RU2469183C2 - Oil deposit development method - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method involves drilling of injection and production wells, pumping of displacement agent (water or water-gas mixture) through injection wells having vertical design, perforation intervals of which are in the deposit below current position of oil-water contact, and product extraction through production wells having vertical and/or horizontal designs and arranged in elevated deposit sections the perforation intervals of which are located at near-roof deposit interval. At water content of extracted products below economically profitable value in oil deposit containing an interlayer of poorly permeable rocks, from vertical injection wells, at deposit bottom there drilled is horizontal shaft or multi-hole branched directed shafts so that they can be arranged under working faces of production wells. As displacement agent pumped to injection wells there used is free gas of hydrocarbon type with content of methane homologues of 25% and higher. At that, pumping of free gas is performed at temperature of 20-40°C and at gas pumping bottomhole pressure that is by 20% lower than saturation pressure. Using recurrent selection of product samples from production wells there determined is value of gas factor and chemical analysis of gas, and when gas breakthrough of separate production wells is defined, sampling of products from them is reduced by 50%. At repeated gas breakthrough to those production wells the gas pumping to injection well from which the gas is supplied to those production wells is stopped and pumping of design volume of viscous liquid is performed. After that, pumping of free hydrocarbon gas to that injection well is restored.

EFFECT: increasing the method's efficiency owing to enlarging the coverage of deposit with displacement agent.

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Description

The invention relates to the oil industry, in particular to methods for developing an oil deposit using gas in the late stages of development.

A known method for the development of oil deposits (patent RU No. 2391495, IPC 8 Е21В 43/20, published in Bulletin No. 16 dated 06/10/2010), including gas ejection with water and injection 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 supplied to the liquid-gas dispersant under pressure, sampling 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 water-gas mixture is injected periodically, alternating in each 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 conditions:

P _g <P _s <P _in ,

where R _with - bottomhole pressure when injected into the reservoir water-gas mixture;

P _g and P _in - bottomhole pressure, respectively, with the injection of only gas or only water,

moreover, the values of P _g , P _c and P _in each cycle vary from a predetermined minimum to a predetermined maximum value, 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 varied within specified limits , or the gas flow rate is kept constant, and the water flow rate is changed within predetermined limits.

The disadvantages of this method are:

- firstly, the complexity of the method, due to the fact that the water-gas mixture is injected periodically, alternating in each cycle with the injection of either only gas or with the sequential injection of water and gas or gas and water;

- secondly, it is necessary to constantly monitor the development of the oil reservoir, since in each cycle the pressure varies from the specified minimum to the specified maximum values, while 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 specified limits, or the gas flow rate is kept constant, and the water flow rate is changed within the specified limits.

The closest in technical essence is the method of developing an oil reservoir (patent RU No. 2090742, IPC 8 ЕВВ 43/20, published in Bulletin No. 26 of 09/20/1997), including drilling of injection and production wells, circulation of a displacing agent in the reservoir injected through injection wells and sampled through production wells, while the displacement agent is injected and forced formation is extracted through wells located in the interval below the current position of the oil-water contact, and between them at elevated sections of the structure have oil producing wells and oil is taken through a vertical wellbore from the bed interval and / or through a horizontal wellbore located in the bedside interval and / or a horizontal well or cavity formed in the bedside interval of the reservoir and / or adjacent to it the interval of overlying rocks, and at the same time with the selection of oil in elevated sections of the structure of the bedside interval of the reservoir, the filter part of the bottomhole formation zone periodically they are hydrophobized, while the bottom-hole zone of the formation is hydrophobized by pumping oil, an emulsion, a solution of a surfactant, gas into the well, and water and a water-gas mixture are used as a displacing agent.

The disadvantages of this method are:

- firstly, the small coverage of the reservoir with a displacing agent, since the agent is injected at intervals of perforation of vertical injection wells;

- secondly, the use of water or a gas-gas mixture as a displacing agent in the late stages of development of an irrigated oil reservoir containing a layer of poorly permeable rocks (clay, salt, gypsum, anhydrite) is ineffective, since it is practically impossible to displace residual oil from the reservoir into the trunk production wells through a layer of poorly permeable rocks;

- thirdly, uncontrolled injection of a displacing agent (water and / or gas mixture) can lead to a breakthrough into production wells and even greater watering of produced products.

