RU2740597C1 - Method for forecasting change in production rate of production wells during propagation of elastic vibrations in bottomhole formation zone - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to intensification of oil production from terrigenous reservoirs by means of wave action on bottom-hole formation zone. Method includes stages: obtaining characteristics of productive formation, creation of three-dimensional mechanical model of geological medium based on characteristics of productive formation, designing the intensification using the created mechanical model of the geological environment, calibrating the intensification project based on actual data, simulating the projected intensification and predicting production, estimating the projected intensification. At the stage of creation of three-dimensional mechanical model of geological environment, modeling is carried out using a fine-scale mesh. At the stage of intensification design mechanical simulation of propagation of elastic oscillations on a fine-scale grid is performed; change of permeability to damping point of elastic oscillations in formation is determined, forecasting of change of yield of producing well after wave action is performed on large-scale grid.

EFFECT: technical result of the invention is higher accuracy of forecasting of oil production intensification.

1 cl, 3 dwg

Description

The invention relates to the intensification of oil production from terrigenous reservoirs using a wave action on the bottomhole formation zone.

From the prior art, there is a method that intensifies the flow of oil for treatment of bottom-hole zones of wells, disclosed in the application for invention of the Russian Federation No. 94015214, 1994. According to the method, prior to stimulation, an analysis of geological information on a complex of wells is performed in order to preliminary assess the feasibility of carrying out stimulation measures, assessment of the overall decline in the productivity of each well from the selected ones, determination of the component of the decline in productivity of each well due to the natural increase in water saturation of the bottomhole formation zone (BHZ) during operation, calculation of the decline in productivity of each well due to BHZ contamination, forecasting oil production and additional oil production in the case of production stimulation, taking into account the degree of BHZ contamination determined for each well, the choice of wells for production stimulation by comparing the values of additional oil production with the boundary values of economic expediency stimulation spines, stimulation in selected wells.

The disadvantage of this method is that predicting the increase in the production well flow rate after BHZ treatment is based on the degree of well productivity decline due to BHZ contamination, calculated by isolating the component of the productivity decline rate due to the natural increase in BHZ water saturation during operation, which does not guarantee oil production intensification. since watering of wells can occur as a result of many reasons not related to the pollution of the bottomhole formation zone.

From the prior art there is a method for predicting the behavior of a well, disclosed in the patent for invention of the Russian Federation No. 2573746, 2014. The method contains the stages at which: identify the input variables that have an impact on the output indicator, identify a subset of the set of input variables, where this subset has a relatively greater impact on the output. A physical property model is constructed to predict the output as a function of a subset of the set of input variables. The estimated changes to a subset of the set of input variables are ranked in probability using a physical property model. The behavior of a physical system is predicted based on the level of expected changes.

The disadvantage of the known method is that the probability ranking of the expected changes in a subset of the set of input variables using a physical property model without modeling on a fine-scale grid is not able to simulate the propagation of elastic deformations in the bottomhole zone.

From the prior art, there is a known method for treating a productive formation, disclosed in the patent for invention of the Russian Federation No. 2478778, 2013. The method for treating a productive formation consists in a cyclically alternating operation of repression to the formation with the injection of process fluids into the formation and drawdown into the formation with the call of inflow. Wave action is carried out by elastic vibrations on the treated medium by a hydrodynamic generator installed in the well opposite the productive interval. They regulate the magnitude and / or rate of repression and depression in cycles. A regular wave action controlled by amplitude-frequency parameters is carried out. Monitoring of the development of filtration processes, decolmatation and fracturing in the reservoir environment, on the basis of which, in the feedback mode, control parameters, parameters of wave action in subsequent cycles of repression and depression and the duration of these cycles in time are determined and assigned. Moreover, the magnitude and / or rate of creation of repression and depression in the cycles is regulated with their sequential increase. At the same time, their initial minimum values are determined and assigned depending on the filtration-capacitive parameters of the formation medium and at the same time periodically create hydropercussion pressure pulses in the well fluid.

The disadvantage of this method is that the control parameters, the parameters of the wave action in the repression and depression cycles and the duration of the cycles in time are determined and assigned already in the process of stimulation of production in the feedback mode during monitoring of the development of filtration processes in the reservoir environment, decolmatation and fracturing.

