out in two main sequential stages, the first of which is aimed at restoring the reservoir pressure, at which 2-10 m are injected into the well ³ / hour working fluid - water with a total mineralization of 0.8-1, 2 from the total mineralization of produced water, injection is carried out until the wellhead pressure rises to a value of not more than 0.2-P, then it is pumped under wellhead pressure (0.2-0 , 4) P solution of 1-10% surfactant in the working fluid, the total volume of injected surfactant solution is determined from the calculation of 0.5-5.0 m ³ per meter of effective oil-saturated thickness of the reservoir, after which the working fluid is again pumped up to increase in wellhead pressure up to 0.4-P, technological exposure is carried out for no more than 48 hours, during which the wellhead pressure drop is analyzed and, when it falls, the working fluid is pumped up to wellhead increase pressures up to 0.4-P, the second stage aims to influence the rock skeleton by injecting a complex acid composition with the addition of surfactants, water, inhibitors of the acid-rock reaction, clay stabilizers, reagents to create self-deflecting acid compositions and / or acid emulsions the composition and concentration of which is determined by laboratory studies depending on the filtration properties of the formation, and the concentration of pure acid in the complex acid composition is set at 12-20%, injection is carried out at wellhead pressure of not more than 0.45-P, the volume V _{K of the} injected complex acid composition is determined at the rate of 1 -7 m ³ per meter effective oil of the given thickness of the formation, they push through the complex acid composition with a working fluid with a volume of (0.2-1.0) · V _K under wellhead pressure of not more than 0.45-P, after which technological aging is carried out for no more than 24 hours, the well is developed by swabbing, or the use of deep-pumping equipment, they put the well into operation, operations to increase the oil recovery of the carbonate oil reservoir in this well are repeated every 2-4 years.

SUMMARY OF THE INVENTION

The oil recovery of a carbonate oil reservoir is significantly affected by the energy state of the reservoir and the reservoir impact system. Existing technical solutions do not fully allow you to most effectively complete this task. In the proposed invention solves the problem of increasing oil recovery carbonate oil reservoir. The problem is solved as follows.

The method is implemented as follows. A well operating a carbonate oil-saturated formation with a current reservoir pressure of not more than 0.6-P is selected at the field’s deposits, where P is the initial reservoir pressure. The operations are carried out in two main sequential stages with the extraction of deep-well pumping equipment, or without its extraction.

The first stage is aimed at restoring reservoir pressure. In the well pumped with a flow rate of 2-10 m ³ / hour, the working fluid is water with a total mineralization of 0.8-1.2 from the total mineralization of produced water. The injection is carried out until the wellhead pressure rises to a value of not more than 0.2-R.

According to studies, at a current reservoir pressure of more than 0.6-P, the operations of the proposed method is characterized by a smaller increase in oil recovery compared to the prototype. In most cases, injection of a working fluid with a flow rate of more than 10 m ³ / hour leads to the opening of natural or the formation of new fractures in the formation, which increases the water cut of the product and reduces oil recovery, while less than 2 m ³ / hour increases the reservoir pressure only a few meters around the well. Injected water (working fluid) with the indicated total salinity is used as a deflecting component in acid treatments. When the working fluid is injected into the well, the highly permeable part of the formation is filled, the pressure field is redistributed, and gravitational displacement of the introduced water by oil from unreached areas of the formation. In addition, favorable conditions are created for large-volume treatment of the formation with acid. Injection of water with a total salinity of less than 0.8 of the total salinity of the formation water of a given formation leads to swelling and / or migration of clay particles, while the injection of a working fluid with a total salinity of more than 1, 2 of the total salinity of the formation water of a given formation leads to precipitation of salts in bottomhole formation zone. In both cases, the permeability of the reservoir decreases, which ultimately reduces the increase in oil recovery from the application of the method. When pumping a working fluid to increase wellhead pressure to a value of less than 0.2-P, the efficiency of subsequent acid injection is absent due to the lack of pressure redistribution.

Next, a solution of 1-10% surfactant in the working fluid is pumped under wellhead pressure (0.2-0.4) P. The total volume of injected surfactant solution is determined from the calculation of 0.5-5.0 m ³ per meter of effective oil-saturated thickness of the reservoir.

