RU2789872C1 - Method for determining geological and physical properties of formation and oil reserves - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: method for determining the geological and physical properties of a formation and oil reserves is claimed. The method includes the stage at which the boundaries of the developed oil reservoir are set. Also, the method includes a step at which geological reserves are determined and initial oil saturation distribution maps are set. Adjacent areas are also distinguished, through the dividing lines of which the absence of hydrocarbon flows is allowed. For each selected area, divided into cells, the maximum width of each of which is less than the minimum equivalent well influence radius, a system of nodes is determined, each of which is characterized by the parameters of a real or fictitious well, located in the cell node. Also, for each production well, influencing injection wells are set, the distance from which to the corresponding production well is less than the specified maximum distance. For each of the production wells, the share in production of the corresponding production well of each of the given influencing injection wells is determined. The share of influence decreases with increasing distance according to a predetermined dependence on the distance between wells. The total impact of the influencing injection wells on the oil production of the corresponding production well corresponds to the already accumulated oil recovery for the specified well. For production wells, the shape of the zone of influence of the production well is determined, such that the zone of influence is formed by a polygon with at least four vertices, where each of the vertices of the polygon is located on one of the rays emanating from the corresponding production well. The method also includes the step of scaling the zone of influence so that the area of the polygon having the shape of the zone of influence is equal to the area of a circle with the previously calculated radius for the corresponding well, and the polygon built on vectors determines the body, the volume of which is reservoir conditions corresponds to the volume of oil sampled by the well. According to the parameters of oil production of production wells and injection wells, the current distribution of oil saturation of the formation is determined. Also, various parameters of geological and technical measures on the wells of the formation are set. The change in oil saturation is predicted for given parameters of production and injection wells by taking into account the parameters of wells and mutual influence, and the parameters of geological and technical measures of the formation are used, which, in accordance with the forecast, provide the maximum level of oil recovery for carrying out geological and technical measures.

EFFECT: improving the accuracy of determining hydrocarbon reserves in underground reservoirs, the degree of watering and calculating the determination of optimal oil recovery, providing the possibility of increasing the efficiency of hydrocarbon production from underground reservoirs.

3 cl, 6 dwg

Description

The invention relates to methods for estimating the parameters of an oil reservoir, which can be used to improve the efficiency of reservoir development and measures to enhance oil recovery. The results of using the invention can be applied, for example, to the evaluation of recoverable reserves, the development of hydrocarbon recovery concepts, for example, using hydraulic fracturing or "fracking" or other technologies of a similar purpose. The invention can be implemented using computer systems that provide automatic and automated data processing.

The main problem solved by the invention is to provide the possibility of determining the current parameters of the oil reservoir without additional technical measures. In this case, both the oil saturation parameters of the formation and the content of associated fluids in the formation structures can be determined.

From the patent of the Russian Federation RU 2669980, a method is known for determining the hydrodynamic parameters of productive formations, the implementation of which uses point or interval measurements of well parameters using measuring instruments in an open borehole, followed by processing the data obtained by numerical methods of data interpretation.

The disadvantage of this method is that it is used at the stage of geological exploration and is not suitable for recording well operation data.

The closest analogue of the invention is the method disclosed in the patent of the Russian Federation RU 2757848, which consists in the fact that for a given set of wells, the initial properties of the field are formed, a cellular geological and hydrodynamic model of the area is formed, for a data array on the performance of the well stock, including at least the flow rate fluid and water cut of each well, build water cut analysis metrics according to the dependence of the current water cut on the fluid flow rate for each well, conduct additional hydrodynamic and field geophysical studies for wells, specify the characteristics of the cells of the geological and hydrodynamic model of the area in which wells are located with the addition of a water-saturated formation, based on the results of additional hydrodynamic and field geophysical studies, they build an updated geological and hydrodynamic model of the site and identify promising zones of concentration of residual reserves in the updated geological and hydrodynamic model onakh with unproductive production.

The disadvantage of this method is the limited scope, as well as the need for additional exploration activities to clarify the parameters of the field.

