RU2539485C1 - Method for oil bed development - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention refers to the oil and gas production industry and can find application in developing heterogeneous terrigene or carbonate producing beds. In the method for an oil bed development, involving the oil bed water-flooding, injection of water solution banks containing alkali, a polymer, a surfactant, a microorganism culture and a nutrient medium, into injection holes, and sampling of products from the production wells, at the initial stage a deposit is developed by water-flooding in an amount adequate to achieve the collected compensation of water-flood liquid sampling of not less than 50%; once the oil sampling reaches 70% of the initial recovered reserves, residual prospective oil distributed over specific 1 m² is mapped; the worked-out compartments are detected to inject the above solution into the centre injection holes with the following proportions, wt %: alkali - no more than 5, polymer - no more than 1, surfactant - no more than 0.5, microorganism culture - no more than 0.05, nutrient medium - no more than 0.5, water - the rest with varying the concentration C of the ingredients in the above solution proportional to the specified prospective oil for each C centre is determined depending on $$C_n^k=y_n\cdot C_{\max }^k,$$

wherein k is a type of the ingredient, n is the number of the centre, y is a proportionality factor of each centre; y is calculated by a linear equation y=a·x+b, wherein x is the specific prospective oil of the centre, t/m², a, b are linear equation factors determined if y for x_max equals to 0, and if x_min equals to 1 from a system of equations

wherein x_max and x_min are the maximum and minimum specific prospective oil values, respectively; injection cycles of the bank injection are repeated if an oil flow rate decreases to the pre-injection level.

EFFECT: higher displacement factor and better oil recovery of the productive formation.

1 ex

Description

The invention relates to the oil industry and may find application in the development of heterogeneous terrigenous or carbonate reservoirs.

A known method of developing an oil reservoir, including the sequential injection into the reservoir through an injection well of an aqueous solution of alkali with a nonionic surfactant and polymer, followed by flooding and selection of oil through a producing well. An aqueous solution of alkali with a nonionic surfactant with a predetermined optimal concentration is pumped into a low-oil reservoir with a predetermined optimal concentration, after which the well is stopped for a time sufficient to obtain the maximum oil displacement coefficient achieved during the capillary impregnation process (RF patent 2070282, class E21B 43/22, publ. 10.12.1996).

The closest in technical essence to the proposed method is a method of influencing an oil reservoir with heterogeneous reservoirs, including the selection of oil through a production well and alternating injection into the formation of alkaline rims of a clay suspension and polymer dispersion. Surfactant surfactants are additionally introduced into alkaline rims and pre-foamed, while the comet-P reagent is additionally introduced into the polymer alkaline dispersion (RF patent No. 2211317, publ. 08/27/2003 - prototype).

A common disadvantage of the known methods is the low displacement coefficient in the development of heterogeneous reservoirs, especially hydrophobic or with mixed wettability and, accordingly, low oil recovery.

The proposed invention solves the problem of increasing the displacement coefficient and increasing oil recovery of the reservoir.

, где к - вид компонента, n - номер очага, y - коэффициент пропорциональности каждого очага, причем у рассчитывают по линейному уравнению y=a·x+b, где x - значение удельных ОГЗ очага, т/м², a, b - коэффициенты линейного уравнения, которые определяют при значении y для x_max, равном 0, и при x_min, равном 1, из системы уравнений:The problem is solved in that in a method for developing an oil reservoir, including the development of an oil reservoir by flooding, injecting into the injection wells a rim of an aqueous solution containing an alkali, a polymer, a surfactant, a microorganism culture (CM), a nutrient medium (PS), and selection of products from production wells, according to the invention, at the initial stage, the development of the field is carried out by water injection in an amount sufficient to achieve the accumulated compensation for liquid selection by injection of at least 50%, after reaching about boron on the initial oil recoverable oil more than 70% of the specific build maps of 1 m ² of area of the residual oil in place (ZUS) detected developed portions of the reservoir, wherein a focal injection wells is carried out of said injection solution in the following ratio, wt. %: alkali no more than 5, polymer no more than 1, surfactant no more than 0.5, KM no more than 0.05, PS no more than 0.5, water the rest, with a change in the concentration of C components in the specified solution in proportion to the established value of the OGZ for each focus C is determined by $$C_n^{\mathrm{to}}=y_n\cdot C_{\max }^{\mathrm{to}}$$

, where k is the type of component, n is the source number, y is the proportionality coefficient of each source, and y is calculated according to the linear equation y = a · x + b, where x is the value of the specific OGZ of the source, t / m ² , a, b - the coefficients of the linear equation, which are determined with a value of y for x _max equal to 0, and with x _min equal to 1, from the system of equations:

where x _max and x _min are the values of the maximum and minimum specific OGZs, respectively, the injection cycles of the rims of the composition are repeated when the oil production rate drops to the level before the composition is injected.

