RU2297524C2 - Method for treatment of a deposit of highly viscous oil - Google Patents

Abstract

FIELD: oil and gas extractive industry, in particular, technologies for increasing efficiency of extraction of highly viscous oil deposits.

SUBSTANCE: method includes drilling primary pilot boreholes for future product and force wells with opening of productive formation. Water is forced in, pressure change in borehole of product well is registered, water forcing is stopped after upsurge of face pressure, being a sign of massive structure of productive formation within limits of extraction element being researched. Aforementioned element is drilled with vertical and/or horizontal product and force wells with area positioning system thereof. Faces or boreholes of wells are distanced so that product wells are used to open the productive formation near its ceiling, while force wells are used to open the productive formation either above or below the water-oil contact. Oil is displaced in vertical direction with forcing mode of working agent, primarily water, based on condition that current formation pressure in extraction element is not lower than original formation pressure. Forced into force wells is water thickened with polymer on condition of prevention of premature influx of working agent into product wells. In accordance to second variant, faces or boreholes of wells are distanced so that at first stage product wells are used to open the productive formation approximately in the middle, and at second stage side horizontal shafts are drilled close to ceiling of productive formation.

EFFECT: increased efficiency when extracting a deposit of highly viscous oil.

2 cl, 1 ex, 2 tbl, 4 dwg

Description

The present invention relates to the field of oil and gas industry, namely, to increase the efficiency of development of high-viscosity oil deposits, with a massive reservoir structure, layer-by-layer heterogeneous in reservoir properties and with an insufficiently stable reservoir.

A known method of developing deposits with a layered heterogeneous reservoir based on drilling production and injection wells and injecting a solution into the formation, for example, BP-92 biopolymer in order to align the injectivity profile of the injection well (see Vlasov S.A., Kagan Y.M. O possible mechanism for enhancing oil recovery for oil fields developed in waterflooding mode. Oil industry, No. 2, 2005, p. 70-73 and Information from the meeting of the Central Development Commission. Oil industry, No. 2, 2005, p. 74-75). The disadvantage of this method is the relatively low increase in the coefficient of oil recovery (CIN). So, according to the authors and the CCR, the increase in oil recovery factor based on laboratory research and field work is estimated at 10-15%. Such an increase in oil recovery factor is not able to make the process of flooding a reservoir of high-viscosity oil profitable.

There is also a method of increasing the rate of oil production based on the drilling of production and injection wells and waterflooding of the reservoir during the overcompensation mode, when the volumes of injected water exceed the volumes of produced reservoir fluids (see Zakirov S.N., Zakirov E.S., Zakirov I.S. ., Baganova MN, Spiridonov AV New principles and technologies for the development of oil and gas fields. Moscow, 2004, p.13-14). The disadvantage of this method is the excess of the current reservoir pressure over the initial pressure. As a result, in practice, the formation of technogenic fracturing took place, and accordingly, premature flooding of production wells. There were also difficulties with overhaul in connection with the flowing of wells.

Closest to the proposed method is a method of developing a gas condensate reservoir in a cycling process with a vertical spacing of the faces of production and injection wells (see Zakirov S.N., Leontyev I.A., Musinov I.V., Shvedov V. M. Maintaining pressure in a gas-condensate reservoir with reservoirs heterogeneous in properties. Trucks of VNIIGAZ. Development of gas-condensate fields with maintaining pressure. Moscow, 1988). The alleged disadvantage of this method in relation to deposits of highly viscous oil is the lack of oil recovery factor to justify its use in normal water flooding.

The basis of the present invention is the creation of an effective method for developing deposits of highly viscous oil through the integrated use of the positive properties of known methods. In particular, due to the transformation of some of their negative properties into positive ones.

The task is achieved by the fact that the proposed method for developing a highly viscous oil reservoir involves drilling a development element with vertical and / or horizontal producing and injection wells with an area system for their placement, bottom holes or wellbores are distributed in such a way that the producing wells open the formation near the top of the formation, and injection wells - above or below the water-oil contact and organize the displacement of oil in the vertical direction with the mode of injection of the working agent a, preferably water, such that the current pressure in the reservoir development element does not drop below the initial reservoir pressure, wherein the hole is injected into the injection water from the gelled polymer conditions avoiding premature breakthrough working agent to production wells.