The objective of the invention is to increase the coverage of the reservoir with a displacing agent, as well as to increase the efficiency of displacing residual oil from the reservoir into the producing well through a layer of poorly permeable rocks at a late stage of development of an irrigated oil reservoir with monitoring the state of development of an oil reservoir by sampling produced products.

The problem is solved by a method of developing an oil deposit, including drilling injection and producing wells, pumping a displacing agent, which is used as water or a gas mixture through vertical wells, the perforation intervals of which are in the reservoir below the current position of the oil-water contact, and the selection of products through production wells made vertical and / or horizontal and located on elevated sections of the reservoir, the perforation intervals of which are located in the bedside interval of the reservoir.

What is new is that when the water content of the produced products is below an economically viable value in an oil reservoir containing a layer of poorly permeable rocks from vertical injection wells, a horizontal trunk or multi-branched branched shafts are drilled at the bottom of the reservoir so that it (and) is located ( (i) under the bottom of production wells, and as a displacing agent injected into injection wells, free hydrocarbon gas with a methane homologue content of 25% or more is used, at ohm, free gas is injected at a temperature of 20-40 ° C and at a bottomhole gas injection pressure of 20% lower than the saturation pressure, while periodically, by sampling the selected products from production wells, the gas factor and the chemical composition of the gas are determined and if a gas breakthrough is detected in individual production wells reduce the selection of products from them by 50%, and when the gas breaks into these production wells again, gas injection into the injection well, from which gas enters these production wells, is stopped and carried out injection of the calculated volume of viscous fluid, after which the injection of free hydrocarbon gas into this injection well is resumed.

In figures 1 and 2 shows a diagram of an implementation of a method for developing an oil reservoir.

The proposed method is as follows.

A method of developing an oil reservoir 1 (see Fig. 1) includes drilling injection 2; 2 '; ... .2 ⁿ and extractive 3; 3 '; ... 3 ⁿ wells on any well-known grid, for example, according to the one shown in figure 1. Injection wells 2; 2 '; ... 2 ^{n are} made vertical, and their respective perforation intervals 4; four'; ... 4 ⁿ are in reservoir 1 below the current position of the oil-water contact (WOC) 5 (see figure 2), and production wells 3; 3 '; ... 3 ⁿ (see Figs. 1 and 2) are made both vertical and horizontal, placed on elevated sections of reservoir 1, perforation intervals 6; 6 '; ... 6 ^{n of the} corresponding extractive 3; 3 '; ... 3 ⁿ wells are located in the bedding interval 7 deposits 1.

Make arrangement of injection 2; 2 '; ... 2 ⁿ and extractive 3; 3 '; ... 3 ⁿ wells of oil reservoir 1. Then into the injection wells 2; 2 '; ... 2 ⁿ inject the displacing agent, which is used as water or gas-water mixture. Using borehole pumps (not shown in FIGS. 1 and 2), products entering the shafts at perforation intervals 6 are selected; 6 '; ... 6 ⁿ (see figure 2) of the respective horizontal and vertical production wells 3; 3 '; ... 3 ⁿ .

As the development of oil reserves from oil reservoir 1, it is watered and its development becomes lower than the economically viable value. The economically viable amount of development of oil reservoir 1 (see FIGS. 1 and 2) depends on the degree (percent) of water cut of the produced products and is determined individually for each oil reservoir. For example, the development of the oil field of the Romashkinskoye field of the Republic of Tatarstan becomes lower than the economically viable value if the water cut of the produced products exceeds 93%. In addition, the presence in the oil reservoir of a layer of poorly permeable rocks 8 complicates the displacement of residual oil from reservoir rocks.

When the water content of the produced products exceeds 93%, for example, when the water content of the produced products is 95%, from vertical injection wells 2; 2 '; ... 2 ⁿ in the sole of deposit 1, drill a horizontal wellbore or multilateral well-branched trunks, for example, corresponding to these injection wells 2; 2 '; ... 2 ⁿ horizontal trunks 9; 9'; ... 9 ⁿ , so that he (s) was located under the faces of the producing wells 3; 3 '; ... 3 ⁿ (see figure 2). As a displacing agent injected into injection wells 2; 2 '; ... 2 ⁿ , use free gas of the hydrocarbon type with a methane homologue content of 25% or more.