EFFECT: improved accuracy of determination of hydrocarbon reserves in underground reservoirs, degree of watering and calculation of optimal oil recovery, providing the possibility of increasing the efficiency of hydrocarbon production from underground reservoirs. In particular, when using the invention, an increase in the accuracy of determining oil saturation is provided both for the entire reservoir and for individual wells, while reducing the amount of calculations. The reduction in the volume of calculations is achieved by reducing the dimension of the data matrices used in the calculations. In addition, the use of the invention provides automation of the processes of generating solutions for the development of field infrastructure, reducing the costs of generating solutions, as well as increasing accuracy and reducing risks when using solutions. The invention provides the possibility of prompt adjustments to the execution processes, by eliminating the human factor, both when tracking development processes and in the process of making adjustments.

The technical result is achieved due to the fact that in the method for determining the geological and physical properties of the reservoir and oil reserves, which can preferably be used as a method for determining changes in the parameters of the oil reservoir during geological and technical measures, within the boundaries of the developed oil reservoir, for which the geological reserves and the distribution of initial oil saturation is predetermined, adjacent areas are identified, through the dividing lines of which the absence of hydrocarbon flows is allowed, for each selected area, divided into cells, the maximum width of each of which is less than the minimum equivalent well influence radius, a system of nodes is determined, each of which is characterized parameters of a real or fictitious well located in the node of the cell where:

fictitious injection wells of the selected area have parameters that provide simulation of water inflow into the corresponding selected area through the dividing line;

fictitious vertical wells located at a predetermined interval along horizontal wells have parameters that simulate the equivalent use of the respective production and injection horizontal wells, while the corresponding horizontal wells are excluded from further consideration;

the equivalent radius of influence R _oil of each of the production wells is taken equal to:

где

Where

- накопленный отбор нефти;

- accumulated oil recovery;

h - oil-saturated thickness;

m - porosity;

S ₀ - initial oil saturation at the well;

S _t - current oil saturation at the well;

каждой из нагнетательных скважин принимают равным:equivalent radius of influence

each of the injection wells is taken equal to:

где

Where

- эффективная закачка воды скважиной, объем которой эквивалентен объему вытесненной нефти;

- effective water injection by a well, the volume of which is equivalent to the volume of displaced oil;

set the maximum distance between mutually influencing wells;

for each production well, influencing injection wells are set, the distance from which to the corresponding production well is less than the specified maximum distance;

for each of the production wells, the share in the production of the corresponding production well of each of the given influencing injection wells is determined, so that the share of influence decreases with increasing distance according to a predetermined dependence on the distance between the wells, and the total influence of the influencing injection wells on the oil production of the corresponding production well corresponds to the already accumulated oil recovery for the specified well;

determine the vectors λ _ij of the interaction of each of the production wells with the corresponding influencing injection wells,

где

Where

each of the vectors is directed from the production well to the corresponding injection well,

i and j - indices of production and injection wells, respectively;

b - current volumetric water cut of the production well in reservoir conditions;

- приемистость нагнетательной скважины;r _ij - distance between wells, and

- injectivity of the injection well;

determine the shape of the zone of influence of the production well such that the zone of influence is formed by a polygon with at least four vertices, where each of the vertices of the polygon is located on one of the rays emanating from the corresponding production well, and all adjacent rays are directed at the same angle to each other to each other, and the length λ _k of each of the rays is determined based on the dependence:

Where dλ _ij θ is the angle between the beams, M is the number of beams, k is the beam number, and α _j is the counterclockwise angle between the horizontal and the direction from the production well i to the injection well j;

the zone of influence is scaled so, with such a coefficient η, that the area of the polygon having the shape of the zone of influence was equal to the area of a circle with radius R _oil for the corresponding well, and the polygon built on the vectors L _k =ηλ _k determines the body, the volume of which in reservoir conditions corresponds to the volume of oil sampled by the well;

according to the parameters of oil production of production wells and injection wells, the current distribution of oil saturation of the reservoir is determined;

set various parameters of geological and technical measures on the wells of the formation,

predicting the change in oil saturation for the given parameters of production and injection wells by taking into account the parameters of the wells and mutual influence, and using the parameters of geological and technical measures of the reservoir, providing, in accordance with the forecast, the maximum level of oil recovery, for carrying out geological and technical measures. In a particular implementation, if there are impermeable structures in a straight line between the wells, the wells are considered not to influence each other, regardless of the distance between the wells. In another particular case, implementations preliminarily specify the distribution of values of the initial oil saturation of the reservoir, for which:

form a set of wells with a starting water cut of up to 30%, which excludes wells that could be watered as a result of the operation of injection wells from the environment, launched before the start of wells from the set;

taking into account only the wells from the set, the distribution of the initial oil saturation and the initial water cut of the wells of the reservoir is determined, and if the predetermined distribution of oil saturation and the initial water cut of the wells not included in the set do not correspond to the predetermined distribution of oil saturation, the distribution of the initial oil saturation and the relative phase permeabilities of the reservoir in terms of oil and water are adjusted according to the values of the starting water cut of the wells with the preservation of geological reserves for the object.

