RU2103487C1 - Method for development of tectonically screened oil-gas deposit - Google Patents

Abstract

FIELD: oil and gas production industry. SUBSTANCE: this relates to development of deposit which is tectonically screened into separate sections with no hydrodynamic connection between wells. Method implies cyclic injection of liquid into producing well to cause hydraulic breakage of rock mass. Liquid is of higher density as compared with density of bed fluid. After period of gravitational and capillary displacement, oil is recovered from same producing wells with reduction of bottom-hole pressure to minimal possible. EFFECT: high efficiency. 1 tbl

Description

 The invention relates to the development of oil and gas deposits and can find application in the oil industry in the development of tectonically shielded into separate blocks of oil deposits in the absence of hydrodynamic communication between wells.

 There is a method of developing an oil reservoir by a system of producing and injection wells, with the help of which oil is produced in a fountain way while maintaining reservoir pressure by injecting a liquid and gaseous agent into the formation using injection wells [1].

 The disadvantages of this method include the need to maintain reservoir pressure by injecting large volumes of water and the mandatory presence of hydrodynamic communication between wells.

 A known method of developing an oil reservoir using water flooding by cyclic selective injection of water into the formation through a system of injection wells and selection of formation fluid by producing wells in a fountain way. Selective water injection is carried out cyclically depending on the reservoir properties of the formation [2].

 The method involves the production of oil and gas from reservoirs of heterogeneous permeability in the presence of a hydrodynamic connection between all wells and in the presence of filtration of displaced fluid and injected water in the reservoir.

 There is a method of developing oil fields [3], which consists in injecting gas with a maximum flow rate into the well and extracting oil from the same well, the gas being pumped through the upper perforation holes of the well in volumes equivalent to the volumes of oil produced through the lower perforations of the same well. The principle of production is based on the use of gravitational forces, which make gas and oil migrate up and down the inclined formation to the horizontal plane.

 The disadvantages of this method are the use of expensive compressor equipment for pumping gas at maximum costs, and in the presence of a horizontally located reservoir, the method of extracting oil will not be effective.

 Closest to the invention is a method of developing oil deposits, based on gravity production of viscous oil through a single horizontal well, using steam and soluble gas [4].

 High-viscosity oil is produced by injecting steam and solvent gas into the formation through the upper perforations of the horizontal part of the wellbore. High-viscosity oil is heated up and saturated with gas. Heated gas-saturated oil under the pressure of gravity falls to the bottom of the formation, collecting around the horizontal wellbore, and then penetrates into the well through the lower drainage channel of the casing string, from which, under the influence of pressure in the formation created with a working agent, oil is extracted to the day surface .

 The disadvantages of this method of developing deposits containing highly viscous oil are the use of expensive underground and ground equipment, including the need to drill horizontal wells; the layer must lie at a shallow depth and must have high porosity and permeability.

 The purpose of the invention is the development of oil and gas deposits having heterogeneous hydrodynamically isolated on separate collector blocks in the absence of a supply circuit.

 For this, cyclic injection of fluid into production wells is carried out. The fluid is injected with a higher density compared to the density of the reservoir fluid to displace the latter from the heterogeneous reservoir up to the fracturing pressure of the rocks. After a period of gravity and capillary replacement, they are taken from the same wells with a decrease in pressure at the bottom of the wells to the minimum possible. The end time is the period of gravity and capillary replacement is determined by the steady-state pressure at the wellhead or the oil level in the annulus. The fluid used is any fluid having a higher density compared to the density of the reservoir fluid and not miscible with it. As such a liquid may be water, brine, etc.

The method is carried out using the following steps:
determine the well stock in the field with no hydrodynamic connections;
pump fluid of increased density compared with the density of the reservoir fluid;
close the well for the time of gravitational and capillary replacement;
open a well for oil after completion of the replacement process;
fluid is again injected into the formation up to the fracturing pressure of the rocks;
close the well for the time of gravity and capillary replacement, after which the oil is again taken until the pressure drops to a minimum.

 Further oil recovery from the formation is repeated in the same sequence.

An example of a specific implementation. Permo-Triassic and Filipov oil deposits in the Astrakhan gas condensate field, which lie above the Bashkir gas condensate deposit, are complicated by tectonic disturbances. For this reason, they are fractured and shielded in separate blocks. Studies conducted in the wells of Permo-Triassic and Filipov deposits showed a complete absence of hydrodynamic connection between them. The initial short-term flow rates for wells 59, 313, 431, 929 and others ranged from 150 to 300 m ³ / day. The wells worked from a few weeks to 2 to 3 months, after which the selection of oil by the fountain method ceased.

The studies at well 59 during oil production from the Permian-Tatian deposits showed that the hydraulic conductivity of the formation is reduced, which indicates the closure of cracks in the bottom-hole zone of the formation. From that moment, the well stopped gushing with oil, continuing to work with gas at a decreasing flow rate. The value of the open porosity of the reservoir, according to studies of core samples of Permo-Triassic and Filipov deposits, is in the range of 0.04 - 0.06. The permeability of the collector matrix is of the order of 0.001 μm ² . Wells that opened the Philippov horizon and separated from each other at a distance of 300 m showed a complete lack of hydrodynamic connection between them. After stopping the flowing of the well, the reservoir pressure practically did not recover. All this testified to shielding to individual blocks of the reservoir and did not allow the use of known methods for developing oil and gas deposits.

Under these conditions, a test operation of the reservoir was carried out by gravitational and capillary replacement of reservoir oil and gas with a liquid with a higher density compared to the density of the reservoir fluid. Artesian water with a density of 1020 kg / m ³ was used as a substitution fluid in well 929, and brine with a density of 1200 kg / m ^{3 was used} in well 313. The volumes of injected fluid varied over a wide range from 20 to 600 m ³ . After each injection of water or brine, the well was left alone for the duration of the replacement process.

 After conducting pilot water injections and oil extraction from the same wells, the optimal replacement time was determined, which amounted to 10 days.

 Data on water injection and oil production from the Philippov horizon obtained from two wells are shown in the table.

 Actual economic effect on well 313 as of 01.01.96 amounted to 130 thousand rubles. per 1 t. of extracted oil.

 Thus, the proposed model of gravitational and capillary replacement to carry out the process of developing deposits that cannot be carried out by known methods.

Claims (1)

 A method of developing a tectonically shielded oil and gas reservoir, including the cyclic injection of fluid into wells located on the reservoir, the selection of reservoir fluid from the same wells in a fountain or mechanized manner after periods of gravity replacement, characterized in that the development is carried out by producing wells into which a higher density fluid is injected compared with the density of the reservoir fluid to displace the latter from the heterogeneous reservoir to the fracture pressure of the rocks, and after and gravity and capillary substitution take oil from the same wells with a decrease in pressure on the bottom of the wells to the minimum possible.

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