The task is also achieved by the fact that the proposed method for developing a highly viscous oil reservoir involves drilling a development element with vertical and / or horizontal producing and injection wells with an area system for their placement, bottom holes or wellbores are distributed in such a way that the producing wells open the formation approximately in the middle of the thickness productive formation, later horizontal lateral trunks near the top of the formation are drilled from these shafts, with injection wells they pump the formation above or below the water-oil contact and organize the displacement of oil in the vertical direction with the injection mode of the working agent, mainly water, from the condition that the current reservoir pressure in the development element is not lower than the initial reservoir pressure, while polymer-thickened water is pumped into injection wells from the conditions for preventing premature breakthroughs of the working agent to production wells.

The methods are as follows.

The first way.

Within the development element, it is drilled according to one of the following alternative development systems.

- The area development element, for example a five-point one, is drilled with four vertical producing wells and one injection. Production wells are opened from the top of the reservoir, but not more than half of the thickness of the reservoir, injection wells from the OWC or the bottom of the reservoir, but not more than half the thickness of the reservoir. The location of the wells is shown in figure 2.

- The areal development element, for example, a five-point one, is drilled by four producing horizontal wells with trunks near the top of the reservoir. A previously drilled vertical well is left as an injection. Or, a horizontal injection shaft is drilled from it near and parallel to the VNK. The layout of the wells is given in figure 3.

- The formed development element is put into operation. The pressure at the bottom of the wells is maintained based on the condition of preventing destruction of the skeleton of the reservoir, or preventing degassing of oil, or other technological restrictions. Water injection is carried out, for example, from the condition of maintaining constant reservoir pressure.

The mode of overcompensation of fluid withdrawal by injection of a working agent. This will lead to an increase in reservoir pressure above the initial one. As a result, it becomes possible to increase the bottomhole pressure in production wells. This solution allows you to prevent sand during the operation of unstable collectors.

If repair work is necessary in one of the wells, the reservoir pressure is reduced in the area of the development element under consideration, for example, by translating the injection well into the water production mode. Therefore, the negatively proven in practice mode of overcompensation becomes technologically necessary in the proposed method. It is also necessary because of the more intense pushing of high-viscosity oil to the bottom of production wells.

- In the options for the extraction of highly viscous oil, it is planned to pump water thickened with polymers into the reservoir. It is easy to see the difference in the use of polymer solutions that arises in relation to the traditional approach. In their traditional use, they serve to align the injectivity profile in the injection well. In the proposed method, their purpose is to prevent premature breakthroughs of the working agent to the producing wells when organizing the displacement process mainly not in the lateral but in the vertical direction.

- Monitoring of production processes allows you to make certain refinements and adjustments to the ongoing development system. Naturally, through the use of a 3D hydrodynamic, adaptive model of a highly viscous oil reservoir.

The stated elements of development technology are based on numerous 3D mathematical experiments. Therefore, their evidence base is considered in the next section.

The second way.

Within the development element, it is drilled according to one of the following alternative development systems.

- The area development element, for example a five-point one, is drilled with four vertical producing wells and one injection. Production wells are opened from the top of the reservoir, but not more than half of the thickness of the reservoir, injection wells from the OWC or the bottom of the reservoir, but not more than half the thickness of the reservoir. The location of the wells is shown in figure 2.

- The areal development element, for example a five-point one, is drilled by four producing horizontal wells. Trunks are located approximately in the middle of the thickness of the reservoir. Subsequently, lateral horizontal trunks are drilled from these trunks and placed near the top of the formation. A previously drilled vertical well is left as an injection. Or, a horizontal injection shaft is drilled from it near and parallel to the VNK. The layout of the wells is given in figure 4.

