RU2386795C1 - Development method of oil field with water-oil zones - Google Patents

Abstract

FIELD: oil-and-gas production.

SUBSTANCE: method includes perforation of casing string in oil-saturated zone of producing stratum, installation of packer, installation in well of deep-well working barrel, pumping of oil from oil-saturated zone and sampling of strata fluid from well on surface. Perforation of casing string in oil-saturated area of producing formation is implemented with separation of producing formation for two part. It is installed packer at a distance from two to five metres higher than water-oil contact. Then it is installed deep-well working barrel of double-acting over producing formation so that suction valve of pump is located higher than installed packer in top part of producing formation. In the process of extraction of strata liquid part of withdrawn oil from top part of producing formation it is pumped into producing stratum lower than packer.

EFFECT: oil-extraction increasing, increasing nonaqueous operation period of well ensured by reduction of watering of extracted production, increasing of coefficient of comprehension by generation of oil stores, prevention of coning and reduction of incentive consumptions for extraction of oil ensured by overlap of function producing and injecting wells.

1 dwg, 1 ex

Description

The proposed method relates to the oil industry, in particular to the field of development of oil deposits with oil-water zones.

A known method for the development of oil deposits in carbonate reservoirs of fracture-pore type (patent RU No. 2204703, IPC E21B 43/22, publ. 05.20.2003). The method involves drilling production and injection wells, product selection through production wells, waterproofing work in production wells by injection of a plugging reagent of selective action, followed by treatment of the bottomhole zone of the well with an acid composition. Then the batch injection of said plugging reagent is carried out with its pushing to a certain distance, and the bottom-hole zone of the well is treated with an acid-oil mixture with fracturing of the formation blocks through a system of fractures, the same mixture being used as a squeezing fluid.

The disadvantage of this method is the reduction in oil production as a result of a drop in reservoir pressure in the reservoir and a rapid increase in water cut of the product. In addition, the method provides for stopping the process for conducting waterproofing work in production wells.

There is a method of developing a waterlogged oil reservoir (patent RU No. 2179234, IPC E21B 43/00, published February 10, 2002), according to which a vertical well is first drilled, the reservoir is opened by perforation, oil is extracted until the reservoir is depleted, then horizontal lateral is drilled trunk. The entry point of the horizontal wellbore is located below the dynamic fluid level in the well. The same reservoir is perforated in the sidetrack. Then, a double-acting pump is installed in the vertical shaft (patent RU No. 63864, IPC E21B 43/38, published on June 10, 2007, Bull. No. 16) so that the oil pump intake is positioned higher than the side-entry point, and the pump intake for water - below this point. The pump is equipped with a shank with a packer, which is installed in the interval from the entry point to the roof of the reservoir in a vertical shaft. The water that came with the oil from the lateral horizontal well is pumped into the same reservoir through a vertical well without raising it to the surface.

The disadvantages of this method are the low efficiency in the operation of watered deposits, cone formation, contributing to the rapid watering of the produced products.

The closest in technical essence to the proposed one is a method of oil production in the late stages of development, including perforation of the casing in the oil-saturated zone of the reservoir, installing a packer, installing a downhole pump in the well, pumping oil from the oil-saturated zone and taking formation fluid from the well to the surface (patent RU No. 2175377, IPC E21B 43/00, published on October 27, 2001). The method provides for perforation of the casing string in the oil and water zones of the formation. Then, the packer is installed in the casing at the level of the oil-water contact, and during production, a portion of the well fluid from the oil-saturated zone of the formation is pumped into the water zone of the formation to form a rim from the oil-water emulsion in the area of perforation of the water zone of the formation, which screens the water.

The disadvantage of this method is that for deposits in the late stages of development is characterized by a significant water cut in the layers. In addition, part of the oil is pushed under the reservoir into the aquifer of the reservoir. This reduces the coverage of formations by water flooding and oil recovery from them. The presence of fractured rocks increases the likelihood of water entering the intervals of perforation and complete watering of the produced products.