From the prior art, there is a method for stimulating oil inflow, disclosed in the patent for invention of the Russian Federation No. 2454527, 2012. According to the method, before stimulating production, the frequency of natural vibrations of the casing walls in the circumferential direction in the perforation interval is determined by calculation so that the depth of penetration of elastic vibrations into the formation is maximum, the depth of penetration of the sound wave into the formation is determined, and then work is carried out to stimulate production.

The disadvantage of this method is that the frequency of the wave (acoustic) impact and the depth of penetration of elastic vibrations are determined without taking into account the actual mechanical parameters of the formation, as a result of which the reliability of the calculations is reduced, and the forecasting of the change in flow rate must be calculated manually.

The closest method for the same purpose to the claimed method in terms of a set of features is a method for stimulating oil production, which includes the stages of obtaining characteristics of the productive formation, creating a three-dimensional mechanical model of the geological environment based on the characteristics of the productive formation, planning a well, designing stimulation using the created mechanical model of the geological environment, sizing the stimulation project based on real data, modeling the projected stimulation and forecasting production, evaluating the projected stimulation, real-time optimization of the projected stimulation, managing the stimulation operation based on the optimized stimulation plan in real time; determining the quality of the reservoir and the quality of completion along the side segment of the well; creating a set of quality indicators from a variety of well logs and combining a set of quality indicators to form a consolidated quality indicator, a system for performing well stimulation operations (RF patent No. 2663011 dated 01.08.2018). This method is taken as a prototype.

Prototype features that are common with the claimed method are a method for predicting changes in the production rate of production wells during the propagation of elastic vibrations in the bottomhole formation zone, including the steps: obtaining the characteristics of the productive formation, creating a three-dimensional mechanical model of the geological environment based on the characteristics of the productive formation, designing stimulation using the created mechanical model of the geological environment, calibration of the stimulation project based on real data, modeling of the projected stimulation and forecasting production, evaluating the projected stimulation.

The disadvantages of the known method taken as a prototype include the fact that at the stage of intensification design, the calculation is performed using a mechanical earth model (MEM), the minimum resolution (cell size) of which is one meter, while at the wave The impact on the formation of the phenomena occurring in the bottomhole formation zone (BHZ) (stress distribution) requires modeling with a higher resolution (up to a meter) using a fine-scale grid. Another disadvantage of the prototype is that at the stage of stimulation design, the calculation is performed only using a mechanical model of the geological environment, which does not allow simulating the hydrodynamic phenomena that occur in the bottomhole formation zone (BHZ) after carrying out such methods of oil production stimulation, such as, for example, wave treatment wells, and requires an analytical approach to forecasting production.

The indicated disadvantages of the prototype, namely: the inability to accurately simulate the phenomena in a saturated porous medium on a mechanical model, as well as the inability to simulate hydrodynamic phenomena, reduce the accuracy of predicting the intensification of oil production.

The problem to be solved by the claimed invention is to increase the accuracy of forecasting the intensification of oil production.

The task was solved due to the fact that in the known method for predicting the change in the production rate of production wells during the propagation of elastic vibrations in the bottomhole formation zone, which includes the following stages: obtaining the characteristics of the productive formation, creating a three-dimensional mechanical model of the geological environment based on the characteristics of the productive formation, designing stimulation using the created mechanical model of the geological environment, calibration of the stimulation project based on real data, modeling the projected stimulation, forecasting production, evaluating the projected stimulation, according to the invention, at the stage of creating a three-dimensional mechanical model of the geological environment, modeling is performed using a fine-scale grid, and at the stage of stimulation design, mechanical modeling the propagation of elastic vibrations on a fine-scale grid, determine the change in permeability to the point of attenuation of elastic vibrations in the area Aste, the prediction of changes in the production well rate after the wave action is performed on a large-scale grid.

Signs of the proposed technical solution, distinguishing from the prototype: at the stage of creating a three-dimensional mechanical model of the geological environment, modeling is performed using a small-scale grid; at the stage of intensification design, mechanical modeling of the propagation of elastic vibrations on a fine-scale grid is performed, the change in permeability to the point of attenuation of elastic vibrations in the formation is determined; prediction of changes in production well flow rate after wave action is performed on a large-scale grid.

Thanks to the new features, the proposed method makes it possible to simulate the propagation of elastic vibrations in the bottomhole formation zone, to estimate the damping radius of elastic vibrations, to assess the change in permeability in the bottomhole formation zone and to predict the increase in the production rate of a production well for oil. Distinctive features in combination with the known ones will improve the accuracy of forecasting the intensification of oil production.