SUMMARY OF THE INVENTION

The oil recovery of a terrigenous or carbonate oil reservoir, developed using physicochemical methods for increasing oil recovery (EOR), such as ASP (alkali, surfactant and polymer injection) and various biological EOR, is significantly affected by reservoir heterogeneity and its hydrophobicity. Existing technical solutions do not fully allow fulfilling the tasks of increasing oil recovery in such conditions. The proposed invention solves the problem of increasing the displacement coefficient and increasing oil recovery of the reservoir. The problem is solved as follows.

The method is implemented as follows.

A productive reservoir of an oil field, represented by a terrigenous or carbonate type of reservoir, is developed by focal water flooding: in the center of each focus there is an injection well with producing wells around.

Productive layer is developed by injection of fresh, waste or produced water. After the accumulated compensation of liquid extraction by at least 50% is reached and oil extraction from the initial recoverable oil reserves of more than 70% is reached, distribution maps of specific for 1 m ² of OGZ area are built. The maps reveal the developed areas of the reservoir. For foci with the smallest OGZ, a rim of the solution is injected containing the following components, wt. %:

- alkali - not more than 5,

- polymer - not more than 1,

- surfactant - not more than 0.5,

- KM - not more than 0.05,

- PS - not more than 0.5,

- water - the rest.

, где к - вид компонента, n - номер очага, y - коэффициент пропорциональности каждого очага, причем y рассчитывают по линейному уравнению y=a·x+b, где x - значение удельных ОГЗ очага, т/м², a, b - коэффициенты линейного уравнения, которые определяют при значении y для x_max, равном 0, и при x_min, равном 1, из системы уравнений:With a change in the concentration of C components in the specified solution in proportion to the established value of the OGZ for each focus C is determined by the dependence $$C_n^{\mathrm{to}}=y_n\cdot C_{\max }^{\mathrm{to}}$$

, where k is the type of component, n is the source number, y is the proportionality coefficient of each source, and y is calculated according to the linear equation y = a · x + b, where x is the value of the specific OGZ of the source, t / m ² , a, b - the coefficients of the linear equation, which are determined with a value of y for x _max equal to 0, and with x _min equal to 1, from the system of equations:

where x _max and x _min are the values of the maximum and minimum specific OGZs, respectively.

Thus, for the largest OGZs, only water is injected without adding a substance composition (i.e., the content of alkali, polymer, surfactant, microorganisms with a nutrient medium is 0). For intermediate OGZ values, a composition with a concentration of substances C is pumped in proportion to the residual reserves.

According to the calculations, if the compensation for fluid withdrawal by injection is less than 50%, the reservoir is not sufficiently water-filled and the increase in oil recovery from injection of alkali, polymer, surfactants and microorganisms is practically the same as water injection without these substances. Also, if the selection of oil from the initial recoverable oil reserves is less than 70%, the calculations showed that the injection of substances is not economically feasible due to the possibility of using conventional water flooding and achieving similar rates of selection. Thus, it is advisable to carry out the application of the method for more flooded and more developed reservoirs.

A similar approach with injection into zones with the smallest oil reserves of the maximum concentration of substances in water makes it possible to better develop these areas by increasing the displacement coefficient. Moreover, the greater the oil reserves, the concentration of substances in the water must be reduced. Thus, the method allows to increase the uniformity of oil reserves development and, accordingly, the oil recovery coefficient.

The injection cycles of the rims of the composition are repeated when the oil production rate drops to the level before the injection of the composition.

Development is carried out until the full economically viable development of the reservoir.

The result of the implementation of this method is to increase the displacement coefficient and increase oil recovery of the reservoir.

An example of a specific implementation of the method

The oil reservoir, represented by the carbonate type of reservoir, is developed with waterflooding. Four injection wells and nine production wells were drilled into the producing formation along a 300 × 300 m grid. Each injection well with surrounding production wells is a waterflood. Thus, four foci are distinguished.

After the accumulated compensation for liquid selection by 50% injection and oil recovery from the initial recoverable oil reserves of 70% is achieved, maps of the distribution of specific per 1 m ² area of residual geological reserves are built. The maps reveal the developed areas of the reservoir. So the average specific residual geological oil reserves for each outbreak are:

- 0.2 t / m ² for the first focus,

- 0.4 t / m ² for the second outbreak,

- 0.8 t / m ² for the third source,

- 0.7 t / m ² for the fourth outbreak.

