RU2439308C1 - Method of oil and gas condensate field development - Google Patents

Abstract

FIELD: gas and oil production. ^ SUBSTANCE: method of oil and gas condensate field development involves well drilling in viscous oil bed with horizontal wellbores, heat carrier injection, and viscous oil extraction. Viscous oil bed id reamed with additional wells with horizontal wellbores. A part of horizontal wellbores in all wells is positioned in a plane by 0.5-1 m higher than oil and gas interface (OGF) and used as injection wells. The other part is made in a plane by 0.5-1 m lower than water and oil interface and used as production wells. Length of horizontal wellbores lies within 50-1000 m, and distance between horizontal wellbores lies within 100-500 m. Bed water is produced in water intake well of the field and used to prepare heat carrier which is injected into the bed first as reheated steam in volume sufficient to form condensed bed water layer of 1.5-2.5 m depth above OGF, then as polymer solution in bed water heated to 90 - 95C. Heated polymer solution is injected into the bed in volume sufficient to heat viscous oil to the temperature where oil viscosity falls to 1/3 of initial value of bed oil viscosity or less. Viscous oil production is performed in production wells with injection of heater polymer solution running. Supply of heated polymer solution is stopped when polymer solution layer in the OGF reaches 15% of the bed zone volume through which it is injected into the bed. ^ EFFECT: increased efficiency of viscous oil production due to extended area and section coverage of oil-saturated bed area. ^ 3 dwg, 1 ex

Description

The invention relates to the oil and gas industry, in particular to the field of development of oil (oil and gas / oil and gas condensate) fields, and in particular to methods for developing viscous oil or bitumen deposits during simultaneous and separate exploitation of producing and injection horizontal wellbores with steam and thermal treatment of the formation.

Currently, the existing technical and economic estimates show that oil reserves in the sub-gas zones (oil rims) of oil and gas condensate fields are being developed on a small scale. This is mainly due to the unfavorable geological and physical characteristics of such objects for development and the lack of effective technologies that can be used to develop sub-gas zones.

Deterioration of the structure of liquid hydrocarbon reserves not recovered from the bowels, large total oil reserves in the sub-gas zones dictate the need for the creation and implementation of new technologies for the active development of oil rim reserves.

Based on the processes obtained in the physical and geological and mathematical modeling in the sub-gas zones, a method is proposed for developing an oil and gas condensate field under conditions of high oil viscosity (viscosity value from 10 to 100 mPa · s).

Closest to the proposed method is a method of developing an oil and gas condensate field, including drilling a well in the reservoir of viscous oil of a field having horizontal shafts, pumping coolant into the reservoir and selecting viscous oil from it (see RF patent No. 2350747, class E21B 43/24, 2009 )

The disadvantage of this method is the low efficiency of the extraction of viscous oil from the developed reservoir, due to the low degree of coverage in the area and section of the oil-saturated formation when exposed to it.

The technical result, the achievement of which the present invention is directed, is to increase the efficiency of the extraction of viscous oil (the value of viscosity from 10 to 100 MPa · s) from the developed formation by increasing the degree of coverage over the area and section of the oil-saturated formation when exposed to it.

This technical result is achieved due to the fact that in the method of developing an oil and gas condensate field, comprising drilling a well in a viscous oil reservoir of a field having horizontal shafts, pumping coolant into the reservoir and selecting viscous oil from it, according to the invention, the viscous oil reservoir is drilled with additional wells having horizontal trunks, one part of the horizontal shafts of all wells is placed in a plane 0.5-1 m above the gas-oil contact (GOC) and used as injection wells, and the other part of them - in the plane 0.5-1 m below the oil-water contact (WOC) and used as oil producing wells, the length of the horizontal wells is set in the range of 50 - 1000 m, and the distance between the horizontal wells is set in in the range of values from 100 to 500 m, produced water is extracted from the water well constructed at the field and is used to prepare the coolant, which is first pumped into the formation in the form of superheated steam in a volume that ensures the formation of condensed water embedded formation water of a layer with a thickness of 1.5 - 2.5 m above the GNA, then in the form of a polymer solution in the produced water heated to 90-95 ° C, the viscosity of which is controlled by changing the polymer concentration until the viscosity of the polymer solution becomes equal to the oil viscosity, the heated polymer solution is pumped into the reservoir in an amount sufficient to warm the viscous oil to a temperature at which its viscosity decreases to a value not exceeding 1/3 of the initial oil viscosity in the reservoir, Often wells while continuing injection into a heated solution of the polymer layer, wherein the formation on the surface layer of the STC from the polymer solution volume equal to 15% of the volume of the formation zone, through which it is injected into the formation, supplying the heated polymer solution was stopped.