The proposed technical solution can be implemented in the form of a software and hardware complex and is intended to provide a decision-making process for carrying out geological and technical measures and investing in the development of deposits.

The possibility of implementing the method is illustrated by the drawings, where in Fig. 1 shows the sequence of operations for implementing the method.

An example of a graph of the Buckley-Leverett function is shown in Fig. 2.

In FIG. 3 illustrates the flow of fluid through an element of the OWC circuit.

In FIG. 4 shows fictitious injection wells,

In FIG. 5 shows a representation of a set of production well interaction vectors with injection wells.

In FIG. 6 is a schematic representation of a model of impermeable faults/pullouts.

As shown in FIG. 1, at stage 1, the boundaries of the developed oil reservoir are set, at stage 2, geological reserves are determined and initial oil saturation distribution maps are set, at stage 3, adjacent areas are identified, through the dividing lines of which the absence of hydrocarbon flows is allowed, at stage 4, for each selected area, divided into cells, the maximum width of each of which is less than the minimum equivalent radius of influence of the wells, define a system of nodes, each of which is characterized by the parameters of a real or fictitious well, located in the node of the cell;

at step 5, for each production well, influencing injection wells are set, the distance from which to the corresponding production well is less than the specified maximum distance;

at step 6, for each of the production wells, the share in the production of the corresponding production well of each of the given influencing injection wells is determined, so that the share of influence decreases with increasing distance according to a predetermined dependence on the distance between wells, and the total influence of the influencing injection wells on production oil of the corresponding production well corresponds to the already accumulated oil production for the indicated well;

at step 7, for production wells, the shape of the zone of influence of the production well is determined such that the zone of influence is formed by a polygon with at least four vertices, where each of the vertices of the polygon is located on one of the rays emanating from the corresponding production well,

at step 8, the zone of influence is scaled so that the area of the polygon having the shape of the zone of influence is equal to the area of a circle with the previously calculated radius R_oil for the corresponding well, and the polygon built on vectors determines the body, the volume of which in reservoir conditions corresponds to the volume of oil sampled by the well;

at step 9, the current distribution of oil saturation of the formation is determined by the parameters of oil production of production wells and injection wells;

at step 10, various parameters of geological and technical measures on the wells of the formation are set,

and at step 11, the change in oil saturation is predicted for the given parameters of production and injection wells by taking into account the parameters of the wells and mutual influence, and the parameters of geological and technical measures of the formation are used, which, in accordance with the forecast, provide the maximum level of oil recovery for carrying out geological and technical measures.

As the initial data obtained from the results of operation and geological exploration, when implementing the method, values are used, each of which corresponds to a point or area with certain coordinates. Due to the fact that the visualization of such data is usually done in the form of maps, in the future the term "maps" can be used to define a set of values of various parameters associated with geographic coordinates.

As initial data for the implementation of the method, a map of the initial oil saturation, a map of the porosity of the formation rocks, a map of the effective thickness of the formation are used, while the value maps may contain descriptions of areas within which the parameter values differ from each other by predetermined values. It is preferable to represent areas as adjacent rectangles.

When describing more complex contours, for example, oil-bearing contours, the description of regions of an arbitrary form is used by describing the coordinates of points located on the boundaries of the regions. In this way, the outer contour of the oil content can be described, while the points can be presented sequentially, for example, in the order of the points on the map clockwise or counterclockwise. Also, when implementing the method, the values of the PVT-properties of the formation fluid are used, including the volumetric coefficient of oil, reservoir m3/stm3; volumetric coefficient of water, reservoir m3/stm3; density of oil in surface conditions, g/cm3; water density in surface conditions, g/cm3; viscosity of water in reservoir conditions, cP; oil viscosity in reservoir conditions, cP.

When implementing the method, information about hydraulic fracturing performed on wells can also be taken into account, including well coordinates, hydraulic fracturing date, fracture half-length, m; crack azimuth, deg.