It is known that an irrigated oil reservoir containing poorly permeable rocks 8, called tires (fluid supports), which are clays, salts, gypsum, anhydrites and some types of carbonate rocks, does not allow the residual oil contained in reservoirs to migrate as terrigenous (sands, silts) , sandstones, siltstones and some clayey rocks), and carbonate (limestones, chalk, dolomites) rocks, which remain in the reservoir at a late stage of development through these poorly permeable rocks, while oil dissolved in se may migrate through such rocks. Gas, dissolving in oil, increases its volume and reduces density, viscosity and surface tension, and free hydrocarbon gas is the best from this point of view.

In terms of chemical composition, free hydrocarbon gas is a mixture of hydrocarbons from CH ₄ to C ₅ H ₁₂ , nitrogen (N ₂ ) carbon dioxide (CO ₂ ) hydrogen sulfide (H ₂ S), hydrogen (H ₂ ), helium (He), carbon monoxide ( СО), argon (Ar), mercury vapor (Hg), etc.

The solubility of free hydrocarbon gases in oil is about 10 times greater than in water. It is known that fatty gas with a methane homologue content of 25% is better soluble in oil than dry, lighter oil dissolves more gas than heavy.

The injection of free hydrocarbon gas should be carried out at a certain optimal mode of gas dissolution in oil.

Studies have shown that free hydrocarbon gases dissolve worse in oil with increasing temperature. So, for example, in Romashkinskoye field oil of the Republic of Tatarstan at bottomhole gas injection pressure P ₃ = 15 MPa and temperature t = 40 ° C, 59 m ^{3 of} gas dissolves in 1 m ^{3 of} oil, and already at a temperature t = 60 ° C, while the same pressure P ₃ in 1 m ^{3 of} oil dissolves 53 m ³ , and vice versa, if the volume of the gas phase significantly exceeds the volume of oil, then at bottomhole pressure of gas injection P ₃ = 20-25 MPa and a temperature of 90-95 ° C, reverse solubility occurs - liquid hydrocarbons begin to dissolve in the gas, and at certain pressure and temperature the fluid mixture is completely revratitsya a gas.

The use of hydrocarbon and carbon dioxide is more preferable, since their high solubility in oil leads to a decrease in the viscosity of the oil in contact with the gas in the reservoir and an increase in the displacement coefficient. In addition, the injection of pure hydrocarbon gas, and especially carbon dioxide, is safer than the injection of air, in which the formation of explosive mixtures with hydrocarbons is possible.

Free gas is injected using a compressor (Figs. 1 and 2 are not shown) at a temperature of 20-40 ° C and at a bottomhole gas injection pressure 10-15% lower than the saturation pressure P _us , i.e. the pressure at which gas begins to be released from the oil, in addition, the free hydrocarbon gas must be cleaned of nitrogen, since nitrogen is poorly soluble in oil. So, for example, if the saturation pressure P _nac = 18 MPa, then the bottomhole pressure of the gas during the injection should not exceed P ₃ = 15.3-16.2 MPa, therefore, when injecting gas, the bottomhole pressure should not exceed P ₃ = 15.3 -16.2 MPa.

Gas in injection wells 2; 2 '; 2 '' ... 2 ⁿ (see FIGS. 1 and 2) and, respectively, in their horizontal trunks 9; 9'; ... 9 ^{n is} pumped through the tubing string (not shown in FIGS. 1 and 2), lowered to the top of the perforation interval 10 of the horizontal shaft 9 (see FIG. 2) into the sole 11 of the oil reservoir 1. The annular space between the tubing and the injection casing the wells are blocked by a packer (not shown in FIGS. 1 and 2) installed in the lower part of the tubing. This is done to isolate the casing, which does not always withstand high injection pressures, and in depleted fields, the casing is leaky due to corrosion.

Gas falling into the sole 11 (see FIG. 2) of reservoir 1 dissolves in oil, which leads to a decrease in the viscosity of oil in reservoir 1 and to an increase in the displacement coefficient, therefore, oil from the reservoir rocks located in the sole 11 of oil reservoir 1 rises up and displaced through poorly permeable rocks 9 and through perforation intervals 6; 6 '; ... 6 ⁿ , and the product enters the trunks of producing wells 3; 3 '; ... 3 ⁿ . Where products are pumped to the surface.