The essence of the invention is illustrated in figures 1-3, where figure 1 shows a diagram of the development and operation of an oil and gas condensate field with viscous oil, figure 2 shows the profile and plan of the oil rim indicating the shafts of injection and production wells, and figure 3 The scheme of steam injection during the development of oil and gas condensate field is shown.

In figure 1, 2, 3 adopted the following notation:

1 - gas saturated formation; 2 - oil saturated formation; 3 - water saturated formation; 4, 5 - injection wells; 6 - producing wells, 7 - zones of perforation of wells, 8 - oil-water contact; 9 - gas-oil contact (GOC); 10 - water well; 11 - reservoir reservoir fluid; 12 - block desalination and water treatment; 13 - deoxygenation station; 14 - water pump; 15 - ejector; 16 - steam generator; 17-19 - parts (articulated joints) of an articulated steam line; 20 - downhole fittings for injecting steam or hot mixture of produced water; 21 - block dosing of reagents; 22 - tank for reagents.

The method is implemented as follows.

An oil and gas condensate reservoir with gas-saturated 1, oil-saturated 2 and water-saturated 3 layers is drilled to develop oil reserves by vertical wells 4-6 having horizontal shafts (not shown in the drawings). The design of horizontal wells implies the presence of zones 7 of perforation of wells along the entire length within gas-saturated 1 and oil-saturated 2 layers. Therefore, in the practical implementation of zone 7 of perforation of horizontal wellbores 4-6 have a characteristic length of 50 to 1000 m. In addition, it should be noted that these trunks are located either in the plane of the oil-water contact 8, or 0.5 - 1 m above the gas-oil Contact 9. The distances between the horizontal sections of the wells can be from 100 to 500 m.

The upper layer of horizontal shafts is an effective (working) part of the injection 4.5 wells, the bottom is oil producing wells 6 (Figs. 1 and 2). In practical implementation, horizontal trunks of both the upper and lower layers are equipped with high-precision pressure and temperature sensors, the information from which is automatically transmitted to the corresponding control panels.

To develop viscous oil, the oil-saturated formation 2 is hydrodynamically isolated from the gas-saturated formation 1 (gas "cap") and heated with a coolant. For this purpose, a water well 10 is constructed in the field. The produced water extracted from the water well 10 is used to prepare a coolant, which at the first stage is pumped into injection wells 4, 5 in the form of superheated steam (from produced water) in a volume sufficient to form condensed liquid a layer with a thickness of 1.5 - 2.5 m above the GNA, and in the second stage - in the form of a polymer solution in formation water heated to 90-95 ° C, the viscosity of which is selected by changing the polymer concentration. The viscosity of the solution is changed until its value becomes equal to the viscosity of the unheated oil.

Such a obtained polymer solution is pumped into the SOC plane of the oil-saturated section of the reservoir in a volume sufficient to warm the oil to a temperature at which the viscosity of the oil in the rim will decrease to a value not exceeding 1/3 of its initial viscosity. It should be noted that the thickness of the polymer solution layer must be not less than the thickness of the created additional layer of condensed fluid in the formation, having a thickness of 1.5 - 2.5 m. In this case, the total thickness of the layers of the water-polymer barrier will reach 3 - 5 m.

