RU2537446C1 - Method of determination of filtration rate of formation fluids - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: in killed well temperature is measured, and the temperature change rate is measured in the depth intervals located within the productive formations, and in the depth intervals located in immediate proximity from productive formations. In the depth intervals located within the productive formations, the sections are separated, the temperature change rate in which is much higher than the temperature change rate in the depth intervals located in immediate proximity from productive formations. The numerical model of temperature change in a killed well is developed which takes into account the influence of formation fluid filtering at the temperature change rate in the killed well, the measurements results are compared with the results of numerical simulation and using the best agreement of measurement results and simulation results the filtration rate of formation fluids in the depth intervals located within the of productive formations are determined.

EFFECT: identification of depth intervals, where fluid flow occurs, and estimation of rate of their filtering in the location of observation well.

8 cl, 7 dwg

Description

The invention relates to geophysical research of wells and is intended to determine the flow rates of formation fluids in oil wells.

To optimize the mutual arrangement and operating modes of production and injection wells, it is desirable to have information on the directions and velocities of the flow of formation fluids in oil deposits, where tens and hundreds of wells have been drilled. This information will clarify the hydrodynamic model of the oil reservoir. Of particular importance is the information on the movement of reservoir fluids in the case of the production of highly viscous oil. In addition to the heterogeneity of the properties of the oil reservoir, which may be known from geophysical studies, heterogeneity of the filtration properties of the reservoir associated with the composition of the reservoir fluid occurs during production. Between the injection and production wells, channels filled with water (having a low viscosity) can arise through which the injected water enters the production well and does not provide for oil displacement and heating of oil-containing sections of the reservoir. For these reasons, the development of methods for controlling the movement of reservoir fluids in an oil reservoir with a large number of production and injection wells is of great interest.

Currently, the control of the movement of reservoir fluids in an oil reservoir is carried out indirectly, by monitoring the hydraulic connection between the wells by the method of hydraulic listening (see, for example, Amanat U. Chaudhry, Oil Well Testing Handbook, Elsevier Science, 2004, p. 429-462 ) This method is based on observations of changes in pressure in idle wells when changing operating modes of disturbing wells.

A more direct method is tracing filtration flows using indicator substances (see, for example, G. Michael Shook, Shannon L. Ansley, Allan Wylie, Tracers and Tracer Testing: Design, Implementation, and Interpretation Methods, 2004, INEEL). The method consists in adding an indicator substance to the fluid injected into the well and recording the moment of appearance and concentration of the indicator in the fluid coming from the producing wells. Various chemical and radioactive substances are used as indicators, which should be well soluble in water, not precipitate, not be sorbed by rock, be recorded in a wide range of concentrations, etc. Tracing filtration flows is a rather expensive and time-consuming method, which is used relatively rare. In addition, tracing allows you to evaluate only the average fluid filtration rate between the injection and production wells. The fluid filtration rate at the location of the producing well (if it were stopped) remains unknown.

The technical result achieved by the implementation of the invention is to provide the possibility of identifying intervals of depths (layers), where the movement of fluids, and assessing the speed of their filtration at the location of the observation well.

The specified technical result is achieved in that, in accordance with the proposed method for determining the rate of filtration of formation fluids in a stopped well, temperature is measured and the rate of change of temperature is determined at depth intervals within productive formations and at depth intervals in close proximity to productive formations . At intervals of depths located within the productive formations, sections are identified where the rate of temperature change is significantly higher than the rate of temperature change at intervals of depths located in the immediate vicinity of the productive formations. A numerical model of the temperature change in a stopped well is created, taking into account the influence of formation fluid filtration on the rate of temperature change in a stopped well, the results of measurements are compared with the results of numerical simulations, and the filtration rate of the fluids in the selected sections of the depth intervals located in limits of productive formations.

In accordance with one embodiment of the invention, the temperature in a stopped well is measured using an optical fiber meter.

According to another embodiment of the invention, the temperature in a stopped well is measured by at least three thermal logs of that well.