Two-stage drilling was previously developed by Acad. A.P. Krylova (see Zakirov S. N. Analysis of the problem "Well grid density - oil recovery". Grail Publishing House, 2002, pp. 108-110). It was supposed at the first stage of drilling production and injection wells to be placed on a rare and uniform grid. These wells of the operational fund carried out additional exploration of the reservoir. Then the wells in the second stage of drilling were located where they provided the highest oil recovery factor, the largest increase in annual oil production or water injection. Therefore, such a two-stage drilling can be called areal.

The proposed principle of two-stage drilling can be arbitrarily called vertical - two-stage vertical drilling. One of its main purposes is to intensify the rate of production of high-viscosity oil.

- The formed development element is put into operation. Pressure is maintained at the bottom of the wells, based on the condition of preventing destruction of the skeleton of the reservoir, or preventing degassing of oil, or other technological restrictions. Water injection is carried out, for example, from the condition of maintaining constant reservoir pressure.

The mode of overcompensation of fluid withdrawal by injection of a working agent. This will lead to an increase in reservoir pressure above the initial one. As a result, it becomes possible to increase the bottomhole pressure in production wells. This solution allows you to prevent sand during the operation of unstable collectors.

If repair work is necessary in one of the wells, a decrease in reservoir pressure in the area of the development element under consideration is performed, for example, by transferring the injection well to the water production mode. Therefore, the negatively proven in practice mode of overcompensation becomes technologically necessary in the proposed method. It is also necessary because of the more intense pushing of high-viscosity oil to the bottom of production wells.

- In the options for the extraction of highly viscous oil, it is planned to pump water thickened with polymers into the reservoir. It is easy to see the difference in the use of polymer solutions that arises in relation to the traditional approach. In their traditional use, they serve to align the injectivity profile in the injection well. In the proposed method, their purpose is to prevent premature breakthroughs of the working agent to the producing wells when organizing the displacement process mainly not in the lateral but in the vertical direction.

- Monitoring of production processes allows you to make certain refinements and adjustments to the ongoing development system. Naturally, through the use of a 3D hydrodynamic, adaptive model of a highly viscous oil reservoir.

The stated elements of development technology are based on numerous 3D mathematical experiments. Therefore, their evidence base is considered in the next section.

An example of the implementation of the proposed development methods.

For the purpose of greater clarity, 3D mathematical experiments were carried out on the development elements shown in figures 1-4. Corresponding calculations were performed numerically in a 3D two-phase (oil-water) formulation.

In all cases, the design element of development is adopted layerwise heterogeneous in reservoir properties. The corresponding initial data are given in table 1.

The viscosity of oil in reservoir conditions is 180 centipoise, the viscosity of water is 1 centipoise. Initial reservoir pressure is 87.5 atm, reservoir temperature is 19.5 ° C.

Production wells in all cases are operated with the same depression on the reservoir - 15 at. Maintenance of reservoir pressure, where this is not specified, is made from the condition that the flow rate of fluid from the element is equal to the flow rate of water in the injection well. Predictive calculations are completed when one of the following restrictions is reached: water cut of produced products - 95% or well production rate for oil - 1 t / day.

The grid dimensions of the investigated development element are 13 × 13 × 13 unit cells for the model with vertical production wells and 15 × 15 × 13 unit cells for the model with horizontal production wells. The grid near production wells is crushed. The cell sizes therefore vary in area from 1 m to 25 m for a model with vertical production wells and from 1 to 20 m for a model with horizontal production wells.

The calculation results will be summarized in table 2. Here are the most characteristic indicators of oil production from the considered element of development. The corresponding indicators do not need special explanations. For they ultimately determine the efficiency of the production of highly viscous oil from a dedicated development element.

Option 1. Basic. The traditional method of waterflooding is considered. In vertical production wells, the formation is opened from the roof up to 6 m before reaching the mark of the oil field. In the injection vertical well, the formation is opened from the roof up to 6 m below the VNK (see figure 1).

According to table 2, this option is characterized by low efficiency. First of all, the CIN is small - only 0.1351.

Option 2. Here we study the effectiveness of the vertical spacing of the intervals for the selection of oil (liquid) and water injection (see figure 2).