After that, the hot polymer solution is continued to be pumped into the GOC and the selection of viscous oil warmed up at 10-30 ° C by production wells 6 is started until a polymer rim is formed, the volume of which is 15% of the volume of the formation zone through which it is pumped into layer. In this case, the flow of the heated polymer solution is stopped. Further, the viscous oil is displaced by hot formation water until it breaks into all producing wells 6. After the water flooding is 98-99%, the injection of cold formation water, pushing the hot liquid in oil-saturated formation 2 to the BHC zone 8, begins.

Thus, when implementing this method in the process of displacing viscous oil, a certain ratio of the viscosities of the polymer solution and the heated oil is maintained. As a rule, it is 3.

According to the proposed method, the coolant is pumped into injection wells 4, 5, and the selection of viscous oil is carried out from production wells 6 of the field. The coolant (hot water) injection itself continues even after a barrier having a height of at least 3 m - 5 m is formed from the produced water and the polymer solution in the produced water at the gas-oil contact 9.

All equipment for the preparation and injection of the coolant should be calculated by productivity and operating pressure in accordance with the geological and geophysical characteristics of the development object. A water well 10 fills reservoir 11 with formation water. Next, the produced water is filtered, desalinated using a desalination and water preparation unit 12, and supplied to a de-oxygenating station 13. Using water pump 14, de-oxygenated water enters the steam generator 16 through the ejector 15. An articulated steam pipeline, consisting of parts (articulated joints) 17-19, is fed into the borehole fittings 20 for injecting steam into the mouths of the injection wells 4, 5. The articulated steam pipeline, as a rule, consists of three articulated eneny. This facilitates the supply of hot coolant to the destination and increases the safe working conditions of technical personnel. Steam is injected until about half of the water barrier is formed, while the first stage of creating the barrier ends. In the process of implementing the method, all communications must be provided with thermal insulation.

Next, the equipment for the preparation and injection of the coolant (Fig.3) is transferred to the injection mode of a hot polymer solution having a temperature of 90-95 ° C. In this case, the water coming after the water pump 14 is mixed in the ejector 15 with the reagent coming from the reagent dosing unit 21. As a reagent, in particular, a polymer solution in the reservoir 22 can be used.

The thus prepared mixture of produced water with the necessary reagents is heated in the steam generator 16 to a temperature of 90-95 ° C and is supplied to the borehole fittings 20-19 through the articulated joints constituting the steam pipe 17-19 for injecting steam into the mouths of the injection wells 4,5. In this case, a hot polymer solution is pumped in a volume sufficient to warm the oil in the GOC region to a temperature at which the oil viscosity decreases to a value equal to 1/3 of the initial value of the oil viscosity. The volume of the solution in this case should not be less than necessary to create a layer with a thickness of 3-5 m. At this point, the second stage of creating the barrier is completed. The required viscosity of a hot polymer solution is provided by selecting the polymer concentration in the produced water.

Then the actual development of the oil rim begins. For this purpose, a hot polymer solution with a temperature of 90-95 ° C is continued to be injected into injection wells, while at the same time starting the selection of liquid from horizontal trunks of the lower layer. After some time, the entire oil-saturated formation 2 is warmed up. Using pressure and temperature sensors, the injection of the polymer solution and the selection of oil are synchronized so that the automated control system for the injection and selection processes provides the specified oil production rates for producing wells 6 by necessary adjustment of the pressures in the horizontal boreholes of the respective wells. Oil is displaced by a hot polymer solution until a polymer “rim” is formed, the volume of which is 15% of the volume of the zone of the formation through which it is pumped into the formation 2. In this case, the polymer content in the solution is selected so as to ensure a three-fold excess of the viscosity of the solution over the viscosity of the heated oil . After the formation of the "rim" of the polymer, oil is displaced only by hot formation water.

Thus, in the proposed method, a water barrier is created first by injecting superheated steam and condensing it in the formation, then (after lowering the viscosity of the oil in the formation by heating) by injecting a polymer solution whose viscosity is 3 times the viscosity of the heated oil. After that, the oil is displaced by hot formation water until the displacing agent breaks into all producing wells 6.