The applicant is not aware of the use in science and technology of the distinctive features of the method for predicting changes in the production rate of production wells during the propagation of elastic vibrations in the bottomhole formation zone, with obtaining the specified technical result.

FIG. 1 shows a block diagram of operations for implementing the proposed method.

FIG. 2-3 shows an example of creating a mechanical 3D model of the geological environment using a fine-scale grid based on the characteristics of the reservoir. FIG. 2-3 show:

1 - well in the mechanical model of the geological environment;

2 - stress in the bottomhole formation zone along the section at distance from the well;

3 - section;

4 - stress distribution around the well.

The method for predicting changes in the production rate of production wells during the propagation of elastic vibrations in the bottomhole formation zone is carried out as follows (Fig. 1).

Preliminary geophysical, petrophysical and geological studies of the productive formation are carried out.

Based on the studies carried out, at the first stage, information is selected on the shape and size of the reservoir area, thickness, dissection, net-to-gross of the productive formation.

Based on the results of the core study, the following data are taken:

- physical and mechanical properties of the rock:

1) density;

2) strength for uniaxial compression, tension;

3) moduli of elasticity of a saturated porous medium;

4) Young's modulus;

5) Poisson's ratio;

6) graininess;

7) wettability;

8) structure;

9) texture;

10) type of cement;

- physical properties of the liquid:

1) density;

2) viscosity;

3) gas-containing;

- filtration-capacity properties (FES) of rock:

1) porosity (absolute, open, effective);

2) permeability (absolute, phase);

3) tortuosity of pore channels.

On the basis of the obtained characteristics of the productive formation at the second stage, a mechanical 3D-model of the geological environment is created using a fine-scale grid (Fig. 2). The model contains physical and mechanical properties and reservoir properties of a saturated porous medium. The model is subject to all-round compression corresponding to the real geological conditions of the area. Inside the borehole wall 1 is a dynamic impact with a certain frequency and amplitude.

In order to determine the depth of attenuation of elastic waves of different frequencies in the bottomhole formation zone, one can use the equations of mechanics of saturated porous media, using the physical and mechanical properties of the reservoir and the fluid. As a tool for modeling and determining the attenuation depth, you can use the software packages ABAQUS, ANSYS and others, which allow you to simulate the propagation of elastic energy in the bottomhole zone by the finite element method on a fine-scale grid.

An alternative method for determining the depth of damping of elastic vibrations during stimulation of oil production by the wave method can be a calculation using the Biot equations, in accordance with which the elastic energy into the reservoir

where Р, R, Q - elastic modules of the skeleton e, fluid ε and the modulus of their connection, taking into account the mechanical properties;

ρ ₁₁ , ρ ₁₂ , ρ ₂₂ - coefficients that take into account the unevenness of the relative flow of fluid in the pores;

b - the ratio of the friction force of the fluid against the pore walls to its average velocity of movement;

F (κ) - universal complex function; κ is a dimensionless variable.

The depth of penetration of elastic waves into the saturated BHZ in this case is determined by the damping coefficients

where L _c is the relative wavelength of propagation in the bottomhole zone, m;

- расстояния до точки в ПЗП, м;

- the distance to the point in the PPP, m;

γ ₁₁ , γ ₁₂ , γ ₂₂ and σ ₁₁ , σ ₁₂ , σ ₂₂ are parameters that take into account, respectively, dynamic and elastic properties of the matrix and fluid;

z ₁ , z ₂ - complex coefficients;

f, f _c - respectively, the frequency of elastic vibrations and the frequency up to which the Poiseuille law is fulfilled (for laminar flow of liquid through channels of circular cross-section), Hz.

After creating a mechanical 3D model of the geological environment, at the third stage, the design of production stimulation is performed at various amplitude and frequency of impact. The design is carried out in such a way that the dynamic characteristics of the wave action do not exceed the dynamic strength of the porous medium saturated with liquid. Several simulation scenarios are performed.

The fourth step is to calibrate the stimulation design based on real data.

At the fifth stage, the propagation of deformations in the bottomhole formation zone is modeled on a mechanical model during the intensification of the inflow (2-3, Fig. 3), the depth of damping of oscillations is determined under various scenarios (combinations of amplitude and frequency) (4, Fig. 3).

Mechanical simulations can be performed with the following assumptions:

- the direction of the maximum stress σ ₁ in the productive formation coincides with the axis of the well;

- horizontal stresses in the reservoir are isotropic

- the wellbore in the interval of the productive formation is not cased;

- elastic deformations of the collector;

- the porous medium is represented by one phase (rock matrix).