According to research work, when injecting surfactants such as Sulfen-35, for example, a multiple increase in the permeability of a reservoir model with residual oil saturation was observed when using a 1 -10% aqueous solution of a composite surfactant. “Sulfene-35” allows to increase the permeability of the formation, to destroy water-oil emulsions and to clear the pore space of the formation of oil film and asphalt-resinous deposits. When the surfactant concentration in the solution is less than 1%, almost no additional increase in oil production was obtained, then as with more than 10% - did not lead to a further increase in the efficiency of the method. When injecting a surfactant solution under wellhead pressure of less than 0.2-P, the penetration of the solution into the formation is insignificant, while when more than 0.4-P leads to the opening of natural or the formation of new fractures in the formation. With the total volume of injected surfactant solution at the rate of less than 0.5 m ³ per meter of effective oil-saturated thickness of the reservoir, there is practically no increase in oil production, while with more than 5.0 m ^{3 the} implementation of the measure is not economically effective due to the lack of further improvement of the method's efficiency.

After that, the working fluid is again pumped up to increase in wellhead pressure to 0.4- R. The process is held for no more than 48 hours, during which the wellhead pressure drop is analyzed and, when it falls, the working fluid is pumped up to wellhead pressure increase to 0.4- R.

According to calculations, when injecting the working fluid and increasing wellhead pressure to a value of more than 0.4-P, there is a risk of hydraulic fracturing, which reduces the increase in oil production. Technological exposure after injection of the working fluid is necessary for the redistribution of pressures. With a duration of technological exposure of more than 48 hours, further necessary redistribution of pressure does not occur. The pumping of the working fluid to increase the wellhead pressure to 0.4-P is necessary to restore pressure in the reservoir, because when it decreases, the subsequent injection of acid does not lead to uniform coverage of the formation by exposure.

The second stage aims to influence the skeleton of the rock. To do this, they carry out the injection of a complex acid composition (based on hydrochloric or other acids) with the addition of a surfactant (for example, Sulfen-35), water (for example, wastewater), inhibitors of the reaction of the acid with the rock (for example, TXP-1), stabilizers clays (for example, potassium chloride), reagents for creating self-releasing acid compositions (for example, VDA or OilSeeker technology) and / or acidic emulsions (for example, ITPS-010K solvent and ITPS-804E emulsifier can be used). The composition and concentration of additives is determined by laboratory studies, depending on the filtration properties of the formation. The acid retarder THP-1 is designed to produce a prolonged inhibited hydrochloric acid with respect to carbonate rocks. The concentration of pure acid in the complex acid composition is set at the level of 12-20%. The injection is carried out at a wellhead pressure of not more than 0.45-R. The volume V _{K of the} injected complex acid composition is determined at the rate of 1-7 m ³ per meter of effective oil-saturated thickness of the formation.

According to studies, at an acid concentration of less than 12%, the reaction of acid with most carbonate rocks is minimal, and at more than 20%, the risk of negative effects on well equipment increases. Injection of a complex acid composition at wellhead pressure greater than 0.45-P leads to the discovery of natural or the formation of new cracks in the reservoir and the injection of the entire volume of acid into these cracks. Injection of a complex acid composition in a volume of less than 1 m ³ per meter of effective oil-saturated thickness of the formation leads to low formation coverage, and at more than 7 m ³ per meter of effective oil-saturated thickness of the formation, it makes no sense, because further increase in oil recovery is not observed.

Next, the complex acid composition is pressed through with a working fluid of volume (0.2-1, 0) L / _c under wellhead pressure of not more than 0.45-R. Technological exposure is carried out for no more than 24 hours. The well is developed by swabbing, or using deep pumping equipment . They put the well into operation.

According to studies, the sale of a complex acid composition with a working fluid in a volume of less than 0.2 V _K does not lead to the deep penetration of the complex acid composition into the reservoir, and in a volume of more than V _{K it} leads to a breakthrough of the working fluid and a decrease in the selling efficiency. When a complex acid composition is sold with a working fluid under wellhead pressure of more than 0.45-P, natural cracks open or new cracks form, which reduces oil recovery.