The description of impermeable faults contains the coordinates of impermeable faults in the form of a list of coordinates of segments defining faults in the order of location of points on the map clockwise/counterclockwise.

When implementing the method, to build maps of the distribution of residual oil saturation and residual oil-saturated thickness, the following initial information is used, obtained, among other things, from the results of measurements

Distribution of relative phase permeabilities (RPP) in the oil-water system, oil viscosity, water viscosity in the reservoir zone, where water can be understood as solutions injected into the reservoir, both to displace oil and to enhance oil recovery,

Distribution of initial oil saturations (S ₀ ), tied to the map of the area;

Distribution of oil-saturated thicknesses (NNT), tied to the map of the area in the area of the formation (h ₀ );

The distribution of porosity of the reservoir structures, tied to the map of the area (m ₀ );

The coordinates of mouths and bottoms of wells tied to the map of the area;

For each of the wells, historical information about the production of liquid from the wells, taking into account the oil content in the produced liquid.

Historical data on fluid injection into injection wells

Determination of initial values

For calculations, it is necessary to know the porosity, initial oil saturation and initial reservoir thickness in the wells. These values are read from the respective source maps. In order for the obtained values to describe a certain vicinity of the well, a fixed radius is introduced (usually 250-500 m) and the initial parameters of the wells are obtained by averaging the values from the map of this parameter, collected within a circle of a given radius centered at the location of the well.

Determination of the current oil saturation in production wells is carried out using the Buckley-Leverett function, according to which the current oil saturation S can be set according to the current water cut b:

μ _w and μ _o - viscosity of water and oil;

ƒ _w and ƒ _o - functions of modified relative phase permeabilities for water and oil.

An example of a graph of the Buckley-Leverett function is shown in Fig. 2.

насыщенность остаточной нефтью и S_c - крайняя левая точка на графике функции Баклея-Леверетта, то есть нефтенасыщенность при обводненности, равной 1. Нефтенасыщенность на добывающей скважине определяется методом интерполяции по известной обводненности.For injection wells for which it is accepted

saturation with residual oil and S _c - the leftmost point on the graph of the Buckley-Leverett function, that is, oil saturation at a water cut equal to 1. Oil saturation at a production well is determined by interpolation from a known water cut.

To determine the water cut of the contour, it is considered that under conditions of an incompressible fluid, the entire extraction of oil from the reservoir must be compensated either by the injection of water into injection wells, or by the inflow of water into the reservoir due to the OWC contour.

Under conditions of stationary filtration, the following strict equality should be ensured: Q _f -Q _in -Q _to =0, where Q _f is the volume of the withdrawn fluid in reservoir conditions, Q _f is the volume of water pumped into the deposit in reservoir conditions, Q _to is the volume of intruded due to the OWC water circuit.

To solve the problem of water intrusion due to the OWC contour, parameters are used that correspond to the stationary filtration of an incompressible homogeneous liquid in a reservoir homogeneous in terms of filtration properties.

For n wells with known fluid flow rates (positive for production wells and negative for injection wells), using the superposition principle for linear equations, the pressure disturbance ΔР(х,у) at an arbitrary point of the reservoir has the form of dependence:

μ is the viscosity of the liquid;

k - reservoir permeability;

h is the effective thickness of the reservoir;

R _k - contour radius;

(x _i , y _i ) - coordinates of well locations,

.For a known pressure, as shown in Fig. 3 for the OWC contour, the fluid flow through the element dl of the OWC contour in the direction of the internal normal can be determined

.

Fluid inflow dQ into the reservoir through the contour element is equal to:

- вектор скорости фильтрации в точке (х, у).

- filtration velocity vector at the point (x, y).

According to Darcy's law:

or

Where:

And when using equation (3) to determine the pressure, the dependence dQ has the form:

To take into account the water introduced from behind the OWC contour, as shown in Fig. 4, inflow emulation is applied using fictitious injection wells located along the permeable contour in such a way and with such inflow that their work at any time corresponds to formula (8), and the injection for fictitious wells is determined by the equation:

- закачка фиктивной нагнетательной скважины j в месяц t;

- injection of fictitious injection well j in month t;

l _j - distance between fictitious injection wells;

- а) Если скважина i- добывающая, то добыча скважины i в месяц t, взятая с положительным знаком;

- a) If well i is producing, then the production of well i in month t, taken with a positive sign;

b) If well i is injection, then injection of well i in month t, taken with a negative sign;

x _j , y _j - coordinates of fictitious injection wells;

x _i , y _i - coordinates of real wells;

α _j - counterclockwise angle between the horizontal and the vector in the direction from fictitious well j to well i.