в насыщенный терригенный коллектор можно оценить, используя уравнения (1)-(4)Alternatively, the depth of penetration of elastic deformation

into a saturated terrigenous reservoir can be estimated using equations (1) - (4)

where ρ _g.p. - density of rock and liquid, kg / m ³ ;

K, G - moduli of elasticity of a saturated porous medium;

f is the frequency of the wave action, Hz;

A is the amplitude of the dynamic load on the borehole wall, N.

At the sixth stage, the zone of change in the permeability of the bottomhole zone is determined, and the change in the permeability of the bottomhole zone is assessed depending on different amplitude and frequency of impact.

The change in the permeability of the bottomhole formation zone during treatment can be determined using an equation that takes into account the frequency of dynamic impact:

where k ₀ - initial fluid permeability of the rock, μm ² ;

с - coefficient taking into account the cleaning of the pore space from deposits, units;

α ^∞ - tortuosity of pore channels, units;

ρ _w - density of the saturating liquid, kg / m;

f is the frequency of the wave action, Hz;

η - dynamic viscosity of the liquid, Pa⋅s;

Λ — ratio of sample pore volume to grain surface area, m;

φ - porosity, dol. units

At the seventh stage, forecasting of hydrocarbon production is performed on a filtration (hydrodynamic) 3D model of the geological environment using a large-scale grid.

If we assume that the size of the bottomhole formation zone during wave processing is determined by the damping depth of elastic vibrations, then, taking into account equation (6), the well flow rate in the case of a plane-radial inflow of a single-phase fluid can be determined by the formula

where R _PL and R _c - pressure, respectively, in the formation and at the bottom of the well, Pa;

μ - dynamic viscosity of reservoir fluid, mPa⋅s;

h - formation thickness, m;

- соответственно радиус до точки в пласте и ПЗП, м;R _pl and

- respectively, the radius to the point in the reservoir and bottomhole formation zone, m;

k_УЗП - проницаемость соответственно призабойной и удаленной зон пласта (УЗП), мкм.

k _USP - permeability, respectively, of bottomhole and remote formation zones (UST), μm.

If the predicted increase in oil production satisfies the intensification project, then at the eighth stage, they move to the choice of the wave action method that provides the required amplitude and frequency to obtain the predicted increase in oil production. After that, at the ninth stage, the well is treated, a comparative analysis of the results obtained with the model ones is performed. Calibrate the model if necessary.

As an example, let us consider the calculation of the change in the production rate of production wells after wave treatments of the bottomhole formation zone of terrigenous (development targets C1tl, C1bb, C1rd) oil deposits. Before treatment, the bottomhole formation zone of the wells was characterized by deteriorated properties - permeability from 0.02 to 0.3 microns, while the permeability of the remote formation zone was from 0.13 to 0.76 microns. The oil flow rate of the wells before treatment ranged from 0.5 to 3.9 t / day. As a result of the calculation according to the proposed method, results were obtained that confirm the receipt of the claimed technical result, namely, an increase in the accuracy of predicting the intensification of oil production. The deviation of the actual indicators from the forecast does not exceed 8%.

If the predicted increase in oil production does not satisfy the stimulation project, the process of selecting the parameters of the dynamic impact is repeated until the optimal scenario is found.

The advantage of the invention is that modeling on a fine-scale grid, determining the depth of attenuation of elastic waves in the bottomhole formation zone, determining the change in permeability to the attenuation point, as well as hydrodynamic modeling on a large-scale grid can improve the accuracy of predicting the intensification of oil production in terrigenous reservoirs of oil fields.

Claims (1)

A method for predicting changes in the production rate of production wells during the propagation of elastic vibrations in the bottomhole formation zone, including the steps: obtaining the characteristics of the productive formation, creating a three-dimensional mechanical model of the geological environment based on the characteristics of the productive formation, designing stimulation using the created mechanical model of the geological environment, calibrating the stimulation project based on real data, modeling the projected stimulation and forecasting production, evaluating the projected stimulation, characterized in that at the stage of creating a three-dimensional mechanical model of the geological environment, modeling is performed using a fine-scale grid, and at the stage of designing intensification, mechanical modeling of the propagation of elastic vibrations on a fine-scale grid is performed, the change is determined permeability to the point of attenuation of elastic vibrations in the reservoir, predicting changes in the production rate of a production well by After the wave action is performed on a large-scale grid.

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