From table 2 follows the high effectiveness of this method of increasing the efficiency of development of deposits of high viscosity oil. So, KII, in comparison with the base case, increases from 0.1351 to 0.2602. In this case, a noticeable decrease in the oil-water factor occurs - from 10.31 to 6.67.

Option 3. For all initial positions, it corresponds to option 2. The difference is that water thickened with polymer with a viscosity of 20 cps is pumped into the formation.

This method of increasing the development effectiveness is also characterized by good efficiency. According to Table 2, in the third variant there is an increase in the SIF to 0.3519 in comparison with 0.2602 in the second variant. The injection of polymer-thickened water leads to a further decrease in VNF from 6.67 to 0.34. This is a strong result, given that today in the country even low-viscosity oil deposits are developed in conditions of high water cut of the produced products.

The increased efficiency of the use of polymers is due to the fact that oil is displaced to wells thickened with polymers by water not in the lateral but in the vertical direction. And then layer-by-layer heterogeneity does not interfere, but helps the efficient extraction of oil.

Option 4. Here we study the feasibility of a development method based on overcompensation of the selection of the polymer-injected water injected. In all other respects, this option repeats the previous one.

Overcompensation aims to intensify the process of oil production, which really leads to a reduction in the development period of the element under consideration by 37 years compared to the previous one. At the same time, contrary to expectations, there is a slight increase in the SIF - from 0.3519 to 0.3693.

The following options explore the feasibility of using horizontal wells in the development of high-viscosity oil deposits.

Option 5. In this embodiment, the horizontal production trunks are located near the roof of the reservoir (see figure 3). And the injection horizontal barrel is above the VNK. In connection with the vertical spacing of production and injection wells in option 5, it should be compared with option 2. According to Table 2, option 5 with respect to option 2 has the following advantages

- there is a multiple reduction in the period of development of the element (from 175 years to 74 years),

- CIN increases slightly - from 0.2602 to 0.2693,

- CIN increases for the 20th year - from 0.0374 to 0.09, which, as noted, is important from the point of view of the NPV criterion.

Option 6. The difference between this option and the previous one is that polymer thickened water with a viscosity of 20 cps is pumped into the formation.

This way of influencing the development process is fully justified. So, according to Table 2, the CIN increases from 0.2693 to 0.3532. The GNF decreases by a multiple - from 6.09 to 0.25. Such indicators are given at the cost of increasing the development period from 74 to 112 years.

Option 7. The purpose of this option is to consider the possibility of reducing the development time due to some overcompensation of the selection by injection. As in the case of vertical wells, this method also manifests itself on the positive side.

So, according to Table 2, the development period is reduced by 9 years. There is some increase in CIN - from 0.3532 to 0.3678.

Option 8. In this option, the feasibility of replacing a horizontal injection well (as in option 7) with a vertical one is being investigated. With the opening of the reservoir, as in the 2nd embodiment.

According to table 2, the transition to a vertical injection well does not impair development performance. So, the CIN increases slightly (from 0.3678 to 0.3713). The development period is reduced by two years. The GNF increases slightly (from 0.40 to 0.49).

Option 9. This option, like the previous one, is based on a vertical injection well, as it is less expensive.

Mining horizontal trunks of the first stage of drilling are located in the 6th interlayer. On the 10th year in these wells provides for drilling of BGS with their placement near the roof of the reservoir (see figure 4). In many important respects, this option is superior to all previous ones.

So, according to Table 2, here we have the highest CIN - 0.4802. An important advantage of the option is the CIN for the 20th year - 0.1818. Here, the development period is 101 years, as in version 8, when the recovery factor is 0.3713. True, there is some increase in GNF - up to 3.41. However, not every low-viscosity oil field developed in the country is characterized by an oil recovery factor of 0.4802 at a GNF of 3.41.

Thus, the proposed method for the development of high-viscosity oil deposits is characterized by high efficiency in the implementation of a fairly simple development method - water flooding. It is known that water flooding cannot be compared with thermal methods of influencing filtration processes during the extraction of high-viscosity oil both in terms of huge capital investments and operating costs.