то принимается, что

исходя из предположения, что разработка ведется оптимальным образом, без вытеснения нефти за контур ВНК.If by calculation

then it is accepted that

based on the assumption that the development is carried out in an optimal way, without displacing oil beyond the OWC contour.

To reduce the time of computational operations and achieve maximum compliance with the actual waterflooding dynamics used in the calculations of the model, it is recommended to introduce a restriction on the distance between wells (usually 1500-3000 m). Wells i located at a distance greater than the specified distance from well j are not included in the calculation (9).

During the development of deposits, zones of influence of different wells are formed in different ways due to the possibility of choosing different development systems and the instability of the equipment. At the same time, the shape of the influence zone is usually far from the circle, in the form of which the well production zone is represented in simple engineering calculations. Determining the shape of the zone of influence of the well and its size is necessary for a correct assessment of the development of the deposit.

When determining the interaction of injection wells with the environment, the parameters of which are necessary for the correct formation of the zone of influence of the wells, when implementing the proposed method, the method shown below is used to take into account the influence of the operation of the wells of the environment on the production zone of individual wells.

можно рассчитать радиус R_oil цилиндра в окрестности добывающей скважины, подвижный (извлекаемый) объем нефти, которого был бы равен накопленному объему отбора нефти из скважины:According to cumulative oil recovery

it is possible to calculate the radius R _oil of the cylinder in the vicinity of the production well, the mobile (recoverable) volume of oil, which would be equal to the accumulated volume of oil extraction from the well:

h - oil-saturated thickness;

m - porosity;

S ₀ - initial oil saturation at the well;

S _t - current oil saturation at the well.

The shape of the zone of influence of the well is determined by converting the base of the above cylinder into a figure having an irregular shape while maintaining the area calculated for the base of the cylinder according to equation (10).

To assess the degree of interaction between production injection wells, the following assumptions are used:

The proportion of compensation by some injection well for fluid withdrawal by the production well is the greater, the greater the injectivity of the injection well;

The proportion of compensation by some injection well for fluid withdrawal by the production well is the greater, the closer it is to the production well.

и монотонно убывающая функция от расстояния между этими скважинами r_ij. В том случае, еслиThe proportion of compensation λ _ij for fluid withdrawal from the i-th production well by injection into the j-th injection well, according to the accepted assumptions, is a monotonically increasing function of the injectivity of the injection well

and a monotonically decreasing function of the distance between these wells r _ij . In case if

α ₁ , α ₂ >0,

according to the theory of stationary fluid filtration in a homogeneous reservoir, when a well is operating with a fluid flow rate Q _liq at a distance r from the well, the filtration rate is proportional to the ratio of the flow rate to the radius. In this case, α ₁ =α ₂ =1, and the coefficient γ is determined from the equality:

As a result

at any given point in time, the proportions of liquid withdrawal compensation of the i-th production well by the j-th injection wells are determined from the equation:

and the compensation shares of oil recovery at a given time are defined as:

b - current volumetric water cut of the production well in reservoir conditions.

When summing the values obtained using equation (15) for the entire history of the well operation over time T, the share of compensation for the accumulated oil recovery of the production well i by injection wells j is formed:

b ^t - volumetric water cut of the production well at step t;

- добыча жидкости скважиной i на шаге t;

- fluid production by well i at step t;

- закачка нагнетательной скважины i на шаге t;

- injection of injection well i at step t;

r _ij - distance from production well i to injection well j.

In a particular case, the interaction of wells is limited to a predetermined distance (usually 1500-3000 m), and injection wells located outside the specified distance are excluded from the calculations.

For a production well, interaction with injection wells can be represented as a set of vectors shown in FIG. 5.

The zone of influence of the well is represented as a polygon formed by rays of different lengths emanating from the location of the well, so that the angles between adjacent rays are equal to each other. The selection fraction along each ray is formed as the sum of non-negative projections of the interaction vectors onto the direction of the ray. As shown in FIG. 5 only the vectors λ _ij1 and λ _ij2 are positively projected onto the direction of the ray k=1. For dθ - the angle between the beams, such that M⋅dθ=2π, where M is the number of beams, the sum of non-negative projections of the interaction vectors on the beam k is defined as:

гдеfor all j for which the condition

Where

α _j - counterclockwise angle between the horizontal and the direction from the production well i to the injection well j (Fig. 4);

k - beam number in order (Fig. 6.)

