RU2502861C2 - Development method of oil deposit located above gas deposit and separated with non-permeable interlayer from it - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method involves drilling of vertical and horizontal production and injection wells in oil deposit, pumping of working fluid to injection wells and extraction of products from production wells. Drilling of an additional horizontal well in gas deposit is performed; then, branches directed upwards through a non-permeable interlayer with outlet of branches to oil deposit are drilled out of it. Water is pumped from the head to the additional horizontal well so that gas-water mixture is formed in the same well. At gas leakage to shafts of production wells, product extraction from the same wells is reduced by 40-50% till bottomhole pressure in them is recovered. After that, product extraction from the same wells in previous volume is continued.

EFFECT: increasing oil extraction coefficient.

1 dwg

Description

The invention relates to the oil industry and, in particular, to methods for developing an oil reservoir using gas and / or water-gas mixture (HCV).

A known method of developing an oil deposit (patent RU No. 2391495, IPC 8 E21B 43/20, published in Bulletin No. 16 of 06/10/2010), including ejecting gas with water and injecting in a cyclic mode to increase oil recovery in the oil reservoir along the column elevator pipes of the water-gas mixture formed by mixing gas with water, supplied under pressure to a mixing device, which is used as a liquid-gas dispersant installed at the mouth of the injection well, while gas is taken into the liquid-gas dispersant under pressure, taking either from gas wells or from the gas interval opened by the same injection well, isolated from the injection interval and communicated through the annular cavity through the column of elevator pipes and shut-off and control devices with a liquid-gas dispersant, and the gas-water mixture is periodically alternated in each a cycle with the injection of either only gas, or with the sequential injection of water and gas or gas and water, maintaining the pressure at the bottom of the injection well in the injection interval, subject to hold:

Pg <Ps <Pv,

where Pc is the bottomhole pressure during the injection of a water-gas mixture into the formation;

Pg and Pb are bottomhole pressures, respectively, when only gas or only water is injected, and the values of Pg, Pc and Pb in each cycle vary from the specified minimum to the specified maximum values, while during periods of simultaneous supply of water and gas to the liquid-gas dispersant the water flow rate is kept constant, and the gas flow rate is changed within predetermined limits, or the gas flow rate is kept constant, and the water flow rate is varied within the predetermined limits.

The disadvantages of this method are:

- firstly, the complexity of the implementation, since it is necessary to take gas at the wellhead from the gas interval of the same well, to prepare a water-gas mixture at the mouth of the injection well using a liquid-gas dispersant, and the gas sampling interval must be isolated (packer) in the injection well and injecting a packer water-gas mixture;

- secondly, constant monitoring is required during the injection of the water-gas mixture into the injection well, since during the periods of simultaneous supply of water and gas to the liquid-gas disperser, the water flow rate is kept constant, and the gas flow rate is changed within the set limits, or the gas flow rate is kept constant, and the water flow rate is changed within specified limits;

- thirdly, the wells are made vertical, therefore, its application does not provide the maximum coverage factor for the area of the oil reservoir.

A known method for the development of oil fields with a gas cap (options) (patent RU No. 2312983, IPC 8 E21B 43/24, publ. In bull. No. 35 from 12/20/2007).

According to the first option: A method of developing oil fields with a gas cap involves drilling a reservoir with injection and production wells and injecting hot agent into the oil-gas contact area and the oil rim area through the injection wells, and hot water is injected with a low coefficient of sandiness and large formation fragmentation with a temperature above the initial reservoir temperature and below its boiling point with pressure at the mouth of the injection well, the well is used horizontal ones are used, in which the upper parts open the gas cap, and the lower parts open all oil-saturated interlayers, placing injection wells above the producers in the presence of an impermeable bridge between the gas cap and the oil rim, and in the absence of the specified bridge - between the producers.

According to the second option: A method for developing oil fields with a gas cap involves drilling a reservoir by injection and producing wells and pumping a working gas — a water-gas mixture of HCV into the gas-oil contact area, and with a high coefficient of sandiness and low formation stratification, the HCV is injected with a temperature above the initial reservoir temperature and below the boiling point at a pressure at the mouth of the injection well, HCV is used, obtained by dispersing hot water with gas to form of fine-graded HCV with a density lower than the density of oil under formation conditions, horizontal wells are used, in which the upper parts open the gas cap, and the lower parts open all oil-saturated interlayers, placing injection wells above the production ones in the presence of an impermeable bridge between the gas cap and the oil rim, and in the absence of the specified jumper - between extractive.