The performed 3D mathematical experiments confirm the fairness and effectiveness of all the proposed technological solutions for the rehabilitation of waterflooding methods in relation to high-viscosity oil deposits. Here are the most important points. With regard to the real geological, physical and field conditions, further, more substantive optimization of the individual components in the proposed development method is possible.

Table 1
Capacitive filtration parameters of the development element Layer Total thickness N, m Sandiness, d.ed. Porosity m, unit Permeability K, MPa * s Kh Ky Kz one 8 0.85 0.32 1045 1063 244 2 8 0.83 0.3 308 343 54 3 15.4 0.59 0.28 90 103 fifteen four 12.4 0.3 0.2 fifty fifty 10 5 6.2 0.85 0.29 186 192 65 6 6.2 0.95 0.29 288 306 82 7 6.2 0.9 0.31 408 432 85 8 6.2 0.71 0.31 576 648 60 9 6 0.63 0.3 372 429 fifty 10 6 0.76 0.29 141 156 34 eleven 6 0.81 0.31 546 582 102 12 6 0.84 0.32 1302 1323 250 13 40.2 0.76 0.3 1461 1539 one hundred

table 2
Comparison of sector modeling results Option Number Development period, years Oil produced, thousand tons The extracted amount of water, thousand tons Water-oil factor CIN, shares units. Final Wed reservoir pressure, atm. Quit, fractions of units. Kokhv, shares units. CIN for 20 years, shares of units. Vertical wells one 45 63.32 652.75 10.31 0.1351 87.05 0.58 0.23 0.0697 2 175 121.95 813.08 6.67 0.2602 86.79 0.58 0.45 0.0374 3 246 164.91 55.48 0.34 0.3519 86.75 0.58 0.61 0.0359 four 219 173.08 86.64 0.50 0.3693 95.88 0.58 0.64 0.0367 Horizontal wells 5 74 126.23 844.55 6.69 0.2693 84.8 0.58 0.46 0.0900 6 112 165.56 40.87 0.25 0.3532 84.5 0.58 0.61 0.0716 7 103 172.36 68.48 0.40 0.3678 90.42 0.58 0.63 0.0741 8 101 174.01 84.79 0.49 0.3713 91.49 0.58 0.64 0.0785 9 101 225.07 767.41 3.41 0.4802 108.83 0.58 0.83 0.1818

Claims (2)

1. A method of developing a reservoir of high-viscosity oil, including drilling of priority pilot wells for future production and injection wells with opening a reservoir, water injection, recording changes in pressure in the barrel of a producing well, stopping water injection after a surge in bottomhole pressure, indicating a massive structure of the reservoir in within the considered development element, which is drilled by vertical and / or horizontal producing and injection wells from With the system of their placement, bottoms or boreholes are distributed in such a way that producing wells open the reservoir near its roof, and with injection wells above or below the oil-water contact, and organize the displacement of oil in the vertical direction with the mode of injection of the working agent, mainly water, from conditions so that the current reservoir pressure in the development element is not lower than the initial reservoir pressure, while polymer-thickened water is pumped into injection wells in order to prevent premature breakthroughs working fluid to the producing wells. 2. A method of developing a highly viscous oil deposit, including drilling of priority pilot wells for future production and injection wells with opening a reservoir, water injection, recording changes in pressure in the barrel of a producing well, stopping water injection after a surge in bottomhole pressure, indicating a massive structure of the reservoir in within the considered development element, which is drilled by vertical and / or horizontal producing and injection wells from With their placement system, bottoms or boreholes are distributed in such a way that, at the first stage, producing wells open the reservoir approximately in the middle, and at the second stage, horizontal sidetracks are drilled near the top of the reservoir, injection wells open the reservoir above or below the oil-water contact and organize the displacement of oil in the vertical direction with the injection mode of the working agent, mainly water, from the condition that the current reservoir pressure in HTE development was not less than the initial reservoir pressure, wherein the hole is injected into the injection water from the gelled polymer conditions avoiding premature breakthrough working agent to production wells.

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