The technical objective of the proposed method for developing an oil reservoir with oil-water zones is to increase oil recovery, increase the waterless period of a well by reducing the water cut of produced products, increasing the coverage ratio by producing oil reserves, preventing cone formation and reducing material costs for oil production by combining the functions of an oil and an injection well .

This problem is solved by the method of developing an oil reservoir with water-oil zones, including perforation of the casing in the oil-saturated zone of the reservoir, installing a packer, installing a downhole pump in the well, pumping oil from the oil-saturated zone, and taking formation fluid from the well to the surface.

New is that the casing is perforated in the oil-saturated zone of the reservoir by dividing the reservoir into two parts, installing the packer at a distance of two to five meters above the oil-water contact, then installing a double-acting deep-well pump over the reservoir so that the pump suction valve placed above the installed packer in the upper part of the reservoir, and during the production of reservoir fluid, part of the selected oil from the upper part of the reservoir upload to the reservoir below the packer.

The conducted patent research on the patent fund and the technical library of the TatNIPIneft institute showed the absence of identical or equivalent technical solutions in comparison with the claimed method, which allows us to conclude that its criteria are “novelty” and “inventive step”.

The drawing shows a section of an oil-saturated formation with a vertical well in the oil-water zone and downhole pumping equipment in a vertical well according to the proposed method.

The inventive method is carried out in the following sequence.

An oil reservoir with water-oil zones is drilled with a design grid of wells. In the well 1, drilled in the oil-water zone, open the perforation 2, 3 productive formation 4 with the separation of the productive formation into two parts. The distance from the lower holes of the perforation to the oil-water contact (WOC) must be at least one meter. Packer 5 is installed in the casing in the lower part of the reservoir at a distance of 2-5 m above the oil-water contact, depending on the oil-saturated thickness of the reservoir. Install a double-acting pump 6 over the reservoir. A liner 7 is located under the pump, through which reservoir fluid is pumped into the injection zone. The suction valve of the oil pump 8 is located above the packer in the upper part of the reservoir. The discharge valve of the oil pump 9 is located below the packer in the lower part of the reservoir.

The double-acting pump, due to its location relative to the reservoir 4, takes oil from the top of the reservoir through the suction valve, raises it to the surface. The control of the volume of oil injected into the reservoir, as in foreign analogues (US patent No. 5497832, IPC E21B 43/38, E21B 43/40. Publish. 03/12/1996), is carried out by calculation. To do this, at a given pumping mode, the theoretical productivity of lifting the liquid to the surface and pumping oil into the lower part of the reservoir is calculated. If in the steady-state operating mode of the installation, the amount of liquid raised corresponds to the calculated theoretical (taking into account the allowable supply coefficient) productivity of the double-acting oil part of the pump at a dynamic liquid level in the well corresponding to the level of a conventional borehole sucker rod pump (USHN) in an adjacent vertical well, then from the previously known well flow rate, which was available during the operation of a conventional USHN, the amount of fluid raised by the double-acting pump is subtracted and the surface. The resulting difference will be the volume of fluid injected, in this case oil, into the lower part of the reservoir.

From the injection valve into the lower part of the reservoir, from five to ten percent of the oil production rate is pumped, thereby creating an “oil cushion” 10 that prevents cone formation and formation water from entering the vertical well to the perforation intervals. A smaller amount of injected oil increases the time during which an increase in reservoir pressure occurs. As a result, the process of oil displacement from the lower part of the reservoir to the perforation intervals located in the upper part of the reservoir is slowed down. A larger amount of injected oil will lead to losses due to its excessive injection into the reservoir as a result of the withdrawal of oil into the underlying aquifer 11. The amount of oil injected into the reservoir is determined by geohydrodynamic modeling.

When installing equipment above and below the packer, containers with deep autonomous pressure gauges are installed. The upper pressure gauge 12 is located above the packer, above the upper perforation interval, and the lower 13 - under the packer. During the operation of the well, monitoring of changes in reservoir pressure is constantly carried out. The use of a double-acting pump allows to increase the reservoir pressure in the zone of the discharge valve, as a result of which the oil moves towards the upper part of the reservoir, into the zone of low reservoir pressure, which is formed near the suction valve as a result of oil extraction.