The disadvantages of this method are:

firstly, the high costs for implementing the method, due to the fact that several horizontal wells are drilled, which open both a gas deposit (gas cap) and an oil deposit (oil-saturated interlayers), which requires significant material and financial costs.

secondly, high energy costs for the preparation of a working agent injected into horizontal injection wells, using hot water or a water-gas mixture (HCV) obtained by dispersing hot water and gas at the wellhead until a fine-grained HCV is formed with a density lower than the density of oil in the reservoir conditions, as well as the need to attract additional equipment: boilers, dispersants;

thirdly, the low efficiency of the method in the presence of an impermeable bridge between the oil and gas deposits, horizontal injection wells are located above the production wells, while watering is accelerated and reservoir pressure in the oil reservoir is reduced and, as a result, the oil recovery coefficient (CIN) is reduced;

- fourthly, constant monitoring is necessary during the injection of the water-gas mixture into the horizontal injection wells, since the HCV is pumped at a temperature above the initial reservoir temperature and below the boiling point at a pressure at the mouth of the injection well.

An object of the invention is to reduce financial and material costs by eliminating the drilling of several horizontal wells by drilling branches from an injection horizontal well, as well as reducing energy consumption and eliminating the involvement of additional equipment for the preparation of HCV through the use of gas in the reservoir and in combination with periodic injection water, which forms a water-gas mixture directly in the oil reservoir and increase efficiency by increasing the coefficient oil recovery factor (ORF), which is achieved by increasing the reservoir pressure in the oil reservoir by pumping the working agent from the bottom up to the bottom faces of the producing wells, and gas working gas and water pumped from the wellhead into the branched horizontal well with subsequent formation are used as the working agent HCV in the reservoir, which does not require constant monitoring at the wellhead for the temperature of the HCV.

The problem is solved by the method of developing an oil deposit located above the gas deposit and separated from it by an impermeable layer, including drilling vertical and horizontal production and injection wells in an oil deposit, pumping a working agent into injection wells and selecting products from production wells.

What is new is that an additional horizontal well is drilled in the gas reservoir, then branches are drilled from it, directed upward through the impermeable interlayer with branching into the oil reservoir and with the possibility of communicating the oil and gas reservoirs with each other, during the development of the oil reservoir from the mouth, they inject water into an additional horizontal well with the formation of a water-gas mixture in this well, when a gas breaks into the shafts of producing wells, reduce production from these wells by 40-50% to anovleniya bhp in them, and then resume the selection of products from them in the same volume.

The drawing shows the proposed method for the development of oil deposits located above the gas reservoir and separated from it by an impermeable layer.

The method of developing an oil deposit 1 located above the gas reservoir 2 and separated from it by an impermeable layer 3 includes drilling vertical and horizontal production wells, as well as vertical and horizontal injection wells in the oil reservoir 1.

For example, vertical 4; four'; ... 4 ⁿ and horizontal 5 production wells and vertical 6; 6 '; ... 6 ⁿ and horizontal 7 injection wells in oil reservoir 1.

Produce the injection of a working agent, for example, waste water in a vertical 6; 6 '; ... 6 ⁿ and horizontal 7 injection wells, and the selection of products is carried out from vertical 4; four'; ... 4 ⁿ and 5 horizontal production wells

As the development of oil reserves from oil reservoir 1, it is depleted, reservoir pressure decreases in it, and the subsequent development of this oil reservoir 1 becomes economically inefficient.

In order to extract the remaining oil reserves from the oil reservoir 1, an additional horizontal well 8 is drilled in the gas reservoir 2, then branches 8 'are drilled from it; 8''; ... 8 ⁿ directed upward through the impermeable interlayer 3 with the exit of the branches into the oil reservoir 1.

Launch oil reservoir 1 in development. As a working agent for displacing residual oil reserves from the oil reservoir 1, gas from the gas reservoir 2 and water pumped from the mouth into the horizontal injection well 8 with branches 8 'are used; 8''; ... 8 ⁿ with the subsequent formation of a water-gas mixture (HCV) in an additional horizontal well 8, which does not require constant monitoring at the wellhead for the temperature pumped into the HCV reservoir.

Gas located in gas reservoir 2 through branching 8 ';8''; ... 8 ⁿ , drilled from an additional horizontal well 8, connecting the gas reservoir 2 with the oil reservoir 2 enters the oil reservoir 1, where it displaces the oil from the pores and dissolves in the oil, which reduces the viscosity of the oil in the oil reservoir 1.

Periodically injected water from the mouth of an additional horizontal well 8. Water is pumped from the mouth into an additional horizontal well 8, for example, through a string of tubing (tubing) (not shown in FIG.) Lowered into an additional horizontal well 8.

To implement the proposed method, for example, produced water from the same oil reservoir 1 is used, for example, waste water density ρ = 1120 kg / m ³ , which has better displacing abilities than fresh water.