After watering well production by 98-99% through injection wells 4,5, “cold” formation water is pumped, which pushes hot formation water into oil-saturated formation 2, providing additional production and increasing oil recovery coefficient.

In an advantageous variant of the method, the horizontal shafts of producing wells 6 are located 0.1-0.5 meters below the oil-water contact 8. In this case, although formation water will be present in the produced fluid, the extraction of viscous oil becomes more efficient and complete.

Indeed, the technology of horizontal well drilling does not allow horizontal wellbores to be drawn exactly in the plane of the oil-water contact 8. In addition, the water-oil contact at the field is tracked with some error. In this regard, in order not to lose the produced oil, as can happen in the case of horizontal wells drilling in the “body” of the oil formation 2, it is more expedient to lay the horizontal sections of the producing wells 6 slightly below the plane of the oil-water contact 8.

In addition, the following should be noted. After the temperature in the horizontal shafts of production wells 6 is increased by 10-30 ° C, oil is taken from production wells 6, gradually increasing oil production until the planned design level of wells is reached, coordinating injection and production in accordance with the rate of temperature increase in production wells 6. B In areas of faster temperature growth, both injection and selection can be proportionally increased. At the same time, with the increase in oil production, the uniformity of lowering the technogenic oil-water contact 8 down from the water barrier is controlled. The breakthrough of produced water into production well 6 (the first by this criterion) is a signal to reduce injection to the nearest injection wells 4, 5 or to completely stop injection (depending on the rate of watering of production coming from well 6).

Below is an example of the implementation of the method in relation to the oil and gas condensate field (OGKM) - Cenomanian deposits of the Tazovsky OGKM with a rim of viscous oil.

An example implementation of the method.

The main geological and physical characteristics of the Cenomanian deposits of the Tazovsky oil and gas condensate field with a rim of viscous oil are as follows: the initial pressure in the productive gas-saturated formation is 1-11 MPa, the temperature is about 25 ° C. The thickness of the oil rim is on average about 10 m, maximum 17.6 m. The viscosity of oil in reservoir conditions is approximately 60 MPa · s. The collector, including in the rim zone, is characterized by stratification. The average permeability of the formation is 116 mD, the average porosity is 30.9%.

The oil and gas condensate reservoir for developing primarily oil reserves is drilled with wells with horizontal sections of the barrel, for example, from 50 to 1000 m and with distances between horizontal sections from 100 to 500 m, and the horizontal sections of injection wells 4, 5 are located at 0.5 - 1 m above the gas-oil contact 9, and production wells 6 - in the plane of the oil-water contact 8.

The upper layer of the horizontal sections is an effective (working) part of the injection wells 4, 5, the bottom is the oil producing wells 6 (Fig.1-2). The design of horizontal sections involves perforation along the entire length within the oil saturated formation 2.

In the field, in the case of implementing this method, a steam (hot formation fluid) injection unit is constructed during the development of an oil and gas condensate field (see Fig. 3). All equipment in the field is connected by pipelines to a source of produced water and to injection wells 4, 5 for pumping agents into the formation. All equipment should be calculated according to productivity and working pressure in accordance with the geological and geophysical characteristics of the development object.

After completion of the arrangement of the field, preparation for the development of the reservoir begins. The calculated amount of superheated steam with temperature and pressure, respectively, 350 ° C and 16 MPa at the outlet of the steam generator 16 is pumped into injection wells 4, 5 at the highest possible rate (to reduce heat loss) (see FIG. 3). At the bottom of the injection well 4, the corresponding parameters will be approximately 325 ° C and 12 MPa, respectively. The amount of injected steam after condensation should ensure the formation on the gas-oil contact of 9 deposits of a water barrier with a design thickness of 1.5 - 2.5 m.

