RU2302516C1 - Method to develop oil-and-water zone characterized by high-viscous oil - Google Patents

Abstract

FIELD: oil production, particularly enhanced recovery methods for obtaining hydrocarbons.

SUBSTANCE: method involves preparing development sections by drilling injection and producing wells in each section and injecting water for oil displacement into each producing well bottom; drilling horizontal producing well at one end of development section near reservoir roof so that horizontal producing well bore is parallel to oil-water contact outline. The injection well is horizontal and has bore arranged at opposite end of development section near oil-water contact outline and parallel to oil-water contact outline and horizontal producing well. Polymer and water plugs are alternately injected into injection well. Producing well is operated with drawdown exceeding critical water-free reservoir drawdown. Plugs are injected under well bottom pressure exceeding initial reservoir pressure.

EFFECT: increased efficiency of oil field development.

2 cl, 1 ex, 1 tbl, 7 dwg

Description

The present invention relates to the oil and gas industry, namely to increase the efficiency of the development of the oil-water zone with high viscosity oil.

It is known that each field has a water-oil zone (VNZ) and oil reserves in it are classified as hard to recover. Therefore, the oil recovery factor (CIN) for VNZ usually turns out to be low, and the water cut of the produced products is high.

A known method of developing a water-oil zone with vertical producing wells (see Muslims R.Kh. Modern methods of managing oil field development using water flooding. Published by Kazan State University, 2003, pp. 32-33, 80-81, 160-161, 172-174).

The disadvantages of this method of oil production:

- under the faces of producing wells water cones are formed, which leads to accelerated watering of the produced products;

- as a result of this, an unprofitable oil production rate is reached early, which determines a low oil recovery ratio;

- early and high water cut of the extracted products and low oil recovery factor worsen all the technical and economic indicators of the development of VNZ and the field as a whole.

Closest to the proposed method for the development of the oil-water zone of an oil field is a method of developing horizontal production and injection wells (see Zakirov S.N., Zakirov I.S., Zakirov E.S., Baganova M.N., Spiridonov A.V. New principles and technologies for the development of oil and gas fields. Moscow, 2004, pp. 150-154).

The disadvantages inherent in the considered method are as follows:

- mainly the zone between the horizontal injection and horizontal production wells is subjected to the process of oil displacement by water, and the production of oil reserves in the peripheral zone of the reservoir near the external contour of the oil-water contact is low;

- as will be shown later, in the case of VNZ with high viscosity oil, the considered method does not differ in effective development indicators.

The present invention is based on the task of substantiating an effective method for developing a water-oil zone with high viscosity oil based on the formulation of large-scale mathematical experiments.

The task is achieved in that the proposed method of developing a water-oil zone with high viscosity oil involves the formation of development elements based on the drilling of production and injection wells in each of them and the injection of water to displace oil to the bottom of the producing well, characterized in that at one end of the considered the development element near the top of the formation drills a producing horizontal well with a trunk parallel to the external contour of the oil-water contact, as an injection use a horizontal well, the barrel of which is placed on the opposite end of the development element near and parallel to the external contour of the oil-water contact and, accordingly, parallel to the horizontal production well, polymer rims and water are alternately pumped into the injection well, and also because the production well is operated with a depression exceeding the critical anhydrous depression on the reservoir, and polymer and water rims are injected at bottomhole pressure above the initial reservoir pressure .

The method is as follows.

Oil production from the VNZ of the considered field is carried out on the basis of the formation of a system of similar development elements. Figure 1 schematically shows a three-dimensional image of one of the elements of the development of VNZ with oil of high viscosity.

On this element, a development system is formed from horizontal production and horizontal injection wells. The horizontal wellbore is placed at the end of the development element near the formation roof parallel to the outer contour of the oil-water contact. The trunk of the horizontal injection well is placed parallel to the production well near the outer contour of the oil-water contact (WOC), as shown in Fig.2.

With such wells, the considered element of the reservoir is introduced into development. Polymer and water rims pumped alternately into the formation displace oil to the bottom of the producing well. The production well is operated with a depression exceeding the critical anhydrous depression per formation. The polymer rims and water are injected at bottomhole pressure above the initial reservoir pressure.

An example implementation of the proposed method.

Suppose that the prospects of developing a field with an extensive VNZ are considered. An image of one of the development elements is given in figure 1.

The development element has geometric dimensions of 680 × 220 × 34 m. In three-dimensional (WD) two-phase (oil-water) modeling, the development element is approximated by a grid region of 61 × 20 × 34 unit cells. The lateral size of the cells is 11 × 11 m, vertical - 1 m. The initial geological and physical parameters are taken according to the table. The balance reserves of the element under study are 87 thousand tons of oil.

Studied periodic in the form of a rim and constant injection of a polymer solution with a polymer concentration of 1 kg / m ³ in the injected solution.

The types of producing and injection wells were examined - both wells are horizontal, both wells are vertical, one of the wells is vertical, the other is horizontal. Also, various locations of wells and the waterflooding system - in-contour and contour.