Operations to increase the oil recovery of the carbonate oil reservoir in this well are repeated every 2-4 years. According to calculations, repeating operations to increase oil recovery of a carbonate oil reservoir with a frequency of more than 2 years does not make sense, because for most reservoirs, the effect of operations does not have time to stop, and for more than 4 years, the rate of oil recovery is quite strongly reduced, which leads to a decrease in oil recovery.

The operation is carried out until the full economically viable development of oil reserves in the well drainage zone.

The result of the implementation of this method is to increase oil recovery carbonate oil reservoir.

Examples of specific performance of the method

Example 1. An oil-saturated carbonate stratified layer of a field deposit has a total thickness of 23 m, an effective oil-saturated thickness of 12 m and is uncovered by vertical production wells. The roof of the formation lies at a depth of 810 m, the initial reservoir pressure is P = 8.5 MPa, the average reservoir permeability is 40 mD, and the oil viscosity is 50 mPa-s. The total mineralization of produced water is 220 g / l. A well operating the specified carbonate oil-saturated formation with a current reservoir pressure of 0.6-8, 5 = 5.1 MPa is selected for this deposit.

In this well, downhole pumping equipment is removed. Operations are carried out in two main sequential stages.

Stage I - restoration of reservoir pressure. The working fluid is pumped into the well at a flow rate of 2 m ³ / h. As the working fluid, water is used with a total mineralization of 0.8-220 = 176 g / l. The injection is carried out until the wellhead pressure rises to values of 0.2-8, 5 = 1.7 MPa. Next, injected under wellhead pressure of 0.2-8, 5 = 1, 7 MPa, a solution of 1% sulfen-35 surfactant in the working fluid. The total volume of injected surfactant solution is determined from the calculation of 0.5 m ³ per meter of effective oil-saturated thickness of the reservoir, i.e. pumped in a volume of 0.5-12 = 6 m ³ . After that, the working fluid is again pumped until the wellhead pressure rises to 0.4-8, 5 = 3.4 MPa. Technological exposure is carried out for 48 hours. During this period, the wellhead pressure drop is analyzed. As a result of technological exposure, wellhead pressure decreased to 2.2 MPa. The working water is pumped until the wellhead pressure is restored to 0.4-8, 5 = 3.4 MPa.

Stage II - impact on the skeleton of the breed. Complex acid composition is injected. As a result of core laboratory studies, the optimal composition of the complex acid composition with the following concentrations of components, mass. :

- hydrochloric acid - 12%;

- surfactant "Sulfen-35" - 3%;

- inhibitor of the reaction of acid with breed THP-1 - 5%;

- clay clay potassium chloride stabilizer - 1%;

- additives for creating a self-deflecting acid composition FLAXOCOR 210

- 2%;

- additives to create an acidic emulsion, solvent ITPS-010K - 10%, emulsifier ITPS-804E - 4%;

- produced water with a total salinity of 220 g / l - 63%.

Injection is carried out at wellhead pressure of 0.45-8.5 = 3.8 MPa. The volume V _{K of the} injected complex acid composition is determined at the rate of 1 m ³ per meter of effective oil-saturated thickness of the formation, i.e. injected in a volume of V _K = 1 - 12 = 12 m ³ .

Next, the complex acid composition is forced through with a working fluid of 0.2 V _K = 0.2-12 = 2.4 m ³ under wellhead pressure of 0.45-8.5 = 3.8 MPa. Carry out technological exposure for 24 hours. Develop the well by swabbing. Operations to increase the oil recovery of the carbonate oil reservoir in this well are repeated every 2 years.

Exploitation is carried out until the full economically viable development of reserves in the well drainage zone.

Example 2. Perform as example 1. The reservoir is represented by other filtration characteristics. In this well, operations are also carried out in two consecutive stages, but without removing the downhole pumping equipment.