Temperature measurements are carried out in the well, stopped either after cementation, or after production, or after injection of fluid into the well, or after the circulation of fluid in the well.

It is preferable to identify areas where the rate of temperature change is significantly higher than the rate of temperature change at depth intervals in the immediate vicinity of the productive formations, is carried out at well dwell times of 10 to 30 hours

The invention is illustrated by drawings, in which Fig. 1 shows examples of disturbances in the thermal field of a formation before taking temperature measurements in a stopped well, in Fig. 2 shows the calculated field of temperatures in the formation after production for 30 days, in Fig. 3 - the calculated field of temperatures in the formation after well boreing for 3 days, figure 4 shows the calculated temperature in the well, normalized to the initial deviation of the temperature of the well from the temperature of the formation, figure 5 - normalized to the rate of temperature change for two c Height filtering, Figure 6 - the dependence of the normalized rate of change of temperature on the filtration rate at the time vystoyki hole 20 h, in Figure 7 shows a diagram of the computational domain, which is used to assess the rate of filtration by numerical simulation.

The proposed method is based on the dependence of the rate of temperature change, measured in the observation well, on the presence and rate of fluid filtration in the formation that crosses the well.

The invention is carried out as follows.

Measure the temperature profile over the entire wellbore using thermal logging devices or using a fiber temperature meter in the well stopped after cementing (Fig. 1a), production (Fig. 1b), fluid injection (Fig. 1c) or fluid circulation (Fig. 1d) ) In the case of thermal logging, measurements are carried out repeatedly, at least 3-5 times. In all cases, the initial temperature in the well and in the near-wellbore space differs from the temperature of the rocks far (several meters) from the well.

The rate of change of temperature measured in the well at various depths is calculated: at intervals of depths located within the productive formations, and at intervals of depths adjacent to the productive formations (at a distance of not more than several tens of meters).

Preferably, 10-30 hours after the shutdown of the well at intervals of depths located within the productive formations, areas with filtration of formation fluids are distinguished, where the rate of temperature change is significantly higher than outside the reservoir.

A numerical model of the temperature change in a stopped well is created, taking into account the influence of formation fluid filtration on the rate of temperature change in a stopped well, the results of measurements are compared with the results of numerical simulations, and the filtration rate of the fluids in the selected sections of the depth intervals located in limits of productive formations.

The ability to isolate depth intervals and evaluate the rate of formation fluid filtration has been demonstrated in synthetic cases using the COMSOL Multiphysics 3.5 commercial simulator.

2D modeling of a stationary pressure field (and filtration rate) and an unsteady temperature field was carried out in a horizontally located homogeneous calculation region, including the well.

The equations for pressure and temperature have the form:

,

,

скорость фильтрации флюида, $$\delta =\phi +\left(1-\phi \right)\cdot \frac{{\rho }_m{c}_m}{{\rho }_f{c}_f}$$

, k - проницаемость пласта, µ - вязкость фильтрующегося флюида, λ - теплопроводность флюидонасыщенного пласта, ρ_mc_m - объемная теплоемкость кристаллической матрицы пласта, ρ_fc_f - объемная теплоемкость флюида, ϕ - пористость пласта.Where $$\overline{V}=-\frac{k}{\mu }\cdot \nabla P$$

fluid filtration rate, $$\delta =\phi +\left(\mathrm{one}-\phi \right)\cdot \frac{{\rho }_m{c}_m}{{\rho }_f{c}_f}$$

, k is the permeability of the formation, μ is the viscosity of the fluid being filtered, λ is the thermal conductivity of the fluid-saturated formation, ρ _m c _m is the volumetric heat capacity of the crystalline matrix of the formation, ρ _f c _f is the volumetric heat capacity of the fluid, ϕ is the porosity of the formation.

The boundary conditions for the calculation of the pressure equation (7): impermeable upper and lower boundary of the computational domain and the surface of the well defined P ₁ and pressure P ₂ on the left and right borders of the computational domain. In this case, the pressure difference P ₁ -P _{2 was} selected in such a way as to ensure the required fluid filtration rate at a given value of formation permeability.