As the development of residual oil reserves from reservoir rocks, gas breakthroughs into individual producing wells are possible 3; 3 '; ... 3 ⁿ , which increases the specific gas consumption and energy costs of the process. Therefore, their timely identification and elimination is important. Breakthroughs of gas in producing wells 3; 3 '; ... 3 ⁿ occur along the most permeable interlayers after displacement of liquids (oil and water) from them. To identify them, they monitor the magnitude of the gas factor in production wells and the chemical composition of the gas. Therefore, periodically by sampling selected products from producing wells 3; 3 '; ... 3 ⁿ determine the value of the gas factor, as well as the chemical composition of the gas, and when a gas breakthrough is detected in individual production wells, for example, in a 3 '' production well, the selection of products from them is reduced by 50%. As a result, the bottomhole pressure in the production well 3 ″ increases and the flow of gas through the perforation interval 6 ″ into the bore of this production well 3 ″ decreases or stops completely. If in the same producing wells, i.e. into the 3 '' production well, the gas breakthrough occurred again (judged by the repeated increase in the gas factor and the chemical composition of the gas taken off), then into the injection well 2 with the corresponding horizontal wellbore 9 hydraulically connected to these production wells, i.e. with a 3 ”production well, the gas supply is stopped and the calculated volume of viscous liquid is injected. As a viscous liquid, aqueous solutions of polymers or biopolymers can be used. For example, an aqueous polymer solution using polyacrylamide (PAA) gel manufactured in accordance with TU 6- 01-1049-92, which is added to water at a concentration of from 0.025 to 0.5%, for example at a concentration of 0.05%. By controlling the concentration of PAA, the desired viscosity of the liquid can be achieved. An aqueous solution of xanthan gum biopolymer can also be used. IPA, for example, a liquid xanthan biopolymer (BLC), manufactured in accordance with TU 2458-002-50635131-2003, which is added to water at a concentration of from 0.025 to 0.5%. The use of a viscous liquid based on polymers or biopolymers increases the viscosity of the injected The calculated volume of viscous fluid is determined empirically, depending on the volume of the pore space of the reservoir and the porosity coefficient through which the gas burst into the 3 " A gas breakthrough occurs along a permeable interlayer (not shown in Figs. 1 and 2) among poorly permeable rocks 8 (see Fig. 2). A viscous fluid fills the permeable interlayer and thus makes it difficult to filter gas into the wellbore of the production well 3 ″ by this interlayer, after which the injection of free hydrocarbon gas into the injection well 2 is resumed.

The proposed method of developing an oil reservoir allows to increase the coverage of the reservoir with a displacing agent by drilling horizontal or multilateral well branched-injection trunks from existing injection wells, as well as to increase the efficiency of displacing residual oil from the reservoir into the producing well through a layer of poorly permeable rocks at a late stage of development of a flooded oil reservoir due to the use of free hydrocarbon gas as a displacing agent with monitoring the state of rabotki oil reservoir by sampling crude production and prevent free gas in barrels of production wells.

Claims (1)

A method of developing an oil deposit, including drilling injection and production wells, injecting a displacing agent, which is used as water or a gas mixture, through vertical injection wells, the perforation intervals of which are in the reservoir below the current position of the oil-water contact, and production selection through production wells made vertical and / or horizontal and placed on elevated sections of the reservoir, the perforation intervals of which are located in the bedside interval a reservoir, characterized in that when the water cut of the produced product is below an economically viable amount in an oil reservoir containing a layer of poorly permeable rocks, from vertical injection wells at the bottom of the reservoir, a horizontal well or multi-branched branched trunks are drilled so that they are located under the faces production wells, and as a displacing agent injected into injection wells, free hydrocarbon-type gas with a methane homologue content of 25% or more is used, in this case, free gas is injected at a temperature of 20-40 ° C and at a bottomhole gas injection pressure of 20% lower than the saturation pressure, while periodically by sampling the products taken from the producing wells, the gas factor and the chemical composition of the gas are determined, and if a breakthrough is detected gas to individual production wells, the selection of products from them is reduced by 50%, and when the gas breaks into these production wells again, gas injection into the injection well, from which gas enters these production wells, is stopped and oestriasis download the calculated volume of viscous fluid, and then download free hydrocarbon gas to the injection well is resumed.

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