For the first source with the smallest residual reserves (i.e., with y ₁ = 1), a rim of the solution is pumped with the following components, wt. %:

- waste water - 92.95.

For the third source with the largest residual reserves, only waste water is pumped without adding components. For intermediate values of residual reserves (i.e., the second and fourth outbreaks), the composition is injected with the concentration of components in proportion to the residual reserves. To find the proportionality coefficient, they compose a system of equations of the linear form y = a · x + b, knowing that for specific reserves of 0.8 t / m ^{2 the} value of the proportionality coefficient y ₃ is 1, and for specific reserves of 0.2 t / m ² proportionality coefficient y ₁ = 0:

whence find a = -1.667 and b = 1.333.

Thus, one obtains the equation

where x is the value of the specific residual geological oil reserves for each outbreak, y is the proportionality coefficient.

The proportionality coefficients are found for the second focus y ₂ = -1.667 · x ₂ + 1.333 = -1.667 · 0.4 + 1.333 = 0.667 and for the fourth focus y ₄ = -1.667 · x ₄ + 1.333 = -1.667 · 0.7 + 1.333 = 0.166.

For the second source, knowing y ₂ , calculate and inject the rim of the solution containing the following components, wt. %

- waste water - 100- (3.34 + 0.67 + 0.33 + 0.03 + 0.33) = 95.30.

For the fourth source, knowing y ₄ , calculate and pump the rim of the solution containing the following components, wt. %

- waste water - 100- (0.83 + 0.17 + 0.08 + 0.01 + 0.08) = 98.83.

In each focus, NaOH is used as alkali and RD-1030 (low molecular weight triol polyoxpropylene) as a polymer, surfactant AF 9-20 (neonol according to TU 2483-077-05766801-98), microorganism cultures - Devoroil preparation (strains microorganisms according to TU 9291-0.21-45181233-97), the nutrient medium is diammonium phosphate (GOST 19651-74 with amendment No. 1-4) and hydrogen peroxide (GOST 177-88E with change No. 1).

After downloading the data, the rims of the well are put into operation. The average daily total oil production from all nine producing wells in the first month increased from 40 tons / day to 68 tons / day. The effect lasted 2 years. After the oil production rate drops to 40 t / day, the distribution maps of the specific residual geological oil reserves are again built, the proportionality coefficients are re-calculated, the injection cycles of the rims of the composition are repeated. To stimulate the operation of foci with large specific residual reserves, oil acid fracturing is carried out in production and injection wells.

Development is carried out until the full economically viable development of the reservoir.

As a result of the development of the formation, which limited the watering of production wells to 98%, 188.3 thousand tons of oil were produced from the formation in question, the displacement coefficient was 0.569, and the oil recovery coefficient (CIN) was 0.410. According to the prototype, ceteris paribus, 170.8 thousand tons of oil was produced, the displacement coefficient was 0.517, the recovery factor was 0.372. At the same time, the displacement coefficient during the injection of waste water is 0.462. The increase in recovery factor by the proposed method is 0.038.

The proposed method allows to increase the CIN.

Application of the proposed method will solve the problem of increasing the displacement coefficient and increasing oil recovery of the reservoir.

Claims (1)

A method of developing an oil reservoir, including the development of an oil reservoir by flooding, injection into the injection wells of the rim of an aqueous solution containing alkali, polymer, surfactant - surfactant, a microorganism culture - KM, a nutrient medium - PS and selection of products from production wells, characterized in that at the initial stage, the development of the field is carried out by water injection in an amount sufficient to achieve accumulated compensation for liquid withdrawal by injection of not less than 50%, after reaching the selection of oil from the initial Leca oil more than 70% of the specific build maps of 1 m ² of area of the residual oil in place - ZUS reveal developed portions of the reservoir, wherein a focal injection wells is carried out of said injection solution in the following ratio, wt. %: alkali no more than 5, polymer no more than 1, surfactant no more than 0.5, KM no more than 0.05, PS no more than 0.5, water the rest, with a change in the concentration of C components in the specified solution in proportion to the established value of the OGZ for each focus C is determined by

, where k is the type of component, n is the source number, y is the proportionality coefficient of each source, and y is calculated according to the linear equation y = a · x + b, where x is the value of the specific OGZ of the source, t / m ² , a, b - the coefficients of the linear equation, which are determined with a y value of x _max equal to 0, and with x _min equal to 1, from the system of equations:

where x _max and x _min are the values of the maximum and minimum specific OGZs, respectively, the injection cycles of the rims of the composition are repeated when the oil production rate drops to the level before the composition is injected.