Boundary conditions for the energy equation (Fig. 7): thermally insulated upper and lower boundaries of the computational domain, temperature T ₀ equal to the temperature of the reservoir at the left boundary and free flow condition at the right border of the computational domain.

The calculation was carried out in two stages.

At the first stage, a constant temperature was set at the well boundaries, which corresponds to the temperature of the fluid flowing through the well during production or circulation, and the temperature field was calculated at the end of the circulation, which was used as the initial condition for the second stage. At the second stage, the evolution of the temperature field after well shutdown was calculated. The calculation was carried out in the entire calculation area, including the well.

As an example, consider a field with two productive formations, and production is carried out from the lower reservoir (Fig.1B). Figure 2 shows the calculated temperature field in the upper reservoir (at a fixed depth) after 30 days of production at a filtration rate in this reservoir of 0.25 m / day.

The calculated temperature field in the formation after 3 days of well completion is shown in Fig.3. The well in this figure is shown in a black circle. Since the size of the area where the temperature differs significantly from the reservoir, significantly exceeds the radius of the well, there is a drift of the area of elevated temperature by the filtered fluid. As a result, the temperature measured in the well changes faster than in the absence of flow.

The calculated temperature in the well, normalized to the initial deviation of the temperature of the well from the temperature of the reservoir at filtration rates of 0, 0.12, and 0.25 m / day, is shown in Fig. 4, curve 1 — V = 0, curve 2 — V = 0.12 m / d, curve 3 - V = 0.25 m / d. Figure 5 shows the rate of change of temperature at filtration rates of 0.12 and 0.25 m / day, normalized to the rate of change of temperature in the absence of filtration in the reservoir (curve 1 - V = 0.25 m / d, curve 2 - V = 0 , 12 m / d).

Calculations show that the temperature relaxation rate normalized in this way has the greatest values in the interval of the well dwell time of 10-30 hours. Figure 6 gives the dependence of this value on the fluid filtration rate at the dwell time of 20 h. The specific form of the normalized temperature relaxation rate depends on the well design , thermal properties of rocks and must be calculated in each case, for example, using a commercial simulator COMSOL Multiphysics 3.5.

Nevertheless, it can be seen from FIG. 6 that using the proposed method, it is possible to obtain information on filtration flows having a speed of more than 0.03-0.05 m / day.

Claims (8)

1. A method for determining the rate of filtration of formation fluids, according to which a temperature is measured in a stopped well, the rate of temperature change is determined at depth intervals within productive formations and at depth intervals in the immediate vicinity of productive formations at depth intervals located within the productive strata, areas are identified where the rate of temperature change is significantly higher than the rate of temperature change at the intervals of deep in, in the immediate vicinity of the reservoir, create a numerical model of temperature changes in a stopped well, taking into account the influence of formation fluid filtration on the rate of temperature change in a stopped well, compare the measurement results with the results of numerical modeling and determine the speed of the best match between the measurement results and the simulation results filtration of reservoir fluids in selected sections of depth intervals within productive areas comrade 2. The method according to claim 1, in accordance with which the temperature in the well is measured using an optical fiber meter. 3. The method according to claim 1, in accordance with which the temperature in the well is measured by at least three thermal logs. 4. The method according to claim 1, in accordance with which the allocation of areas in which the rate of change of temperature is significantly higher than the rate of change of temperature at depth intervals in the immediate vicinity of the productive formations is carried out at a well dwell time of 10 to 30 hours 5. The method according to claim 1, whereby the temperature is measured in a well stopped after cementation. 6. The method according to claim 1, in accordance with which the temperature measurement is carried out in a well stopped after production. 7. The method according to claim 1, wherein the temperature is measured in a well stopped after the fluid is injected into the well. 8. The method according to claim 1, wherein the temperature is measured in a well stopped after the fluid circulates in the well.

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