When connecting the ends of the vectors λ _k , a polygon is formed (Fig. 6), the area of \u200b\u200bwhich is equal to the sum of the areas of the triangles that form this polygon:

where it is assumed that λ _m+1 =λ ₀ .

Further λ _k is scaled in such a way that the area of the polygon is equal to the area of the circle with radius R _oil (10). The transition to the required size of the area is made by multiplying the vectors λ _k by η, where η is defined as:

The transition to a polygon built on the segments L _k =ηλ _k determines the body, the volume of which in reservoir conditions corresponds to the volume of oil sampled by the well.

To determine the interaction of injection wells with the environment, the volume of injected water is determined, which actually replaced oil in the reservoir, and did not transit from the injection well to the production well.

полезной закачки, который реально пошел на замещение нефти:This volume is determined by the calculated values λ _ij . Since it took λ _ij ⋅Q _{oil of} water from the j-th injection well to compensate for the oil withdrawal by the i-th production well, all interaction vectors and the volume

useful injection, which actually went to replace oil:

равен:Accordingly, the radius of influence of the injection well

equals:

the formula for the interaction coefficients λ _ji of injection wells with production wells is determined similarly to formula (16):

b ^t - volumetric water cut of the production well at step t;

- эффективная закачка воды скважиной j на шаге t;

- effective water injection by well j at step t;

- добыча нефти скважиной i на шаге t;

- oil production by well i at step t;

r _ji - distance from injection well j to production well i.

To eliminate the possibility of inconsistency between the constructed map of initial oil saturation and RPP of the history of well operation, for example, if the well was put into operation in the ChNZ, but had a high initial water cut, or vice versa, the method of restoring RPP and initial oil saturation map according to production data was used.

To implement the specified method:

1) Wells are selected, the starting water cut of which characterizes the initial water cut of the formation. To do this, all wells with a small initial water cut (up to 30%) are selected, and those that could be watered as a result of the operation of injection wells from the environment are excluded from the remaining ones.

2) RPP functions are used in the form of Corey empirical dependencies.

S _w - current water saturation;

S - residual oil saturation;

S _wc - critical water saturation;

K _ro,max - maximum RPP for oil;

K _rw,max - maximum RPP for water;

n ₀ , n _w - exponents.

The parameters S _wc , K _rw,max , n ₀ , n _w are set arbitrarily, the values of which are further specified, the parameter K _rw,max is taken equal to 1.

3) Water saturation S _w at production wells is calculated using the Buckley-Leverett function for the current water cut b:

S - current oil saturation at the well;

S _w - current water saturation in the well;

μ _w and μ _o - viscosity of water and oil;

ƒ _w and ƒ _o - functions of modified relative phase permeabilities for water and oil.

4) The average water saturation in the reservoir is calculated using the Welge equation:

- средняя водонасыщенность в пласте;

- average water saturation in the reservoir;

S - water saturation in the well;

F(S) - Buckley-Leverett function.

5) The current calculated oil recovery factor and WOR are determined by the formulas:

6) The current WOR and oil recovery factor are determined according to the operation data. To assess the NCD and find the CIN, in the particular case of the implementation of the invention, for example, the Kambarov method is used.

7) The discrepancy is calculated between the theoretical dependence of the logarithm of the WOR on the oil recovery factor, determined by formulas (28) and (29) and the dependence determined from the production data for each selected well.

The discrepancy is minimized by selecting the parameters K _rw,max , n ₀ , n _{w of} the Corey empirical dependences, the parameter S _wc remains unchanged. To minimize the parameters, any optimization algorithm can be used, for example, the method of simple iterations.

8) Further, according to the obtained Corey parameters, the type of the Buckley-Leverett function is determined, which, in turn, is used to find the starting oil saturation. On the OWC contour, oil saturation equal to S _or is set as boundary values. Based on these values, the initial oil saturation map is restored using one of the acceptable point-to-point interpolation methods, such as kriging, Delaunay triangulation, etc.

9) Next, geological reserves are specified according to the calculated map and compared with the design ones. The problem is to minimize this discrepancy by selecting the parameter S _wc while keeping the displacement coefficient constant (in other words, shifting the relative permeability curves to the left and to the right).