I stage. The working fluid is pumped into the well at a flow rate of 10 m ³ / h. As the working fluid, water is used with a total salinity of 1, 2-220 = 264 g / l. The injection is carried out until the wellhead pressure rises to a value of 0.2-8, 5 = 1.7 MPa. Next uploaded under wellhead pressure of 0.4-8, 5 = 3.4 MPa, a solution of 10% Sulfen-35 surfactant in the working fluid. The total volume of injected surfactant solution is determined from the calculation of 5 m ³ per meter of effective oil-saturated thickness of the reservoir, i.e. pumped in a volume of 5-12 = 60 m ³ . After that, the working fluid is again injected until the wellhead pressure rises to 0, 4-8, 5 = 3.4 MPa. Technological exposure is carried out for 48 hours. During this period, the wellhead pressure drop is analyzed. As a result of technological exposure, wellhead pressure at a value of 3.4 MPa did not decrease.

II stage. The complex acid composition is injected, similarly to Example 1, but 20% hydrochloric acid is used. Accordingly, the mass fraction of water in the complex acid composition is 55%. The complex acid composition is injected at wellhead pressure of 0.45-8.5 = 3.8 MPa. The volume V _{K of the} injected complex acid composition is determined from the calculation of 7 m ³ per meter of effective oil-saturated thickness of the formation, i.e. injected in a volume of V _K = 7-12 = 84 m ³ . Next, the complex acid composition is forced through with a working fluid of volume 1, 0-V _K = 1 -84 = 84 m ³ under wellhead pressure of 0.45-8.5 = 3.8 MPa. Carry out technological exposure for 24 hours. Develop a well using deep-pumping equipment. Operations to increase the oil recovery of the carbonate oil reservoir in this well are repeated every 4 years.

As a result of the well’s operation, which was limited to reaching the water cut of the well to 98%, 23.8 thousand tons of oil was produced, the oil recovery factor (CIN) of the formation drainage section of this well was 0.367 units. According to the prototype, ceteris paribus, 18.3 thousand tons of oil was produced, oil recovery factor amounted to 0.282 units. The increase in recovery factor by the proposed method is 0.085 units

The proposed method allows to increase the oil recovery coefficient of the reservoir by restoring the reservoir pressure, exposing the rock skeleton to the injected compositions and increasing the permeability of the formation.

The application of the proposed method will solve the problem of increasing oil recovery carbonate oil reservoir.

Claims

CLAIM

A method of increasing oil recovery of a carbonate oil formation with restoration of reservoir pressure, including the injection of solutions of a surfactant - surfactant, acid, inhibitors of the reaction of the acid with the rock, diverters of acid compositions, water and technological exposure, characterized in that they select a well operating an oil-saturated formation with the current reservoir pressure of not more than 0.6-P, where P is the initial reservoir pressure, operations are carried out in two main sequential stages, the first of which is aimed at restoring the reservoir pressure, at which working fluid is pumped into the well at a rate of 2-10 m ³ / h - water with a total mineralization of 0.8-1, 2 from the total mineralization of produced water, injection is carried out until the wellhead pressure rises to a value of not more than 0.2-P, then it is pumped under wellhead pressure (0.2-0.4) P solution 1-10% surfactant in the working fluid, the total volume of injected surfactant solution is determined from the calculation of 0.5-5.0 m ³ per meter of effective oil thickness of the reservoir, after which the working fluid is again pumped up to the wellhead pressure increase to 0.4-P, the process is held for no more than 48 hours, during which the wellhead pressure drop is analyzed and, when it falls, the working fluid is pumped up to the wellhead pressure up to 0,4- P, the second stage aims at influencing the rock skeleton, for which a complex acid composition is injected with the addition of surfactants, water, inhibitors of the reaction of the acid with the rock, clay stabilizers, reagents to create self-deflecting acid compositions and / or acid emulsions, composition and the concentration of which is determined by laboratory tests depending on the filtration properties of the formation, and the concentration of pure acid in the complex acid composition is set at 12-20%, injection is carried out at wellhead pressure of not more than 0.45-P, the volume V _{K of the} injected complex acid composition is determined at the rate of 1-7 m ³ per meter of effective oil-saturated thickness of the reservoir, selling the complex acid composition is poured with a working fluid with a volume of (0.2-1, 0) V _K under wellhead pressure of not more than 0.45-P, after which technological exposure is carried out for no more than 24 hours, the well is developed by swabbing, or using deep-well pumping equipment , put the well into operation, operations to increase oil recovery of the carbonate oil reservoir in this well are repeated every 2-4 years.