The proposed option (option 6) development (see figure 2) was compared with the following alternative options.

1. Traditional alternative options 1 and 2 of the development of VNZ (see figure 3 and 4) based on vertical wells.

2. Option 3 with two horizontal production and injection wells (see figure 5) (according to Zakirov S.N., Zakirov I.S., Zakirov E.S., Baganova M.N., Spiridonov A.V. New principles and technologies for the development of oil and gas fields. Moscow, 2004, pp. 150-154);

3. Option 4 with a horizontal production well and a vertical injection well (see Fig.6) according to the application No. 042227 (registration No. 2004138840) for the patent S. N. Zakirova and Ya. A. Severova.

4. Similar to the proposed in this application option with the placement of wells, but without injection of polymer - option 5 (see figure 2).

In all cases, five technological modes of well operation were set:

1) downhole pressure in the production well is 143 kgf / cm ² , in the injection well - 163 kgf / cm ² ;

2) bottom hole pressure in the production well is 133 kgf / cm ² , in the injection well - 173 kgf / cm ² ;

3) the bottomhole pressure in the production well is 123 kgf / cm ² , in the injection well - 183 kgf / cm ² ;

4) downhole pressure in the production well is 113 kgf / cm ² , in the injection well - 193 kgf / cm ² ;

5) bottom hole pressure in the production well is 103 kgf / cm ² , in the injection well - 203 kgf / cm ² .

In this case, anhydrous depression is 3 kgf / cm ² .

The forecast of development indicators continues until one of the following restrictions is met:

- water cut of extracted products 98%;

- the minimum allowable oil production rate of 1 m ³ / day.

The results of forecast calculations are compared by the following indicators: the value of the oil recovery coefficient, the oil-water factor (the ratio of cumulative water production to cumulative oil production), as well as the dimensionless development time of the reservoir element and the amount of polymer injected.

The results of the studies are very voluminous. Therefore, as an example, in Fig. 7, the main forecasted production indicators for development options are given depending on the technological modes of the wells, namely the oil recovery factor, the initial oil production rate (q _beginning ), oil-water factor (VNF) and relative (to 50 years) development period (OCP). All these indicators have a direct impact on the economic parameters of the development of VNZ with high viscosity oil.

A review of the data of FIG. 7 shows that the recommended development method is different.

- preferred values of the coefficient of oil recovery of 0.397;

- the smallest oil-water factor - 9 m ³ / m ³ ;

- high initial oil production rates up to 86 m ³ / day;

- the maximum accumulated polymer injection is only 42 tons, which pays off due to the positive consequences in terms of oil production.

From Fig. 7 it also follows that an increase in the depression on the formation in the production well and an increase in the bottomhole pressure in the injection well increases the oil recovery factor, the initial production rate of the production well and reduces the development time. In the recommended embodiment, intensive operating modes of production and injection wells practically do not affect the oil-water factor.

The obtained results take place during the injection of water rims and polymer solution for 12 months alternately.

Thus, the performed exploratory studies show that the recommended method for the development of VIZ with high-viscosity oil is characterized by the best technological and, therefore, technical and economic indicators of oil production in relation to the studied traditional and alternative development methods.

Geological and physical characteristics of the reservoir Options Values Average depth, m 1407 Type of deposit reservoir Collector type terrigenous Porosity,% 12 Average oil saturation, fractions of units 0.70 X axis permeability, darcy 0,100 Y axis permeability, darcy 0,100 Z axis permeability, darcy 0,030 Initial reservoir temperature, ° C 44 Initial reservoir pressure, at 153 Compressibility of the rock, 1 / at 2.2 · 10 ^-5 The density of oil in surface conditions, kg / m ³ 904 The density of oil in reservoir conditions, kg / m ³ 864 Oil viscosity in reservoir conditions, cPz eleven Volumetric coefficient of oil, nm ³ / m ³ 1.06 The viscosity of water in reservoir conditions, SPZ 0.61 The density of water in surface conditions, kg / m ³ 1001 Compressibility of water, 1 / at 4.3 · 10 ^-5 The pressure of oil saturation with gas, kg / cm ² 88 Gas content, m ³ / t 24 Absolute mark of VNK, m 1414 Note: the initial data are taken by analogy with one of the oil fields in Western Siberia.

Claims (2)

1. A method of developing a water-oil zone with high viscosity oil, including the formation of development elements based on drilling production and injection wells in each of them, pumping water to displace oil to the bottom of the producing well, characterized in that at one end of the development element under consideration near the formation roof drilling a producing horizontal well with a wellbore parallel to the external contour of the oil-water contact, using a horizontal well, the well of which is placed as an injection well at the opposite end of the development element near and parallel to the external contour of the oil-water contact and, accordingly, parallel to the horizontal production well, polymer rims and water are alternately pumped into the injection well. 2. The method according to claim 1, characterized in that the production well is operated with a depression exceeding the critical anhydrous depression on the formation, and the polymer rims and water are injected at bottomhole pressure above the initial formation pressure.

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