Thus, RPP are selected and a new map of the calculated initial oil saturation is constructed, which does not contradict the operating data, while maintaining the reserves for the deposit unchanged.

To successfully refine the parameters, wells are selected in such a way that there is confidence that the actual initial water cut of the well was an indicator of the reservoir water cut, and not a consequence of behind-the-casing flows or displacement front movement;

when using the Kambarov method to determine the NCD, it is necessary that the well has a long history of operation (10-15 years) and the natural nature of watering;

the number of points corresponding to the wells for interpolation and / or the uniformity of the map coverage with points provided the possibility of correctly assessing the distribution of oil saturation in areas not covered by points.

In a particular case of the implementation of the invention, for modeling horizontal wells, a set of fictitious vertical wells is used, located at a certain step in the direction from the mouth to the bottom. The production/injection of a horizontal well is evenly distributed among the fictitious ones, so that the total volume corresponds to the production or injection of the corresponding horizontal well.

The modeling of impermeable faults/pullouts is done in such a way that if any of the k beams shown in FIG. 6 intersects an impermeable structure (fault or wedging out), then the radii of influence of the corresponding wells are assumed to be 0 in the direction of ray k.

In order to ensure that after calculating the lengths of the segments L _k there is a guarantee that the polygon does not intersect impenetrable boundaries, while maintaining the required initial area, formula (30) is used for the area of the polygon formed by the ends of the segments with the same origin point, with an angle θ between adjacent vectors and lengths L _k .

If s _i =L _i ⋅L _i+1 ; s _N =L _N ⋅L ₁ , then:

For each of the lengths of the segments that do not intersect impermeable boundaries, a common scaling factor is used, and the lengths of segments that intersect impermeable boundaries are replaced by the distance from the well to the boundary along the corresponding vector. Expression (32) on the right is generally transformed into the following:

the first term is the areas of triangles formed by two segments crossing the boundary, the second is the areas of triangles, one of whose sides intersects the boundary, and the third is the areas of triangles, the sides of which do not cross the impenetrable boundary.

Solving the quadratic equation for k allows you to determine the scaling factor for each of the lengths of the scaled segments, thus defining a new zone of influence polyhedron with the same area as the original one. Calculation of the current distribution of oil saturation for the reservoir is carried out using the material balance equation.

For an arbitrary point i of the reservoir, the material balance equation for the deposit is used:

m _i - porosity at the considered point i;

Ω _i - area of the map cell;

h is the thickness of the formation at the considered point i;

ΔS _i - change in oil saturation at the considered point i;

- объем отбора нефти i-ой скважиной в месяц t в пластовых условиях.

- the volume of oil extraction by the i-th well in the month t in reservoir conditions.

To solve equation (27), it is necessary to use the current value of oil saturation at the reservoir point i according to the known work of wells and their interaction.

In the general case, the change in oil saturation at an arbitrary point of the reservoir i due to the operation of the well j when using the method is determined by:

ΔS _j - change in oil saturation in the i-th well;

ϕ - damping function, which determines the degree of oil saturation drop under the influence of the well;

r _ij - distance from the j-th well to the i-th cell of the map;

R _j - distance from the j-th well to the border of its area of influence in the direction of the i-th cell of the map;

γ is an optimization parameter selected in such a way that the material balance for the deposit is performed (27).

The function ϕ(r _ij , R _j , γ) increases monotonically with increasing R _j and decreasing r _ij , while being in the range from 0 to 1. In a particular case, the function has the form of an exponential dependence:

β>0 - coefficient selected depending on the properties of the oil displacement front.

Values of the parameter β are chosen in the range from 1 to 4. The larger β, the closer the dynamics of the waterflood front to piston displacement. Smaller values correspond to a more "blurred" front.

These dependencies are used to determine the decrease in oil saturation in each cell of the map under the influence of each production and injection well. The final decrease in unsaturation is considered to be the largest of the calculated ones.

In a particular case, the number of wells potentially affecting the cell can be reduced, as shown above, using a constraint on the distance from the cell to the well, for example, from 1500-3000 m. Wells located at a distance greater than the specified distance from the cell are not involved in the calculation and cannot reduce the oil saturation in it.

The result of the calculation is the value of the parameter y and, accordingly, the form of the function (29), in which the oil saturation of the reservoir decreases in such a way that the material balance condition (27) is observed.