Using the water-gas treatment technology of HCV allows you to combine the main advantage of using water, which is the proximity of the viscosity characteristics of water and oil and, due to this, a significant coefficient of coverage by displacement, and the main advantage of gas injection, which consists in high washing abilities of the latter, thereby achieving a high coefficient crowding out.

When gas is injected into the formation, it dissolves in oil and, as a result, decreases its viscosity and density, as well as an increase in gas content and volumetric coefficient. It has been experimentally established that a decrease in the viscosity of oil during the implementation of this method reaches 2.5-3 times. It was also experimentally established that the maximum increase in the oil displacement coefficient was observed when the gas / water ratio in the water-gas mixture was from 1: 2.3 to 1: 1.5.

By controlling the volume (increase or decrease) of the water supply from the wellhead to the horizontal injection well, the above gas / water ratio in the HCV entering the oil reservoir 1 is reached, based on the maximum increase in the oil displacement coefficient (determined by the increase in oil volume selection from the vertical 4; 4 '; ... 4 ⁿ and horizontal 5 production wells.

In addition, in the process of implementing the proposed method, the reservoir pressure (P _PL ) in the oil reservoir 1 increases, which leads to an increase in the displacement coefficient, therefore, oil from reservoir rocks located in the sole 11 of the oil reservoir 1 rises and is displaced through the vertical perforation intervals four; four'; ... 4 ⁿ and horizontal 5 wells. Where products are pumped to the surface.

As the development of residual oil reserves from oil reservoir 1 from reservoir rocks, gas breakthroughs into separate vertical 4 are possible; four'; ... 4 ⁿ and horizontal 5 production wells. Breakthroughs of gas in the vertical 4; four'; ... 4 ⁿ and horizontal 5 production wells occur along the most permeable interlayers after displacement of liquid (oil and water) from them. To identify them, monitor the magnitude of the gas factor in the vertical 4; four'; ... 4 ⁿ and horizontal 5 production wells and the chemical composition of the sampled gas.

Therefore, periodically by sampling products taken from extractive vertical 4; four'; ... 4 ⁿ and horizontal 5 wells determine the value of the gas factor, as well as the chemical composition of the gas, and when a gas breakthrough is detected in production wells, for example, in vertical production well 4 ', the selection of products from this well is reduced by 40-50%. As a result, the bottomhole pressure in the vertical production well 4 ′ increases and the gas flow through the perforation interval into the barrel of this vertical production well 4 ′ decreases or completely stops. Then resume the selection of products from production wells 4 to the previous value.

For example, the selection of products from a vertical production well 4 'is Q _p = 11 m ³ / day, while the downhole pressure (P ₃ ) decreases from 12 MPa to 7 MPa. When gas appears in the sampled product that has fallen into the vertical production wellbore 4 'from the gas reservoir 2, as determined by chemical analysis, the production volumes are reduced by 40-50%, i.e. decrease by (11 · (40-50%) / 100%) = 4.4-5.5 m ³ / day., to the value Q _к = 11 m ³ / day - (4.4-5.5 m ³ / day) = 6.6-5.5 m ³ / day, take Q _to = 6 m ³ / day. Thus, after reducing the volume of production to Q _k = 6 m ³ / day, bottomhole pressure in the vertical producing well 4 'is restored, for example, to 11.5 MPa. After which the selection from the vertical production well 4 'is restored in full (to the previous value) Q _p = 11 m ³ / day.

The proposed method allows to reduce financial and material costs by eliminating the drilling of several horizontal wells, and by drilling branches from an additional horizontal well, and also reduces energy costs and eliminates the involvement of additional equipment for the preparation of HCV through the use of gas located in the reservoir and in combination with periodic injection of water, which forms a water-gas mixture directly in the oil reservoir and to increase the efficiency of the method and due to an increase in the oil recovery coefficient (CIP), which is achieved by increasing the reservoir pressure in the oil reservoir by pumping the working agent from the bottom up to the bottom of the producing wells, and as the working agent, gas from the gas reservoir and water pumped from the wellhead into an additional branching horizontal well with subsequent formation of HCV in the reservoir, which does not require constant monitoring at the wellhead for the temperature of the HCV.

Claims (1)

A method for developing an oil deposit located above a gas deposit and separated from it by an impermeable layer, comprising drilling vertical and horizontal production and injection wells in an oil deposit, pumping a working agent into injection wells and selecting products from production wells, characterized in that an additional horizontal well is drilled into gas deposits, then branchings are drilled out of it, directed upward through an impermeable interlayer with branching output into an oil reservoir and with the possibility of communication not between oil and gas deposits between themselves, in the process of developing an oil deposit from the mouth, water is injected into an additional horizontal well with the formation of a water-gas mixture in this well, when gas breaks into the shafts of production wells, the production from these wells is reduced by 40-50% until the bottomhole is restored pressure in them, after which they resume the selection of products from them in the same volume.

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