Thus, the trunk of a vertical well below the packer installation site acts as an injection well, and above the packer installation site, it acts as a production well. The operation of the wells according to the proposed method allows to increase the waterless period of the well’s operation by reducing the water cut of the produced products, increasing the coverage factor by oil production reserves, preventing cone formation and reducing material costs for oil production by combining the functions of producing and injection wells, reducing the cost of electricity for lifting, preparation and injection of associated water.

Practical example

The implementation of this method, consider the example of an oil deposit in Tournaisian carbonate sediments with oil-water zones (see drawing). The deposit is drilled with a rare grid of vertical wells with a distance between the wells of 300 m, and their arrangement is carried out. Oil-saturated thickness of the reservoir in vertical well 1 is 18 m, water-saturated - 9.4 m. Seven meters of carbonates are perforated in the side part of the reservoir 4. The perforation interval is at a depth of 1081-1088 m. Oil-water contact in a vertical well is set at a depth of 1097 m.

To ensure the injection of part of the produced oil into the lower part of the Tournaisian deposits, the vertical well is additionally perforated in the interval 1094-1096 m. The distance from the lower perforation hole to the aquifer of the formation is one meter. Packer 5 is installed in the casing at the level of the liner in the lower part of the reservoir at a distance of 5 m above the oil-water contact. A dual-action pump 6 is located above the reservoir. A liner 7, through which reservoir fluid is pumped into the injection zone, is located below the pump.

When installing equipment above and below the packer, containers with deep autonomous pressure gauges are installed. The upper pressure gauge 12 is located above the packer, above the upper perforation interval, at a depth of 1079 m, and the lower 13 - under the packer, at a depth of 1093.5 m. The well is put into operation. During the selection of oil, the production rate of the well and water cut are measured. The oil production rate is 8 tons / day and the water cut of the product is 7%. Of these, 0.8 tons / day or 10% of the oil flow rate through the discharge valve 9 is pumped into the lower perforated part of the formation in order to create an “oil cushion”. The result is a zone of high pressure, which prevents the rapid entry of formation water to the perforation intervals from the underlying aquifer 11 of the vertical well and the growth of water cut of the produced products. In the reservoir, as a result of the artificially created differential pressure of the reservoir pressure between its lower and upper parts, the reservoir fluid moves from the zone of increased reservoir pressure (according to the pressure gauge 12) to the lower zone (according to the pressure gauge 13).

During the operation of the well, formation and bottomhole pressures are periodically examined. The readings of the upper pressure gauge 12 record a decrease in reservoir pressure during the selection of formation fluid. The lower pressure gauge in this case records the pressure increase in the lower part of the reservoir, where a double-acting pump pumps part of the oil taken from the upper part of the reservoir. After 2 years of well operation, the oil flow rate decreased to 6.2 tons / day, and the water cut of the product increased to 12%. The reservoir pressure in the reservoir as a whole remained almost at the initial level. The volume of injection was adjusted to 0.6 t / day. The well continued to work.

The proposed method allows to extend the anhydrous period of the well’s operation, to increase the coverage coefficient by the development of oil reserves and, as a result, the final oil recovery. The application of the method allows you to expand the technological capabilities of the development of deposits, to include in the work of the oil-water zone of the reservoir previously not involved in oil production.

Claims (1)

A method of developing an oil reservoir with water-oil zones, including perforating the casing in the oil-saturated zone of the reservoir, installing a packer, installing a downhole pump in the well, injecting oil from the oil-saturated zone and taking formation fluid from the well to the surface, characterized in that the perforation of the casing in the oil-saturated zone of the reservoir is carried out with the separation of the reservoir into two parts, install the packer at a distance of two to five meters above the oil-water contact, for it is set subsurface pump double acting above the producing formation so that the pump suction valve is positioned above the set packer at the top of the producing formation and in production of the formation fluid withdrawn portion of oil from the top of the producing formation is pumped into the producing formation below the packer.

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