The value of γ found at the previous step is used to find the residual oil-saturated thickness at point i:

- начальная нефтенасыщенная толщина в точке i;

- initial oil-saturated thickness at point i;

- начальная нефтенасыщенная толщина на скважине j;

- initial oil-saturated thickness at the well j;

h _j - current oil-saturated thickness at well j, determined through the current water cut of the well according to the formula

Claims (36)

1. A method for determining the geological and physical properties of the reservoir and oil reserves, which consists in the fact that within the boundaries of the developed oil reservoir, for which geological reserves are determined and the distribution of initial oil saturation is predetermined, adjacent areas are distinguished, through the dividing lines of which the absence of hydrocarbon flows is allowed, for each selected area, divided into cells, the maximum width of each of which is less than the minimum equivalent well influence radius, a system of nodes is determined, each of which is characterized by the parameters of a real or fictitious well located in the cell node, where: fictitious injection wells of the selected area have parameters that provide simulation of water inflow into the corresponding selected area through the dividing line; fictitious vertical wells located at a predetermined interval along horizontal wells have parameters that simulate the equivalent use of the respective production and injection horizontal wells, while the corresponding horizontal wells are excluded from further consideration; the equivalent radius of influence R _oil of each of the production wells is taken equal to

Where

- accumulated oil recovery; h - oil-saturated thickness; m - porosity; S ₀ - initial oil saturation at the well; S _t - current oil saturation at the well; equivalent radius of influence

each of the injection wells is taken equal to

Where

- effective water injection by a well, the volume of which is equivalent to the volume of displaced oil; set the maximum distance between mutually influencing wells; for each production well, influencing injection wells are set, the distance from which to the corresponding production well is less than the specified maximum distance; for each of the production wells, the share in the production of the corresponding production well of each of the given influencing injection wells is determined in such a way that the share of influence decreases with increasing distance according to a predetermined dependence on the distance between the wells, and the total influence of the influencing injection wells on the oil production of the corresponding production well corresponds to already accumulated oil recovery for the specified well; determine the vectors λ _ij of the interaction of each of the production wells with the corresponding influencing injection wells,

where each of the vectors is directed from the production well to the corresponding injection well, i and j - indices of production and injection wells, respectively; b - current volumetric water cut of the production well in reservoir conditions; r _ij - distance between wells, and

- injectivity of the injection well; determine the shape of the zone of influence of the production well, such that the zone of influence is formed by a polygon with at least four vertices, where each of the vertices of the polygon is located on one of the rays emanating from the corresponding production well, and all adjacent rays are directed at the same angle to each other to each other, and the length λ _k of each of the rays is determined based on the dependence

where dλ _ij θ is the angle between the beams, k is the beam number, a α _j is the counterclockwise angle between the horizontal and the direction from the production well i to the injection well j; the zone of influence is scaled with such a coefficient η that the area of the polygon having the shape of the zone of influence is equal to the area of a circle with radius R _oil for the corresponding well, and the polygon built on the vectors L _k =ηλ _k determines the body, the volume of which in reservoir conditions corresponds to the volume selected oil well; according to the parameters of oil production of producing wells and injection wells, the current distribution of oil saturation of the formation is determined; set various parameters of geological and technical measures on the wells of the formation, predicting the change in oil saturation for the given parameters of production and injection wells by taking into account the parameters of the wells and mutual influence, and using the parameters of geological and technical measures of the reservoir, providing, in accordance with the forecast, the maximum level of oil recovery, for carrying out geological and technical measures. 2. The method according to claim 1, characterized in that if there are impermeable structures in a straight line between the wells, the wells are considered not to influence each other, regardless of the distance between the wells. 3. The method according to claim 1, characterized in that the distribution of values of the initial oil saturation of the reservoir is preliminarily specified, for which: forming a set of wells with a starting water cut of up to 30%, from which wells are excluded that could be watered as a result of the operation of injection wells from the environment, launched earlier than the start of wells from the set; taking into account only the wells from the set, the distribution of the initial oil saturation and the initial water cut of the wells of the formation is determined, and if the predetermined distribution of oil saturation and the initial water cut of the wells that are not included in the set do not correspond to the predetermined distribution of oil saturation, the distribution of the initial oil saturation and the relative phase permeabilities of the formation in terms of oil and water are adjusted according to the values of the starting water cut of the wells with the preservation of geological reserves for the object.

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