After injection of superheated steam into the injection wells 4.5, the polymer is supplied in the form of a polymer solution in water heated to 90-95 ° C. The viscosity of the polymer solution is changed and selected by changing the concentration of the polymer in the produced water until the viscosity of the unheated oil becomes equal. The injection of such a hot polymer solution is carried out until the oil viscosity in the zone of active influence on the oil-saturated formation 2 decreases to a value not exceeding 1/3 of its viscosity at the beginning of the process. In this case, an additional layer of a water-polymer solution with a thickness of 1.5 - 2.5 m should be formed.

Thus, the total thickness of the layers of the water-polymer barrier reaches 3 - 5 m. The injection of a hot polymer solution is continued, gradually warming the oil-saturated formation 2.

An increase in temperature in the horizontal shafts of production wells 6 (by supplying heat to the formation from injected steam and a hot polymer solution) by 10-30 ° C is a sign of an increase in temperature at the bottom of injection wells of 4.5 to a value of 65-70 ° C and a decrease in oil viscosity approximately 3 times to values of 20-22 MPa · s.

From this moment, oil is started to be taken from production wells 6, gradually increasing production to reach the design level, coordinating injection and production in accordance with the rate of temperature increase in production wells 6. In areas of rapid growth in temperature, both injection and production are proportionally increased, and injection the polymer solution is continued until the rim of the polymer solution is formed, comprising about 15% of the volume of the formation zone, through which it is pumped into the oil-saturated formation 2. After this, Oil is pumped with hot formation water until the displacing agent breaks into all production wells 6. At the same time, the uniformity of lowering the technogenic oil-water contact formed by successive injection of superheated steam and polymer solution in formation water heated to 90-95 ° C is monitored. At the same time, they strive to prevent sharp watering of production wells 6. Water breakthrough into production well 6 (the first by this criterion) is a signal to reduce injection to the nearest injection wells 6 or to completely stop the injection, depending on the rate of watering the well production. If the production of the well is less than 98-99% flooded, the injection into the next injection wells 6 is continued.

After the water cut of the product is 98-99% (all oil producing wells 6 go into the category of “breakthrough”), the impact agent is replaced, subsequently pumping “cold” water, pushing the hot formation water and the polymer solution into the oil-saturated formation 2. B In this case, the final washing of the oil-saturated formation occurs and stable flow rates and oil production are ensured.

Using the present invention allows to increase the efficiency of the extraction of viscous oil from the developed reservoir by increasing the degree of coverage of the oil-saturated volume of the reservoir by area and section and increasing the amount of oil produced.

Claims (1)

A method of developing an oil and gas condensate field, including drilling a well in a viscous oil reservoir of a field having horizontal shafts, pumping coolant into the reservoir and selecting viscous oil from it, characterized in that the viscous oil stratum is drilled with additional wells having horizontal shafts, one part of horizontal shafts of all wells placed in a plane 0.5-1 m above the gas-oil contact (GOC) and used as injection wells, and the other part in a plane 0.5-1 m below the water-oil contact and used as oil producing wells, the length of the horizontal wellbores is set in the range of 50-1000 m, and the distance between the horizontal wells is set in the range of 100 m to 500 m, produced water is extracted from the constructed well at the field for the preparation of a coolant, the injection of which into the formation is carried out first in the form of superheated steam in a volume that ensures the formation of a layer from a condensed formation water of a thickness of 1.5-2.5 m above the GNA, then in the form of heated to 90-95 ° C polymer solution in the reservoir fluid, the viscosity of which is controlled by changing the polymer concentration until the viscosity of the polymer solution becomes equal to the viscosity of the oil, the heated polymer solution is pumped into the reservoir in an amount sufficient to warm the viscous oil to a temperature at which its viscosity decreases to a value not exceeding 1/3 of the initial value of the viscosity of the oil in the reservoir, the selection of viscous oil is carried out by producing wells while continuing to pump into the reservoir of polymer solution, wherein the formation of a layer of the STC from the polymer solution volume equal to 15% of the volume of the formation zone, through which it is injected into the formation, supplying the heated polymer solution was stopped.

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